Almost every piece of software scales images incorrectly (including GIMP and Photosho

[Florin Andrei]

http://www.4p8.com/eric.brasseur/gamma.html

There is an important error in most photography scaling algorithms. All software tested have the problem: The Gimp, Adobe Photoshop, CinePaint, Nip2, ImageMagick, GQview, Eye of Gnome, Paint and Krita. Also three different operating systems were used: Linux, Mac OS X and Windows. These exceptions have subsequently been reported: the Netpbm toolkit for graphic manipulations, the developping GEGL toolkit, 32 bit encoded images in Photoshop CS3, the latest version of Image Analyzer, the image exporters in Aperture 1.5.6, the latest version of Rendera, Adobe Lightroom 1.4.1, Pixelmator for Mac OS X and Paint Shop Pro X2.

Photographs that have been scaled with these software have been degradated. The degradation is often faint but probably most pictures contain at least an array where the degradation is clearly visible. I suppose this happens since the first versions of these software, maybe 20 years ago.

 

[Austin Glass]

I suppose this happens since the first versions of these software, maybe 20 years ago.

And it's taken us this long to notice it?

 

[Bruce Allen]

Nice!

BTW, if you use After Effects in Linear mode, it scales correctly.

Bruce Allen
www.boacinema.com

 

[Florin Andrei]

And it's taken us this long to notice it?

That's the weird part, isn't it?

 

[Roberto Lequeux]

Thanks. I always stick to 25% and 50% as possible, and use 16-bit in CS3... this sucks... lol... I guess I should go to 32-bit before resizing, huh? Bet it also helps when having to resize to "off % numbers" (not 12.5-25-50, etc).

 

[Stacey Spears]

I posted about this a while ago. http://www.reduser.net/forum/showthread.php?t=29588&page=2

 

[Gavin Greenwalt]

Yep. This is the old 1+1 = 4 scenario.

And it's taken us this long to notice it?

It's only the tip of the iceberg. Don't get me started on Photoshop's other gamma 'quirks'. Adobe is at the forefront of confusing users about gamma.

 

[David Rasberry]

Thanks for posting the article. I learned a lot from this one. Definitely confirmed the crappy quality of my laptop display among other things.

 

[Wayne Beck]

http://www.4p8.com/eric.brasseur/gamma.html

Crapp! I don't have the gray-matter to track this kind of data. Perhaps worse, I couldn't see solid gray blocks when backing away from my monitor. Then they all disapeared along with the monitor.

The info is great for those with pliable brain cells. My question is: how detrimental is the present processes to the overall quality visually, and does or would 64bit processing change things? How detrimental has it been to the visual quality of animated features for example? In laymen's terms.

Thanks,

Wayne
3B Digital

 

[Pawel Achtel]

Brilliant! It looks like I got caught up on non-linear brightness too when writing my own de-flicker image processing utility for processing time lapse sequences. Perfect explanation why my averaging didn't work well. :banghead:

What a mess! It looks like Photoshop and most other software are a mine field with just about every operation performed under non-linear gamma (which is almost always the case).

No, 64 bit computing doesn't do anything useful to fix this. You need to switch to high precision (preferably 32-bit), convert to linear gamma, do all the resizing and grading, then convert back to gamma 2.2. What a nightmare!

 

[Matthias Hutter]

I noticed that too. Some high quality downscales allways looked better in Lightroom than in Photoshop, no matter what trick or plug-in I tried.

Regards, Matt

 

[Michael Romano]

Add Aperture to the list.

 

[Matthias Hutter]

Not Version 3 though, as far as I've heard.

/Edit: That what the page stated:

These exceptions have subsequently been reported:
[...]
The image exporters in Aperture 1.5.6 (but Aperture 3.0 won't scale images down correctly)

 

[Brandon Kraemer]

OK, I'll bite... how about Redcine?

For red footage, I do 90% of my scales in Redcine, rendered out in LOG space.

Thoughts on the clarity of these scales?

 

[Pawel Achtel]

Redcine may perform correctly because Red RAW is linear (no gamma applied). It depends whether they apply gamma before or after the scaling. And, if they apply gamma before the scaling, whether or not they adjust for non-linear brightness scales. So, there is 75% chance Redcine does it right

 

[Brandon Kraemer]

Redcine may perform correctly because Red RAW is linear (no gamma applied). It depends whether they apply gamma before or after the scaling. And, if they apply gamma before the scaling, whether or not they adjust for non-linear brightness scales. So, there is 75% chance Redcine does it right

I'd be interested to hear what Gramme has to say on this topic.