Histogram question

[amandalee]

Can someone tell me how to use the histogram on the camera to correct things then and there? Even in post? I know how to pull them up but I don't know how to read it. On my camera it will just blink in different places and in PS I just see colors and the seismic activity :mrgreen: Thanks!

 

[480sparky68 67]

Histograms are basically pixel counts. If they peak on the left, the image is counting a lot of dark pixels. If the histo peaks in the middle, your exposure means everything is close to 'good' exposure. To the right, it's overexposed. This is just a guide, however. A single, small red rose with a black blackground will show a histo far to the right, but the rose might still be properly exposed.

Some cameras only show one histo, a combination of red, blue, green, and luminance. Some will show all four separately.

The thing to really look for is a peak so far to the left or right that the peak is at either end of the graph.... that indicates either no shadow details (left) or blown-out highlights (right).

The blinking in places is probably telling you that those areas are pure white (255:255:255) and will never be able to recover any detail no matter what you do in post.

 

[Compaq]

Your histogram is divided into 5 equal parts, see?

| | | | | |
| | | | | |
|dark/black | dark grey | middle grey | bright grey | bright/white |
| | | | | |
| | | | | |


*prays to the lords that it won't fail*


If the peak is in middle grey, that means the camera has "registered" the most values from the middle grey part. If the peak is in bright/white, the camera has registered a very bright scene. When highlights are blown, the graph exceeds bright/white and shoots upwards. That's when you lose detail in the highlights. The same goes for black.

An image with a very narrow peak will be low contrast. Contrasty images have both dark and bright areas.

What I use the histogram for, is to check whether I've blown anything (although I use the blown highlights thing as well) and to see if I've got enough signal on the sensor in any given part of the histogram that I want. If I'm shooting silhouettes, then I want much of the graph in the dark area. If I'm shooting snow, I want much of the graph to cover the white/bright part.

That's a very quick and dirty explanation, at least

edit: my three-minute visualisation of a histogram epicly failed!

 

[amandalee]

Ok that makes sense about the blinking! I've noticed that in post. Thanks so much for explaining!

 

[amandalee]

lol thanks for trying tho! lol too funny but I understood! So what is the "blown highlights thing"? I think thats what I mainly need to be using since a lot of my skies tend to get blown.

 

[480sparky68 67]

Keep in mind there is no all-purpose, universal look to a histo. If you want a low-key image, then you'll get a peak to the left. High-key shots will peak at the right. And completely black or white backgrounds tend to throw things off to make an all-image histo meaningless.

If you can zoom into a portion of an image in your camera's LCD while viewing the histo(s), see if they/it change as you zoom in. If they do, then you're seeing the histo for just that portion of the image. This is a great feature to have, and can really help you narrow down 'proper' exposure while in the field as opposed to trying to correct it in post.

"Blown-out highlights" means the camera has recorded pure white... no colors and no details. It's white, and the only thing you can do with white in post is to make it gray (unless you want to edit something else in instead). Darkening the image in post will not gain anything in that area except a sick-looking gray in a very dark image.

 

[Compaq]

In my Canon camera, I can turn on something called "Highlight Alert". It's basically the same as the blinking on the computer, except that it shows when watching your image in-camera. It shows where your highlights are pure white (or 255-255-255 on RGB channels as sparky said. Remember white is when a pixel is on full blast in each channel: red, green and blue), and all detail is forever lost

 

[joealcantar]

lol thanks for trying tho! lol too funny but I understood! So what is the "blown highlights thing"? I think thats what I mainly need to be using since a lot of my skies tend to get blown.

-
Set your camera to show "blinking highlights" that way you see right away what is blown without detail. More than likely if you want to show the histogram it will just take a push of a button. You don't have to look at every shot once you set the camera unless of course the light changes.
Understanding Histograms
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Shoot well, Joe

 

[epmi314]

Like others have said the histo is a guide nothing less. There are great shots that don't fit. Utimately it is about the shot itself. Over and under exposures can be used creatively.

 

[D-B-J]

Understanding Digital Camera Histograms: Tones and Contrast

 

[amandalee]

Thanks guys! This will definitely help tons!

 

[jkzo]

thanks a lot for throwing light on histograms

 

[KmH]

Understanding Digital Camera Histograms: Tones and Contrast

At the bottom of that link be sure and click on the link to the follow up page Understanding Digital Camera Histograms: Luminosity and Color

If your camera can do it, use the RGB, color channel histogram.

 

[D-B-J]

Understanding Digital Camera Histograms: Tones and Contrast

At the bottom of that link be sure and click on the link to the follow up page Understanding Digital Camera Histograms: Luminosity and Color

If your camera can do it, use the RGB, color channel histogram.

And i should also state that i wouldn't be able to link that if Keith hadn't introduced me. So thanks Keith!