OK I know you've answered this question before. I confess I get confused at times, and need to be reminded. I'm in the process of backing up my artwork to CD. The most practical way is to zip entire folders and save them. Will I lose image quality here? Perhaps I stand to lose the most image quality on jpgs, because they are a "lossy image type?!" I'm saving most of my images to PhotoShop PSD format before going anywhere else. Is the PhotoShop PSD file format safer when it comes to potential loss of image quality, after being zipped? I usually save pz3 files of important art work. That way I can always bring it back and render again. I'm totally amazed at how much room these images take up. I had one folder that was about 1GB. That's more than you can get on one CD. Your insights and tips are valuable as always. Ron

Zipping files does not affect image quality or actual file size as it is not changing the actual data. I've zipped all kinds of files and archived to over 35 cd's with no loss of quality or data. Just make sure that files still work before deleting the originals. Image quality is affected only when saving the file from your paint program, such as when saving as jpeg and you adjust the image quality then. -darlisa

Hi Ron.Im new to this forum, but I think I know this one. No you do not loose any quality by zipping your images. I am 100% sure.I know how to loose weight too.I heard you are trying hard.Here it goes.Stay off fats,and on the bike. Dont eat white bread,and only drink low fat milk,water and juice.No beer!I hope these tips helps. Renderhawk

The thing that confused me is that I thought zipping a file is in essence removing some repetitive or un-necessary data. Jpg is a lossy format because it does the same or similar function. I tell you I am easily confused at times. I do trust my friends! What is your preferred format for "default saving of images?!" 1.) PSD (PhotoShop) 2.) TIF 3.) JPG 4.) Other? Do you routinely save your images in pz3 format, as insurance? What are your reasons? Renderhawk. 1.) I often eat "dark bread," although I have a temporary craving for "Texas Toast" 2.) I don't drink alcohol much (long story) 3.) I drink 2% milk (close enough?!) 4.) I drink lots of natrually flavored sparkling water, and some juice. Thanks again for your wisdom, friends. Ron

zipping is a compression without any loose of detail.Thats why you can zip programs or any thing else and after unzipping you have the same as before. Usind *.jpg on images to make them smaller, thats when you loose details. but you get smaller files as if you would zip a tiffimage.( normally )

I save everything as *.tif. No loose of details and you get the alpha-channel from poser that is a big help in seperating your rendered figure from background

One way to think of it: ZIPping or similar file-compression actions (RAR, LZH) make perfectly unique and perfectly reversible 'codes' that happen to be smaller (in most cases, not always) than the original. But JPEG makes an estimate of pixels. It's like cutting off the last three decimal places before writing down a measurement. When you build the object using these estimates, the result may well be good enough -- provided you have chosen the right amount of rounding. The real world, like the human eye, has a certain amount of built-in tolerance and adjustment. But when the estimate (JPEG) has a pixel valued at 3.14, there's no way to determine whether the original was 3.14159 or 3.14284. So a decompressed version may not exactly equal the original.

ZIP, ARC, RAR, SIT, and other archiving formats are lossless; they are intended to compress data and reconstruct it to its original state. If it were lossy, you wouldn't be able to ZIP computer software, because the code would be messed up. Lossless compression has its limits, because there's only so much redundant or repetitive information you can flag. Nothing really gets thrown out or lost, it just looks for repeating patterns, makes note of where they occur, and keeps only the first instance of that pattern. When the file is unzipped, it's reassembled. Many image file formats support lossless compression, so when you use them, you end up with smaller file sizes, and the image itself is unchanged. Examples include GIF, TIFF, and TGA (Targa). Even Windows BMP has a compression option called run-length-encoding (not very efficient, but better than nothing). The PNG image format is also lossless, has good compression, and supports alpha channel; it works like GIF, but can support 16- and 32-bit color images. I don't believe that regular Poser supports the format, although Pro Pack does. You can convert to and from PNG with third-party software, in any case. JPEG and a few other formats use lossy compression. The compression loses some of the original information. It takes advantage of the fact that small changes in color are less noticeable than changes in brightness. The compression level is variable, so you can increase the compression to get smaller files; the tradeoff is increasingly worse image quality. PSD (Photoshop's native format) is great if you want to maintain all of an image project's original layers or channels. Its compression scheme is run-length-encoding (lossless), so it's perfectly safe; no loss of image quality. I prefer to use lossless schemes to archive my images, despite the fact that the compression isn't as efficient, because (like George Lucas) I might come back and tinker with them again. I need to work from the originals, because saving and resaving to a lossy format results in cumulative image degradation. When I post an image to the web, I'll crunch it down to something manageable with lossy JPEG compression, because a lot of people are stuck with slow dial-up. I still have the original, so it doesn't matter.

But .psd is horrifically bulky. If you save from Photoshop with jpeg quality set to 8 or higher, you will get images of sufficient quality that you won't notice the difference, and reasonable file sizes. Only save as .psd if you want to keep editing layers intact.

If you only save to jpg, you're cutting out any chance for doing extra work. Something like that. So what is the alternative? Tif? I think that's the bulkiest of all.

I like uncompressed .jpg the best myself. .Uncompressed TIFF is my second choice. I loathe all forms of compression and don't use any of them, LZW and jpeg compression will both ruin your image but if you set the jpg compression to the lowest setting the image retains it's quality through many resavings. Zipping won't effect image quality at all. Gif may be 'lossless' in some technical way but it reduces the number of colors in the image and generally screws it up pretty badly, if you care about how it looks. PSD and PSP formats are fine until you go to put them out, then you should change to a more universal format. About the only time I save in those formats is when I want to save an image with layers still separated, I think you need TIFF or PSD to keep alpha channel information if you use that.

LZW compression as used by Gif, Tif and Zip is completely lossless. There are different flavours of LZW depending on implementation, but they all work by looking for repeating patterns of data and replacing them with a single copy and a count of repeats. ("Run length encoding") e.g. 0,2,4,5,0,2,4,5,0,2,4,5 could be replaced by 3,4,0,2,4,5 or 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0 by 15,1,0 To uncompress the data the process is reversed. - Mark