Photos are shooted with a digital machine at 6 Mpixels, with automatic interpolation at 12 Mpixels.

So pics are in Jpg format with 100 or 300 dpi resolution (web or print version)

Dimensions depend on image cut, for example: a full photo can be 4048x3040 pixels with 300dpi resolution and have 8-10 mb weight.

In every photo sheet you can find resolution and dimensions parameters.