Combining multiple photos and resizing

[torrent]

I have several low resolution 160x120 images that I want to combine (with columns and rows) and print in 4R.

When I do a 4x4 i.e. 16 photos (640x480 pixels), the photolab couldn't print it because of cropping issues but I have other 640x480 shots (single photos) that were able to be printed. Why is that so? What is the best way to determine how many photos I can combine this way for optimum 4R printing?

 

[catchlights]

you need to know a 4R print, the paper size is 4"x6" and it is in ratio of 2:3 ,

and your single image of 640x480 is ratio of 3:4, printed on a 4R photo, some part of the image will be crop away, to see the whole image without cropping off, you need to print it on DSC_4R or Jumbo 4R. but since it is a single image, you might not notice the cropping issue, so it is acceptable to you.

now if you print your composite of 16 images with the 640x480 on a 4R photo, some of the images will be totally crop off. so it is not acceptable.

Hope this help.

 

[torrent]

So what ratio should I go for seeing as my pics are 4:3? Can I use 3x4 i.e. 12 pcs?