On the weekend I was asked to help another photographer understand about photographing blacks as they were going on a trip to photograph gorilla’s. The photographer had been out with a friend recently and that person had said that to photograph blacks one needs to underexpose to bring out the black. Why, well we know that the camera light meters are all set to expose for 18% grey and as most of us don’t carry around a 18% grey card. Just using the light meter will not result in blacks.
Now whilst this is correct I wondered if in practise it is what one should actually do. After all under exposing results in much less information being collected by the camera. Something like 90% of the information collected sits in the image information that the histogram portrays on the right hand side.
How would one compensate for the grey when one wanted blacks?
So it was time to take a few shots of a piece of black cloth. Now I used a flash because I wanted to avoid the noise artefacts that come from using a high ISO I would have had to use to get a reasonable image.
So the raw image looks like this. Plenty of grey with just a touch of black where the shadows fell. Certainly not what one would like to represent a black object.
So I loaded the image into Photoshop and proceeded to play with the levels adjustment and by just adjusting the grey slider to the right I get this.
Plenty of black and I may have gone a bit to far with the slider, however that is just a simple tweak to get the look that one wants.
So how does that compare with an underexposed shot. To get the underexposed shot with a flash I set the flash in manual mode at about 1/8th power and left the rest as it was. This is the result. By the way it took four shots to get this, had to play with flash levels and speed settings initially. Eventually found that if I left the speed at 1/200th (the setting for the first set) and adjusted the flash output down I could get greys into blacks . If one was actually photographing a gorilla in the wild the opportunity may well have been lost.
It is black and generally much of the detail is there, (I looked a the pixel level), however to do this was in many ways more difficult than just letting the camera have its way and adjusting in photoshop after. In addition if one had to use higher ISO because a flash is not available or could not be used then noise is going to be a very big problem. Why, well as previously discussed the more underexposed an image is the more the signal to noise ratio is pushed in the wrong direction resulting in those horrible and difficult to remove noise spots.
So to sum up, if photographing black objects I would still expose to the right to gather as much information and hence detail as possible and reduce noise. One can then correct for blacks in ones favourite application for processing. Just remember when in exposing to the right to not overexpose and produce clipping in the areas you can’t crop.