Correct Exposure : LUSENET : Large format photography : One Thread

Hi Folks: I am taking a close up of a deep yellow flower under uniform light. Spot metering the yellow petals of the flower indicated a shutter speed 350 for a certain F stop.

I metered a grey card next to the flower under the same light and took a reading - shutter speed: 500 ( same F stop )

What settings should I use to get a better exposure of the yellow flower ? 350 ( reading from the flower ) or 500 ( reading from the grey card )

Thanks Allen

-- Allen Border (, November 29, 2001


Place you camera settings on the gray card reading. Pat P.S. If you want to learn the difference do one at each setting.

-- pat krentz (, November 29, 2001.

Allen: Pat is right on. If you meter for the yellow petals, the meter tries to turn the flower to medium grey. That is how meters operate. They measure the amount of light needed to produce medium grey. Incidentally, an incident light meter works a lot better in a situation like this.


-- Doug Paramore (, November 29, 2001.

Do as Pat suggested. Don't forget to calculate for bellows extension. Your 6" lens probably became a 12" to get that frame filled with flower. J

-- Jim Galli (, November 29, 2001.

Doug: Just to check my own understanding of things: I think that metering a gray card in the subject position utilizing a relfected light meter IS taking an incident reading. No? -jb

-- Jeff Buckels (, November 29, 2001.

Jeff -

How so?

-- Matt O. (, November 29, 2001.


Reflected light and incident light are two different things. Incident light is the light around you that allows you to see an object. Reflected light is the light that is reflected off an object, which may or may not be the same as incident light. For example, take two objects that are the same color, but one with a glossy or metallic finish and one with a dull or matte finish. If you did a reflected light reading on the two objects you would get two different results because the shiny object would reflect more light. The incident light reading would likely be between the two (depending on how much light was absorbed by the dull object).

Sir Ansel talks about this in The Negative in nauseating detail starting on page 10.

-- Jennifer Waak (, November 29, 2001.

If you have a proper grey card, positioned in light from the same direction and of the same intensity as you measure with your meter in the incident mode, and if your meter is calibrated for that same grey (not all of them are, and even if they were, they may have drifted with time and travel) then the reflected and incident readings should agree. If you look back at the original post we're talking about a difference of about 1/3 stop here....and we don't even know if this is a color photograph.

-- Kevin Crisp (, November 29, 2001.

Let's see, a third of a stop would be about right to make that flower a DEEP yellow which is what we're after. Place those petals about Zone 4 2/3 to get them deeeeeep. J

-- Jim Galli (, November 29, 2001.

Allen: The two types are different, although both should render a medium grey card as grey. The incident meter measures the amount of light falling on the subject. In theory, a properly calibrated incident light meter (I ain't never seen one), would render the subject properly, with light tones light and dark tones dark in the prper shades dependant upon surface reflections. A reflected light meter measures the light reflected from the subject. It then meters that light to give the exposure 18%grey, or medium grey. If you meter a white wall, it will give an exposure that results in medium grey. If you meter a black wall, it will give an exposure that raises the value to a medium grey. That is the advantage of using Adam's Zone System with a reflected light meter. You can place the exposure zones where you want them and tailor the neg with more or less development, within a range of several stops. It's really less complicated than it sounds. The incident light meter is very fast to use as long as the meter is in the same light as the subject. Coupled with a bit of experience to change exposure a bit when need, it can render good results. Most movies are shot using incident light meters for color films. I didn't intend to ramble on so much.


-- Doug Paramore (, November 29, 2001.

personally, I am quite surprised to find a yellow flower reflecting less light than a grey card. incident and reflected metering are very simple concepts. in this example, as in all reflected reading, the photographer must now make an assessment of what the proper reflection correction offset is. that is the difficult aspect of the process, obviated in our example by having both a grey card reference and an incident dome to integrate the light.

-- daniel taylor (, November 29, 2001.

I'm suprised also. I would expect the yellow flower to indicate a faster shutter speed than the gray card, all things being equal. This is the reason I almost always use incident metering. I find I get more keepers with incident.

-- Ron Shaw (, November 30, 2001.

Keep in mind, if its a Sekonic spot meter, (and possibly others) they are calibrated to 13% grey, not 18%. That means you have to reduce the amount of light by 1/2 stop to accomodate for this difference. This assumes you have a true 18% grey card.

-- Bill Glickman (, November 30, 2001.

Either will work fine, especially with negative film. There's less than a half stop difference between the two shutter speeds and the latitude of negative film is much greater than that.

-- Brian Ellis (, November 30, 2001.

Bill.....could you elaborate on that bit of info about Sekonic meter calibrations?I recently bought a Sekonic spot and did find my negs slightly hot,1/2 stops in fact.This is a new meter.My older sekonic Dual Spot was very precise though and gave me results I expected (usually!)Cheers,A.

-- Andrey Belopopsky (, December 01, 2001.

Reflective readings do have some short comings. The first is the refectivity of the surface you are reading. 18% is intended to provide a good approimation of typical surfaces. Thus, I always try to read dull refective surfaces. I never spot shiny surfaces or glare. Colors of the same gray value will vary as much as a stop on some meters even though they should give you the same reading. I have found that greens and grays give similar readings for all of my meters and thus, I restrict my readings to greens and grays to minimize the errors that color can cause. Incident meters are immune to most of these problems unless you are reading colored light such as stage light. Unfortunately, they are not really practical when shooting grand scenics. In most cases the readings you need are far from where you and the camera reside. However incident meters are perfect for studio and portrait work.

Bill - I have a Sekonic 507 and found that when I calibrate it using a densitrometer I end up using a significantly different ISO setting. Perhaps basing their setting on a 13% reflective surface would account for this. What this tells me is that Sekonic believes that 13% provides a better approximation of typical real world reflective readings. Interesting.

-- Stephen Willard (, December 01, 2001.

> 18% is intended to provide a good approximation of typical surfaces > 13% provides a better approximation of typical real world

spot metering has nothing to do with real-world readings or approximations as mentioned. it is simply a conversion that relates light to an exposure value. you, the photographer, need to understand the characteristics of your film, such that a given value of light will render a predictable density on film. within the meter, the conversion correlates to an ISO standard of film speed, that you, the photographer, can bias to match your requirements.

integral, incident, or algorithmic metering modes do involve a conversion constant because the area is integrated. you, the photographer, need to assess this integration constant as to the relationship between it and your film density. simple.

-- daniel taylor (, December 01, 2001.

Daniel, well said....but the disturbing part is the fact most people think their spot meters are calibrated to 18% grey, not 13%. 1/2 a stop is a lot to be off. It seems more logical in todays world, where we all use 18% grey cards, to have a spot meter calibrated to the same, however this is not the case. I have confirmed this with Sekonic (Mam USA) a few times. BTW, this is not limited to Sekonic, supposedly most of the spot meters on the market are calibrated to 13%, not the 18% which many of us assumed. Of course, the worst part is, its hard to find this in the manuals. Another mystery for us to solve! Wonderful! I beleive Gossen is also 13%....

-- Bill Glickman (, December 01, 2001.

Moderation questions? read the FAQ