Image Export Quality Settings confusion

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Sewie
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Image Export Quality Settings confusion

Post by Sewie » 20 Jan 2014, 13:26

:!: I just noticed that when exporting images through the Export Footage panel the quality setting are not consistent and confusing!

For example;

When selecting PNG export, we can choose a Quality Setting from 1 to 10; where 1 is lowest compressed and 10 is highest compression. (Confusing because I would expect Quality 10 to have the maximum quality and thus least amount of compression.)

When selecting Jpeg export, the Quality Setting is completely reversed; 1 is highest compression and 100 is least compressed.

This is unnecessarily confusing and counter-intuitive! The quality scale should be consistent for ALL image export settings. Also the term "Quality" is confusing in this context. Better to use the term "Compression" instead,where the highest number is maximum compression and the lowest number has the least amount of compression.

To me this is very important! The export setting are often used at the end of a deadline where the pressure is highest and when settings like these are contradictory like this it can get us in awful trouble with clients to whom we often have to deliver these image sequences.
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Elodie
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Re: Image Export Quality Settings confusion

Post by Elodie » 20 Jan 2014, 13:31

Actually, PNG is not a compressed format. When you set "10", you just lower the size, without affecting the quality.
It's just a question of time : when you use 1, you export very fast, but your files are heavy / when you choose 10 your files are light, but it needs more time to export.
(But the quality is the same, whatever if you choose 1 or 10).

Concerning JPEG, the "quality" is in % : 100% = excellent quality = big file / 1% = horrible quality = light file.

So, "Quality" is correct for JPEG, but for PNG, it should different, like "size compression".

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Sewie
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Re: Image Export Quality Settings confusion

Post by Sewie » 20 Jan 2014, 14:58

But where does the size difference go to with PNG?
Those extra mb's must consist of something...
Last edited by Sewie on 20 Jan 2014, 21:31, edited 1 time in total.
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slowtiger
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Re: Image Export Quality Settings confusion

Post by slowtiger » 20 Jan 2014, 15:14

Run Length Encoding. You can have each and every single pixel stored (that's the biggest files), or the algorithm counts how many pixels of the exact same value follow each other, and writes just this. There's more to that, like comparing lines and do the same with lines of identical content, each of those measurements reduces file size further without compromising the quality, since still each pixel gets described correctly.
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ematecki
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Re: Image Export Quality Settings confusion

Post by ematecki » 20 Jan 2014, 15:47

And JPEG throws out data, depending on the compression ratio, and those data can never ever be recovered when you load the file back.

When you throw a lot of things out, you get much lighter :)
But at some point in time you'll regret having thrown out some of the stuff...
Quicktime is DEAD. Get over it and move on !

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Sewie
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Re: Image Export Quality Settings confusion

Post by Sewie » 20 Jan 2014, 21:40

Thanks for the info, guys. I find it strange though that one can choose a setting for PNG that adds enormously to the filesize but has no effect on quality. If there is no point in choosing a higher filesize, why have that setting at all? But I'll do some reading.
Elodie wrote: So, "Quality" is correct for JPEG, but for PNG, it should different, like "size compression".
Perhaps you're right. With an "Inline Help" message explaining the size compression scale (which is max, which is min).
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Re: Image Export Quality Settings confusion

Post by Elodie » 21 Jan 2014, 07:11

I'll tdolist this ;)

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Peter Wassink
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Re: Image Export Quality Settings confusion

Post by Peter Wassink » 21 Jan 2014, 09:30

i agree with Michael some more feeddback would be good.

it would be very nice if you could see the actual frame sizevalue in kB (for the current frame) change as you move the slider
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Paul Fierlinger
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Re: Image Export Quality Settings confusion

Post by Paul Fierlinger » 21 Jan 2014, 10:49

Peter Wassink wrote:i agree with Michael some more feeddback would be good.

it would be very nice if you could see the actual frame sizevalue in kB (for the current frame) change as you move the slider
This would be more helpful and informative than a thousand words!
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Re: Image Export Quality Settings confusion

Post by Elodie » 21 Jan 2014, 12:07

nice idea :)

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Re: Image Export Quality Settings confusion

Post by ematecki » 21 Jan 2014, 14:12

Paul Fierlinger wrote:
Peter Wassink wrote:i agree with Michael some more feeddback would be good.

it would be very nice if you could see the actual frame sizevalue in kB (for the current frame) change as you move the slider
This would be more helpful and informative than a thousand words!
Do you really care about file size ? (not that we won't add it, it should be pretty easy, at least for image fileformats)
Isn't image quality the prime concern ?
Did you notice that the preview in the export panel shows the quality of the exported image ? (I think it only works with 'image' formats (jpeg,png,...), not 'animation' (avi,mov,...) )
Export a nice picture, select jpeg, and play with the compression slider... oh does it get ugly at the bottom range :)
Quicktime is DEAD. Get over it and move on !

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Paul Fierlinger
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Re: Image Export Quality Settings confusion

Post by Paul Fierlinger » 21 Jan 2014, 14:37

Hmmm... true, and I haven't exported an image sequence in years, but would it be impossible to do the same for animation? I had to just take a guess which is most likely to be the best and have been lucky that my guess was a lucky one. There shouldn't be guess work involved in either image options or animation, so I thought either there should be visible text or better yet, what Peter has suggested, and in that case a full size frame would give the most information IMO.
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Soom
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Re: Image Export Quality Settings confusion

Post by Soom » 21 Jan 2014, 15:17

Paul Fierlinger wrote:Hmmm... true, and I haven't exported an image sequence in years, but would it be impossible to do the same for animation? I had to just take a guess which is most likely to be the best and have been lucky that my guess was a lucky one. There shouldn't be guess work involved in either image options or animation, so I thought either there should be visible text or better yet, what Peter has suggested, and in that case a full size frame would give the most information IMO.
Most video codecs use algorithms, that are different from a still image, because most of them work temporally by calculating pixel values from one frame to another, or from one time point to another, and implementing the system of different levels of importance of frames. I believe that's why it's almost impossible to see the quality on the fly, unless you use an uncompressed format, but then you don't need to preview anything... There are certain settings for each codec, that usually produce expected results - so we just stick to them and that's it...
Elodie wrote:Actually, PNG is not a compressed format. When you set "10", you just lower the size, without affecting the quality.
It's just a question of time : when you use 1, you export very fast, but your files are heavy / when you choose 10 your files are light, but it needs more time to export.
(But the quality is the same, whatever if you choose 1 or 10).
as for PNG - most software don't even have this compression level setting, and I never experienced long export times, or exaggerated file sizes. Is it really so vital to have this setting? I believe modern computers don't make the speed difference so obvious...?
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my1ironlung
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Re: Image Export Quality Settings confusion

Post by my1ironlung » 09 Jun 2016, 23:27

Related to this subject,
Is there a way to adjust the PNG compression setting in george script? I'm searching the tv_saveMode command, and I can't find anything. thanks,
harry

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