Monica,
I wonder if he did indeed print it out because, the size difference may just be 560kb as viewed unopened using Explorer from the file listings and your 2.5mg size is with the file opened in PSE. I assume we are talking jpg here, which compresses a file and then decompresses when you open it.
Hi Nancy,
Thank you for your quick response & you are soo right about the sz difference on his end, I panicked when I called to check on "size" expecting him to tell me it was in Megs, instead of kb. He had uninstalled his Paint Shop Pro & mentioned that he needed to reinstall it, do you think that when he opens the pic it will be the size it is supposed to be. In the meantime I told him to trash it & I would resend, but the struggle continued on my end. The size of the file on my end in PSE is 2.52M (jpg). I sent it via attach to e mail. Am I making sense? I know that when he sends me pics I open in PSE & they are the perfect size for printing. Again, thank you.
Monica
In attach to e-mail did you mistakenly click auto-convert? If you did this it will resize photo prior to sending.
—
Have A Nice Day, 🙂
James W. Hutchinson
http://www.pbase.com/myeyesview
Monica,
The file size in PSE…if you have it open in the program, it is uncompressed. When sent, the file will be closed and jpg compresses (compacts) files to reduce the file size. After saving that file, view the file size, but not with it open in PSE. Just open the folder that contains it with Explorer and all the files will be listed with their file size. What size is it on your computer when not open?
Hi Nancy,
File size is 300 kb when not open in PSE. ??? Wish I knew what the heck I was doing. Thank you
Monica
Monica,
I just compared to a jpg on my computer. My jpg file size, unopened, as listed by Explorer, is 857kb. This file when opened in PSE is 14mg. So you can see there is a huge difference in size depending on whether it is open or not in the program. I don’t know why the difference between your 300kb and his 560kb though, unless you resaved it at a higher commpression. When he opens that 560kb file in PSP, it will have a much larger file size.
Hi Nancy,
You have SOLVED my problem & saved my sanity. I simply could not understand the size diff. If he had opened the file in his PSP it would have shown the megs & not the kbs. RIGHT?? In the future will I be safe in just sending my photos thru PSE via attach to email? Now I can enjoy my Thanksgiving & I hope you have a great day. Thank you thank you.
Monica
Monica,
Well good, hope this has helped. When he opens your emailed file in PSP, it will really expand! (note the size difference in my own example). Version 1, which I still use, does not have the attach to email function. I just save my image, open my email client and attach the image to my email. This is automated for you in version 2. Do an experiment…email that same image to yourself using the ‘attach to email’ feature in PSE and see what you receive, then you will know for sure if using that option sends exactly what you intended to send.
Hello,
I hate to be a wet blanket, but JPEG is a lossy compression format. It does not "uncompress" when the file is opened. However, JPEG files are definitely smaller than native PSD (Photoshop) documents.
I also am completely confused about file sizes in Photoshop and I am looking for a tutorial somewhere that explains why none of the numbers ever seem to correspond! The photo file I import is one size (usually very large, as it should be), the stated file size when saving as JPEG is smaller, the file size shown by my computer is different yet… Then if I open a tiny JPEG file, PSE shows it as being huge again, and I know it isn’t because JPEG is not reversible!
Is there a clear explanation of resolutions and file sizes somewhere???
Thanks,
— Eric
Eric,
The Elements file sizes are different because it’s telling you the size of the uncompressed file. Imagine taking a compressed JPEG file and converting it to a plain (uncompressed) TIFF file; that’s the size that Elements is reporting.
Hi Lou,
I thought that originally, but it doesn’t make any sense! Once you convert a PSD file into JPEG, it will always be the size of the JPEG. It cannot be converted back into uncompressed, so why would PSE try to tell me the uncompressed size?
Or is that the size of a "new" document in which the JPEG data is interpolated back up to the dimensions and resolution of a PSD file? That’s crazy, and it would look horrible.
There is some piece of information missing here and unfortunately the PSE manual does not have enough detail to help. Does anyone from Adobe monitor these forums?
— Eric
Or is that the size of a "new" document in which the JPEG data is interpolated back up to the dimensions and resolution of a PSD file? That’s crazy, and it would look horrible.
Don’t worry, there’s no interpolation going on. Interpolation only occurs when you change the dimensions (width and/or length). In going from PSD or TIFF to JPEG and back again we’re changing the file size (bytes) not the dimensions (width or length).
If I understand correctly, in order for Photoshop Elements to work on an image, it has to be "full size", meaning uncompressed, generally 3 bytes per pixel, one each for red, green, and blue.
OK, this is getting too complicated already. The core of what you need to understand is that going from PSD or TIFF (uncompressed) to JPEG (compressed) is lossy, but going from JPEG to PSD or TIFF is completely lossless. It’s only when you take it back to a JPEG does it get lossy again. This is why it is recommended to always convert your JPEGs to PSDs right away and do all formatting/editing in PSD. Only when you need the final image should you then save a copy as a JPEG.
Hope that helps.
Lou,
Sorry, I dropped this thread for a few days (as you probably have). You said one thing that I think might hold the answer to the mystery: The idea that PSD files must be "full-size" and have data for all three color channels.
However, make no mistake, if you have a 100KB JPEG file, you will NEVER get any more detail out of it than it has. If you open it in Photoshop, and save again as a PSD, you have not "gained" any resolution. If the PSD file is much larger than the JPEG (which it is) it must be due to additional data that Photoshop uses, or the way it structures the file for the best processing (which is basically what you said), but the "full-size" file will still have the artifacts that any JPEG has. They are now part of the PSD version.
I’m going to do some tests myself and see if I can intuit the definitive answer (I looked in about 10 PS books and nobody explained this issue).
Thanks,
— Eric
Eric, I didn’t go back and read the rest of this thread, but I’d like to suggest a few points:
1) The starting point for a digital image is a group of pixels captured by a camera or scanner. The number of pixels captured is dependent on the capture device and the format in which it’s saved is also device-dependent.
2) When the image is opened in Photoshop, it is no longer a JPEG or a TIFF
or any other format; it’s an array of pixels of the same dimensions as those captured by the camera or scanner. The important measure is found in Image Size pixel dimensions. That’s all the ‘real’ information that Photoshop has to manipulate.
3) If the pixel dimensions are changed by cropping or downsampling, pixels are discarded. If the pixel dimensions are changed by upsampling, ‘calculated’ pixels are added to the ‘real’ pixels based on an algorithm. No additional ‘real’ information is gained.
4) Photoshop creates the color channels from the information it receives from the scanner or camera. I don’t believe color channel information adds materially to the size of the stored file, although that’s one I have to think through a bit more.
5) When the image is subsequently saved, the pixel dimensions at the time of saving are preservered – no matter what save format is used. TIFF and PSD will save all the information in ‘lossless’ format; hence, the storage files are very large. Also, if layers are created in the editing process, they’ll be preserved in TIFF or PSD format and increase the file size (but not the pixel dimensions). JPEG, on the other hand, takes all the information and runs it through an algorithm that stores the information in ‘lossy’ format; it will take large expanses of the same color and tone and store them as a block described by a formula as opposed to individual pixels. Depending on the amount of compression, the image will be degraded (i.e., lose detail and sharpness) vs. lossless storage.
I guess that was a long way of saying I fundamentally agree with you: no ‘real’ information is gained by changing storage method and, if JPEG is used, information is going to be lost.
Chuck
Chuck,
Okay, so we agree on how file formats work! The original question (at least for me) was: Where does Photoshop get it’s "file size" numbers that appear in the lower left corner of the page? If you open a 100KB JPEG photo, why do those numbers say something crazy like 3MB? What does that number really mean??? NOBODY seems to know!
— Eric
Eric, hi. The number reflects the average size of an uncompressed (TIFF or PSD) of those pixel dimensions and reflecting the layers present if any. If you were to save your 100 kb JPEG as TIFF, it would ‘blossom’ to 3 MB or more depending on how much compression was used on the original JPEG. Not a particularly valuable number if you’re going to save in JPEG…. You can always get that more precise number by doing a Save As….JPEG, picking your compression/quality and letting Elements calculate the storage size and download speed.
Chuck
Okay, so my earlier guess was correct… in a sense. Photoshop does not care that the file you imported was a JPEG. It takes whatever is there and turns it into "native" format. If the image was a heavily compressed JPEG, the artifacts that are part of that image will become part of the "new" PSD version, as though they were actually part of the content of the photo. It does not attempt to interpolate a 50dpi image up to 300dpi, it simply assigns 300dpi worth of pixels across the existing size of the image and calls that the PSD. In effect, the image is "resampled" at the native PS resolution regardless of how it started. Is that accurate?
This is starting to make some sense…
— Eric
Eric,
Hmmmm. Interesting point about file size vs. what the status bar says. I just tried some tests and got some weird results.
I had a JPEG file that I had already saved as a PSD. The operating system reports a size of ~18MB. Opening in Elements shows a size of "9M/9M" in the status bar. Resaving the file results in a file size of 18MB (hasn’t changed).
If, however, I had a solid layer on top and save it, the file is now displayed as 9.4MB in the operating system. If I hide the solid layer and add a 50% gradient layer, the operating system reports a size of 12.9MB (halfway between 9 and 18). All the while, Elements still shows a file size of 9MB.
I have Save Image Preview (icon only, not full size; Win & Mac Thumbnails) turned on in Preferences, but surely the thumbnails wouldn’t take that much space. Or would they? Maybe Elements saves a full sized (yikes!) "icon" and compresses it, which is why the solid color layer on top would create a smaller file.
So I guess I have no idea why Elements says 9M/9M, and why saving with different layers displayed has such a huge effect on file size. <shrug>
Nonetheless, Chuck gave a very nice, detailed explanation. The only thing I can add to that is to think of a digital image as a things you pack for a trip. OK, it’s a little wacky, but it works. You lay all your items (clothes, toiletries, etc.) out on your bed–this is an uncompressed file. You squeeze all of that stuff into your suitcase, and it takes up a lot less space (as in disk space) but all your stuff is still there–this is lossless compression. Another way to fit everything in the suitcase is to leave some things out; do you really need 3 kinds of shampoo and 25 pairs of green socks? If you leave them out, you can still fit everything in the suitcase and you end up with pretty much the same thing you had before, but it’s not *exactly* the same–this is JPEG (lossy) compression.
So when you have lossless compression (you squeeze hard until everything fits in your suitcase), you can pack and unpack all you want, but you never lose anything. Hence, lossless compression.
But when you leave a few things out every time you pack, then gradually over time, you lose more and more each time you pack and unpack. Those extra green socks and two extra shampoo bottles are easy to get rid of the first time, but after 5 times of throwing things out each time you pack, you might run out of fresh underwear. And then things get ugly. 😉
So the moral of the story: Don’t forget your underwear when you pack. 🙂
Eric, the amount of compression has doesn’t change the pixel dimensions; a heavily compressed JPEG will open with the same pixel dimensions as a lightly compressed JPEG or non-compressed TIFF of the same picture. The difference is that the decompressing of the JPEG fills in all the pixels based on the reversing of the algorithm that compressed them in the first place. It’s sorta like resampling, but it’s not changing pixel dimensions so it’s not resampling as defined by Photoshop. And ‘yes’ on the original artifacts becoming part of the new image – and multiple compressions of edited images will likely introduce more artifacts. JPEG saving is great for space considerations, but not for retaining image quality as editing proceeds.
Chuck
Lou,
That’s a cute analogy for the general concept of lossless vs. lossy. I may use that with some of my clients! Plus, in this case the analogy stretches even further because the dimensions of the suitcase do not change–so that represents the pixel dimensions of the image. When you take a 2048×1536 pixel image (which is 3.2 MPixel camera raw) and save it as a Quality 1 JPEG, the file size drops dramatically, but the dimensions stay the same. Therefore, it’s like keeping the same suitcase but taking out much of the contents; the empty space that’s left is the loss of detail. FYI, the program comes up with 9M because it calculates the pixel size for three color layers. If you make the image grayscale the size is roughly 1/3.
However, I disagree that it uses the same algorithm to reverse the process when it opens the file. JPEG is a one-way process. When you open the 2048×1536 JPEG Q1 file, it shows you exactly what was lost when the compression occurred!
Incidentally, I’m a television engineer so I see deal with this stuff all the time. The one thing I was struggling with is what the file size number ACTUALLY means. The answer is: File size based on *pixel dimensions*. I’m not used to thinking that way. I would not even attempt to figure out why the size of various PSD images varies depending on content–there’s all kinds of data in there that may be saved in various ways for the program’s own purposes.
Thank you all for helping to turn on the lightbulb in my head! It’s a shame Adobe does not have a tutorial on all this stuff somewhere…
— Eric
Eric,
Glad I could help.
I would not even attempt to figure out why the size of various PSD images varies depending on content–there’s all kinds of data in there that may be saved in various ways for the program’s own purposes.
Yes, but what’s weird is that if I add a (single color) layer, the file size drops by half?! That seems counterintuitive.
Lou.
