Some old curmudgeon of a photographer once said that any scene that has more contrast than slide film can handle isn't worth photographing anyway. I think he was exaggerating a bit, but there is an important point hiding in there.

The point is that excessively contrasty pictures are rarely very appealing, and thinking in terms of exposure may not be the best way to approach the problem: the first thing to do would be to think in terms of composition -- try framing the picture in a way that the overall contrast is reduced. For example, leave out the sky, shoot either front-lit or back-lit (adding fill-in flash if needed), look for bright surfaces that'll reflect soft light into the scene, and so on.

In my opinion, the above holds only for color photography. B/W thrives on contrast -- blown-out whites and blocked shadows can actually give a picture a lot of pop, and B/W pictures are often printed intentionally to achieve this.

Run through time, Tyre, 2002 (Canon FD 50/1.4, Kodak T400CN)

However, blown highlights do happen in color photography as well, and when properly handled they're entirely acceptable. IMO the thing to watch out for is blown out *areas* -- like the entire sky, large swathes of sunlit area, and so on. Blown-out point-like or outline-like areas can actually add "pop" to the picture, and aren't distracting at all. While the beak is blown out in the picture below, there's enough detail retained to hint at the texture and color: the blow-out doesn't really constitute a defect.

Watch it, buster! (Canon EF 90-300/4.5-5.6 USM, Canon EOS 10D)

In night photography, of course, the light sources will blow out no matter what you do.

As to exposure technique, I do usually underexpose by 1/3 to 1 1/3 stops when shooting in bright daylight (center-weighted average mode). Then I pull up the curve in post-processing. There's so little noise in ISO100 that this doesn't visibly degrade the image.

But "how much is acceptable?" There's no answer to that... unless it is, "however much you manage to work into the composition or other aesthetic character of the picture." Personally, if I get a picture that has some merit otherwise but has lost the highlights, I try to see if it works better in B/W, and quite often it does.

Dead and fake (Canon EF 35/2, Canon EOS 10D)

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