"Image Size" is telling you the memory requirement for the 400 x 400 pixels. It's a bitmap, so 8 pixels per byte => 160000 / 8 bytes => 19.5 KB.
The TIFF file will include information in addition to the pixel data. Also, if the file has an icon then that'll be included in the size reported by Finder.
That's really helpful, thanks.
Ok... next... a client has sent me a tif file that is 19KB, when viewed through 'Images Size' AND 'Get Info'.
Is there anyway to save a tiff file so that it's pixel size and 'Get Info' size are the same?
The client has specified a 19KB file size... and as they aren't proficient with P'shop, they will probably look at the 'Get Info' size and reject the files.
Any further help would be greatlly appreciated.
All the best, RP
I'm sure that the TIFF file and Photoshop "Image Size" are both 19 KB by coincidence. The "Image Size" is the number of bytes consumed by the uncompressed pixel data. A TIFF file has to contain a header, so the image data in the file will be compressed then the file header will be bringing the file's total size to 19 KB.
Photoshop embeds metadata in TIFF that your client most likely does not need. Use your Mac's Preview app to reduce the size of TIFF:
In Photoshop, copy the image to the clipboard.
In Preview, do "File > New from Clipboard" followed by Save with format TIFF and compression enabled.
(Do not open Photoshop-saved TIFF with Preview and then re-save, because the unnecessary info will be maintained. Use the clipboard.)
That was inspired!! Thanks so much. It works a treat.
All the best and many thanks, RP