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09/29/2006 03:50:28 PM · #1 |
I know a lot of photographers use these to tell whether the photo is over/underexposed, contrast, high/low key. I don't know anything when it comes to this. Can y'all explain it to me?
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09/29/2006 04:01:47 PM · #2 |
It is a graph of how many pixels exist with each of the 255 available levels of brightness/color. If you don't have any pixels at either end of the graph, you'll either have blown highlights or blocked shadows; as a general rule you want to have some pixels across the entire range.
If you have Photoshop, you can see the 'histogram' of an existing image by looking under the Image menu; I suggest opening a variety of types of images until you get a feel for the shape of the graph as it relates to the scene.
Message edited by author 2006-09-29 16:04:17. |
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09/29/2006 04:06:07 PM · #3 |
| Blown highlights will show as a big wall at the right end of the 'histogram'. Take an image of yours, use the Levels tool and pull the rightmost of the 3 arrows more and more to the left. Watch the 'histogram' window (it is on the same little toolbox as the colors palette, click the 'histogram' tab), as you see the highlights in your image lose all detail and go completely white you will see the right side of the 'histogram' get a big black line growing higher and higher. This is why, when you use levels to make adjustments, you need to watch that external 'histogram' and make sure you are not destroying areas of your image in the process. |
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09/29/2006 04:09:19 PM · #4 |
Here is a good article explaining histograms.
Understanding Histograms
I use the cameras meter as a starting point and after taking a shot, look at the 'histogram' to see if im off either side and adjust accordingly. This of course is done with the cameras built in 'histogram' display on the lcd.
You can also view histograms in many of the photo editing software packages as well but at that point the image is already taken so wont help if your trying to determine correct 'exposure'..
Message edited by author 2006-09-29 16:10:44. |
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