Your sense is correct, the slider is variable compression--12 is least compression/largest file size. Due to compression pecularities, each time you re-save a jpeg using the same file name you collect more jpeg artifacts, even at the largest size, so saving under a different name is preferred. Also, editing a duplicate layer rather than directly editing the base layer is non-destructive (base image layer remains intact). [edit: after creating layers you must save as a .psd or .tiff, which are not compressed. If you save as a jpeg the layers are flattened and cannot be adjusted later.]
The number of files on the PC can grow pretty quickly using this scheme and if you've been stitching panos, you know that lots of layers can push image size above 100MB pretty easily. Don't email those to aunt Betty.
Editing RAW files forced a different mindset on me, but since switching to Lightroom I've become a lot more efficient (huge gobs of time saved). Further manipulation still requires Photoshop (which is a bitmap editor disguised as a photo editor) but most of the basics can be handled using the RAW sliders and the other RAW tools (like cropping and graduated filter).
The LR two-up before/after window is a godsend for monitoring progress.
Yes, if you increase image size &/or pixel density using PS "image size" it will interpolate to add the pixels, if you direct it to resample the image. You have five algorithms to choose from a pulldown menu (different ones for increasing and decreasing image size). You can also change bit depth, switch from RGB to CYMK and change the color mode.
Cheers,
I get 8+MB files when I stitch two or more photos together. I can shoot RAW with my camera so these files are very large.
What I was trying to ask was this: when pushing the "save" in Photoshop, you then get a menu with a slide-bar that goes from 0-12 for file size. I am not clear if 12, the largest size, is the same as the input photo, or larger. I think that if you use 12, you get the same number of pixels you start with. But I really cannot be sure. MB file size is influenced by more than number of pixels in a photo. So does 12 mean no compression? On other photo processing packages there are settings that let you choose %compression. I cannot find that on my Photoshop.
You can take 100x100 pixels and then divide each for a 200 x 200 pixel photo so you can get a larger number of pixels than the original. There are algorithms that divide a single pixel based on the surrounding pixels and even trends shown several pixels away. You get more resolution, but it is artificial. These algorithms are used a lot in satallite image processing. Does Photoshop do this too?
So far my RAW files end up worse than the JPGs. Evidently I am not processing the RAW files to their optimum. I have a lot to learn with this!
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