Gamma correction vs. brightness correction?

[dalemccl]

When I have a clip that is too dark, I have been using Pro X2's Color Correction tool to increase the brightness by sliding the Brightness slider to the right.

I just noticed that increasing the Gamma also brightens the clip.

Can someone explain when you would want to use Gamma correction vs. when you would want to use Brightness correction?

[Ken Berry]

Gamma usually also increases the contrast, so if you have a spot on the video which is a light colour and relatively bright, then if you increase gamma, the overall colour balance/contrast improves, but the lightening of the colour combined with this usually results in any detail being washed out of that bright part.

[dalemccl]

Gamma usually also increases the contrast, so if you have a spot on the video which is a light colour and relatively bright, then if you increase gamma, the overall colour balance/contrast improves, but the lightening of the colour combined with this usually results in any detail being washed out of that bright part.

Thanks, Ken. I find that increasing the brightness can also wash out the bright highlights in an overall dark scene.

By the way, do you find the sliders in Color Correction to be extremely finicky and hard to make small adjustments? The slightest movement of the mouse can jump the slider more than desired. I have to keep monkeying with it to get to the slider where I want it.

[Ken Berry]

Sorry. Can't help you on that one since I have only ever used those filters once or twice on some pretty old analogue-source video, and it required some pretty big jumps and no real fine tuning!

[Ron P.]

For a detailed confusing explanation on Gamma correction/adjustment read the following:
http://homepages.inf.ed.ac.uk/rbf/HIPR2/pixexp.htm. Basically Gamma enhances high intensity pixel values.

There's plenty more websites to read through, just do a Google search for Gamma image processing. Most all are engineering based, and quite scientific.

[dalemccl]

For a detailed confusing explanation on Gamma correction/adjustment read the following:
http://homepages.inf.ed.ac.uk/rbf/HIPR2/pixexp.htm. Basically Gamma enhances high intensity pixel values.

There's plenty more websites to read through, just do a Google search for Gamma image processing. Most all are engineering based, and quite scientific.

Thanks vidoman. Actually, I did do a Google search before posting the question and found what you stated: scientific explanations that were hard to read and understand - like the one you linked. Your description of that article as "detailed and confusing" is accurate.

I'd just like to find a layman's explanation of when to adjust gamma vs. when to adjust brightness and contrast.

[Ron P.]

Brightness/contrast settings affect the entire range, from shadow to highlight, whereas Gamma settings affect mostly the midrange. Here's a better page to read. It explains them using PaintShop Pro...

http://www.n9pby.com/psp/psp3%20-%20bri ... trast.html

To find the above, I used the search terms "Gamma vs contrast and brightness settings"...

[dalemccl]

Thanks, Ron. That link explains it well, and is exactly what I was looking for.

[erdna]

When I have a clip that is too dark, I have been using Pro X2's Color Correction tool to increase the brightness by sliding the Brightness slider to the right.

I just noticed that increasing the Gamma also brightens the clip.

Can someone explain when you would want to use Gamma correction vs. when you would want to use Brightness correction?

Brightness correction changes all pixel levels in the same amount. Gamma correction keeps the highlights (white if present) and the lowlights (black if present) at a constant level but changes the middle levels. If you have a scene where most of the content is in the midlevel, gamma correction will look like changing the brightness.

[dalemccl]

My thanks to all who replied. I understand it better and now think I should be using gamma correction in many cases where I have been using brightness and contrast correction.

I have some clips of the Las Vegas strip at night where very bright points of light are already burned out in the raw clips, but the overall scene is too dark.

Using the brightness control just makes the burned out areas worse. I will try using gamma correction for these clips to brighten the mid-tones while leaving the brightest and darkest areas unchanged.