Changing sizes etc.

Question

Hi Guys
Can someone tell me why Photoshop keeps changing settings for placing objects, image size etc.?
For example: I create a new Photoshop document:
     ppi: 300
     Width: 160 mm
     Heigth: 160 mm
after clicking "OK", these go to 160,2 mm or less than 160 mm.
The same with the sizes and places of objects etc. I create a 20 x 20 mm circle. One click later it is 19,89 x 19,89. I set it's location to X: 80 mm, Y: 80 mm. One click later: 80,02mm
Is this a "problem" that can be solved?
Thanks!

Answer 1

Change the units to Pixels/centimetre and use 120 - that comes close enough.
It's an interesting concept though, and one that causes problems for an awful lot of new users of apps like Photoshop, Elements etc. Until very recently, Photographic Societies accepted digital image competition entries at a maximum 1024 (horizontal) by 768 pixels (vertical). It is amazing how hard that seemed to be for most new Camera Club members. They would either submit images at full res, or if a portrait mode image, submit their images at 1024 pixels high. A lot of competition organisers _still_ state a DPI for competition entries (usually 72), but I suppose it is possible that it could conceivably affect the displayed sized of the image — although I can’t think of anything other than printing where that would hold true.
In the last nine months or so, I have seen requests for entries at 1400x1050 (which maintains the aspect ratio of SVGA) through 1600x1400 (which is almost square, and the projectors are VERY expensive).  Thankfully, our National body PSNZ decided to make 1080p the new standard from May this year, which while having a 16:9 aspect ratio, at least the projectors are affordable.