Histograms how to.....

[Mthorpe_Davies]

read them, I haven't got a clue. All I know is that a nice even hump is what you want to get. Can anyone help.

[martcol]

They're just a graph showing the distribution of brightness in an image. So if the Histogram shows a hump in the middle and tails off at both ends it indicates that most of the pixels in that image are in the mid-range of brightness. It doesn't always follow but if the histogram leans heavily to the left it indicates underexposure and to the right, overexposure. However if your image is of something dark and gloomy or bright and lots of highlights you can expect the histogram to show that too. On the 10D the review image with info setting also shows "clipping" in the image where the image is blown out so, using both these indicators will give a better idea of exposure...

This probably says it better http://www.dpreview.com/learn/?/key=histogram
Martin

[Pekka]

Very good histogram essay: http://www.luminous-landscape.com/tutorials/understanding-series/understanding-histograms.shtml

[Jesper]

You don't always want a nice even hump. What you want the histogram to look like, depends on the subject. For a high-key image, you'll want most of the histogram on the right side; for a low-key image, you'll want most on the left side. In general, you should watch out that you don't get a large part crammed towards the right or left side, which indicates that your photo is over- or underexposed.

Here's another article:
A Practical Guide to Interpreting RGB Histograms (http://www.sphoto.com/techinfo/histograms/histograms.htm)

[Webster]

Just in case things haven't gotten too confusing, there are those who advocate exposing so that the histogram tends toward the right, as here (http://www.luminous-landscape.com/tutorials/expose-right.shtml).

Personally, while I do check the histogram, I more often try to expose just under the point where the info display shows the blow-out blink.

[karusel]

...which is exactly what I do. Basically all you need to know is, when you 'expose to the right' you get much richer color values than if you expose to the left.

However it would definetely not hurt to read the histogram basics, so just do a google search.

[robertwgross]

I use the histogram a bit differently. If I keep trying to find the "ideal histogram", I'll never find it.

On a difficult subject, I shoot and notice the humps and spikes and tails of the histogram. On the resultant images, I notice whether those humps and spikes and tails are getting me closer to the ideal image. If they are going the wrong way, like giving me one big hump at the far left, then I know I am seriously underexposed.

I use histograms more after the image is captured and it is in the computer. If I have spikes at the left and right, sometimes there is a need to develop the tone curves more, sort of like "auto-equalization".

---Bob Gross---

[MediaMagic]

One pretty cool tip I can pass on is, try to guess what the histogram will look like prior to actuating the shutter. Picture it in your mind as you view your composition. You'll be amazed at how quickly you can sharpen your luminosity "eyes".

I don't think I've ever nailed one exactly, but I have become much more "aware" of the varying luminosities in sections of an image. I'd recommend trying it on a regular basis.

[G3]

I don't think there's any way to explain what to look for in a Histo. It's going to depend entirely on the tonality of the image. I think the best thing to do is to learn how the Histogram works and what each piece of it represents. Then you can learn to "read" the scene you are trying to shoot and use the in-camera histogram to check your exposure. It's not an exact science, but you can sure get close. You will get to the point that you pretty much nail the exposure 90% of the time and the rest of the time, the image will at least be saveable in PS. The Histogram is equally valuable in post-processing. I don't know if I could correct a photo anymore without it, I've become so dependent on it.

I do some product photography sometimes, this past weekend I was shooting floral arrangements for a Wedding Florist for her website. Which, by the way, is a good example of one thing leading to another...you meet these folks at a wedding you happen to be shooting and mention to them that you do other kinds of photography...the phone rings, and you're off...

Anyway, one of the photos I shot was an existing light shot of a white flower (about 10% of the image), another white flower (about 8%) a red flower about (8%) some green stuff like leaves and things (about 10%) and a stark black background. The Histogram was a big spike at about tone value 10 to 30, a small "hill" at about 100 to 120 and a big spike at about 230 to 245 or so....weird looking but the exposure was right on for the image.

The point is, if I had been trying to "expose to the right", or get a "big hill in the middle", I would have never gotten the exposure correct. I used a card that has gray, black and white sections, put it in the first photo, then metered off the gray. Had the exposure been off, I could have used the shot with the card in it, and in 3 clicks in Levels, accurately corrected the color and exposure because I had a true white, an 18% gray and a true black in the photo. Then I could have just used those same values in batch mode and corrected the whole series at once.

[robertwgross]

One pretty cool tip I can pass on is, try to guess what the histogram will look like prior to actuating the shutter. Picture it in your mind as you view your composition.

The only subject that I can imagine that way is a three-tone exposure target (black, gray, white). You get three spikes.

---Bob Gross---