[K-9]

I've been reading about histograms from various sources, and I seem to get differing views. Some places say if the histogram even touches one side or the other, it's over or underexposed. Other sources say an even range, even touching both sides is accurate and only if there is a large plateau or build up on one side or the other is the exposure off.

Are my shots overexposed when only a small part of the histogram touches the lower right, or where just a tiny, slim sliver of a line rises up the right side? Is it just when a "mountain" or larger portion rises up the right side for overexposure? I've seen where just a small portion touches and it does look a little overexposed, although I haven't tried playing with the exposures in PP.

[flyer]

The histogram is only telling you the brightness of any given pixel. If you take a piture of a white wall, you should have (theoretically)only a spike right next to the edge on the right. So, your picture is well exposed, but it doesn't spead all across. With experience (no, you can't buy that), you"ll learn to interpret your histogram in relation to what you are photographing. If your histogram is even across, it just means that you have evenly distributed brightness in your picture, but you can't get that with a subject that's bright or dark.

[Marc Sabatella]

The hitogram can show you information about what the pixels *are*, but it can't tell what they "should have been". That is, the histogram might be showing a lot of pixels at the far right, but it can't tell you how many of them *should* have been further over but were clipped. So you reort fo intelligent guesswork. If there is an apparent pike at the right, then chances are greta those pixels *should* have been further over to the right and were clipped. But it *could* indded be a white wall that was expsed *perfectly* just shy of clipping. there is no way to tell for sure. You have to think it through scene by scene. But sure, as a general rule of thumb, if there is any sort of spike at the right edge, that's usually not a good sign. If the histogram is trailing off and just barely hits the right side, well, maybe a few pixels were clipped, but maybe that's OK. Especially if you shoot RAW, since the hsitogram is only showing the reuslt of the in-camera JPEG conversion, not the original RAW data.

[attack11]

you should also be aware that it represents the output and is in no way a gauge for shooting on site. any change you make with in camera processing, or later with post production will change the histogram in real time.

it also changes as you modify individual colors via levels or curves.

the usefulness of the histrogram diminishes if you're doing any work on an uncalibrated monitor.

[Gooshin]

do not rely on the histogram completly

a dark scene with highlights will give you a one sided histogram with blown out highlights

because guess what, your highlights are blown!

the histogram should be used in conjunction whith the rest of the image, combine both to understand what to do next.

[Ash]

As said, it's just a guide to tell you where your pixels are in the brightness scale.
A low-key image with black background with have the majority of pixels clipped in the shadows, but this does not mean the image is underexposed.
The converse is true for a high-key image with white background.

It's all about which specific areas of the image you want to be adequately exposed...

[CWyatt]

It's also important to note you can't retrieve totally white or black parts of an image. Also, if you have blown out parts of a photo, 'retrieving' the very bright parts that are close to, but not completely blown out, will create some visible and ugly contrast. Retrieving parts close to black will not be too pretty either. There's only so much you can do in post-processing. (but do shoot RAW if you can!).

As others have said, the histogram is going to change with the subject of the photo. A graph with very bright and very dark parts might just be what you went for, and shows your exposure was correct and created strong contrast.

[K-9]

I have only been shooting RAW right now so I guess I shouldn't go too crazy. While I'm out shooting, I see the histogram hitting the right side and I always think my camera got the exposure wrong. Then I read where it can touch the side if it's even across the whole histogram. I think the confusing part is sometimes you get a photo with one hump in the middle and nothing even close to hitting either side. But I take it that this doesn't necessarily mean that it's the most perfectly exposed shot, it just means there's not a lot of extreme light or dark in the shot.

Maybe I just need to shoot as I always did before, and not worry so much about the stupid spikes! I mean when I look at the shots that barely touch the right side, they're never that far off, but may have few slightly blown areas that don't really wreck the shot.

[ChrisJ]

If the histogram touches the left hand side then all these pixels (and any beyond them even further to the left) will be black and have no detail. Likewise with a histogram on the right except these pixels will be white with no detail.

If your histogram goes right across from left to right it means your trying to record a scene that has more dynamic range than your sensor can cope with.

As a rule of thumb it's better to keep the histogram over to the left, but not touching it, as digital sensors will have more detail in the darks than they will have with burnt out highlights.

ChrisJ

[Bobr99]

Here is a link to a video that helped me a lot with understanding histograms. There is a series of 3 videos I think. You may want to watch them all.

YouTube - Photography Tutorial - Perfect Exposures, The Histogram Pt 1

Also from what I've read the histogram you see on your camera is only from a jpg file. Even if you are shooting in RAW format.

This has been driving me nuts for the longest time. I would take a photo and the histogram and image on my camera looked good. But when I loaded it onto my computer they would always be darker than I wanted. Did some research and found out about the jpg histogram. Changed my camera settings as far left as they would go and haven't had a problem yet.

Hope this helps

Bob

[Class A]

Also from what I've read the histogram you see on your camera is only from a jpg file.

The histogram is created from the image that results from the application of all camera settings (including white balance) to the RAW image. So depending on your settings (e.g., boosted contrast) it will not reflect the real RAW exposure.

Also note that unless a histogram shows all three colour components separately, you may have individual colour channels (e.g., red on flower or indoor shots) clipping while the histograms looks fine because it only shows a mixture of all components (mainly, or in some cameras even only, the green channel).

[K-9]

The color channels sometimes look better than the overall histogram, but now I'm getting confused with this whole .jpg being the histogram rather than the RAW. Does this mean if I use exposure compensation the histogram won't reflect that?

[Lowell Goudge]

there are a lot of things to be confused with in the histogram.

As others have pointed out, t really represents a graph of the distribution of light and dark in the photo.

whether it covers the entire range of the graph or not, whether there are parts off either end end or not, are all part of how you elect to expose the shot and nothing more.

go back to basics, a uniformly lit surface should give you a sharp spike in the center (at least with pentax cameras)

This is what the meter interprets as "correct"

everything else is up to you and what you want to see.

It may be desireable to shift to the left, right, expand or compress the histogram to get the image you want, so don't get bent out of shape with generalizations about shifting to the right, left, or having the histogram spread across the entire range. Without knowledge of the subject, these generalizations are meaningless.

for example, you have a subject backlit with a bright sky, and no flash. look at the histogram from 2 exposures, one based upon the sky one based upon the subject. the one based on the sky will be centered but the subject black and undistinguishable, the one based on the subject willl have 90% at the right edge (over exposed) but the subject will be correctly exposed. Neither of these is wrong, just different, and they tell you about the overall scene, that's it. In a photo editor, you may be able to look at a histogram for only a portion of the scene, and this is much more useful.

For an "average scene" what ever that is, the hystogram is usually across the entire scene, IF you want to see details in both the highlights and shadow, but note that this can sometimes make the image appear flat. YOu need to adjust the contrast ad exposure to get the image you want. If, for example you fid you are always adjusting contrast i PP, then you are not interpreting the histogram correctly in the first place. Increasing contrast in PP means you had the histogram too spread out when you shot the image.

Remember, you have to think about the scene you took, and then decide how you want the camera adjusted, the hiostogram gives you a measure of this performance.

[Lowell Goudge]

but now I'm getting confused with this whole .jpg being the histogram rather than the RAW. Does this mean if I use exposure compensation the histogram won't reflect that?

no the histogram shows the final captured image, if you used exposure compensation this will be factored into the image

[debbie]

no the histogram shows the final captured image, if you used exposure compensation this will be factored into the image

The color channels sometimes look better than the overall histogram, but now I'm getting confused with this whole .jpg being the histogram rather than the RAW. Does this mean if I use exposure compensation the histogram won't reflect that?

the sensor (or the RAW-file) doesn´t know it has been exposure compensated.