PNG at high-res... no artifacts?

[jamesx521]

After editing my hi-res digital camera shots, I want to save them with lossless compression. PSD (flat) are way too big. TIFF (w/o LZW compression) are even bigger. JPG at the highest setting probably cuts the file size in 1/2, but ruins a little.

I tried PNG (both kinds that Photoshop 7 offers); the files become about 1/4, 1/3 smaller than the PSDs (good!). Then, I wanted to test if PNGs produce artifacts on the image. In Photoshop I placed my PNG saved file exactly on the top of a PSD file (same image), so the top layer is the PNG and the bottom background layer is the PSD. I changed the layer mode settings on the top layer to difference, so I can see if any artifacts will appear through... that will tell me if the PNG's pixels have been degraded. No! No artifacts!

Searched on the internet for PNG info and I found some info that PNGs are not good for photos?!

M'I safe to use PNG for high-res images, or not?

[bathurst_guy]

I guess it depends on what the purpose is for the images. Obviously it is aways a good idea to keep the images in RAW format and save any new versions as copies. Seeing as though you are asking this in a web developer forum I am guessing that you are using the images for view on the Internet?

[jamesx521]

I want to keep the files hi-res for printing purposes. And the copies that go for the web, I optimize with Fireworks.

When I take the pictures I use full-res highest-setting JPG and I can't see any artifacts in the images. However, I do post-production, so I have to save it as something else other than re-save it as JPG in Photoshop. My camera's writing RAW speed is 10 sec. Not only that, but I also don't know much about taking pictures at RAW, nor editing them. But some of the editings I do are Photoshop effects & tools anyway, so RAW wouldn't do me good even if I knew how to manipulate the images saved in RAW.

Now, if you're saying to save the edited images as RAW from Photoshop, that confuses me; in Photoshop I opened an edited PSD (that was once a JPG shot) and I re-saved the file as RAW... and it gave me a file-size twice bigger than the PSD... not only that, but the RAW file would open as a damaged file with some black and white lines and the file was no longer RGB too but Grayscale. Now I'm thinking that I probably need to have Adobe Camera Raw and open the file from there instead. But anyway, can RAW be a smaller file size than PSD?

[KDLA]

A PSD is a Photoshop-specific file. The file size comes from all the manipulations you do to the image, such as adding layers. (If your camera has a PSD option, it's highly likely that the photo is being optimized for editing in Adobe.... or, they're pitching for you to go out and buy it! ;) )

RAW is a photographic format, because it is not yet processed and ready to use with a program; neither is it for print or for web display. It is an archival format.

(for more info. see http://en.wikipedia.org/wiki/RAW_format)

Most printers (I mean people, not machines) prefer high resolution JPG files, because PSD is, as I said, Photoshop specific. If they do not have Adobe products (instead using Corel or such), they aren't able to manipulate the file.

KDLA

[jamesx521]

Suppose I start taking the shots with RAW format (which make big file-sizes), then the unprocessed info is manipulated and saved as PSD... or can you save the processed info back as RAW? Will that RAW file be smaller in size than a PSD?

Again, I'm thinking back to PNGs; is it safe to save my 300dpi manipulated images as PNGs, since their compression seems lossless? Does it seem, or is it for real that PNGs do not degrade the image quality?

[KDLA]

RAW is the original format. You can't process an image then attempt to revert back to RAW, because RAW is by definition "unprocessed." That would be like adding lemon to water, then presenting it as water: it's not, it's now flavored water. You've changed the chemical make-up of it by enhancing it.

PNG (http://en.wikipedia.org/wiki/PNG) is relatively lossless. It's probably the best at retaining color and complex shading out of all the file formats out there. PNG also affords you transparency options that are not possible with other file formats. I've not encountered problems with using PNG, except that the file sizes are very large, and consequently make the image hard to distribute via email or through web publishing.

What I suggest you do is to offer thumbnails of your images in compressed JPG, then link to a WinZip file with the PNG, or just to the PNG, itself.