Using a gray card with black objects

[phthenry]

Kodak recommends that when photographing a black object, you open up the f-stop 1 to 1 1/2 stops from what the gray card reads. I've always ignored this advice until today, when I took two photographs of a black cat. In the first, the black cat lies on a light carpet. I set my exposure to what the gray card read. The colors came out like I expected, with the cat looking black, and the carpet looking light.

In the second photo I took a close-up of the black cat, with just his fact filling the frame. Again, I used the gray card to set my exposure. This photo looked too dark, with not enough detail.

So it seems that you do have to allow 1 f-stop more of light when shooting a completely black object.

I just did a test. I took three pictures of a black bag. The first one I set at the gray card reading. This picture came out with the right amount of blackness, and showed enough detail to allow you read the letters on the bag.

In the second test I set the exposure a full stop more light than the gray card reading. The bag might have been a bit lighter than full black, but you could see a lot more detail in the picture, or rather, you could read the detail better.

The third photo I took at 1 1/2 stops more light than the the gray card reading. This photo came out too light.

I use ambient light to set my exposure. I don't use the zone system. I shoot 35 mm. However, let me bring in the concepts from the zone system. (I hope I am using them right.)

When one sets the exposure according to the gray card, a very black object, like a cat, is in zone III. Kodak is telling you to put that object in zone IV in order to get more detail.

In contrast, if one had a mixture of black and white objects, one should keep the black object in zone III.

Is that the correct way to look at this?

 

[jsfyfe]

A gray card is always (almost) going to give you an exposure for Zone V (middle gray). Also, all averaging meters will try to normalize at Zone V. If you had metered the cat directly it would have placed it on Zone V and the cat would have come out middle gray. If you then took a picture of a white cat and metered the cat directly it would have come out as Zone V - middle gray.

If the scene is all black and you meter using a gray card then that scene will probably fall on Zone 1 or 2. If the scene is mostly light then that part will fall on Zone 7 or 8. If the scene is a mixture, as was your first shot, then the tones will generally come out as expected, especially if you are using an averaging meter. Opening or closing the aperture by 1 stop from the gray card reading moves the subjects up or down by 1 zone. If the scene is mostly black and you expose from the gray card reading then you are likely to end up with very little detail since the subject will fall on Zone 1 or 2. Opening up a stop or two will move it to Zone 3 or 4 which will give more detail. However if there happens to be any light objects in the scene they will move higher on the Zone scale (maybe Zone 9 or 10) and will be washed out.

I think you are looking at the problem correctly, however, if you always place the black objects on Zone 3 then you run the risk of pushing the light objects off the scale and have no detail in them. So, if the value range of the scene is so great that moving Zone 1 values to Zone 3 sacrifices the Zone 7 and 8 values on the high end, you need to decide what is most important. If the scene is of average contrast with a relatively good mix of dark and light, then just use the gray card reading as an average exposure value. If you are using or can get a hold of a spot meter I would pick out the most important object in the scene and place it on the Zone where you want it (e.g. place the black cat on Zone 3 and let everything else fall wherever it falls.

Remember, capturing all of the detail possible in the negative is the key. Even if your 1 1/2 stop increase resulted in a photo of the bag that was too light, I'll bet you had all the detail in the negative and you could just print it darker and it would look just fine.

 

[phthenry]

>>If the scene is mostly black and you expose from the gray card reading then you are likely to end up with very little detail since the subject will fall on Zone 1 or 2. Opening up a stop or two will move it to Zone 3 or 4 which will give more detail.

Thanks. Everything in your post makes perfect sense. I didn't realize that a black object was in Zone 1 or 2. I thought it lay in zone 3. I thought that if you took a picture in direct sunlight of a black car, the blackness would lay in zone 3. If any of the black car lay in shadow, that part would lay in zone 1 or 2. I guess I'll have to do some more reading on the zone system.

As I said, I usually meter by ambient light. In fact, when I can help it, I don't use a meter at all.

http://www.fredparker.com/ultexp1.htm

For example, open shade almost always has an EV value of 11.5. (That is, a gray card would read 11.5 for ISO 100 film.) Normally, if you just set your shutter and aperature for EV 11.5, you'll get perfect exposure; the blacks will be black, the whites will be white. A person's face will have good tone, not too washed out and not too dark.

Now, however, I realize I have to adjust my exposure for very black or very white objects.

 

[markbarendt]

A thought from a relative newby to exposing for the shadow and developing for the highlights.

You might try, as you have, opening the exposure enough to get the detail you want in the cat or bag, but then shorten up on the developement to save the highlight detail.

 

[Chuck_P]

I use ambient light to set my exposure.

Ok, but when using the ambient light with the gray card, the card and the subject must be illuminated with the same intesity of light. Otherwise, the card is less than helpful to metering the scene correctly.

 

[Vaughn]

My best guess is that in your first two shots of the cat, the film received the same amount of exposure -- and the light values of the cat are the same in both the distant and close-up shots. Or at least they should be if you metered the same way (holding the gray card at the same angle to the ambient light source, etc.). It is only you eyes/brain that is telling you one is fine and the other too dark. Basically in a print, very small areas of black with no detail/information are acceptable, but large areas of no information are not...unless you have the skill of a Brett Weston and can use large areas of pure black in wonderful ways.

Light meters are maps -- they are not the territory. Applying rules such as "Always meter with a gray card" or "Always place your shadows in Zone III" will not lead one to new country...just the same comfortable places one has visited before. But occasionally one accidently stumbles off the well-worn path and sees something new. it is called getting lucky.

Vaughn

 

[Claire Senft]

I do not believe that you are looking at it correctly. You are using a grey card and then opening up a stop. This is being done when photographing a very dark object and one in which you wish to make certain to have more detail. You are reading a Zone five object and placing it on zone six. In reference to the very dark object you have increased the zonal placement of the dark object but you must be very careful to not to believe that it has been placed upon a certain zone. Your increased exposure has merely made certain that the dark object has been raised so that it does not sit on the extreme toe and has adequate exposure.

You have stated that when you took a closeup of the cat your negative taken at the reading of the grey card was underexposed. You do not say what method was used to take this reading. Usually when taking a grey card reading with a thru the lens meter the card is out of focus.
When taking a closeup photo of a cat...I do not know how close you were...exposure compensation may very well be required. If a seperate meter is being used then it is certain that no allowance for being closeup was included. A close up photo...again I do not know how closeup... could easily require an additional stop of exposure.

I suspect that if your photo using a setting from the grey card was correct for the not closeup shot that the closeup photo was underexposed due to no exposure compensation being given.