Histogram Q

Hi

Today I saw a funny looking histogram (probably not the 1st time) while taking some macro pics. It looks like a "U" shape in the middle of the axis with a bit of space on both the Right & left. The pic turned out good, exposure wise.

Does anybody know how to interpret such a histogram.

Thanks.

A "U" histogram means that you have a lot of very dark tones and a lot of very bright tones, and not much else in between. It depends on what effect you were trying to achieve, but often you can improve that by correcting the tone curve with your editor.

Again, it depends, but a normal scene will produce exactly the opposite histogram, i.e., a bell-shaped curve.

---Bob Gross---

Thanks Bob,

After reading your explanation, it makes sense now. All the flowers I was photographing have either dark centerer and light leaves or the opposite.

Thanks for the explanation.

Bob is correct as usual. The histogram can only show what is there. If the scene doesn't have much in the way of midtones, that's what you get. Try not to leave much room on the right of the histogram. Much more data is captured on the right then the left. Keep it as close to the right as you can without going over and shoot raw. This give better results then trying to pull detail out of dark shadows.

Regards,
Scott

Thanks Scott, and congrats for becoming a mod. We should really congratulate ourselves for having such a nice and helpful person as a mod (like the other mods are).

What you said above about left & right sides raise an interesting question (at least to a noob like me). See, people talk about the "width" of the graph, but not often the "hight" of it. So was wondering what does the highs mean. I interpret it as the intensity of light/exposure. Is that correct.

Thanks again and sorry if it's a silly question.

The height of the histogram tells you how many pixels in the image are of that particular tone or brightness level. The higher the vertical axis for that tone, the more pixels there are in the image made up of that particular tone.

The intensity of of the light or exposure is indicated by the horizontal axis, with black (0 intensity) being on the left of the histogram and white (full intensity) being on the right and everything in-between are grays of differing intensities between 0 and the max (4096?).

Thanks Leo,

So if I understand you correctly, it means the higher the y-axis the better, as there will be more info in that tone. Am I right.

Thanks again.

No, not quite. Actually, there is no good or bad histogram, per se. All the histogram tells you are the intensity of tones that make up the image in front of you, as well as how many of the pixels that would make up the image is of a particular intensity.

There is a preference to have the graph of the histogram lean towards the right as far as possible without blowing out the highlights but that's not always a good thing either, IMHO. If you're going to be shooting RAW, then yes, by all means, shoot towards the right as you can always "undo" the overexposure with post-processing. However, if you're going to be shooting JPEG without doing any post processing at all, then your images may come out over exposed, depending on how much to the right from "normal" you set it. For example, an almost black gray cat on a black background shot to the right will come out looking almost white. Obviously that's not right (no pun intended) so the image would have to be corrected with post processing. So, as much as there is good wisdom in "shooting for the right", it doesn't always makes sense to do that. As with any other good advice, one should always try to see if the advice is applicable for one's particular case or needs.

Thanks Leo. Your help is appreciated.

So, Leo, let me get this straight.

If I have an almost black cat on a gray background, then I want the cat leaning to the right? But what if the cat is a Democrat? How do we know that the left-leaning cat isn't just a Liberal Democrat?

If you pushed the exposure too far right, then you might blow out some of the highlights, and that would be a cat-astrophe.

---Bob Gross---

Bob, get a grip on yourself. That's blatant humor. We'll have none of that here.

You're a riot, Bob.

(Ordinarily, I would put a laughing face created by the combo but I've become emoticon challenged ever since the forum switch so the only thing I know I can do right is the mrgreen face. )

Scottes wrote:
Bob, get a grip on yourself. That's blatant humor. We'll have none of that here.

Yeah, Bob. Think of your reputation that's at stake here.

[See, what did I tell ya. I'm emoticon challenged! ]