Levels: Why lowering white level makes image brighter?

[Sonic]

Greetings,

 

I had a newbie question about using levels. Why does lowering the white level make image brighter instead of darker? Is it like compressing the tonal range, boosting output close to the threshold?

 

Thanks for any advice.

[lepr]

.

 

[gdenby]

Considering only black and white, levels define black as 0, and white as as the maximum in the collr space, say 255 in 8-bit color space.

 

Images do not always have that range. The lightest may not be true white,but a light shade of grey.  When the "white" level is adjusted to lower than 255, such as  in an image which might be no more intense than 216,  everything gets interpolated upwards. 

 

The reverse is that black adjustment for levels shifts everything darker.

 

And, hi! To me, image processing is very complicated. Luminosity, saturation, chromatic aberrations, hue equalization.. yikes!

[Sonic]

Thanks all for the replies! Image processing does seem complicated and sometimes counter intuitive, just need to understand the logic a bit more. Thanks again!

[anon1]

you definitely want to look into curves because this is just the single most important thing where most other adjustments are a mere subset of curves (which is especially true for levels)

 

 

working through this example was what helped me to grasp it, but it takes effort, but it's worth it

 

hope that helps

cheers 

 

 

 

PS

if you are really just beginning to understand, a quick look at this overview will probably clear up some terminology ....

 

... and incase it does not, leave a comment