Crop & Print

When you bring your shot up in photoshop and crop it and print if its not cropped right and you print on a 4X6 sheet or any other size, sometimes it dont fit right you have white showing on a borderless photo. So my question is how do you know what amount to crop and keep the aspect ratio right so to have borderless print be borderless.

In photoshop you can crop to a specific size by entering the dimensions. Not sure what program you're using or how to do something similiar.

A 4x6 would fit perfectly on 4x6 paper. Any paper in the 3:2 aspect ratio would be filled perfectly since that's the aspect ratio of your camera's sensor. Sounds like you need to click the "print borderless" option in your printer's settings if you aren't getting borderless prints on the 4x6 inch papers. 8x10s and anything else NOT in the 3:2 aspect ratio will need cropped to fit first...

When I open my photo in Photoshop CS2 and I crop first, then I click borderless on my printer, I still have white on some photos because I cropped wrong.

Then you need to fix how you're cropping. Specify the size of the print you want (8x10, 4x6, whatever) when you crop. Note that if you're not on, say, 8x10 paper but rather 8.5x11 photo paper, you'll still have edges because the paper is bigger than the actual printed area. Trim that off.