Expert: LizaL - 2/4/2005

Question
Lisa...
 The 31" wide file in MyComputer is 254Mb. The lower-left-corner size shows 146/315Mb.
 The 61" wide file in MyComputer is 140Mb. The lower-left-corner size shows 291.8/340.8Mb.
 All I did was to increase the Canvas Size of the 31" file to 61" and did a 'Save As'. All files are PSD. Each file has 40 layers; each layer has one image, each about 4" x 6", at 250 resolution.
 I was watching an Adobe Photoshop training video and I thought there was something that stated that there was some compression with PSD files. I will try to find it and let you know if I come up with anything.
 I am not sure what the lower-lef-corner info means. Hope this helps. I can replicate the results of the 'SaveAs' of the layered file. I don't have any plug-in for compression. Very strange...
  Thanks... Gary
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Followup To
Question -
In my project of creating a large montage of images in Photoshop CS, I have come up with a confusing result with the file size. All images are PSD.
  I started out with a file with images (40 layers) that has a background layer size of 27" x 31" at a resolution of 250. Then I decided to add more images so I increase width to 61". I increased the Canvas Size to 27" x 61", keeping the same resolution of 250, and did a SaveAs with a new filename. The original file size (in MyComputer) with the 27" x 31" layer was 256Mb. I expected the file size to increase. However, increasing the Canvas Size actually decreased the file size to 140Mb.
  Can you tell my why the file size would decrease when the Canvas Size is increased? Did Photoshop compress the layers when I did a SaveAs of the PSD file?  Thanks... Gary
Answer -
Hi Gary,

I've never heard of this, and I've never had it happen! A couple of things come to mind: Do you have any third-party plug-ins installed? I know there's a dynamic range plug-in that will automatically compress, upon regular saves.

The other thing I'm thinking of is Save to Web, although it sounds like you clearly didn't do that. But as you know, that will drastically compress and lower your file size (and resolution).

I tried my best to re-create your situation; I created two documents, both with the same size specs, but each with the same 10 layers. And when I followed the steps you did, I didn't have this happen. So I'm baffled.

Let me ask you this: When you look at your documents, what are the file sizes in the document window? Like, what numbers do you see at the lower left corner of the window? I'm referring to this area of the window:
http://little-works.com/all_experts/file_size.png

I've never heard of Save As doing any form of compression, so this has me confused. And it didn't happen on my files.

If you can, post back with the size numbers you see in the lower left corner, and any more specific details you might have about the files. But for right now, I can't say anything's wrong, because I've never heard of this problem, and I can't make it happen! In the meantime, I'll do some more research as to what could be going on.

I won't be available to answer questions this weekend, but feel free to email me at lizal@little-works.com.


Lisa


Answer
Hi again Gary!

It'd be great if you could find that training info and send it to me, 'cause I can't find anything concerning "Save As" and compression, and I've been burning up the search engines on this one! But I had a thought about this:

Are the images you're using photographs? Or are *any* of them photographs that were previously saved as JPEGs? If you save a JPEG you do get a form of compression (called "lossy"). That is, if your images are JPEGs, and you save a file full of JPEGs, I think that might be where the compression is coming from.

Let me explain myself from the beginning, though -- if you had a file you imported from your digital camera, chances are very likely it's already a JPEG, as a default. That's very typical of most digital cameras, unless you specify (via the camera) to import it into Photoshop as RAW. So if you opened that file in Photoshop and saved it as a JPEG after you edited it, it would go through some lossy compression, just by virtue of your saving it as a JPEG.

Or maybe some of your images have been saved as JPEG before, depending on their origins.

So my guess -- and at this point it's a guess, I have to admit! -- is that maybe if some or all of your images are JPEG to begin with, and you do a Save As, they're being saved as JPEG again, even though your file is a .PSD. It would almost be like each layer (and therefore each image) is going through its own compression routine, as well as being saved within the whole file when you Save As a .PSD.

Does that make sense?! At this point, that's about all I can figure, LOL! But the good thing is, this IS a good thing, and I wouldn't think it's anything to worry about.

I would start worrying if you started having absurd file sizes that you *know* have to be incorrect. Or if the software starts to act strange in any other way. So you might just want to keep an eye on it.

Oh, I asked you about the lower-left corner of your window. If you click on the triangle to the right of where you see those numbers, you'll find a pop-up menu that displays a lot of stuff, but the Document Size view is first on the list.

The Document Size view will display information on the amount of data in the image. The number on the left represents the printing size of the image -- the approximate size of the saved, flattened file in .PSD format. The number on the right shows the file's approximate size (including layers and channels).

So that's what those numbers are for. I was thinking that if you had the Document Size view showing, somehow those numbers might not correspond to your file size, and we could consider that your program is buggy, but now I don't think that's the case.

The only other thing I can think of, even remotely, is that somehow Photoshop is running out of memory and trying to access the designated scratch disk, and can't, and is therefore trying to reconcile that issue by supplying some erroneous information. But again, that's just a guess, and that would also mean that the problem is not your file, but the way Photoshop is installed on your machine.

Anyway, all this probably isn't much help, but this is truly the first time I've ever heard of a "problem" like this! And I can't make it happen on my end, and I can't find any information on it. As I said, though, I'd keep any eye on things and just make sure nothing acts really strange, to where you're sure it can't be right. Then we might consider a reinstall of the program.

Please keep me posted and let me know what you find out!


Lisa


P.S. Here are a couple of links for Photoshop info, in case you want to contact some other sources and see if anyone else has run into this:

Photoshop 911:
http://photoshop911.typepad.com/help/

The good old forums at Adobe:
http://www.adobe.com/support/forums/main.html

Planet Photoshop also has a forum on their site:
http://www.planetphotoshop.com/