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Old Mar 4, 2010, 11:33 PM   #1
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Default Gamma correction

Is the following information something that is regarded as a priority?

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"The Gamma Correction can be used to set a different gamma value for pictures. The gamma value is responsible for the contrast and therefore indirectly for the brightness of pictures. It would be a technical detail that is managed by the operating system alone were it not for there being Windows in addition to the Mac OS and both systems working with a different gamma value. All versions of the Mac OS presume the target gamma is 1.8, Windows 2.2. Pictures optimized on a Mac without gamma correction therefore appear to be high contrast and too dark under Windows. Pictures from the Windows world, however, appear slightly too flat on Macs.
If pictures edited under the Mac OS are to be published on the Internet or on CD-ROM, for example, they may be viewed on a Windows PC and appear too dark. Therefore change the gamma value accordingly under Effect/Gamma Correction either to the universal mean value of 2.0 or 2.2. for Windows PCs. ... if, for example, you are exclusively creating pictures for the Internet, the mean value of 2.0 would be a worthwhile alternative."
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Old Mar 5, 2010, 6:32 AM   #2
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The actual difference between a Gamma value of 1.8 and a Gamma value of 2.2 isn't very much.
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Old Mar 5, 2010, 9:32 AM   #3
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Actually, that information is inaccurate - the current version of Mac OS (v10.6, 'Snow Leopard') actually uses a standard Gamma value of 2.2, v10.5 and lower use 1.8 - basically, Macs and PCs now use the same value.

Getting your photos to look the same on different systems is trickier than it ought to be. I tend to embed a colour profile (i.e. sRGB IEC61966-2.1) in my images to minimise any inconsistencies.
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Old Mar 7, 2010, 7:53 PM   #4
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Thank you Tcav and mrmacmusic. The information is from the Help Manual of the post processing program I am using and as I am still on Tiger OS X 4.9 on a PPC I am using the version that is compatible with that. Maybe the info will be updated when I manage to upgrade to Snow Leopard.

What would you, or anyone else, consider to be the minimum post processing a 'good' off-camera shot should need?
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Old Mar 9, 2010, 2:39 PM   #5
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Quote:
Originally Posted by onlooker View Post
...What would you, or anyone else, consider to be the minimum post processing a 'good' off-camera shot should need?
Obviously none! If everything works well, and you have an amenable subject, the image straight from the camera ought to be fine. I myself leave most of my images as I took them. Only if I want to make the very best of them (e.g., for display here), or if post-processing can rescue a shot I couldn't manage in-camera (e.g., difficult lighting) do I put in the hard work at the computer. Unless you're a professional, it's supposed to be fun!

Quote:
Originally Posted by onlooker View Post
Is the following information (on gamma)something that is regarded as a priority?
The way to find out whether you need it is to stick a few images in an image editor, and try adjusting the gamma to see what it does. If you want to get technical, you could look at the histogram before and after. If you're worried about how it'll look elsewhere, try mailing it to friends who live nearby, and see how looks on their display equipment.

Last edited by Alan T; Mar 9, 2010 at 2:47 PM.
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Old Mar 10, 2010, 8:02 PM   #6
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Quote:
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I myself leave most of my images as I took them. Only if I want to make the very best of them (e.g., for display here), ... do I put in the hard work at the computer. Unless you're a professional, it's supposed to be fun!
Thanks Alan. Second the 'fun' sentiment! What pp steps do you normally use to "make the very best of them (eg for display here)". I've been trying out levels, local enhanced contrast and unsharp mask 3 x3 on my better shots. (What does the 3x3 stand for?)

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Last edited by onlooker; Mar 10, 2010 at 8:40 PM. Reason: Typo
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