Comments on: Photoshop JPEG quality 51 trick http://www.roytanck.com/2007/07/12/photoshop-jpeg-quality-51-trick/ Fascinated by new technology Sun, 12 Feb 2012 00:04:16 +0000 hourly 1 http://wordpress.org/?v=3.3.1 By: Orionhttp://www.roytanck.com/2007/07/12/photoshop-jpeg-quality-51-trick/comment-page-1/#comment-165661 Orion Thu, 02 Jun 2011 19:56:47 +0000 http://www.roytanck.com/2007/07/12/photoshop-jpeg-quality-51-trick/#comment-165661 Thanks for this! It can work the other way too - I find that for my images, the bump in filesize from 50 - 51% comes with no visible advantage, so I use 50%. Thanks for this!
It can work the other way too – I find that for my images, the bump in filesize from 50 – 51% comes with no visible advantage, so I use 50%.

]]> By: hospitalhttp://www.roytanck.com/2007/07/12/photoshop-jpeg-quality-51-trick/comment-page-1/#comment-38271 hospital Thu, 19 Mar 2009 15:44:59 +0000 http://www.roytanck.com/2007/07/12/photoshop-jpeg-quality-51-trick/#comment-38271 thank you very nice thank you very nice

]]> By: Thomas Rutterhttp://www.roytanck.com/2007/07/12/photoshop-jpeg-quality-51-trick/comment-page-1/#comment-34300 Thomas Rutter Fri, 02 Jan 2009 12:28:33 +0000 http://www.roytanck.com/2007/07/12/photoshop-jpeg-quality-51-trick/#comment-34300 The reason for this is that at 50% and below, Photoshop uses 4:2:0 color subsampling for the saved image. This means that it reduces the color channels (as opposed to the luminance channel) to half the resolution, both horizontally and vertically. At 51% and above, Photoshop saves all channels at full resolution.When using "Save As" instead of "Save for web", it uses a scale of 0 to 12 instead, where '7' is the equivalent of 51%. At 6 and below, Photoshop uses 4:2:0 color subsampling.More information can be found here: http://en.wikipedia.org/wiki/Chroma_subsamplingIn particular, compare the top image below, before applying color subsampling, with the bottom, which has 4:2:0 subsampling. This image was chosen for its contrasting colors. http://en.wikipedia.org/wiki/File:420-original444.png http://en.wikipedia.org/wiki/File:420-progressive-still.pngColor subsampling is also used in compressed video (ie, MPEG like on DVDs and digital TV). The reason for this is that at 50% and below, Photoshop uses 4:2:0 color subsampling for the saved image. This means that it reduces the color channels (as opposed to the luminance channel) to half the resolution, both horizontally and vertically. At 51% and above, Photoshop saves all channels at full resolution.

When using “Save As” instead of “Save for web”, it uses a scale of 0 to 12 instead, where ’7′ is the equivalent of 51%. At 6 and below, Photoshop uses 4:2:0 color subsampling.

More information can be found here:
http://en.wikipedia.org/wiki/Chroma_subsampling

In particular, compare the top image below, before applying color subsampling, with the bottom, which has 4:2:0 subsampling. This image was chosen for its contrasting colors.
http://en.wikipedia.org/wiki/File:420-original444.png
http://en.wikipedia.org/wiki/File:420-progressive-still.png

Color subsampling is also used in compressed video (ie, MPEG like on DVDs and digital TV).

]]> By: Maxhttp://www.roytanck.com/2007/07/12/photoshop-jpeg-quality-51-trick/comment-page-1/#comment-30103 Max Sat, 25 Oct 2008 09:57:58 +0000 http://www.roytanck.com/2007/07/12/photoshop-jpeg-quality-51-trick/#comment-30103 huh for all my life I used a brainless 80, only on sundays 65. But it seems like I'm now gonna switch to 51. :-) kudos roy!! huh for all my life I used a brainless 80, only on sundays 65. But it seems like I’m now gonna switch to 51. :-) kudos roy!!

]]> By: Sinthttp://www.roytanck.com/2007/07/12/photoshop-jpeg-quality-51-trick/comment-page-1/#comment-7005 Sint Thu, 26 Jul 2007 20:28:40 +0000 http://www.roytanck.com/2007/07/12/photoshop-jpeg-quality-51-trick/#comment-7005 Maybe you should study the JPEG compression procedures and report to us what the mathematical reason for this kind of behaviour is...Lot's of information in this article: http://en.wikipedia.org/wiki/JPEG ;-) Maybe you should study the JPEG compression procedures and report to us what the mathematical reason for this kind of behaviour is…

Lot’s of information in this article: http://en.wikipedia.org/wiki/JPEG ;-)

]]> By: Roy Scholtenhttp://www.roytanck.com/2007/07/12/photoshop-jpeg-quality-51-trick/comment-page-1/#comment-6909 Roy Scholten Wed, 25 Jul 2007 07:25:15 +0000 http://www.roytanck.com/2007/07/12/photoshop-jpeg-quality-51-trick/#comment-6909 Heeej, still designing for bandwidth? :-) Wel een goeie vondst; the jpeg quality tipping point…Hoe'st nou? Heeej, still designing for bandwidth? :-)
Wel een goeie vondst; the jpeg quality tipping point…

Hoe’st nou?

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