Does zip-ing jpegs, then unzipping them degrade the quality?

[JR6ooo4]

I have a 7 gig file of jpegs. If I zip it, it is about 4 gigs, which will fit nicely on a DVD.

I do still have all the RAW files. I could recreate the jpeg again.

Mikeeee

 

[YesDear]

I am not the techno geek here but it is my understanding that every time you copy an jpg it degrades the image slightly. So I would not copy often.

 

[shafke]

Zipping an unzipping a jpg should not degrade the quality.
I think what YesDear means is that everytime you save a jpg the quality degrades slightly. So when you are editing a jpg it is better the make all changes and save once rather than save after each change.

 

[MarkBarbieri]

JPEG uses a "lossy" compression algorithm. That means that every time you use JPEG to compress a file (not just copy, move, or rotate but actually open, change, and resave it), it will lose some image quality. ZIP uses "lossless" compression algorithms. When you zip a file and unzip it, the result is exactly the same as the file that you started with. So feel free to zip, copy, and unzip your JPEG files as much as you want.

Here's a bit of a mental puzzle. If you take all possible files of a given size and ZIP them, most of them will get larger rather than smaller. If that doesn't sound right, think about for a while.

 

[JR6ooo4]

JPEG uses a "lossy" compression algorithm. That means that every time you use JPEG to compress a file (not just copy, move, or rotate but actually open, change, and resave it), it will lose some image quality. ZIP uses "lossless" compression algorithms. When you zip a file and unzip it, the result is exactly the same as the file that you started with. So feel free to zip, copy, and unzip your JPEG files as much as you want.

Here's a bit of a mental puzzle. If you take all possible files of a given size and ZIP them, most of them will get larger rather than smaller. If that doesn't sound right, think about for a while.

Ok, I give up. Why?

Mikeeee

 

[jann1033]

i have read a few places that degradation isn't the horrendously important big deal it's made out to be... read the last 2 comments with egs.http://photo.net/digital-darkroom-forum/00IggH. i have read this a few other places, from long term photographers.

 

[manning]

i have read a few places that degradation isn't the horrendously important big deal it's made out to be... read the last 2 comments with egs.http://photo.net/digital-darkroom-forum/00IggH. i have read this a few other places, from long term photographers.

If you notice the comparison of the original red bird pic and the one saved 10x you really can't tell the difference if at all.