Expert: Glen Demers - 4/26/2010

Question
QUESTION: Hi,
I need to print an image 20 x 20cm at 300 dpi.
At present my TIFF file size is way too big (40MB+) so I need to downsize the file but maintain the print size and resolution.
In the Image Size window I've tried to adjust the pixel dimensions but then the document size shrinks as well.
Sorry if this is a dumb question but it's driving me mad.
Can you help?
Much appreciated
Dan, UK.

ANSWER: Hi Dan,

In the image size window you can set the file size to 20cm by 20cm and the resolution to 300dpi, make sure resample image is selected. When you click okay the image on screen will shrink as Photoshop displays it at the same magnification, but you can change this using the magnifying glass or going to the view menu.

BTW, a 20 x 20cm image at 300dpi will be about 5.32 megabytes per channel (16Mb for RGB, 21.3Mb for CMYK) and be 2362 by 2362 pixels.

Hope this helps,
Glen Demers
Adobe Certified Expert, Photoshop 7
Prepress Technician, Best Printing Online
www.bestprintingonline.com

For more Photoshop tips please visit our help pages here: http://www.bestprintingonline.com/photoshop.htm

---------- FOLLOW-UP ----------

QUESTION: Thanks Glen,
The problem is that the image is already set to 20 x 20cm and 300 dpi but the file size is 42 MB. How can I get that lower without losing quality?
Kind regards,
Dan

Answer
Hi Dan,

An image file size greater than the ones I gave in my previous answer indicate extra channels or layers. Go to the Channel palette and delete any extra channels that are there, you should have one composite color channel and one channel for each color. Any saved selections that you made will show up here as Alpha channels.

Go to Layers>Flatten Image to remove any hidden layers, composite the other layers and put it all on the background layer. Obviously, this should be done on a copy of the image if you intend to go back and edit any of the layers.

A quick way to accomplish this is to go to File>Save As... and in the Save section of the dialog box check As a Copy and uncheck Layers and Alpha Channels. Photoshop will save a flattened copy of the image.

Also, check in Image Size that you are indeed set to Pixels/inch and not Pixels/cm, as this will drastically increase file size.

Hope this helps,
Glen Demers
Adobe Certified Expert, Photoshop 7
Prepress Technician, Best Printing Online
www.bestprintingonline.com

For more Photoshop tips please visit our help pages here: http://www.bestprintingonline.com/photoshop.htm