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Old Sep 22, 2005, 3:08 AM   #1
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I read a few times "read your histogram" in the forum,so I looked it up on the internet. This is a good start link


I get the idea behind the histogram, but I fail a little to understand how you use it in practice (stupid wasp!!).

So, how do YOU use your histogram? Is there anything I can use on the forum (don't seem to find any thread on that particular topic)?
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Old Sep 22, 2005, 5:45 AM   #2
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I assume that you are talking about the histogram display available on the LCD of some digital cameras. In a correctly exposed picture the histogram should be a bell curve extending from the left edge to the right edge of the display. If the histogram is clustered to the left it usually indicates under exposure, if clustered to the right it's overexposed. This tends to be a better measure of exposure than looking at the picture itself on the small camera screen. If the histogram shows the wrong exposure you can correct and reshoot.
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Old Sep 22, 2005, 10:13 AM   #3
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Unfortunately Nagasaki isn't exactly right.

In the uncontrolled "real world" there is no general rule for what a historgram should look like. In a controlled environment like a studio, then you can.

I evaluate the scene with my eye and generally guess "is there a lot of dark? A lot of light?" and from that I look at the histogram. Maybe the histogram shows a lot of data to the right... and that is correct. Maybe I'm in the desert? Maybe there is a lot of briht sky in the shot? (which, can confuse the camera, but if you push the sky right and nearly blow it out you'll probably slide the rest to the proper place. But the historgram will show lots way to the right in this situation.)

The same logic applies to the left side of the histogram. In some shots, there just is a lot of dark area... so that is life. The histogram will show more to the left.

What you really don't want is much data all the way to the left or right. That almost certainly means you didn't capture part of the image (pitch black or blown hilight, either way... no usable data there!) How the histogram looks inbetween is image specific.

You have to use your brain and think about what the scene is showing you, and then with that understanding interperate the historgram.

An even better tool is the picture on some camera LCDs will blink the over exposed areas of the shot. That is a really good way to tell if the hilight on the flower you're shooting caught the sun and was over exposed. Very quick and easy way to alert you to the problem.

This web page is really good for its articles (And the photographer who runs it is really good.) I highly recommend this tutorial, and all the others I have read there.

As to how I use the historgram... the answer is as above (most often to judge over exposure) and not nearly often enough. I've missed shots because I didn't peek at the exposure when I should have. I shoot wildlife and even the glance down can cost me a shot... of course, not checking the exposure and blowing it does as well. Tough call.

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Old Sep 23, 2005, 9:20 AM   #4
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I agree with Eric – there are no simple rules for what a histogram should look like. You have to develop a basic understanding of what it is telling you and then learn to relate it to the specific situation.

Even the general rule that you don't want the histogram bunched against either end has exceptions you encounter regularly. If you take a photo of a house with a pure white roof the histogram is going to be bunched on the right for a proper overall exposure. Backing off on the histogram so the right edge isn't bunched will likely lose considerable shadow detail and the photo would be too dark. If you wanted to capture subtle detail in the roof and didn't care about the rest of the photo being dark you would want to EV shift toward less exposure until the white from the roof wasn't completely squished against the right, but there would still be bunching because there is a lot of pure white in the image you want to keep white.

Most people show preference for not blowing highlights and pay more attention to the right edge. Blown highlights are just gone, but shadow detail can usually be brought out in post processing – albeit with noise. If your noise reduction software is a plug-in you can usually make the shadows look decent without losing detail in the midtones and highlights.

I keep the histogram always in view with my two EVF cameras. It was an irritation for at first, but since the first few days I hardly notice it's presence unless I refer to the histogram. Unless I am in a hurry for a grab shot I try to relate the scene to the histogram. That is the only way to become competent with its use IMO.

My little pocket camera has a large LCD and a nice four channel histogram, but I don't usually have it in view. There are too many situations in bright sunlight that I can't see it well enough to make subtle decisions with it, so I use other methods. I often use spot metering and pre-meter on different parts of a scene, then switch to matrix to let the camera do its thing. It isn't very scientific, but at least one of them usually comes out fine.

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Old Sep 23, 2005, 9:30 AM   #5
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Another problem is that histograms are not implemented the same by each manufacturer, so it's pretty relative. Best thing to do is try some tests, noting where the histogram falls with various exposures, then looking at them on your computer to see how they stack up when viewed. The "general rule" is "shoot to the right" as with slides (and opposite to conventional negatives), namely give the frame as much exposure as possible without blocking out the highlights (i.e., going past the right border of the histogram). As others have noted, however, in real life there are many low-contrast occasions when the histogram is stacked toward the middle, and in such cases it doesn't make any sense to give lots more exposure just to get it more to the right side

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Old Sep 28, 2005, 2:21 PM   #6
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eric s wrote
In the uncontrolled "real world" there is no general rule for what a historgram should look like. In a controlled environment like a studio, then you can.
I shot a studio job last week. Set up and metered my lights, then shot a grey card and read the histogram of that image. Very useful. OTOH, an outdoor portrait of a bride & groom would probably be very different. Lie all tools the histogram us very useful when it's useful. :-)
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Old Sep 30, 2005, 1:55 AM   #7
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thanks for your input. That will give me a better start using the histogram actively!

I find that the link from eric sgives a good summary, so if any other is intereted, go there!

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Old Sep 30, 2005, 8:25 AM   #8
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Related to this topic: I use an FZ20. The histograms that my camera gives are very differentfrom those I get on the photos from PhotoShop or PaintShopPro. Has anyone else noticed this? It looks like the histogram is magnifying the bottom 10% or so of the scale in the camera, clipping the actual distribution of data. Am I just imagining this?
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