File Sizes

[daryl]

Hi can anybody tell me why a digital file from camera that is 2.29meg, when opened in photoshop is 17.5 meg how does this work? tah daryl

[Delane_B_Rouse]

Because the file is compressed. You really need this book...

[DougAxford]

Daryl,
I would assume that the original file is a jpg and when you are reading the file size in PS, it's probably a tif, psd, or otherwise. If it's still a jpg, then it's been re-sized.
You can simply tell PS how to large to make the file by re-sizing it - increasing dpi causes file sizes to increase far more than actual inches. It's not suggested that you re-save a jpg of a jpg - sorta like a copy of a copy, you'll lose photo information that may show.
Your question is a little vague, hence the book suggestion is a good one. PS is a software that has ocassionally caused even the brightest to question their sanity at times.
Doug

[daryl]

thanks for the info from what i understand photoshop is merely uncompressing a compressed JPG file makes sense when its p[ointed out.tah [img]images/icons/smile.gif[/img]

[DanielBrewster]

It is extremely unlikely that photoshop is uncompressing a jpg from 2 to 17 megs. Did you open in photoshop and then save as a tif? or psd?

or perhaps, as the other guy said, you resized/resampled the image in ps.

[daryl]

No the file size when viewed in a folder is 2.29 meg JPG when opened in PS is 17.5 meg JPG

[Lon_Larsen]

Daryl,
The actual file size is determined by the size of the image. For example if you have an image that is 4"x6"x 300 DPI, the file will open up as a 6.18 meg file. If you save the file as an unconpressed tiff file, it will save as a 6.18 mb file, and will show up as a 6.18 mb file in your windows explorer. When you save a file as a jpeg, some of the information is thrown away. I looked around for a good defination of what happens when you "jpeg" a file, and this was the best I could come up with. --"JPEG and MPG are examples of destructively compressed pictures. A JPEG picture is saved in a quite complicate format, which takes in mind the human eye and perception. Things that are not very visible, are removed when saving, and then approximately re-generated when reloading the picture. "-- So your 4x6x300 jpeg image needs fewer mb to save on your hard drive, because some of the information has been trown away. Photoshop will try to make up the parts that were throw away when the file is uncompressed and reopened into Photoshop. If you have a digital camera shoots in jpeg format, the camera is throwing away information inorder to store more images on your memory card.

If you change the 4x6 from 300 DPI to 72 DPI, that same file is will only be 365 kb as an uncompressed tiff file. When opened in Photoshop it all goes back to size times resolution.