Expert: Glen Demers - 7/27/2008

Question
I place advert in A4 magazine sometimes, the press often request us to send them photo with 300dpi for output, but no matter how large is the pixel of the photo, the resolution in photoshop always shown as 72 pixel/inch.  Some say u just need to change 72 to 300 but the file size will become too large.  I wonder how can I make sure my photo is suitable for 300dpi output.

Answer
Hi Abby,
An ad at A4 size at 300 dpi CMYK will be 34.5 megabytes. This is 2539 pixels by 3567 pixels which allows room for bleed on your ad.
To safely resize an image, go to Image >> Image Size.. to bring up the image size window. Uncheck resample image. Change the resolution to 300 pixels per inch. This will change your resolution from 72 dpi to 300 dpi without changing the file size, just the pixel density. You'll notice that the physical dimensions (document size width and height) of the image become smaller but the pixel dimension and memory required stay the same.
Hope this helps,
Glen Demers
Adobe Certified Expert, Photoshop 7
Prepress Technician, Best Printing Online
www.bestprintingonline.com

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