Some doubts here regarding the DPI issue for digital print out.
I used 1024X768 and 1600X1200 resolution on my A40, and I realise that both resolution setting has 180dpi.

I crop the image into 3:2, so....

1024X768 --> 1024X682.67
1600X1200 --> 1600X1066.67

In 4R (6"x4") Print out

The 1024X682.67 resolution yield 170.67dpi

1024/6 = 170.67dpi
682.67/4 = 170.67dpi


1600X1066.67 resolution is 266.67dpi

1600/6 = 266.67dpi
1066.67/4 = 266.67dpi

My question is, why both resolutions have the same dpi on the A40? I supposed it should be different.