Photoshop Adds to my dimensions.

[BradyBrother100]

Hi,

I've been designing panels and decals in Photoshop for the past couple months and something I've noticted while doing so is whenever I set sometime to a certain dimension, Photoshop will add to those dimensions. For example. I want the canvas to be 111mm x 61mm. I put that in the box and press enter. But now, the canvas is 111.12mm x 61.03 mm. Why is that? This could be another issue but that also might affect the fact that when I print said decal, the demensions are not what I put in the box and certainly not 100% scaled. They are always off.

Help would be appreciated,

Brady

[Per Berntsen]

Digital images don't have physical dimensions, they only have pixel dimensions.

How large these pixels will be printed depends on the PPI value.

PPI stands for Pixels Per Inch, and determines how many pixels that will be used to print one inch (25.4 mm) of the image.

Pixel dimensions divided by the PPI value = Printed dimensions in inches.

Since you cannot have fractions of a pixel, there will be rounding errors.

At 300 ppi, the closest I get to 111 x 61 mm is 111 x 60.96, that's 0.04 mm shorter on the short side.

You can use the up and down arrow keys in the Resolution field of the Image size dialog (Resample must be unchecked) to see how changing the PPI value affects physical dimensions.

Photoshop lets you create images with physical dimensions, and does the math for you.

But the images still contain no reference to physical dimensions – there is only pixel dimensions and the PPI value, which BTW is optional metadata.

If your prints come out the wrong size, that's a different problem, which you have to discuss with your printing service.

If you do your own printing, make sure that no scaling is applied in the Photoshop Print dialog as well as in the printer driver.

[davescm]

If you are working in mm then use pixels per cm for resolution rather than pixels per inch and choose a value that gives whole pixels for your dimensions.

For example 111mm x 61mm at 120 pixels per cm = 1332 pixels x 732 pixels.

Dave

[BradyBrother100]

Thanks for your response

That still doesn't work for me. Setting the the image size to 61mm x 111mm and setting the resoultion to 300 ppc or 120 ppc, and the scaling to 100% the printout is actually 107mm x 59.5mm. It could be an issue with my method of printing.