Very newbie question on contrast ...

[fmazzanti]

Hi folks,

This is my first post here because I'm most certainly starting with PI. I've seen there are several tutorials over there so that encourages learning, which is good. However I have basic question that I would like to ask. I hipe this is the right place for very basic questions, otherwise please somebody point me to the place to address...

In any case here it goes the first one: i have several computers (macs, PCs, at home, at work...) and when I process an image, they always look different on each one. On the macs everything seems darker, on the PCs all seems lighter. So when I try to set the contrast points on my processing images, I don't know whe to set the levels... Is there a proper way to set them, so that everybody agrees the background has a right balck level, and the brillant parts of the image are properly contrasted?

You see and as I promised, this is really basic, but any hint will be more than appreciated.

Thanks.

[pfile]

probably this is an issue of monitor calibration. although the topic can be quite complex (human color perception, color spaces, etc.) it's probably enough to calibrate your monitor. there used to be a way to roughly calibrate your monitor using software only (at least in OSX) but i have not looked at that in a long time. you can get relatively cheap hardware calibrators though. i had a bad time with the low-end eyeOne but it seems that's not for sale anymore. currently i use a spyder3, if i remember correctly.

rob

[fmazzanti]

This I understand, thanks ...
Still I'd love to know if there something such as a 'good practice' for balck and white levels in a black and white image, at least some guidelines. I start to think that I'm very bad at setting these points, so I hope the's something like a good rule of thumb by looking at the histogram, or something similar.
Thanks again.

[pfile]

astrobin shows the histogram of posted images, so you could look at a few images and see what you like. if the left edge of the histogram is far away from the left edge of the graph, you're going to see a bright background. this is not always a bad thing, since you may be able to reveal some faint structures as long as the noise is not too overwhelming. a lot of people really clip the blacks, i guess in an effort to mask noise or uneven color in the background.

rob