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Whiinch
Joined: 25 Oct 2009
Posts: 2
Location: Canada
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 Posted: Sun Oct 25, 2009 5:30 pm Post subject: Compression: PNG vs. JPEG |
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I just have a quick question for those who understand how the compression processes work with JPEG and PNG files:
I'm just looking for an answer that explains why there are separate options for compression available with both file formats, i.e. you have the option of choosing 12 different quality levels when saving as JPEG, as opposed to PNG, where you can only choose between saving interlaced or non-interlaced.
Can someone help me out with this? Or if not, is there a place that might have the answer where someone can direct me to?
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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: Sun Oct 25, 2009 5:39 pm Post subject: |
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Hi Whiinch,
JPEG compression is lossy so the lower you have the setting, the more detail it 'throws' away. PNG is lossless compression so it does not 'throw' any information away, so it's either compressed, or not.
Hope that helps
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Matt
3photoshop.com
http://www.3photoshop.com |
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Whiinch
Joined: 25 Oct 2009
Posts: 2
Location: Canada
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| Posted: Sun Oct 25, 2009 5:50 pm Post subject: |
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Alright, thanks a lot! Just one more thing I'm curious about, then: if no data is lost in PNG compression, what happens in the two settings (interlaced vs. none)? Because in one of them, the file size is smaller?
Sorry, I'm trying my best to make sense; I'm just starting to learn stuff about compression so I don't know exactly what I'm talking about.
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Patrick
Administrator
Joined: 14 Feb 2003
Posts: 11945
Location: Harbinger, NC, U.S.A.
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| Posted: Fri Oct 30, 2009 11:46 am Post subject: |
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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 6:44 pm Post subject: |
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No probs, it's an interesting subject.
Interlaced PNG's are used for web graphics and enable the browser to display parts of the image before it is fully downloaded. A standard PNG will only display over the web when the whole file is downloaded onto the local computer. Interlaced files are slightly larger in size but good if displaying lalargefiles over a slow connection.
Hope that helps
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Matt
3photoshop.com
http://www.3photoshop.com |
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