Histograms

Hey all,

Recently I've decided that I really need to take the time to learn how to properly expose pictures from the get go; this brings me to two questions (for now! )

1. The histogram -I hear a lot of chatter about people always glancing at the histogram to see how their picture turned out. Can someone enlighten me as to how to read the histogram; what is it supposed to look like when a picture is properly exposed; how to fix it on the spot if it is incorrect (ie. too far to the left or the right). I hear the histogram should be in the middle?

2. When you're taking pictures of a bridge, and the sun is in the general direction of the bridge, how to do you handle this? When I was trying to take some shots I think the sun was throwing off my metering.

Thanks everyone!

Here's a quick link. It's actually fairly simple, but can lead you astray if you get hung up on the "shape" of you histogram.
http://www.workshopsfo​rphotographers.com …hniques/reading​-histogram

1 Mainly the histogram should ideally be in the middle, but it can be either side, so long as it isn't too left (dark) or too right (over exposed)

2 How do you mean throwing off your metering? Was the sun directly in front of you? If so, it shouldn't be, if you are pointing to the part where it was reflecting off the bridge too much, i.e. a metallic part of the bridge, then no you shouldn't do that

thanks. I found it very useful!

A_lee wrote in post #10017837
Hey all,

Recently I've decided that I really need to take the time to learn how to properly expose pictures from the get go; this brings me to two questions (for now! )

1. The histogram -I hear a lot of chatter about people always glancing at the histogram to see how their picture turned out. Can someone enlighten me as to how to read the histogram; what is it supposed to look like when a picture is properly exposed; how to fix it on the spot if it is incorrect (ie. too far to the left or the right). I hear the histogram should be in the middle?

2. When you're taking pictures of a bridge, and the sun is in the general direction of the bridge, how to do you handle this? When I was trying to take some shots I think the sun was throwing off my metering.

Thanks everyone!

Histograms display the count of pixels (y-axis) within a defined range of luminances (x-axis). So for the B&W histogram, the camera will display a histogram for the image as if it were a B&W image. If your camera supports RGB histograms, you'll see 3; one for each primary color channel.

If you really want to take advantage of your sensor for ultimate image quality, you DO NOT want your histogram to be bunched in the center! You want to take an exposure that makes the histogram appear as "pushed" as far right as possible, without having the review image blinking in large sections. Then correct this in post processing (assuming you shoot raw). If you shoot JPEG, then this technique is not for you.

If I am imagining your situation correctly (that the bridge is backlighted by the sun), this is a scenario that is very difficult to expose for because the dynamic range of scene is likely beyond the capabilities of the camera sensor. You have to decide which tones are most important to you, highlights, midtones or shadows, and exposure accordingly to get the most detail in that area.

Light meters measure the incoming light and make a calculation for an exposure that will render a "neutral" or "middle" gray tone. The more contrast that a scene has, the less likely the camera will come up with an exposure that captures the image in the way you want the image to be.

As stated above, "Histograms display the count of pixels (y-axis) within a defined range of luminances (x-axis)." So if all the pixels of a scene are within the left and right bounds of the histogram, you have a 'correct histogram'.

Apart from that criteria, you have no 'correct' or 'wrong' histogram. For example, if all the scene is dark tones (black cat in coal mmine), the histogram peak could be near the left edge; if all the scene is light tones (Finnish bride in white wedding gown on a snowy day), the histogram peak could be near the right edge; if all the scene is middle tones (gray dove on a green lawn), the histogram peak could be near the center. All of those are 'correct', none of those is 'wrong'.

Expose to the Right (ETTR) strives to make better use of the 4096 tonal values of the digital image, so that more of the 4096 levels are used to capture darker tonal detail. But...The problem of using Expose to the Right (ETTR) to the first example, is that it overexposes the dark tones and renders them much too bright for their inherent brightness, and they should be corrected back in post processing, to make them appear at their inherent brightness...a black cat in a coal mine should NOT appear to be a light gray cat against light gray rocks, as it incorrectly portrays the scene!

Important point! Shooting highly reflective subjects like cars, I use this to be sure that the bright areas "at the right" are the bright areas I want to keep, & I can measure Incident light in much the same way as hand held meter does it. The result is that some unimportant brights areas will be blown out:
Need an exposure crutch?

And I use manual mode, too. Why?
Post #47

Wilt wrote in post #10021182
Expose to the Right (ETTR) strives to make better use of the 4096 tonal values of the digital image, so that more of the 4096 levels are used to capture darker tonal detail. But...The problem of using Expose to the Right (ETTR) to the first example, is that it overexposes the dark tones and renders them much too bright for their inherent brightness, and they should be corrected back in post processing, to make them appear at their inherent brightness...a black cat in a coal mine should NOT appear to be a light gray cat against light gray rocks, as it incorrectly portrays the scene!

I agree with this, and this is an important aspect of ETTR that many people forget. The point of ETTR is to pick up as much detail as possible without blowing anything out*. That does NOT mean it is a properly exposed image, just that you've caught as much detail as possible. You then need to adjust the photo so it looks right, with the benefit being that the adjusted photo should look better because you had that extra detail to work with.

*- Some things, like the sun, will blow out anyway, so don't even worry about that.