slide exposure

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I would appreciate if any member of this forum could further expansiate on slide film exposure specifically Fuji velvia rated at ISO 40. The rule of thumb is that you meter for the important highlight. However,by how many stops do you vary the exposure factor ? +1 or half stops. To further illustrate, for instance lets say the important highlight is metered at F16 using reflected mode measurement. Do I open up by 1, 1/2, 1/3 or 2 full stops to correctly place the important highlight. I know that the exposure latitude for slide film is vey narrow. I have tried to read a lot of books but ended up getting the whole thing confused. Informative explanation would be most welcome. From a newbie. Thank you.

Mo Kenny

-- mo kenny (mokenny74@hotmail.com), September 25, 2001

Answers

Well Mo,

Re-think this question. Then write down what it is you want to ask. Then copy it verbatim from your notes. Then you might get an answer.

-- Matt O. (mojo@moscow.com), September 26, 2001.


I figure about a stop and a half. But, I suspect this also depends on the particular film and the particular scene. The best way is to do a test. Take 3 or 4 transparencies of a scene that includes a highlight, meter the highlight, and then take photos at half stop increments, beginning by opening the lens by one stop. (i.e. 1, 1.5, 2, 2.5 stops.) After development, look for the first transparency that gives you texture in the highlight. The same could be accomplished with a 68% gray card.

-- neil poulsen (neil.fg@att.net), September 26, 2001.

Mo, 1-1/2 stops is what I used to use also, but testing is good and bracketing sensitive subjects is better! (By the way, your question is perfectly clear. Don't let the grumps in this forum scare you away!) Regards ;^D)

-- Doremus Scudder (ScudderLandreth@compuserve.com), September 26, 2001.

Mo, let me suggest other ways : measure incident light or, if an incident reading is not possible, reflected light on a midtone area of your frame. In both cases no correction is needed. I personnally rate Velvia at ISO 32 and ISO 100 slide films (Provia, Ektachrome E100) at ISO 80. But this is not related with the subject I shoot, it is related with films.

-- Jean-Marie Solichon (jardin-exotique@monte-carlo.mc), September 26, 2001.

Mo - remember also how you want your important highlight to look - the more you open up, the more detail you lose, until its entirely washed out white. Also, at ISO 40 you're already overexposing your film slightly. A good start with any metering is to see what the exposure range of your scene is - take readings from the brightest and darkest areas first, that will give you an idea of how much of the scene you can hold within the films' latitude. Velvia has a very narrow range, maybe five stops useable. At ISO 40, I'd try a stop and a half over your reading, that should retain detail. Two stops would probably wash out. Hope this helps, let us know your results.

-- Michael Mahoney (mmahoney@nfld.com), September 26, 2001.


Latitude is important, especially with Velvia. In low light, I'll often expose for the shadow values (keeping in mind the highlight values) and then UNDERDEVELOP the film by one stop. This essentially increases the latitude of the film. I can get detail in the shadow areas, yet maintain the highlight values as well. HOWEVER, if the highlight values are MORE IMPORTANT than the shadow values (and this is often the case in low light situations), I will expose for the highlight values and DEVELOP NORMAL. The shadows will lose detail. A loss I accept with Velvia film. I'll often return to the scene and re- shoot with color negative film.

-- L. Wolfe (lw@hotmail.com), September 26, 2001.

Mo, There is no one correct answer to your question. The amount you open up is going to depend on the tonal value you want to assign to that highlight. For example, if the highlight is snow you may want to open up 1 1/2 to 2 stops, if the highlight is a light green foliage you may want to open up only 1 stop.

I found John Shaw's landscape and nature photography books to be helpful in understanding this approach as is Charles Campbell's chromazone system. These sources gave me a basic understanding of the concept of assigning tonal values to various portions of the scene and deriving my final exposure based on these values. Ultimately there is no substitute for experience.

-- Mark Windom (mwphoto@nwlink.com), September 26, 2001.


since my CT printing is all digital now, i expose CTs the same way i expose my b/w negs. i meter the brightest and darkest areas i care about retaining detail, expose half-way between them, and bracket as much as i feel like i need to depending on the conditions. the best advice here is to experiment, so you have a personal feel for what works and what doesnt. try not to turn it into some confusing, mentally-challenging exercise. experience can often be a better indicator than your light meter...

-- jnorman (jnorman@teleport.com), September 26, 2001.

#1.) Velvia is ISO 50. The ISO stands for International Standards organization (I think) and rthe number refers to a fixed reference scale, which has nothing to do with color is rendered or even Fuji , just how black and white and a gray scale are rendered. Individualsrate velvia at 50, or 40, or 32, or 64 or 80 depending on their their camera and lenses and shutters and their processing process, depending on how they want they finished piece of film to appear.

2.) yes you can meter for the most important highlight you want to retain detail in, but you should also look at the opposite end of the scale to make sure you retain (place) the shadow detail where you need or want it to be.

3.) Choosing a film speed (what photographers who use the Zone System refer to as an "E.I." (exposure Index) rating) affects the rendering of shadow detail primarily andthe highlight renderings secondarily. The reason for this isthat it takes much less light to move shadow rendering around than it does a highlight. To change the gradation in contrast from shadow to highlight you can have who ever is doing your processing change the developer timing. The photo jargon for changing developer time is "pushing" (extending) or "pulling" (shortening) wh ile you might say "I want this pushed 1/2 stop" the lab is thinking "+ 12% in time in the 1st developer" (that is merely an arbitrary example). As i said this primarily affects the contrast graduation, but also increases the base+fog level giving you an apparent increase in film speed.

3.) transparency film has about a 5 stop contrast range. while that is narrow compared to color negative film, it isn't when you compare it to a print madefrom a color negative.

4.) You have to think in terms of overall latitude of the scene and of the final result to determine how much you should increase (open up) your exposure. Two stops is probably the margin of safe, and it might look better at opening up 1+2/3rds, but it really depends on what that important highlight actually is. A specular reflection off of water is different from a white blouse, which is different from the average patch of Northern European skin, and a lot is also going to depend on what visual effect you are trying to create.

-- Ellis Vener (ellis@ellisvener.com), September 26, 2001.


Here's what experience has taught me and it may be completely different than what others are doing. With Velvia, I don't worry too much about highlight or shadow in high contrast situations. I evaluate what's important in my picture, and I then DO worry about where zone 4, 5, and 5 are going to land. If there are highlights or shadows that are going to get away from me that I can't do anything about, what percentage of the picture are they? More than 10% and I might look elsewhere, or use a different lens. If you're using velvia, you're going for the "punch", and that range is 4, 5, 5, so get those right, and let the rest take care of itself. Actually in spite of what's published I find Velvia to be more forgiving than it's rated to be. Shadows that I figured I would have to forego are often there, and the same for highlights. I use a Minolta F spotmeter, and I get good chromes doing just what I've outlined here, simple as it may sound.

-- Jim Galli (jimgalli@lnett.com), September 26, 2001.


I figure highlights with a bit of detail with chromes are 2.3 stops above a middle gray reading. This works well in practice for daylight as well as artificial light. Gives me a good white with just a hint of detail which is just what is often needed when shooting a building with bright details.

-- Dan Smith (shooter@brigham.net), September 26, 2001.

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