Friday, July 1, 2005

July/August 2005 HelpLine

JPEG Reloaded

    * Saved By JPEG
    * Timing Of File Saving
    * It's All In The Name

DPMag Published in HelpLine
JPEG Reloaded

    * Saved By JPEG
    * Timing Of File Saving
    * It's All In The Name

I received a lot of responses to a HelpLine question regarding JPEG and its effect on image files that ran in the May issue of PCPhoto. That much interest shows that readers are concerned about image quality. Since this is an important issue, I thought I'd revisit the topic. So, with apologies to the Wachowski brothers, here's "JPEG Reloaded."      
Saved By JPEG

Q)  I've heard from many sources that a JPEG file that's opened and resaved multiple times will lose quality. But I'm starting to wonder how much this is really a factor. I did a quick test and showed the results to others in the office, and no one could tell the difference after 10 saves. Your thoughts on this?

Tim Jenkins
Via e-mail

A)  I appreciate and welcome your skepticism. It shows how much you care about image quality. There are many occasions where I'm skeptical, too. It helps us understand the technology and how it can be used to make great images.

I've run a simple test on a large file. The image printed here was photographed using a Canon EOS 20D shooting in the RAW mode. I took the image into Photoshop CS2 via Camera Raw, doing little to optimize the shot. I saved the file as a .psd file, the native file format for Photoshop.

Next, I saved a copy of the file as a JPEG, using maximum quality settings, and called the file c01.jpg. (Keep in mind, however, that in many image editors, maximum isn't the default setting.)


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