A. T.

I attended a photo class and the instructor had us lock in 18% gray in order to get a correct exposure. I have never heard this explained that way and would like someone to expand on this topic. I use the gray card to get the proper white balance and my exposure meter and exposure compensation to get the proper exposure. Am I missing something here?

PixelStan77 Loc: Vermont/Chicago

When I took my university photography students out in the snow, I would place my Grey card in the snow and had them meter it an take an image. The card came out grey and surrounding snow came out white.
A grey card is designed to help photographers to adjust their exposure and white balance settings consistently by providing a reference point. This reference point will set a white balance, or color balance, point for a particular image set and all images captured thereafter.

A. T.

Okay, so I guess I was correct in my thought process?

Gene51 Loc: Yonkers, NY, now in LSD (LowerSlowerDelaware)

Grey cards are for exposure calculation. ColorChecker Passports are the correct tool for white and color (tint) balance. Grey cards are sorta ok in a pinch, but they cannot be trusted to remain color-neutral over time. And camera meters/hand held meters etc are calibrated to 12%, so if you use a grey card for exposure you are likely going to be 1/2 stop underexposed.

https://www.slrlounge.com/when-your-camera-meter-is-wrong-and-what-to-do-about-it/

Kozan Loc: Trenton Tennessee

A gray card is used mainly for the proper exposure. But all gray cards are not equal. Some will not be 18% gray, but maybe 1/2 stop over or under. It's hard to tell which gray card is exactly 18% gray. Some experimentation on your part may be necessary. Perhaps use a gray card with someone holding it and then after the image is taken, use Photoshop or another editing software to judge whether the exposure is correct. If it is you can say the gray card is accurate.

The gray card also can be used for whiter balance IF when you take a picture of the gray card, the red, green, and blue components of white light is shown in equal amounts as shown on your cameras HISTOGRAM. Again, all gray cards do not reflect RGB in equal amounts (necessary to get proper white balance). You need to experiment with your cameras HISTOGRAM to be able to tell. It is probably best to use a pure white card to set white balance.

Again, all white cards are not pure white. Never use printer paper. It will not be pure white and you might get a slight color cast to your images.

To be honest, I would only use a gray card (maybe) in a studio setting. I have had to use the Custom White Balance a few times at high school sporting events such as baseball at night or in a gym for basketball. Auto WB and the in-camera exposure meter is what I use 99.9% of the time.

I always shoot RAW and can easily change in post production, so it's not a big deal.

Good luck.

BTW, 18% gray is the Ansel Adams ZONE 5, which supposedly is in the middle of the ZONES from balck to white. Setting a Zone 5 exposure insures that evrything from black to white will have the proper exposure. That's why you set your camera to 18% gray (ZONE 5).

A. T.

Yes Sir, I use an Xrite color checker and have a master preset in lightroom for more accurate colors.

A. T.

Thanks for your response and for explaining this to me. I shoot RAW as well and use auto WB probably 99% of the time and have never had any issues other than those crazy basketball gyms and some school auditoriums. So, again, I thank you and I will continue to shoot, experiment and most importantly, have fun.

wdross Loc: Castle Rock, Colorado

My teacher back in the film days had us shooting black and white film and doing contact sheets. To demonstrate and show us what the camera was seeing, he had us shoot a photographic black card, shoot a photographic 18% gray card, and shoot a photographic white card, all three at the same time, three times. But the exposures were based off one card at a time. We filled the viewfinder with the black card and used that exposure first followed by the gray card for exposure and the white card for exposure. Since the exposures were done on the same roll with the same lighting with normal processing, everything would be normal. And the exposure for the black card was gray with the gray card white and the white card totally white. The exposure for the gray card was gray with the black card black and the white card white. The exposure for the white card was gray with the black card totally black and the gray card black. The "average" amount of light from a relatively "normal" scene is 18% reflectance or 18% "gray". And that is what exposure is generally set for, 18% reflectance. This is why weddings, with the black tuxes and white wedding dresses, have to be carefully exposed so details are not lost in one or the other. This is why shooting a group of priests in black must be compensated for exposure wise. This is why a snow scene must be compensated for the extra reflectance of the snow. This knowledge is also the basis of low key and high key shooting. I hope this helps you in some way.

A. T.

Absolutely it helps. In that same photography class, we discussed and actually went out and demonstrated high and low key shooting playing with exposure compensation.

A. T.

I have only been shooting with a DSLR for about 13 months but have done an awful lot of studying, taking classes, and hanging out with experienced professional photographers who have been more than helpful in my photography.

wdross Loc: Castle Rock, Colorado

Although there are many professional photographers out there that have forgotten more photography than I actually know, most of the ones I know say they are still learning. Because of their statements, I am fairly certain that photography is a lifetime of learning. Don't ever get too discouraged; we are all out there learning.

billnikon Loc: Pennsylvania/Ohio/Florida/Maui/Oregon/Vermont

Kodak issued these for years. It is the middle ground for correct exposures. BUT, you have to read the card under the same lighting as the subject you are shooting. So, if the sun is coming in behind you make sure you meter read the card with the sun hitting it the same way the sun is hitting the subject.
I carry an Incident Light meter which basically does the same thing but I find it easier to use.

Interesting to note, Kodak 18% gray cards will reflect the equal amount of light that they receive.

cameraf4 Loc: Delaware

Gene, I read the article with great interest. For my entire photographic life I have read/been taught that the light meters in cameras are calibrated to expose for 18% gray. I understand that evaluative meters may be quite different, but in Spot and Center-weighted mode I THOUGHT this was still the case. At what point did Nikon/Canon/et al change their cameras to try to expose for 12%?

fetzler Loc: North West PA

Cameras meters are calibrated for a scene of medium reflectivity. (Adams Zone V or 18% grey) I won't get into the 12% vs 18% thing. If you are shooting on a beach, snow, copying art work or photographing dark objects they are useful. Alternatives are to use untanned Caucasian skin (Zone VI) and open up 1 stop or an incident light meter. For color matching use a white card and color checker if necessary.

BebuLamar

My camera meter (except in matrix mode) is calibrated for 0.125 cd/m² for EV0 @ ISO 100. My hand held meter is calibrated for 0.14 cd/m² in spot mode. In incident mode with the dome it's calibrated for 3.3 lux and with the flat receptor it's 2.5 lux for EV 0 @ ISO 100.