graphics (jpg) question?

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I'm having a disagreement with someone, having to do with JPEG's and how they are handled.

Photoshop, not that it should matter. Photos- originally taken as high quality jpg.

I maintain that the image, when opened in photoshop, is therefore (the whole thing, uncompressed now) in working memory. I make changes, edits, etc, and 'save as' to another jpg.

This guy is saying, you need to FIRST 'save as' as a photoshop (psd) document, then edit, then 'save as' again.

I don't see it though. What's that gain? You now have a 40 meg psd file. True you can then play around with it all you want- but the way I do it, I'm NEVER re-saving the original picture, so what's the difference?

I don't think I'm losing any picture quality. Am I?

i have cheap photoediting program and don't need to save anything in the proprietary format. when i convert from proprietary to jpg i don't think i lose anything, but no need to save in that format first. just need to remember to save as when saving.

The original format is all that matters. If it is in JPEG from the start then that is all you need to keep to have the original quality. You will lose quality if you edit and re-save it in JPEG but there is nothing you can do about that if you need a JPEG.

If you plan on editing and resaving the edited versions then it might make sense to keep those in a lossless format.

JPEG is a lossy image format. When it compresses data it gets rid of some information to save space. Every time you modify and save a JPEG you lose quality. It's like making a copy of a copy. It gets worse each time. That is why high-end digital camaras do not use JPEG.

There are many lossless image formats, PSD (Photoshop), XCF (Gimp), PNG are a few.

thanks for the tip 'coded' i wondered why my photographs were decreasing in quality everytime i edited then. However if the final format needs to be in JPEG, will it inevitably decrease the quality?

JPEG is a lossy format. Every time one is created, data is lost from the original.

Thanks guys that's what I thought. Sometimes I do set the camera to take TIFF's but they're huge- 25 megs or so. Generally the highest jpeg setting is fine.

Numark- what you want to do is always work off of the original. So if you resize it to, say 1/2 screen size, and then want to do a smaller one, go back and do it from the original. That way you're only recompressing it once each time.

Jpeg's aren't fun. I always forget to set/unset the compression and it turns out crap. I stick with tif's if I can.

If you're working in Photoshop, once you open the original, keep saving changes as .PSD's. If you're working with layers, it'll force you to save as a .PSD.

Once you've done all you want to do to the image, (clean it up, add text, whatever,) flatten the image and save it as anything you want to save it as. If you have to use .jpg's, select the highest quality. You'll still have some loss, but not as badly as if you'd kept saving each step as a .jpg. I use the "save for web" feature, it does an even better job at reducing file size while trying to maintain quality.

You don't have to convert to .PSD at any point in the process unless you want to work with layers. You can always flatten the layers and save back to .JPG near the end of the process, then dump the .PSD work file.

For the best possible finished product, do all your editing on a copy of the original full-size, full-quality file. This is especially true if you're planning to scale it down. Edit first, shrink second, reduce the quality last.

i tend to do all my work in PSD files. then only turn to JPEG only for web outpuyt for example my DA account or fro work stuff

Jamie

lets refer to the exact definition of JPEG: Joint Photographic Experts Group, it refers to the pixels involved to display a simple image, a JPEG shows the exact view of a photo, therefore it could be used with any program whether it be photoshop or Microsoft Paint.

If you have images without layers you want to store in full quality: Use the "PNG" format, it'll scale right down. Then you can save the final copy as a jpeg if you like.