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whguh
Joined: 27 Oct 2009
Posts: 2
Location: UK
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 Posted: Tue Oct 27, 2009 5:04 am Post subject: level changes when you reopen a jpeg...why? |
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If I adjust my levels on a tiff fill so I only have data between 5 and 250 then save it as a jpeg the levels remain the same, when i close the jpeg and reopen it the levels have shifted so there is data between 0-5 and 250-255, how can I stop this happening??????? |
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Matt
VIP
Joined: 24 Sep 2007
Posts: 3515
Location: Haverhill, UK
PS Version: Lightroom 5, CS4 & Elements 11
OS: Windows 8.1
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| Posted: Tue Oct 27, 2009 4:35 pm Post subject: |
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whguh
Joined: 27 Oct 2009
Posts: 2
Location: UK
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| Posted: Tue Oct 27, 2009 5:13 pm Post subject: |
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Hey Matt,
Sorry meant to say output levels, those are the ones I'm using
Thanks for the reply though
Hugh |
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Matt
VIP
Joined: 24 Sep 2007
Posts: 3515
Location: Haverhill, UK
PS Version: Lightroom 5, CS4 & Elements 11
OS: Windows 8.1
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| Posted: Fri Oct 30, 2009 6:48 pm Post subject: |
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Does it still happen if you don't save it as a JPEG? Could be down to the lossy compression?
_________________
Matt
3photoshop.com
http://www.3photoshop.com |
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jlphotos
Joined: 23 Oct 2009
Posts: 6
Location: Washington state
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| Posted: Fri Oct 30, 2009 7:15 pm Post subject: |
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When you pull in the blacks or whites with curves or levels in photoshop, and then apply that adjustment to the image, ps throws away the outside and just spreads out the pixel count so that your new 0 and 255 are at the ends. If you click the triangle with teh exclamation point in the histogram to refresh, you are back at 0 to 255. When you save as a jpg, everything is compressed and new, so, when you reopen the jpg, the histogram is looking for info in a range of 0 to 255. Doesn't have anything to do with the original image. Saving as a jpg should be the very last thing done to an image. Each time it is saved it will pick up artifacts due to the loss of pixels, especially so if you are working in 8 bit mode with the tiff or psd files. All those type adjustments should be done in 16 bit in order to keep tonal range. You can see it as white spikes in the histogram. |
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