What to look for in a good Histogram?

Am I the only one here that isn't sure what I'm looking for in the histogram?

 

I've read where others shoot and then check the histogram - what are they

looking for? What does a 'good' histogram look like? I just check the image.

 

I adjust white balance in the camera as well as in Photoshop and Lightroom, and

I adjust Levels in Photoshop but I don't think that is the same thing.

-greg

I check the exposure through the histogram. A good histogram will match the photo, i.e. for

a high-key image, it will be skewed towards the right; for low-key, towards the left. If there's

a gap it must correspond to a gap in the photo.

 

I find it impossible to check exposure accurately by looking at the image on the camera: the

screen is too small and usually too bright.

 

--ben

Refer to this - http://www.luminous-landscape.com/tutorials/expose-right.shtml

If you shoot JPEG, the histogram should appear like Benoit stated. A "good" histogram would be one in which neither end is clipped. However, that may not always be possible if the contrast range of the scene exceeds the range of the sensor. If you shoot RAW, it's often recommended to "expose to the right" meaning bias the histogram to the right side (without clipping it, however). The histogram in Levels is pretty much the same a your camera's histogram in that it shows you the distribution of dark to light pixels.

Two more good links to check; I had posted these before in another thread:

 

http://www.dpreview.com/learn/?/key=histogram

 

http://www.photoxels.com/tutorial_histogram.html

Greg, what camera are you using? Are you having exposure issues?

I look for one thing only; am I clipping the highlights (the right edge of the histogram. But I use this in combination with the flashing overexposure warming on the camera's LCD so I can see where the clipping is occuring in the photo.

Since the histogram show the distribution of dark to light pixels I look at it check exposure and contrast. Also to check the exposure of individual things in the image, like a zone system.

 

For instance shooting a person with their back to a window (backlit) I might want to have a good exposure on the person and blow out the window. The histogram will definately be clipped to the right but I can see the exposure of the person by looking at the rest of the histogram. Preferably I want a bump a little to the right of the middle because that's where a properly exposed face (white) should be.

 

If I wanted to use flash on the person and have detail in the window outside now the histogram should not be clipped (well maybe a little) and the middle section of the histo (where the person is) should still be there.

 

If it was a full length shot and the person was wearing dark clothes I'd want to check the left side of the histo to see that I have detail in the clothes.

I don't think JPEG or RAW has anything to do with my suggestion, I shoot RAW and I try to

make good use of the dynamic of the sensor.

Regardless of where the histogram is located (and I agree it's best if it leans towards the

right), I'm concerned with the shape: there is usually one or two bumps. Where are they? Is

it one of two? Is the histogram flat (no luminosity contrast...)? And I want to make sure

that the shape matches the image I see in the viewfinder.

Also as Peter points out, it is perfectly acceptable for the histogram to clip... as long as it

matched what you're trying to achieve in the photo.

 

Incidentally the RGB histogram is even more useful. For example, for clipping, you can

check whether the clipping occurs on all channels (not recoverable) or is limited to one

channel (usually recoverable in ACR).

I use Nikon's "Hightlight" setting that flashes when something is too bright in the photo. This is more useful for me and doesn't block part of the photo. In the zone system it is "expose for the shadows and develop for the highlights". In digital the oposite is true, expose for the highlights and see how much detail you can drag out of the shadows later in PS. I think a good histogram should be as flat as possible even if it means turning down the camera's contrast setting.

Thanks for all the input.

 

I shoot with a D100 (almost always with bounce or fill flash). I'm not having exposure issues - I'm just not sure if I should be using or how to use the histogram while shooting.

Thx,

-g

The histogram is the strangest thing about shooting with digital. Virtally all of the data is captured in the right quadrant. If you want to make a low contrast subject dark and moody, you need to shoot it so that it looks grossly overexposed and then post process it to get the most out of it.