"Right" exposure for given light setup?

[Tom Camilleri]

Given a particular lighting setup, should I be able to determine camera settings that will be correct for any subject shot in the setup? Camera settings will be made manually.

I have some tungsten lights (2 white umbrellas plus softbox) and am shooting subjects of various tonalities against a white background with a Digital Rebel. The white background makes metering difficult in most cases, so I have been experimenting with setting up lights in a standard way and metering a grey card to determine exposure, then bringing in the object to photograph. Shouldn't I be able to use this exposure to get good shots of virtually anything I place in the standard setup? Or is this oversimplifying?

This should certainly work perfectly for anything which is approximately the tonality of the grey card. Let's call this case 1. I'm thinking that it should also work for anything which might vary in tone, but for which the most important areas are also the same tonality as the grey card. Call this case 2.

What about case 3, where the subject varies in tone and the most important areas are brighter or darker than the grey card? It seems to me that if the camera is set to correctly record neutral tones in the given lighting conditions, it ought to correctly (by "correctly" I mean in correspondence to reality, or what the eye sees) record dark and light tones as well.

But then why have I seen tutorials in which areas of several tonalities are spot metered and exposure is set by factoring in these readings?

[mbze430]

A grey card metering will give you approx. mid-tone in a scene. However it is the film and the sensors ability to capture all of Zone 0 thru Zone 10 that makes the problem. Our eyes can easily change the tonal curve of a scene. However film and sensors are fixed. This is why we spot meter different zone, and set for an avg of these zone.

In a studio, lighting is easy to get compromize. You just add or subtract light to get an area to your avg mid-tone.

So to answer your question in the simplest form, no even with a 18% grey card setup, not all subject will have the right mid-tone when place within that area.

[Tom Camilleri]

A grey card metering will give you approx. mid-tone in a scene. However it is the film and the sensors ability to capture all of Zone 0 thru Zone 10 that makes the problem. Our eyes can easily change the tonal curve of a scene. However film and sensors are fixed. This is why we spot meter different zone, and set for an avg of these zone.

In a studio, lighting is easy to get compromize. You just add or subtract light to get an area to your avg mid-tone.

So to answer your question in the simplest form, no even with a 18% grey card setup, not all subject will have the right mid-tone when place within that area.

Thanks. So under the same light, a correct exposure for an area of a given tonality is not necessarily correct for an area of different tonality. Are the Zones 0 through 10 ranges of tone values?

Trying to get my mind around this. Under the same light, would the correct the exposure for a very dark object be more or less than the correct exposure for a neutral object? It seems it would have to be MORE than for a neutral object, so when you correctly expose a dark object you are going to overexpose a neutral or bright object in the same shot. Correct?

[scottbergerphoto]

The basic principle of any zone system of metering, is that if you correctly expose for a single tone, then all the other tones will be properly exposed as well. If you have an 18% Grey card and you place it in the same lighting as your subject, and you meter with partial metering and the grey card fills the viewfinder or partial metering circle, then your subject will be properly exposed if you use those settings. Your white background should have no effect on this measurement.

Your best bet in a studio setting though, is to use an incident light meter rather then your camera's reflected light meter. No corrections for tone are required with an incident meter. A good incident light meter that can also be used for flash metering is the Sekonic L358.
Regards,
Scott

[PacAce]

Thanks. So under the same light, a correct exposure for an area of a given tonality is not necessarily correct for an area of different tonality. Are the Zones 0 through 10 ranges of tone values?

Trying to get my mind around this. Under the same light, would the correct the exposure for a very dark object be more or less than the correct exposure for a neutral object? It seems it would have to be MORE than for a neutral object, so when you correctly expose a dark object you are going to overexpose a neutral or bright object in the same shot. Correct?
What you need to do is get yourself an incident meter and meter the lights. Whatever reading you get that way will be applicable for any subject, whether it be dark-toned, mid-toned or what not. This is so because you are measuring the actually iincident light instead of the reflected light.

And, as an aside, from a photogenic point of view, the same lighting setup is not always appropirate for all subjects. Some lighting setup are more flattering to certain type of subjects while the same setup could exaggerate features that make the subject look less than flattering. There are several types of lighting arrangements and each one would be suitable for different types of subjects. There may be one that might be "safe" for all subjects but then, it'll probably be the one that produces the most boring portrait, too.

[edit]Oops. looks like Scott beat me to it...again. :) Well, at least you have a second [and reaffirming} opinion on the matter. :mrgreen:

[IndyJeff]

Yes a light meter is what you need. Sit your subject up and meter in different locations around the subject and see the variences. Average it out and you should have a decent exposure level. If your strobing the subject make sure you trip the storbes so you can get the reading under the actual lighting you will be shooting.

[Tom Camilleri]

Thanks to all for your help! I'm beginning to get a grasp of this. Will take a look at the L358.

[Tom Camilleri]

The basic principle of any zone system of metering, is that if you correctly expose for a single tone, then all the other tones will be properly exposed as well. If you have an 18% Grey card and you place it in the same lighting as your subject, and you meter with partial metering and the grey card fills the viewfinder or partial metering circle, then your subject will be properly exposed if you use those settings. Your white background should have no effect on this measurement.

Thanks for responding.

This is due to the zone system's assumptions and calculations, right? Correct exposure as far as the zone system is concerned is the just best that the camera's algorithms can do with a given image and is really based on multiple light measurements. Things would be completely different, I'm guessing, if I was manually metering several areas of different tonality. Each different area would yield a different exposure value, and no two tonalities could be exposed simultaneously according to their meter-determined values. It would be up to me to determine which areas to average to get the "correct" exposure. From the film or sensors' reference point, under given lighting the best exposure value for each of two different toned images will be different? Am I getting this or am I still confused?

[gary_hendricks]

Hey how about posting some pictures of your set up? I'm pretty curious how they look.

[Tom Camilleri]

Here it is. I took these with my old Olympus C2000 with just the florescent room lights. Two Lowell Totalights w/ umbrellas (500 W). One variable 1200 W lightbox. Digital Rebel with Canon 50mm compact macro.

[Tom Camilleri]

I tried using a light meter- a cheap one I had bought a few years ago. Amazing difference! Best shots I've gotten so far. Amazingly, the meter was right on. Varying the time value slightly in some ases allowed me to get what appear to be textbook perfect exposures, according to the histogram. We'll see what they look like processed; will post a few. As a fairly inexperienced person, I think I can now say that THE way to start understanding exposure is to use incident light metering. All compensations I made were quite intuitive and seemed to produce expected results. I'm excited.

Thanks again to all for excellent inputs!

[scottbergerphoto]

Thanks for responding.

This is due to the zone system's assumptions and calculations, right? Correct exposure as far as the zone system is concerned is the just best that the camera's algorithms can do with a given image and is really based on multiple light measurements. Things would be completely different, I'm guessing, if I was manually metering several areas of different tonality. Each different area would yield a different exposure value, and no two tonalities could be exposed simultaneously according to their meter-determined values. It would be up to me to determine which areas to average to get the "correct" exposure. From the film or sensors' reference point, under given lighting the best exposure value for each of two different toned images will be different? Am I getting this or am I still confused?
No. The Zone System is based on the fact that all reflected light meters, be they in camera or a hand held spot meter are based on an 18% Grey Card. This has nothing to do with camera algorythms. If you correctly meter any tone by filling the viewfinder or partial metering circle with it(standard exposure) and correct for its difference from 18% grey(Correct Exposure), then all the other tones will be exposed correctly unless they are in different lighting.
Scott

[Merle]

Your grey card will help you determine if your color is correct but not you exposure. Good rule of thumb white card or paper and use your histogram when you you have about 5% of the white card blinking black in the histogram then move 1/2 stop up your aperature scale

[scottbergerphoto]

Your grey card will help you determine if your color is correct but not you exposure. Good rule of thumb white card or paper and use your histogram when you you have about 5% of the white card blinking black in the histogram then move 1/2 stop up your aperature scale
I am very puzzled by your post given your 32 years experience as a wedding phographer.
The main purpose of the 18% Grey card, it's reason for being, is to guage exposure. It's so you can give your meter something it's calibrated to read off of. When you take a reflected meter reading off of an 18% Grey Card, the Standard Exposure and the Correct Exposure are the same. If you take a reading off of a different tone(standard exposure), you have to correct that reading based on the tone's difference from 18% Grey(correct exposure). That's why you increase what your meter tells you is right by one to two stops to get white snow and decrease by 0ne to two stops less for a black tuxedo. It isn't a coincidence that your camera meter/handheld meter and 18% Grey card are both calibrated for the same tone.
Yes, an 18% Grey Card can be used to correct for a color cast if you include one in your first picture in a series under the same light, but that's not what it has been used for years for. There are better tools to guage color, like a Gretag-Macbeth color card.
Scott

[PhotosGuy]

Given a particular lighting setup, should I be able to determine camera settings that will be correct for any subject shot in the setup? Camera settings will be made manually. You can use a gray card or white card to set the exposure as everyone has said. See the "Gray Card" threads at :
http://photography-on-the.net/forum/showthread.php?t=52418

In the interests of simplifying "But then why have I seen tutorials in which areas of several tonalities are spot metered and exposure is set by factoring in these readings?", since you are already very close to the correct exposure in a studio situation, why not shoot RAW & make your minor corrections from there? I think the Zone System was designed to balance the exposure compensation WITH adjusted development of THE ONE 8X10"negative for contrast control and was something of a PITA for roll film users since they couldn't baby one sheet of 8X10" film through the process. If I were you, I'd try the gray card + RAW, shoot some typical subjects, & see if you can produce the type of print/jpg that satisfies your vision. ;-)

[scottbergerphoto]

I think the Zone System was designed to balance the exposure compensation WITH adjusted development of THE ONE 8X10"negative for contrast control and was something of a PITA for roll film users since they couldn't baby one sheet of 8X10" film through the process.
There are different ways of using the zone system. The technique that I use and reliably so comes from two books, The Confused Photographer's Guide to Photographic Exposure and a Simplified Zone System of Photography , and Spot Metering by Farzaad.

[PhotosGuy]

There are different ways of using the zone system. Yup! Use what works best for you. The final result you see in print is what counts. ;-)