Too many Zones?greenspun.com : LUSENET : Large format photography : One Thread
First off, let me say that I'm not a disciple of the zone system. I'll go along with the underlying philosophy of pre-visualisation, but IMHO there are more intuitive ways of getting there. I favour incident light measurement, coupled with compensation for the specific subject to be photographed, or effect to be acheived; so my question is really aimed at devoted users of the zone system.
The reference point in the zone system (and for the calibration of exposure meters for that matter) is stated as being "mid grey", zone 5, or 18% reflectance. Now 18% reflectance is only two-and-a-half stops down from a theoretical 100% reflecting diffuse surface, which one would expect to be rendered very near flat white in a print. A whitewashed wall comes close, for instance, and this isn't even Zone 8, so where do the higher zones fall? It seems to me that zones higher than 8 are only of relevance if a source of illumination or specular reflection is included in the picture, and we are willing to let objects which should normally appear near-white in the print slip down the scale to grey.
These days, you can't even expect the film to compress the highlights by flattening off toward maximum density. If you look at a film like T-Max, or even Plus-X developed in T-Max developer, the density curve just keeps going up and up in a straight line, putting the densest highlights well beyond the range of the toe of the paper curve. Remembering that the zone system was thought up when a typical film (or plate!) had an "S" shaped curve.
The conventional zone system answer to this is to add even more zones beyond 10 to accomodate the wider density range, but how are these extra zones to be accommodated in the print? Reduced development and contrast will simply make our prints look flat. The only answer that I can see in reality is to burn the highlights and/or dodge the shadows. What do you do with a contact print?
How many users of the zone system regularly make use of zones more than plus or minus one stop from the "norm"? I'll confess that most of the time I end up exposing within a stop of what the incident light meter recommends. How about you zone system users? I'd be interested to know how much the "expert" exposure deviates from the idiot-guide on the leaflet included with the film (i.e. June to September, cloudy-bright - 1/125th at f/8).
-- Pete Andrews (firstname.lastname@example.org), June 27, 2000
It is possible to get an S-shaped curve with today's films, but not with T-Max developer. Most developers produce a straight-line curve, but some give an S-shaped curve. D-23 gives a shoulder with HP-5+ that begins around Zone 7. Microdol-X should do the same, since it is basically D-23, but with the addition of sodium chloride, a silver solvent.
I have tested the HP-5+/D-23 1:1 combination for N-4 through N+2 development. N-4/N-3/N-2 is great for extreme contrast, which is rather common in outdoor photography. I have used N-3 to photograph architecture with one side of the building in bright sun, and the other in shade. N-2 and N-1 are great for portraits, since they lower the contrast and hide blemishes. N+1 is useful for low-contrast situations like fog. I often use N+2 for alternative processes. I would say about 30% of my shots get N development.
-- William Marderness (email@example.com), June 27, 2000.
Most Zone System followers use a spot meter, not an incident light meter. Additionally, Zone System controls come into play not in the initial camera exposure settings, but rather in the subsequent development the film is given later. The initial camera exposure settings will only vary slightly for typical Zone System use, the subsequent film development will vary much more.
At the risk of oversimplifying, the Zone System can be briefly summarized as follows: "expose for the low values, develop for the high values". The key to this is that the high values in the negative respond much more quickly to increased or reduced film development than do the low values.
Before putting the Zone System to use, initial film testing should be done to determine your particular exposure index (EI) for the specific film/developer/meter/lens shutter combination you've chosen. Additionally, Zone System testing should be done to determine your N(ormal), N-1, N+1, etc. film development times.
There are a ton of books/guides available describing this initial film speed test, and the subsequent testing procedures to detemine film development times, so I will not go into it here. However, a densitometer is almost a necessity to perform these tests.
In short, you should determine the specific film EI you should use to yield a net Zone I density in your negative of between 0.08 to 0.11 (or so), so this density can consistently be reproduced in your negatives during the initial camera exposure. This film speed test should be done for every film/developer/meter/lens shutter combination you anticipate using.
Subsequent development time tests for N, N-1, N+1, and so on, are more involved, and should be conducted taking into account your own printing equipment, light source, printing paper/print developer, personal tastes, and a whole host of other considerations.
I'll briefly describe my own procedures for using the zone system:
1. I will spot meter (Pentax Zone VI) a scene initially, to determine the actual range of values in the scene. This initial evaluation will tell me what I can ultimately expect when doing a more detailed and specific measurement of the scene.
2. I'll then look at the important low values in the scene, to determine which ones should be metered, and where they should be placed on the Zone scale. This low value placement will determine my camera exposure settings.
Let's take a typical landscape scene, with a full range of tonal values. I'll first place the important low values--those low values where I want to retain full texture/information in the final print, and not have them print as non-textured/non-detailed, blank dark areas--on a Zone III or IV.
This will be my starting point in determining camera exposure. Often, an incident reading, taken in the same light, will yield a very similar exposure recommendation.
3. I'll then look at the highest important values in the scene, meter them with the spotmeter, and determine where they will fall in relation to the Zone III-IV placement of the important low values.
For illustration puposes, in a typical landscape we'll use clouds as an example of important high values. Nothing looks worse in a landscape print than a bunch of clouds that are reproduced as blank paper white. Ideally, clouds in a landscape print should have a full range of texture and subtlety.
I'll meter the lightest sunlit areas of the clouds with the spotmeter and see where they fall in relation to my Zone III-IV placement of the important low values. If they fall at about a Zone VIII, wonderful; I can just develop the negative normally to reproduce these important high values in a satisfactory fashion. But, in a typical scene, they usually won't fall so neatly on the zone scale.
Let's say these clouds typically fall on or about a Zone IX, maybe as high as a Zone X. This tells me that if I want to be able to retain these important high values in the final print, and not have them print as pure paper white, with no subtlety or highlight texture, I'll have to reduce the negative's development, to compress the tonal range. To do this I'll give the negative a reduced development time, N-1 or N-2.
If the important high values fall on a Zone VII, in relation to my important Zone III-IV low value placement, then I'll have to increase the negative's development--to expand the tonal range. Constricted high values in a print will look dull and lifeless. In this case, I'll give the negative a N+1 development time to expand the high value placement from Zone VII to a higher Zone.
4. I'll note these measurements in my records, and proceed to make the initial exposure, as per my meter's indication, for the Zone III-IV important low value placement. The only change I will make in my initial exposure will be to slightly (no more than 1/3 to 1/2 stop) increase or reduce my initial exposure settings.
5. If I anticipate a subsequent N-1 development for the scene, I'll increase the initial exposure setting slightly, in order to maintain the low values as initially visualized/placed. If I anticipate a subsequent N+1 development of the scene, I'll slightly decrease the initial exposure for the same reasons.
In summary, your initial camera exposure settings may not vary much, when comparing traditional Zone System practices to an incident light reading, but the subsequent development given to the negative will vary a great deal when using the Zone System.
Hope this adds something to the discussion, Sergio.
-- Sergio Ortega (firstname.lastname@example.org), June 27, 2000.
Pete, You are making a basic error in assuming that 18% gray is two-and-a- half stops away from maximum white. The beauty of the Zone System is that, through manipulation of development times, one can control the amount of one-stop doublings in the subject (read subject contrast range) that make it onto the limited usable contrast range of the negative. I routinely use developments that allow me put a 2 to 6 stop subject contrast range in the area between Zone V and Zone IX in the final print. Also, I routinely use N-2 to N+2 developments, and N+3 and N-3 often enough that I have calibrated them thouroughly. It all boils down to knowing what your film/paper combination will do and how to expand or contract the subject contrast range so that it will fit into the limited contrast range necessary on the negative to make an expressive print. Regards, :^D)
-- Doremus Scudder (ScudderLandreth@compuserve.com), June 27, 2000.
The reference zone is Zone I, the threshold of exposure, not Zone V. Zone I is really the only density on the H&D curve that has very little variation with development, thus its use as the primary reference.
Regarding Zone V being 2.5 zones below 100% reflectance, yes this is correct, assuming both reflectances are illuminated by the same light.
Recognize also, that 2.5 zones below Zone V is very dark (virtually black to most people), giving you 5 zones total range. Think about this: that 5 zone range is the total range you can get from a diffuse reflecting surface, like a photographic print. This fits my impression of the range of exposure that easily fits on film and easily prints.
Where you get a greater range of zones is when different parts of your subject are illuminated by different light: a landscape with part in broad daylight, and part in shadow. The eye easily sees detail in both, but you have to compress this type of subject to fit it onto the paper. Note: paper not film. As you point out, modern films easily cover a much greater range of densities/zones, but you can't print the extreme density range straight onto paper. You are absolutely correct that the solution is to dodge and burn so that you compress.
By the way, many modern printing papers have a long toe to accommodate the lack of a shoulder on these mondern films. End result is the same, you just do it in a different part of the process.
For contact prints, you also dodge and burn as you need to if your negative has too great a density range.
As far as choosing a different method other than the zone system, if it works for you, great. I have a Pentax digital spot meter that I like. I bought a selenium cell incident light meter a year ago. My battery went out on my Pentax and I didn't have a spare battery. But I had a spare meter that doesn't use batteries. They both have their uses. So does the "sunny 16" rule alluded to in your "idiot guide".
Your message seems like you have a grudge against the zone system. If you do, it seems pointless. Many of the great photographers in the early part of the 20th century didn't use meters. What counts is results. The advantage of studying the zone system, even if you don't use it, is that it gives you a better technical understanding of practical sensitometry.
-- Charlie Strack (email@example.com), June 27, 2000.
"I'd be interested to know how much the "expert" exposure deviates from the idiot-guide on the leaflet included with the film (i.e. June to September, cloudy-bright - 1/125th at f/8)."
Just to address your last sentence....under those paramaters....these's not a lot of deviation. The negatives created in this fashion are very printable, I have printed many 40, 50 or 60 year old negatives and they make beautiful prints. Remember when the "idiot-guide" was used, it was used for lack of any exposure meter. The suggested exposure was not arrived at by calculations and metering, i would guess it was taked from real life situations. Someone probably went out under those circumtances and exposed film made notes and arrived at the suggested times. Those times yielded and still yield properly exposed negatives.
Now we must compensate for an "average" incident meter reading and adjust the exposure accordingly to create a negative that will be easily printable. When I use my spot meter, I am adjusting the exposure to accomplish the same end, create an easily printable negative. Different roads to the same destination. The Zone System is just that, a system. It can be very complicated, or as simple as determining your "key day" exposure as suggested by Fred Picker and that is in reality just your own personal "idiot-guide".
-- Marv (firstname.lastname@example.org), June 27, 2000.
Pete: Your comment about there being 2.5 stops between 18% reflectance mid- grey and 100% reflectance is correct. However, this does not describe the full tonal range in the scene. One needs to consider that not all objects in the scene receive the same illumination. It is the variance in illumination times the reflectance of each object that gives rise to the complete tonal range in the scene. Taken together the intensities of light reaching the film from the various objects in the scene can cover a very wide band of values - in theory an unlimited number of zones - but in most daylight scenes the tonal range will be within a 5-10 zone range. Dave
-- David Lewis (email@example.com), June 27, 2000.
Dave hits the nail on the head, and also identifies one of the major differences between outdoor incident and reflective metering. Almost no flatly illuminated subject has a brightness range of more than five stops. However, in full sunlight, the difference between a gray card in full sun and one in full shadow is four stops; with very deep shade (e.g. heavy woods) the difference can be more than five stops. Thus, a typical nature scene in full sunlight will have a total brightness range of 10 stops, even though the subject brightness range is only 5 stops.
With regard to the question about careful measurement versus sunny 16, it is useful to remember that Ansel Adams developed the zone system as a teaching tool to explain exposure to students -- most of his own great photographs were made without it. In fact, once you are used to a particular environment and film, much of the time careful measurement with a spot meter or use of an incident meter with something like Davis's Beyond the Zone System will lead to exactly the same exposure as no meter and experience. For example, if it is June in Alaska, a sunny day between 8am and 8pm and I am shooting a landscape with mountains in the background and forest in the foreground, I don't need my spot meter to tell me to expose HP5+ with a Wratten 12 filter at f/22 for 1/50 and develop 12 minutes in PMK. When I was learning, I did need the whole system.
-- John Lehman (firstname.lastname@example.org), June 28, 2000.
Of course Ansel used the zone system before he invented it--it is nothing more than applied sensitometry. Who doesn't do that? (not counting idiot guide usage).
-- mark lindsey (email@example.com), June 28, 2000.
Thanks for the responses.
To clarify things slightly: What prompted the question was my own experience in attempting to apply the zone system to exposure control some years ago. On numerous occasions then, and since, I've attempted to be "clever" with metering and exposure control, only to arrive back at more-or-less the same old exposure value that a simple grey-card or incident reading, or even the "idiot guide" would have given me.
I've also just been reading a book called "Perfect exposure" which strongly advocates the zone system, (with zones up to 12!). However, a lot of the illustrations, while undoubtedly being good pictures, are admitted to be the result of luck, mistake, guesswork or bracketing. Adams himself, in "The Negative", frankly admits to getting unprintably blocked up highlights in at least one example, and having to resort to dodging and burning in order to print some of his negatives.
Those respondents who were honest enough to own up to it, have so far confirmed my suspicion that, in the majority of cases, the application of complicated methods of exposure determination are largely a waste of time. Note: I'm not saying the same about control of the development process, although this raises the moot point of whether the zone system has any application in colour work, with its far less flexible processing.
I didn't have any grudge against the zone system when I posted this question, but some of the patronising responses of its proponents are making me lean that way. :-) Can I point out: (i) that you don't need to know anything about the zone system to know something about sensitometry and densitometry. (ii) that 18% of a pure white reflector is -2.5 stops (-2.474 stops actually) no matter what development you give it. (iii) That Adams devotes 3 pages of the section on exposure in "The Negative" to defining and emphasising the importance of zone 5 as a reference, and only touches on the use of zone 1 in the section on development. (iv) that, yes, "pulling" development does allow a wider range of subject brightness to be encompassed on a given grade of paper, but micro contrast and acutance are degraded. (v) that multigrade papers have opened up numerous possibilities not even dreamed of when the zone system was invented. (vi) that conventional wisdom should always be challenged from time to time. (vii) that the use of roman numerals isn't very space efficient.
-- Pete Andrews (firstname.lastname@example.org), June 28, 2000.
I'll give my 2 cents on each of your comments.
i) Absolutely true. But if you understand sensitometry and densitometry, you understand the zone system, albeit in slightly different terminology.
ii)Of course this is true. But this is luminance, not density.
iii) The Negative was copyright 1966. Materials have changed. Processes respond differently to the new materials. And even Saint Ansel was wrong on occassion. But he made many wonderful photos. So he is worth paying attention to.
iv) Exactly. See the Film Developing Cookbook, it implies that much of the earlier Zone System work isn't reliable because tools used at the time may not have been accurate.
v) Of course.
vi) Always, always, always. This is one of the reasons I appreciated Fred Picker's writings so much.
vii) True. But in the first Ansel Adam's zone system books he explained the choice: all of the numbers in common use were Arabic: ASA, DIN, f/stops, shutter speeds, ft. candles, candels/sq ft. He wanted to use something that would not be confused with existing measurements.
I can attest and with you that complicated exposure method are not very useful. An incident meter or gray card reflected meter will cover most everything you need. Where spot readings and the zone system help is in very difficult lighting circumstances. They will help you get a negative that can be printed, though it may be very difficult to print.
Then again, the "tip sheet" approach covers 80% of outdoor situations.
-- Charlie Strack (email@example.com), June 28, 2000.
I have a question for you. If you are only using a grey card and/or an incident reading, how do you decide what development is correct for your exposure if you don't know the luminance value range of your subject - especially the area of interest?
As for your "clever metering" problems, I have no idea what that means. I rarely take more than 3 readings from any subject using a spot meter. The subject of interest, the darkest area that I want to retain detail, and the lightest area that I want to retain detail. That gives me my luminance range of interest, which allows me to set the exposure, and determine development. All of that takes, at the most, one minute.
Whether exposure deviates from the "idiot guide" or "sunny 16" rule, or your incident reading method is immaterial. My question is still - how do YOU determine development? Choice of developer, and development time? Or, are those of no consequence?
The Zone System is more than exposure. You can call the method the Zone System or applied sensitometry - they're one and the same. The Zone System is only a method to VISUALLY relate the subject, to the final print. This gives the ability to evaluate exposure and development choices, and their "predicted" effect on the print prior to making the exposure.
Conversely, you can make any exposure of a subject, read the density range on a densitometer, and make a print using the correct paper grade extrapolated from the density range.
However, that method does not allow you to creatively control the tonal representations of the subject quite as well. When you start using filters to alter the look, or exposure to change a flat subject to high key or low key look, then you need a method in the field to evaluate the effect of exposure + development on the final print.
Again, whether you formally use the Zone System or just "intuit" the final results - it's still all sensitometry and you are visualizing the subject range fitted to the film through exposure; fitted to the final print though exposure + development.
Or, perhaps, your method is to just point, shoot, and hope for the best?
As for color work - yes, the Zone System can be applied to color work - but that's another subject entirely.
-- steve (firstname.lastname@example.org), June 29, 2000.
To answer Steve's question. If the subject contrast is low or the lighting is flat, then I'll push the development, but I hardly ever pull it. It doesn't take a meter reading to see a flat subject or an overcast day. If the main subject is in shadow then it'll get a run over with a reflected reading, but I'll also be wary of accepting a reflected reading from bare rock or stonework because it can reflect and store massive amounts of infra-red, and all meters, with the possible exception of Selenium types, are overly sensitive to IR. These are the sorts of exposure "decisions" I take into account, almost without thinking about it.
For outdoor subjects you can't get brighter than full sunlight, not until the sun goes supernova. So my normal development is geared to giving me an easily printable negative of subjects in full sunlight. Even clouds have to obey the laws of reflectance, and unless they're transilluminated they can't be any higher in value than 2.5 stops up from my incident reading. Nothing short of using a welding visor over the lens is going to accomodate the full-on glare of the sun. Although I often use a neutral grad or polariser to control glare, and sometimes a reflector to soften the shadows of close subjects. These techniques are directly transferable to rollfilm and colour, messing about with the development isn't.
Anyway, this didn't start out as an attack on the zone system. It was merely an enquiry about how far from "the norm" most exposures were, no matter how many factors were taken into consideration. As a prime example, take Adams' "Moonrise over Hernandez". He didn't need to know the luminance of the moon in candles per square foot, just the fact that the moon is illuminated by the same light source (the sun) as the earth; and since the moon has no atmosphere, it needs the same exposure as full sunlight on earth, (EV14 at the equator, about a stop less for every 45degrees latitude, or in the moons case, elevation). We end up with our good old friend EV13 (125th at f/8 for 100ISO), correct it for ASA64, a 3x filter, and use f/32, and bingo! we've got the same exposure as good ol' Saint Ansel gave.
I was also questioning the value, if you'll pardon the pun, of even considering zones above 8.
-- Pete Andrews (email@example.com), June 30, 2000.
Rocks and stonework store massive amounts of infrared? Not in the wavelengths that might influence a light meter.
I worked on a US Army project for nearly 3 years for detecting buried landmines. My specialty area on that project was the infrared image processing system. For that system, I used two infrared video cameras. I used a camera with a response range from 1.5 microns to 6 microns, and one camera with a response range from 8 to 12 microns.
One of the problems was detecting the difference between a surface laid mine and a rock - many times they are about the same size and shape. I am here to tell you, that rocks look not much different than the dirt they are sitting on (thank God) while mines do not. IR energy is either stored, transmitted, or reflected. However, the total IR spectrum and the object dictate what is stored, transmitted or reflected. Stored energy will be in the form of "heat" which will be above 8 microns and actually more in the 15-40 micron range. Reflected IR will be in the .8 to 6 micron range. There is no IR in the 6.2-7.5 micron range because the atmosphere absorbs that wavelength "notch."
Transmitted IR can go from .8 - 40 microns but it takes special glasses to transmit IR above 1.2 microns.
While the cells in light meters may be sensitive to IR in the .8 - 1.2 micron range, none of that energy will be stored by the rock, brick etc. That energy will all be reflected and, as such is dependant upon the emissivity of the object. Your postulation that meters will be overly influenced by IR stored in an object is just not true. And, I would question how much they would be influenced by reflected IR as my emissivity tests of various objects, including all types of soil and rocks, show that clay soils reflect more IR than any rock that I tested.
-- steve (firstname.lastname@example.org), June 30, 2000.
"It doesn't take a meter reading to see a flat subject or an overcast day."
Some of the highest contrast situations I have photographed have been on overcast days. Overcast does not necessarily translate to low contrast. How do you account for a high contrast range on an overcast day? Do you have "calibrated eyeballs"? I've been fooled to the point of questioning my meter readings and doing them over again just to make sure I put the numbers into my notebook correctly.
The opposite situation is, on days with full sun at mid-day have been some of the lowest contrast situations as the shadows are nearly non- existant, and the reflected sunlight from sand, rocks etc. has nearly everything at the same EV. Only the color of the different objects provides a reflectance range, and in these cases the colors may not be far apart in reflectance.
"Even clouds have to obey the laws of reflectance, and unless they're transilluminated they can't be any higher in value than 2.5 stops up from my incident reading."
I don't know where you photograph, but in the southwest U.S. with large vistas, it is totally possible to have white areas of clouds being 4 to 4.5 stops higher than an incident reading. How? You can be under a cloud shadow for a very large area around you, meaning everything in your field of view is like shooting on an overcast day, and if you take an incident reading, that's what it will look like. While, off in the distance is a huge thunderhead occupying a signifcant portion of the sky with the top brightly illuminated by reflected sunlight.
"As a prime example, take Adams' "Moonrise over Hernandez". He didn't need to know the luminance of the moon in candles per square foot..."
Really untrue. If you read Adams description of making that photo, it is EXACTLY because he knew the luminance of the moon itself from other photos that allowed him to setup his camera and make the exposure before the light changed. If you read his work further, you will find out it is one of his hardest negatives to print, because he did not have the time to analyze the total luminance range, carefully place the exposure, and then alter development to adjust the final negative tonal range to match the printing paper range. In this case, it was nearly a point-and-shoot with an 8x10 using a known value (full moon) placed on Zone VII - and without a full reading of the scene, he ended up with a difficult negative to print.
"These techniques are directly transferable to rollfilm and colour, messing about with the development isn't."
Not true. You can "push / pull" color film in the first developer which does change the contrast.
-- franki (MrWango@worldnet.att.net), June 30, 2000.
Re: Rocks "storing" IR.
They don't "store" it, they absorb the radiation. They can then re- radiate that energy when. But what you are concerned about is the reflected engergy from your subject, whatever it is. The film won't capture it, but the meter will. This is why a paid a bunch of money to have my Pentax digital modified by Zone VI to filter out the IR, thus reducing the error caused by the IR.
I know the photodiodes and phototransistors detect IR. I've now worked for 3 firms that manufacture photoelectric sensors. We use glass lenses, sometimes plastic, and the IR definitely gets through. We use 880 nm wavelength. Unless you're shooting IR film, a meter that uses a photodiode and phototransistor sees and measures IR that the film is not sensitive to, unless the meter filters it out.
Sometimes it's not the theory that is at fault. It's tools that don't take into account all of the issues they need to.
You can't always be sure of what your eyes see: reads Adam's Examples. One shot was in France. Ansel felt the light had great luminosity, but his negatives didn't reflect this. His eyes were fooled. All of ours can be.
-- Charlie Stracl (email@example.com), June 30, 2000.
You are correct Charlie in your statments that the energy is absorbed and then re-radiated. I used the word "stored" as that is the word Pete used. IR energy can't be absorbed at 30 microns and re-radiated at a different wavelength until the object reaches its energy saturation level. Rocks, bricks etc., don't reach saturation because there is never enough sunlight energy reaching them AND they are in contact with other things (like soil or the building structure that act as "energy sinks" ) to which they constantly transfer energy.
While photodiodes, transistors etc. can be sensitive to IR as can some types of photocells, trying to predict what objects in a scene - such as rocks or bricks - MIGHT be reflectors of IR and effect the exposure reading is impossible as soil itself can often reflect as much or more IR than rocks.
It is safe to say, that any re-radiated energy will be at a level that is above the sensitivity of the photocell in a meter as the energy that is absorbed is above 8 microns - and will be re-radiated at the same wavelength.
The really big point with any type of object, is that they are either absorbing OR re-radiating, but not both at the same time. An object will not re-radiate energy until the energy level incident upon the surface is lower than the absorbed energy level OR the object reaches its energy saturation level.
Also, in my experience, the angle of incidence/reflectance from the sun's direction versus the viewing angle has as much or more bearing on the amount of IR "glint" as the emissivity of the object itself. In some of our Army testing, concave depressions in a surface were not identified as being "mine-like" when running the test vehicle in one direction, while in the reverse direction they were always identified as mine-like because of the sun direction / IR reflection.
The solution was to put a 4.2 micron cut-on filter on the 3-5 micron camera (the platinum silicide sensor was really sensitive from 1.5 - 6 microns). No filter was needed on the 8-12 micron camera because the greatest percentage of IR energy in that wavelength band is absorbed and not reflected by soil, gravel, pavement, rocks etc.
The standard solution to IR sensitivity problems with CCD video cameras is to put IR absorbing glass in front of the sensor. I don't know what is involved with the Zone VI modifications, but, like a standard silicon sensor based CCD camera, a thin piece of IR aborbing glass would be the easiest way keep IR from the meter sensor without effecting visible light.
The idea that using an incident reading meter with a plastic light integrating sphere is going to be more accurate than a reflected light reading with a spotmeter because of IR influence is pure speculation because, as you pointed out, some IR will be transmitted through the plastic. And, then we get back to the direction of the light, reflected IR etc. Basically, it's a specious argument as either type of meter will be effected unless they have been modified to exclude IR.
-- steve (firstname.lastname@example.org), June 30, 2000.
To answer your question about exposure specifically, I have reviewed field notebooks from over 30 years of taking photos. There are 57 exposures with -3 exposure (3 stops under incident reading) with either +2 or +3 development associated with the exposures. There are 122 exposures with -2 exposure with +1, +2, and +3 development. 335 with -1 and either +1 or +2 development.
And then there are lots (the majority of entries) of "normal" exposures with normal, -1, and -2 development. (I got tired of counting after the ones above and didn't want to turn this into an all day project.)
There is probably an amount equal to the minus exposures with plus exposures and minus development. The plus exposures seem to mostly be in the +1 range, I would guess there are at least 200, and a like amount of +1.5 with minus development. I found only about 180 or so with +2 exposure. And only about 45 with +3 exposure.
So - I guess in my work, there is a total 6 stop deviation from a "normal" exposure with a lot of different development combinations (times plus developer types) to compensate for the different total luminance ranges I've encountered.
Does that help you get an idea of exposure/development deviations from normal using a spot metered, sensitometry-based exposure methodology?
-- franki (MrWango@worldnet.att.net), June 30, 2000.
Cheeses! This is going off in all directions for no apparent reason.
Firstly, I apologise for a poor choice of wording. Imagine rocks storing Infra Red! What a ludicrous idea. Though someone who'd just burned their arse sitting on one at the end of a hot day might beg to differ. At least no-one has contradicted the fact that most photometers are overly sensitive to IR. If you don't believe this, try getting a sensible and consistent meter reading through a tri-colour blue filter. The piece of thin glass that completely obscures IR has yet to be invented, and some manufacturers don't even try.
Yes, our eyes can be fooled, but then so can a meter. The underlying premise of the zone system, and indeed the aim of any creative photographer, should be pre-visualisation. If we don't have any faith in the instruments we use for pre-visualising (our eyes and brain) then we might as well give up. If we can't decide that a scene has low, or high contrast visually, then how can we decide what tones we want it to be in the final print? We practise a visual craft, for goodness sake. We should train our eyes and trust their judgement. No metering system will tell you which filter to use and when, and no metering system will turn a poor composition into a good one.
Franki; the example you give of taking an incident reading under a cloud is a classic example of using an incident meter incorrectly. The reading should be taken from the subject position pointing toward the camera, in the same light as the subject. Obviously this isn't always possible, but in the example you give, the top of the cloud is going to be EV15 to 16, if it's in full sunlight, and we can work our way back from there. If you hadn't stopped reading in indignation when I mentioned "Moonrise ....", you'd see that I went on to explain exactly why Adams didn't need to know the luminance of the moon, and why we don't need to spot meter every sunlit cloud, or every crest of surf, or the top of every snow covered mountain. The sun is as constant as, well, the sun. The fact that things come between our light source and our subject occassionally, just makes this an interesting studio.
Let's have none of this sensitometrically holier than thou stuff either. Incident light measurement is based on sound photometric and sensitometric principles too, since the integrating hemisphere automatically takes account of light falling into the shadows of the subject.
-- Pete Andrews (email@example.com), July 03, 2000.
Back on track: Here are my specific answers to your original questions.
Q) A whitewashed wall comes close, for instance, and this isn't even Zone 8, so where do the higher zones fall? It seems to me that zones higher than 8 are only of relevance if a source of illumination or specular reflection is included in the picture, and we are willing to let objects which should normally appear near-white in the print slip down the scale to grey.
A) Zones higher than 8 are pure, textureless white to the eye. Let them show as pure white in the print.
Q) ...but how are these extra zones to be accommodated in the print? Reduced development and contrast will simply make our prints look flat. The only answer that I can see in reality is to burn the highlights and/or dodge the shadows. What do you do with a contact print?
A)If they are pure white to the eye, and you visualize them as pure white, print them that way. If you want texture in the print, you're stuck with dodging and burning. Contact prints are treated exactly as enlargement (burning and dodging), except they have more inherent contrast, so burning and dodging are not needed as much. Lenses have 7 main defects: astigmatism, curvature of field, chromatic abberation, coma, distortion (pincushion, barrel), spherical abberation, and flare. Flare is the loss of contrast. Use of any lens reduces contrast, including the enlarging process. Only contact printing retains the contrast of the negative at the paper.
Q) How many users of the zone system regularly make use of zones more than plus or minus one stop from the "norm"?
A) I haven't got a clue. I sure don't. And with modern films, more than +/- one isn't practical with standard developers. You have to resort to low and high contrast developers.
Q) I'll confess that most of the time I end up exposing within a stop of what the incident light meter recommends. How about you zone system users?
A) On the average, my incident meter reads one stop less exposure than my Zone VI Modified Pentax digital spotmeter. So if we call this a calibration factor, then mostly they match. Incidentally, my film speeds test using the modified Zone VI meter usually match the manufacturer's rating, sometimes 1/3 stop faster. This has been so predictable for me that I suspect the people who get half-speed are just compensating for meters that are out of calibration.
Editorial I am with you on this issue: exposure needn't be complicated. Slight interpolation of an incident reading or spot metering a couple of values is all you need for most shots.
-- Charlie Strack (firstname.lastname@example.org), July 06, 2000.
Well charli, I guess you've never shot film in the southwest. I get scenes that have 3 and 4 stops from normal(?). Or in zone parlance, 7 and 8 stop subject brightness ranges. All that tells me is I need to process in a certain way so I maximize the films ability to hold detail that can be translated by the paper into as full tonally full an image as possible. Zone 5 doesn't always mean a great deal but the subject brightness range means everything. And I do get negs in the zone 7-12 range and print them like that. Go out to White Sands NM on a bright day and tell me what your calibrated meter says. And as far as the zone VI meter it's amazing how many people get such wonderful full tonal range images without the thing. James
-- james (email@example.com), July 08, 2000.
Allow me to be a bit confused by your post.
Is your point that your subjects have an 8-stop range or a 12-stop range? Granted there are both. But I'm not sure what you are trying to say in this regard.
Regarding the Zone VI meter, you can use it or not. It's a tool. A craftsman gets to choose his tools.
I've got at least 5 different major tools for making holes in my shop: hand drills, drill press, sabre saw, roto-zip and router. I choose the best tool for the task at hand. (By the way, if you want to cut a precision hole for mounting a loudspeaker, the router is the best tool.)
I've got 3 hand held meters: Zone VI modified digital Pentax, Sekonic Incident meter, and Polaris flash meter. Each has it's place. You don't have to have any particular meter to make a fine exposure, or even a meter at all.
At the time I bought the Zone VI it it elimated some variables that I know (from my work) are capable of influencing meter readings in a major way, specifically IR. But my meter is at least 15 years old.
I suspect Pentax has made some modifications in the intervening years, perhaps incorporating some of the modifications Zone VI does. This may make the current version less susceptible to these influences than the earlier ones. But in the end it is only the final print that counts, and I will be the first to agree with this.
So I am not amazed that many photographers do exceptionally well without the Zone VI meter. Back to the "idiot guide" or tip sheet, or sunny-16 rule. For decades most amateurs used these because they are cheap and, more importantly, they work.
So I have no problem at all with photographers using whatever tool they choose. I have no axe to grind. But please reciprocate. I find it a useful tool, so allow me to use it.
And by the way, I have shot film in the southwest, but it's been many years and long before I knew anything about the zone system or before I had a clue as to how to make a decent photo. And, by the way, New Mexico is one of my favorite states, so if you live there, please enjoy it for me.
-- Charlie Strack (firstname.lastname@example.org), July 10, 2000.
James. If your getting readings more than 3 stops above a grey-card, what you've got is glare. i.e. glancing reflected light, and I bet you could do just as good a job of controlling it with a polarizer.
As for zones up to 12! Surely zones are defined by their visual appearance in the print, not by their luminance in real life? With 10 being defined as pure base white, it's difficult to see how a paper print can show greater than that. That's the other part of my question that no-one has really answered yet. What use is assigning zone values to luminances that can't possibly be accomodated in a print?
-- Pete Andrews (email@example.com), July 11, 2000.
Zones are measures of light during exposure. Tones are shades of gray in the print. So a zone 12 can be very real but you must do something in developing or printing to bring it into the range of tones that the paper is capable of reproducing.
-- Jeff White (firstname.lastname@example.org), July 11, 2000.
No; EVs, Lux, Lumens per square metre, or candles per square foot are measures of light during exposure. The whole point of zones is to previsualise tones in the final print. An 18% mid grey is only a zone 5 if it's exposed and printed that way. Give it a stop more and it's a zone 6. Give it 7 stops more and it's a mythical zone 12 which can never be printed. Yes, you can cut the development to print it as a zone 10, 9, 8, or even back down to 5, but in doing so the 1 stop per zone relationship is lost, and the relationship of all the other tones in the print is devalued, and that makes the end result very difficult to previsualise. We end up being slaves to a system that defeats its stated and sole purpose of previsualisation.
-- Pete Andrews (email@example.com), July 11, 2000.
It was Ansel who said that "Dodging and burning are to make up for Gods inaccuracy in establishing tonal relationships." Most beginners in the Zone System think that everything should fit in 10 zones, that is just limiting yourself. Local contrast is just as important as the whole subject brightness range. I would not screw up the local contrast of an image just to make sure the sunlit clouds fall on zone VIII or IX. It is a fallacy to think that you make it "all" happen on the negative. Isn't it funny that most of the "greats" that are talked about on this forum are also great printers. Getting the needed information on the negative is what the zone system is about. Making the print that has the look and feel you want is an extension of that. If I am making a negative and something falls on zone XII and I choose to leave it there, that is telling me in the previsualization process that I need to take steps in printing to make it fall in the reproduceable range of the paper. Lower paper contrast, flashing, contrast masking and burning are few ways to accomplish this feat.
-- Jeff White (firstname.lastname@example.org), July 11, 2000.
When I go into the White Mnts. to shoot Bristle Cone pines or into the Four Corners region to shoot canyon scenes, I typically run into an extreme range of subject brightnesses that I somehow must render as 5 stops of tonality in able to render them successfully on a print. The shadowed places within the trees are at times zone II and the brilliant clouds are zone 10-12. Some of the interiors of ruins are in the zone III range whereas the canyon walls outside the overhangs are zone VIII or more. Or the rim top ruins interiors are EV 4 and the clouds are EV 12. The point of previsualization is knowing what you have to start with and knowing where you want to end up. Getting there is where the problem ,and fun, lies. All of the methods outlined above are steps necassary to begin to accomplish the task. The paper is always the bottleneck. It can see 5 tonal zones(7 with AZO I think). that is what AA and all the early pioneers where talking about when they started formulating the Zone System. All the meter does is give a consistent place to start. It renders everything that gets into it's field of view as zone 5 or a middle tone. If I point it at the bright sands of New Mexico and the bright clouds I will have at times a 1 or 2 stop range. The meter tells me it's between EV15 and EV 16. If I leave it there, it will be as flat as a pancake and print as a mid grey with no separation. Or I can expand it to 5 stops ( which is all the paper can give me) but still have 5 zones more info with which I could play with. The neg can see 15-17 stops of density but the paper can only use 5 at any time. I have a negative that takes 20 minutes to print. And it prints 5 stops of tonality beautifully but you can't see a 100 watt light through the density. So yes Martha, there are more than 10 zones of density but paper only lets you use 5 of them on any one image. That's the beauty of B&W material. Lots of variables and lots of ways to use them. Learn all of it so you can really express yourself. James
-- james (email@example.com), July 11, 2000.
The biggest problem with the zone system is sloppy nomenclature. The zone folk I know will call a white wall Zone VIII and green grass Zone V independently of whether they are talking about scene brightness, negative density, or print reflectance. It works in practice, but can lead to confusion in the classroom as both the absolute and the relative values of the physical quantities involved vary as you move from scene to negative to print.
To me, the Zone system has two useful stages. The first is getting the scene information onto the film without compressing or clipping the highlights and/or losing detail in the shadows. The second is getting that information onto your favourite printing paper so that the scene is reproduced with the tonal values you want. Because there is only so much you can do in the darkroom, your knowledge of the second process then feeds back into and influences the first. The best, simplest and most useful explanation of the whole system I have seen was in the Silverprint catalogue (www.silverprint.co.uk).
In a scene, zones are seperated by full stops on a reflected light meter. It's easy to get zones higher than VIII, even if we ignore such things as specular reflections, geographical altitude and latitude, and the eccentricity of the earth's orbit. It's easy because zone VIII is not an absolute brightness standard, but corresponds to whatever object in the scene you want to appear white-with-some-detail in the final print.
If you choose a white wall in shadow to be zone VIII, then a nearby one in sunlight will land on a higher zone. Alternatly, with enough blackout cloth you can create objects in your scene with brightnesses down to minus infinity. If you make one of the low-lying ones white on the print, the walls end up on Zones J and J+1, where J is a large number. The limited dynamic range of the human eye usually stops you taking this to extremes, but it can be fun to try.
Interestingly enough, with high-bit digitisation you get good tonal resolution over a much larger range of negative densities than is possible with printing papers, even self-masking ones like POP and Pt/Pd. Some of the fine art hybrid digital/analogue B+W crowd prefer long straight line films like T-max since they can over-expose highlights to their hearts content without blocking up, and then add shoulders and toes anywhere they like in post-processing before output to paper.
I can't resist a comment on IR. It is perfectly possible for bodies to turn visible light into IR (a.k.a. the greenhouse effect) but the wavelengths emitted are too long to register on either film or photographic meters. The IR that fools your meter and mutates the colours of your bluebells is reflected sunlight with wavelengths from 0.7-1.0 microns. If you want to know if a particular material or subject will cause trouble, the important parameter is the near-IR reflectivity, not the emissivity at longer wavelengths. The two are related, but only those familiar with Hilbert Transforms and complex dielectric functions would call the relationship simple. You can selectively cut these wavelenths with a dichroic 'hot' mirror or with a near-IR filter.
-- Struan Gray (firstname.lastname@example.org), July 12, 2000.