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You are here: MacNN Forums > Software - Troubleshooting and Discussion > Applications > JPEG quality 6 bigger than 7 in Photoshop CS!?

JPEG quality 6 bigger than 7 in Photoshop CS!?
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Martin Mraz
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Feb 22, 2006, 07:42 AM
 
Now this is strange...when I save a file in as a quality level 6 JPEG (optimized) in Photoshop CS, it's actually larger than at quality 7. I've tried it out on a number of different files and it seems to be consistent...can anyone else verify this little bout of weirdness...?
     
Love Calm Quiet
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Feb 22, 2006, 09:46 AM
 
Sorry, as one not having $ to afford full-fledged Photoshop (rather than just Elements), I can't help you.
But I can suggest you see if FREEware (if it came on your Mac) GraphicConverter can't reduce it to equivalence. GC is always where I go first for ease (and freewareness). That'll at least show you if the PS version missed compression opportunities.
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-Q-
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Feb 22, 2006, 11:24 AM
 
Although if it doesn't come with your Mac, GC is not freeware. But it costs significantly less than Photoshop (US$35 or so) and does a lot of cool things. Definitely worth having as a backup to PS.
     
tripletaker
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Feb 22, 2006, 12:03 PM
 
I just tried it in CS2 and it's true. At 7 it saved at 780 kb, and at 6 it saved at 788 kb. How strange.
     
Apfhex
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Feb 22, 2006, 03:42 PM
 
Umm, weird! You can see just by looking in the Save As... dialogue what the sizes will be and 7 is a good handful of K smaller than 6, optimized (not optimized 7 is still smaller, but not by very much).
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Martin Mraz  (op)
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Feb 22, 2006, 04:24 PM
 
OK, I just did a little test, I took a 17.3 MB test image, and saved 12 different versions, one at each level of JPEG. Here are the results: 244, 332, 368, 452, 532, 760, 640, 1.1, 1.2, 1.4, 1.6, 2.2 (the first 7 in kB, the last 5 in MB). Adobe has obviously screwed up. If you plot these values on a graph, it looks like this:



A nice-looking smooth graph, with the boo-boo quite evident...
     
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Feb 22, 2006, 04:50 PM
 
Wow, nice catch. (and nice graph Martin) There is either some odd explanation as to why this happens, or Adobe just screwed up. I tend to lean towards the latter.
     
Martin Mraz  (op)
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Feb 22, 2006, 04:57 PM
 
Thanks, the wonders of the Excel graph wizard
I would also incline towards the latter. Someone mentioned that it's also present in CS2...I'm just surprised that no one's alerted Adobe to such an obvious fault...it's not exactly an obscure function, saving as JPEG is likely the most often used thing in Photoshop...it leads me to wonder how many versions back it goes too...
     
Apfhex
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Feb 22, 2006, 08:05 PM
 
I most often make JPEGs from Save For Web... which uses a % system (which makes more sense than their 1–12 system), or else I'm saving at 8 or higher, so I never noticed (and yeah I'm using CS2 v9.0x196).
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madmacgames
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Feb 22, 2006, 08:17 PM
 
Is 7 actually better quality than 6 though? Maybe they just messed up a reference in the programming and 6 is actually 7 and 7 is actually 6? Or maybe not, and they really did a big boo boo.

Can anyone verify the quality, and see if 7 is actually a better quality than 6?

This also must just be a CS2 issue. I have CS1, but don't see this.
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Martin Mraz  (op)
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Feb 22, 2006, 08:27 PM
 
7 can't be better quality, since it's more compressed...but you're right, they probably switched references, because if you interchange the values for 6 and 7 on the graph, you get a relatively nice smooth curve, so they fall where they should. In any case it's a dumb mistake.

And it does exist in CS1. At least in my version it does...
     
Martin Mraz  (op)
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Feb 22, 2006, 08:33 PM
 
OK, I just checked Photoshop 7, and it's the same there too. Looks like Adobe's been dragging this little gem around for a while...
     
madmacgames
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Feb 22, 2006, 10:25 PM
 
Originally Posted by Martin Mraz
And it does exist in CS1. At least in my version it does...
Well I have CS1 and I have tried with about 5 different images and quality 6 always results in a bit smaller and crappier image than setting of 7 does.
The only thing necessary for evil to flourish is for good men to do nothing
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Martin Mraz  (op)
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Feb 24, 2006, 12:00 PM
 
Hmmm...well, that's strange. So there are different versions of the same version of SW out there. I've seen it in PS 7, PS 8/CS and tripletaker reported seein it in CS2. And others don't see it. Seeing as we're on a Mac forum, I'm assuming that we're all talking Mac versions of the application...

Anyone else out there seeing this issue?
     
glyph
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Feb 25, 2006, 07:02 AM
 
Yeah, I have the same issue on CS2.
     
   
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