Question about white balance

I've read that for digital cameras you should expose for the highlights b/c shadows are easier to get detail from editing software, whereas if highlights are blown out, the detail is lost;
however,
I have also read that, even for digital, to expose for 18% gray (like film). So which is it to get the best exposure?
If it IS gray, you should always have a gray card with you yes? And if you do, in the sun won't the gray card look lighter? What light situation is the gray card "correct"?

Exposure and white balance(color temperature) aren't the same thing.

You are correct that blown highlights are mostly impossible to correct because they contain no data.

An 18% gray card is used to set preset white balance in your camera, when either auto white balance or one of the preset white balance settings in your camera can't get it right. One example would be indoors, with several different types of light(flourescent and incandescent) and sunlight coming in through skylights or a window.

Calibrating your meter with a gray card will give you a baseline to work from when the camera is "confused" by the contrast in a scene. If the difference between light and dark areas is greater than the ability of the ISO/"film" to measure details in the scene. Rendering over and or under exposure in a part of the scene .

If I were to offer advice, i would likely say, "Watch the camera's meter, shoot raw, learn to post process and be done with it"......

effron wrote: If I were to offer advice, i would likely say, "Watch the camera's meter, shoot raw, learn to post process and be done with it"......

Well you were able to offer advice.

Summertime wrote: I've read that for digital cameras you should expose for the highlights b/c shadows are easier to get detail from editing software, whereas if highlights are blown out, the detail is lost

This might work sometimes, but IMO it's bad advice to say use it all the time. Different scenes, lighting conditions, and desired outcomes may require different metering strategies. The best way is to fully understand the tools at your disposal.

With print film you expose for the shadows, because black means clear film. If there is no info there, it can't be recovered. Even if the highlights are very over-exposed it is theoretically possible to burn them in. So you only have to worry about losing detail at one end of the tonal scale. Slide film is positive so you do the opposite: expose for the highlights. White is clear film.

With digital you have this problem at both ends of the tonal scale. If you go too bright you lose highlight detail. If you go too dark you lose shadow detail. Digital requires that you assess both shadow and highlight exposure, and try to avoid problems at either end. Fortunately your camera has a wonderful, easy to use tool for this built in: the histogram.

In my experience it's much better for image quality to darken digital photos than to lighten them. There is a lot more information and steps in the tonal range at the highlight end than the shadow end. As you lighten shadows noise becomes more apparent, and posterization is possible.

Summertime wrote: I have also read that, even for digital, to expose for 18% gray (like film). So which is it to get the best exposure? If it IS gray, you should always have a gray card with you yes? And if you do, in the sun won't the gray card look lighter? What light situation is the gray card "correct"?

Photographic light meters are calibrated to middle gray or 18% gray (or at least that's the official word, there is some controversy). That means if you use the exposure level suggested by the meter whatever you are metering will come out middle gray. If you meter something that is middle gray in the same lighting as your subject then all the shadows and highlights should fall into place. If you meter highlights then the meter under-exposes, trying to make them gray. If you meter shadows the meter over-exposes, trying to make them gray.

Rather than carry a gray card with me, I have used my meter to figure out what the differences are in stops between the gray card and things that are commonly available. My camera bag is 1.5 stops darker than middle gray. My palm is 1 stop brighter than middle gray. A healthy, green grass lawn is approximately middle gray.

The gray card is middle gray in whatever light it's in, so you would meter off the gray card in the same lighting as your subject.

The problem is that the gray card only sets your midtones. The lighting situation can still have a greater dynamic range than the camera can capture. Dynamic range is the difference between light and dark. In a situation where the scene dynamic range is greater than your camera's dynamic range even if you have the midtones set you could still lose highlight and shadow detail. In these situations you need to either make a compromise on the exposure, change the scene lighting, or have a processing plan or technique in mind that can deal with it.

Nice repsonse Henry

Watch your histograms and you should be fine if you can shoot more than once, a tad more difficult when shooting wildlife but as said set the camera up on a healthy lawn if poss

I wrote my first article for PT on these two things here:

www.photographytalk.com/photography-arti...tipusing-a-gray-card

I consider learning about 18% reflectance in the meter a part of the learning process (and is why I insist my students use CWA metering and not Matrix), as that is what all meters are calibrated to (ignoring the controversy here). After you are familiar with that "tone", not the gray color, you can then adjust from it when needed. As HP has pointed out so well above.

As for setting WB you should have and use a WB tool (also called a gray card) for when you want perfect WB with a DSLR. Even if you don't it makes for a good starting point.

HTH,

Matthew

Note that most 18% tools aren't good WB tools. They are designed to have the right reflectance, but are not always color neutral, so the WB isn't quite right.

As for histograms, they are the Zone System tools for digital capture. And like the Zone System for film, I consider it a more advanced method of fine tuning an exposure.

While a mountain that fits between the two edges is ideal, it isn't always possible (when the scene is beyond the cameras Dynamic Range), and this is where a knowledge of what areas can be clipped comes to play.

For example, if you shoot a portait indoors and there is a bright window behind your subject, a "bad" histogram "mountain" is expected. And the student needs to know what tones in the scene are being represented.

Matthew

Also, a "scene" doesn't have a Dynamic Range, it has contrast. It's the digital camera that has a DR limit.