Histogram

[Crimsonandwhite]

Ok, should I check the Histogram after ever picture I take to check the exposure? How accurate of a measure will I get from it? When and where is it ok to look at it and see that the picture is a little under or over exposed?

 

[tirediron]

You will get a very accurate assessment of your picture assuming you know how to interpret it. The ideal histogram (for an "average" scene) if you're shooting .jpgs should look like a Bell curve. Almost but not quite touching each end, rising in the middle and peaking just shy of the top. That means that you've got all of your information. If it goes outside of the display or off the scale anywhere, you've lost data. The farther the histogram is shifted to the left, the darker the image, and the farther to the right, the brighter. If you're shooting raw, some people suggest trying to under-expose a little, so that the histogram is shifted to the left.

 

[Crimsonandwhite]

I will be shooting raw 99% of the time, so knowing that I need to under expose a tad is good to hear. Thanks for the reply Tired, sometimes I think this beginner forum would be dead if it weren't for you....

 

[Big Mike]

Actually, it's better to over expose...so that the histogram is bias to the right. The technique is called...Expose to the Right. The basic idea is that you want the histogram to be as far right as possible, without loosing too much highlight detail. Some cameras, like the Canon 40D for example, have a 'Highlight Tone Priority' mode which helps you expose to the right.

Also, when shooting at higher ISO levels, over exposing can help to prevent noise is the final image. When you bring up an image in post and make it brighter, the noise will show up more prominently. When the image is already bright and you have to adjust it darker, the noise is suppressed.

Here is some more info on Understanding Histograms.

 

[Overread]

I think it depends on the light - I tend to find I you overexpose in the main part of the day (dealing with the naked sunlight) you can get a lot of overexposed points - with no recoverable details. Underexposing a little helps preserve these details.

 

[ksmattfish]

Ok, should I check the Histogram after ever picture I take to check the exposure?

I usually check if the subject or lighting has changed significantly, but not after every exposure.

How accurate of a measure will I get from it?

The histogram is created from a low res jpeg thumbnail. Depending on the in-camera processing settings the histogram for the jpeg can be a little different than the actual raw histogram. I find setting the processing parameters to neutral (or turning them off) gives me the most accurate in-camera histogram when shooting raw.

The Canon DSLRs I've used all add saturation and contrast when set on standard processing. When I'm exposing to the right I'm trying to get everything as far to the right as I can without clipping the highlights. Added saturation and contrast will show in the jpeg histogram as clipped highlights, but the raw file is fine. In the newer Canons with Picture Styles I keep mine set to Neutral or Faithful.

It also depends on whether you are looking at a luminosity histogram or a RGB histogram. The camera works in RGB, and that's going to be more accurate.

When and where is it ok to look at it and see that the picture is a little under or over exposed?

Whenever you need to. The only disadvantage to looking and learning is if you miss a good shot.

 

[three_eyed_otter]

http://www.bryanfpeterson.com/

this guy say's forget about your histogram...I've got a nikon d40 and I don't even know if the sucka displays a histogram.

have a good one
3Eo

 

[Big Mike]

this guy say's forget about your histogram...

It's a lot better than trying use the image on the LCD to judge your exposure.

 

[dklod]

It's a lot better than trying use the image on the LCD to judge your exposure.

I agree with you there. I did a shoot last weekend and it was a bright sunning day and it was next to impossible to get an accurate assessment of the shot on the LCD. I didnt know how to read a histogram until that night when a friend explained what to look for. Thankfully most were under exposed and I was able to salvage most shots.

 

[RyanLilly]

You also need to take into account your subject. I often shoot theatre and many times much of the background will be dark, and the histogram will always be far to the left. That is normal though. Take for instance a mostly dark stage and a person in a follow spot, there is a severe contrast where most of the image is on the far left of the histogram and and It will very obviously clip the top of the left side, but that's not a problem, because That dark area that is lost is not the subject, In fact the subject will probably just create a small blip on the histogram.

One feature I do find very usefull is the highlight-clipping-warning-by-blinking-feature. I dont actually know what its called, but it blinks anypart of the picture that has clipped.

 

[Marco]

I think it depends on the light - I tend to find I you overexpose in the main part of the day (dealing with the naked sunlight) you can get a lot of overexposed points - with no recoverable details. Underexposing a little helps preserve these details.

The technique is actually "expose to the right" which is not necessarily the same as overexpose.
You want to expose to the right as much as possible, but not blow highlights(you care about).

Using the histogram is good if you know how to interpret it. If a scene has a lot of dark/black in it, the histogram will be to the left. A lot of white/bright it will be to the right. Not in all cases you want a bell shaped histogram.