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Up until now, any noticeable JPEG compression without loss of quality has been practically non-existent.
Older versions of WinZip may have been able to give you about a 5% improvement in file size if you were lucky, but that wasn’t a whole lot of help.
WinZip 12 makes significant improvement here with an innovative form of JPEG compression that can give up to a 25% improvement in file size.
In testing of this feature, I found the average compression to yield right around a 22% improvement. That’s not bad, though. Even if you factor the general reduction to be a little lower than that at 20%, this still means that you can store 100 photos in the space that you could only store 80 in before. That’s a pretty big deal if you’ve got a lot of JPEGs on your hard drive.
The JPEG compression feature cannot be manually selected. It’s only available when you choose the “Best method for each file type” compression option. So, you need to be working in WinZip Classic mode rather than using the WinZip Wizard in order to utilize this feature. There may be a way to change the configuration options for the WinZip Wizard to allow for this option, but I wasn’t able to find it. For step-by-step instructions that will walk you through the process, please see: How to Compress a JPEG File With WinZip 12.
This type of compression is not completely compatible with older versions of WinZip or with some other compression programs. Even though I normally use Corel Paint Shop Pro Photo X2 to edit my photos, I have Microsoft Photo Editor set up as my default image viewer so I don’t have to wait long for the software to load if all I want to do is view a picture. I had no problems opening any of the zipped files that used the JPEG compression method in Paint Shop Pro, but it was hit or miss with MS Photo Editor.