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DPChallenge Forums >> Tips, Tricks, and Q&A >> Resizing problems
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Sony DSLR-A100
Sony 75-300mm f/4.5-5.6
 05/15/2003 11:40:25 PM · #1
Am in the current challenge have a good photo the problem being with Photoshop 7 i went to save for the web function to resize the 9 meg file to the size 640 width and got a file about 500 fb at 300 dpi still to large i didn't want to make the photo smaller so i then changed the dpi tp 200 still to big then 150 dpi still to big so then i went 125 dpi got a file of about 140 kb "bingo" i said sent it straight away no getting comments like to small the size 640 x 400 pixels at 125 dpi. ? qeustion how can the dpi affect the size so greatly when viewing them on the pc when the computer screens are noramlly rated at 72 dpi shouldn't the dimensions stay the same and only the dpi should come into play when printing???? PLease help would like some more info on this but not in tech speak make it simple please am not a guru on tech stuff lol
Any help would be great peoples give a guy so help here
Cheers Jason
Nikon D70
Nikon AF Nikkor 50mm f/1.8D
 05/15/2003 11:45:51 PM · #2
jason -- I'm not sure what all that is that you said above, as I'm not very technical in this respect myself, but if you just do all your crops, etc, except the last USM (if you're going to do one) and then go to "image --> resize" and take the longest side and make that 640 and have that box checked (usually is by default)that keeps it proportional, that should shrink your picture for submission, and if its not under 150K, either save at a lower quality (like 9 rather than 12) or make it a little smaller than 640, try 630 or something? Does that help?

Pam
Canon PowerShot S3 IS
Canon 12x IS USM (S3 IS built-in Lens) -- 36-432mm (35mm EQ)
 05/16/2003 02:24:47 AM · #3
Changing DPI does not change the file size unless you change the actual number of pixels, it only affects how many inches of display those pixels are intended to cover.

When you have a file open in Photoshop, the nominal size (displayed in the lower-left corner of the image window) is fixed based on image size and color depth, typcally:

640 x 480 x 8bits x 3channels = 900kb of data.

The file will be 900kb if you save it in an uncompressed format like TIFF. From there, use SaveAs or SaveForWeb to use JPEG compression sufficient to get the JPEG file size under 150kb, but realize this is the space it takes on disk. When you open the image in an editor it will essentially uncompress back to 900kb.

Message edited by author 2003-05-16 02:25:17.
Canon EOS-5D
Canon EF 24-105mm f/4.0 L IS
 05/16/2003 12:33:50 PM · #4
Originally posted by jasonmccarthy:
qeustion how can the dpi affect the size so greatly when viewing them on the pc when the computer screens are noramlly rated at 72 dpi shouldn't the dimensions stay the same and only the dpi should come into play when printing????
Cheers Jason


That DPI that is saved in the Picture file, in the case of DPC file size, is nothing to worry about. That is extra information that computer program use to print (etc) the photo, and you can totally ignore it for our purposes.

But is you are interested... Your 640x400 photo at 125 dpi tells Photoshop (or other program) that the original Photo is 5.12" x 3.2", which may or may not be true (that's just what the text info in the file says). If you goto "Print with preview" (in PS7), that Photo, the default size of the image will be those dimensions.

Again for DPC you can just ignore the dpi.

"I am so smrt! S-M-R-T"
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