Contrast

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Contrast

Postby Pehpsi on Mon Jun 11, 2007 5:36 pm

G'day. i'm working on some night shots and notice when you add a bit of contrast (.05) it can make the dark areas develop patching and ugly noise type stuff. How can i get a bit of contrast via an alternative method??

I use Aperture.

Cheers.
Nikon D70
12-24 DX, 18-70 DX, 70-200 VR

20" iMac Intel C2D
Aperture 2.1
PS CS3

http://www.jamesrobertphotography.com
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Postby ATJ on Mon Jun 11, 2007 6:47 pm

I find Levels and Curves do a much better job for increasing contrast. I don't know if Aperture has either.
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Postby Pehpsi on Mon Jun 11, 2007 7:02 pm

Thanks, yeah Aperture has Levels, and it's working pretty good! I normally don't use it because it looks pretty advanced, but it's doing the job ok. Now i just gota learn how to use it properly :)

Cheers.
Nikon D70
12-24 DX, 18-70 DX, 70-200 VR

20" iMac Intel C2D
Aperture 2.1
PS CS3

http://www.jamesrobertphotography.com
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Pehpsi
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Joined: Tue Nov 07, 2006 10:24 pm
Location: Kingsgrove, Sydney

Postby ATJ on Mon Jun 11, 2007 7:33 pm

Levels are pretty straightforward. They basically stretch the intensity of the pixels. Each pixel is given a score between 0 and 255 based on its brightness. Zero is black and 255 is white. If you set the lower input level to say 20, everything that had a brightness between 20 and 0 is set to black and the pixels above 20 are moved down to stretch them between 0 and 255.

Similarly, if you set the upper input level to say 235, it will set all the pixels between 235 and 255 to white and stretch the rest.

The middle input value sets the gamma and this sets how bright the middle grey will be. A value of 1 is normal. A value below 1 will decrease the brightness of middle grey and stretch everything above. A value above 1 will increase the brightness of middle grey and stretch everything below it.

Note that curves effectively do the same thing, but give you more control over the range of values you modify.
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Postby Pehpsi on Mon Jun 11, 2007 7:47 pm

Thanks for all the info mate, appreciate it.
Nikon D70
12-24 DX, 18-70 DX, 70-200 VR

20" iMac Intel C2D
Aperture 2.1
PS CS3

http://www.jamesrobertphotography.com
User avatar
Pehpsi
Senior Member
 
Posts: 1418
Joined: Tue Nov 07, 2006 10:24 pm
Location: Kingsgrove, Sydney

Postby Matt. K on Mon Jun 11, 2007 9:05 pm

There is no way to brighten up the shadow areas without introducing noise. That's the nature of the technology. You can hide it to some extent with noise removal programs but you will lose any fine details there.
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Matt. K
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