All prints on 8x10 are currently printed at:
8" x 10"
10" x 8"
10" x 10"
Final layout depends on the ratio & orientation of the uploaded photo. The final artwork will be scaled to fit proportional on that sheet, leaving a 1/2" border within which the signature and numbers will be printed.
Although it's ideal to have a 300 dpi image to print from you will be pleasantly surprised by images down in the 150 dpi range. (we've tested extensively)
A 300 dpi file at 8" x 10" would be 2400px x 3000px
Uploading really large files (over 8-10MB) will not yield better prints, and might cause slowdowns on the app.
JPG and PNGs are ideal file types to use with 8x10. They are natively handled on iOS.
iOS apps cannot handle RAW files, please do not try to use them.