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PostPosted: Mon Oct 04, 2010 5:32 am 
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After downloading the 100% JPEG crops of some ISO comparisons I noticed some jpeg artifacts, or at least they looked like jpeg artifacts. In light of the fact that both Internet Explorer and Firefox both support viewing of PNG files, what about a switch?


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PostPosted: Mon Oct 04, 2010 8:52 am 
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Jpegs are compressed files so when you open and close them they lose data and start to degraded through time and leaving noticeable artifacts. Using data files with greater bitrate structure such as PNG's will always insure that all file data is retained longer.

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PostPosted: Mon Oct 04, 2010 9:42 pm 
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PNG is lossless compression, meaning that no original data is lost. Jpeg is lossy, which means it throws away data, but can achieve smaller filesizes.

So far, PNG is the way to go for text in images, but jpeg offers better compression ratio's. Then there's google's new image compression, but that has received positive, as well as very negative feedback.

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PostPosted: Tue Oct 05, 2010 3:34 am 
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Interesting, how many CL members use PNG, amateur or pro.

@Mark, if the Jpeg file is lossy when opened/closed, is that not the fault of our computer systems and not the file type. Any idea how many times a Jpeg can be opened before we can see deteriation.

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PostPosted: Tue Oct 05, 2010 4:30 am 
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Jpegs are compressed files so when you open and close them they lose data and start to degraded through time and leaving noticeable artifacts. Using data files with greater bitrate structure such as PNG's will always insure that all file data is retained longer.

Um that makes no since whatsoever. If you open a file be it compressed or not, your computer copy's the file to RAM, uncompresses it and deletes it from RAM when your done. Absolutely no data is changed on your hard drive in the process. If what you are saying was true then it would be impossible for you to read a JPEG from a read-only medium such as a CD or DVD.

Unless you were talking about opening it in say photo shop and re-saving it. :wink:


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PostPosted: Tue Oct 05, 2010 6:47 am 
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I think you will find it does.

I'm on my iPhone, when I get back to my computer I will write in full.

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PostPosted: Tue Oct 05, 2010 10:34 am 
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A Jpeg file does not change when it's opened, it only deteriorates in quality when you compress it again (like save it as a jpeg again). You can actually see this effect on youtube (but with video). People re-upload other people's videos, and the quality keeps dropping.

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PostPosted: Tue Oct 05, 2010 11:10 am 
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cheers buddy :wink:

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PostPosted: Thu Oct 07, 2010 4:21 am 
Minor pedant:

PNG24 is lossless. Basically, the compression is like zip. It works well for graphics, logos, etc, where there are lots of pixels with the same colours. For photos, file sizes will be bigger.

PNG8 is a lossy format. It uses an 8 bit colour table, which limits the files to 256 colours. PNG8 is quite similar to GIF in many ways. Again, it is more suited to logos and things where smooth gradients and lots and lots of colours are not as important.

JPEG is a lossy format. The compression is specifically designed for images, and how the human eye perceives them. For example, we are more sensitive to changes in intensity than we are to changes in colour. By employing lots of tricks, JPEG can create super small files that still look like highly detailed photos.


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PostPosted: Sun Oct 10, 2010 6:18 am 
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For some reason my post was moved to off topic from the site feedback section. Consequently, I think the post lost its original meaning, that is, I was wondering if Gordon's image quality 100% crops (in his reviews) could take the form of lossless images, as the jpegs sometimes show some artifacting.


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