Is that what you see when it’s open in Photoshop?
Try saving it to disk as a .PSD and getting the File Info in the Finder. It probably around 500k in RGB or just over a meg in CMYK.
The measurement you see in Photoshop at the bottom of the screen isn’t actually the file size on disk – the first number is the size of a flattened version of the file, the second is the file size if saved with all layers. If you save an empty file as a .PSD, Photoshop will understand there is no data in there and give you a correspndingly small file. Now try saving it as a TIFF without compression… you’ll get a file the size of the first figure because the TIFF is referecing everything, empty or not.
So yes, the file sizes seem normal – 10" x 10" at 300dpi is a lot of dots!
Unlike Illustrator which is a vector application and has relatively small file sizes, Photoshop is a raster application.
This means that the info in the file is based on the pixels it contains. So a 10" x 10" @ 300ppi file is really 3000 pixels by 3000 pixels for a total of 9,000,000 pixels.
So a new file which you think of having nothing in it really has 9,000,000 white pixels which take up the same amount of space as a photograph the same size.
Does this make more sense now?
A pixel takes up just as much information whether is is white, black or any colour
If you save an empty file as a .PSD, Photoshop will understand there is no data in there and give you a correspndingly small file. Now try saving it as a TIFF without compression… you’ll get a file the size of the first figure because the TIFF is referecing everything, empty or not.
Her PSD file is small not because there is no data there, but because the PSD format uses RLE (Run Length Encoding) compression. A new blank 3000 X 3000 document of row after row of white pixels would compress quite a bit using RLE compression.
Thanks Charles,
I was thinking of an totally transparent file, but you’re right either way as a totally tranparent file saved to disk is slightly larger than one filled with white. Are transparent pixels compressed by RLE too and any idea why transparent pixels need more data to reference?
On RLE, I’ve seen it crop up in PDF preflighting workflows as an image compression method mainly for images containing large areas of black or white. Does Photoshop uses this selectively or is this the default compression in .PSD files? Sorry to fire so many questions at you – just interested. Pat
Does Photoshop uses this selectively or is this the default compression in .PSD files?
That’s my understanding, default.
Are transparent pixels compressed by RLE too and any idea why transparent pixels need more data to reference?
That would be a question for someone who actually knows what they are talking about. 😉 Chris?
The transparent one has a fourth channel (the transparency).
And the flattened document takes up the same space regardless of what’s in it.
Now, Photoshop does optimize space in memory by keeping solid color areas compressed – but that may or may not be reflected in the final file size.
And you’re still confusing document size, resident memory size, and file size. Those are 3 different things.
