exposure histograms

How much faith do you put in exposure histograms? As far as I can tell, they only let you know if a picture is overexposed or underexposed, and they are only a rough estimate. But maybe if I knew how to read them better, I could tell more. any comments?

Oh gosh - you'll find people who love and use Histograms and those who don't. I think it mostly comes into play when you are on the run, wondering if you exposed the last pix correctly, and it is too light out to really see the image in the LCD. Then some will look at the histogram for added info. I don't use them myself. But, I have many students who cannot tell correct exposure by looking at a pix (duh) but see it is wrong when the histogram looks "funny."

When I start shooting something I always look at my histogram the first few shots to make sure that I am not blowing the highlights in general. This is about the only time I actually look at the lcd display on the camera. I know what I want the histogram to look like and once there by tweaking the exposure levels on the camera I rarely go back and look at it.

I certainly can't look at just the image on the lcd preview and tell whether or not it is good or not. I've looked at some that I thought were good and then you get the images downloaded and they look like crap.

The histogram is the best way to evaluate the exposure of any digital image file. Sure if you really know your display you can tell if an image is over or under, but the histogram is the best way. You need to learn how to read one.

At a reception hall that I was at one day, the photographer from the next room and I were talking in the hall about digital since he was realativly new to digital. He started to say how his lab is telling him he is usually underexposed on most of his images and he did not understand why. "it looks great on my cameras display" he said. I asked him what the historgram shows. He asked "is that the display with all the peaks and lines?" Once I showed him how to get to see the histogram, I showed him that the shot he did of the bride in her white dress was underexposed. The brightest part of the histogram was just past the midpoint. He had made his display brighter so the images looked right.

Again, someone who decided to shoot a digital wedding, without knowing how to really use a digital camera, at the expense of the Bride and Groom.

The histogram is an essential tool, once you understand how to use it. Without it you're relying completely on the camera's metering, which is far from perfect because it doesn't know what you're trying to achieve.

Histogram shows exposure and clipping - based on the white balance selected (whether that be AWB, or CWB).

It doesn't do well for tint nor provides insight into whether the shot was in focus.

But your ability to discern tint and focus utilizing the LCD is very limited as well.

Check this out:

http://www.luminous-landscape.com …standing-histograms.shtml

Hornetzoo. It took me about a year to understand histograms well. The tutorials on Steve Hoffman's web site and Luminous Landscape are good, though "exposing to the right," should not be a religion, especially for "people" photography. Study those two. If you do portrait work, using a 10 second PhotoShop "FACE MASK" histogram as recomended from ShootSmarter.com is an amazing post shoot tool!
Anyway, in Canon dSLRs, the histogram is really a "luminance" or brightness histogram derived from the green color channel only (since there are twice as many green pixels as others, this is a good proxy for the whole image). So, it does not tell you perfectly about exposure of red and blue channels. But, darn it's the best, funnest tool I've ever used for high contrast outdoor work. It truly is the "21st Century Lightmeter" after you spend time with it. Shooting RAW, there is somewhere between 1-2 or even more stops of recoverable information even if the histogram shows clipping. A WHOPPING amount of photographic information. Shooting JPG, all this is lost. I went RAW two months after going digital. Spot metering and light meters are still essential for many people. But, for "on-the-go" casual photography, the histogram really helps get it right, get it better, and teaches you how to read scenes. Hope that helps. Jack

Expose to the right, but don't blow the highlights of what's important in the picture. With RAW you can recover shadows more easily than you can fix overexposed areas.

Do you have a link to this?

Thanks Titus213...another great learning tool!!
Another one added to my favorites...
Dan

Titus213 wrote:
Check this out:

http://www.luminous-landscape.com …standing-histograms.shtml

Face Mask Histogram for Tim.

Tim. Here is the link. It is under an instructor named Will Crockett.
http://shootsmarter.co​m/index.html
They pulled it from general view and now ask users to sign in, like this forum. No biggie. The technique is so in-your-face easy, and works so well in workflow, for selecting best among bracketed shots, you'll wonder why everyone doesn't teach it!
Enjoy, Jack

Some people think that histograms are the best thing since sliced bread. I'm not one of them.

I don't think I've ever used a histogram to determine exposure. There's a much better method - use the LCD (either after the shot or before it, if your camera allows)! Of course its not perfect, but your "keeper" percentage will be much higher if you calibrate your eyeball to the LCD and don't worry about the histogram.

A matter of personal taste and style, as mentioned above. Some factors that have moved me to rely on the histogram are --- 1) It's the only tool I've ever used that can help me avoid blown highlights 2) The image in the review screen looks different in bright sun, cloudy days, indoors, etc... the histogram is more robust. 3) In high-contrast situations, after I've pushed the historgram to the right without blowing highights, I can judge whether there's too much lost in deep shadow and adapt to that (such as fill flash)

This will give you problems eventually. The LCD illumination might be set high or low, so it might be displaying the image as light or dark when the image is stored only one way.

On a dark evening, I will set my LCD to mid-bright. On a sunny day, I have it set to maximum. My histograms do not vary.

---Bob Gross---

One thing to keep in mind is that the in-camera histogram is taken from the jpg thumbnail of the shot, and may or may not accurately reflect what you get with the raw data, as far as clipping at high or low end goes.