Your photo should have one of the supported formats, e.g. TIF or JPG. For good results we need an minimal size that is related to the print format.
On format selection page there is an symbol shown for each format to indicate the suitability of the picture.
The size of your photo affects the quality of the print. In the left picture you see what happens, if your picture is clearly smaller than the indicated minimum. The middle picture represents the quality for the indicated minimum. And in the right picture you see, how the quality can rise with larger image size.
If you upload your own photo, be sure to observe the following: Do not scale up small photos, just to get a green indicator in the format selection, the print will be blurry and pixelated almost certainly. Furthermore, an image that looks blurry already on the monitor, then also the print will look blurry.
The measures mentioned represent the minimum requirements, the print is getting better with larger images.
It is not necessary to increase or decrease the size of your image to reach the indicated minimum measures.
After you uploaded your image, the suitability for the respective formats is marked by an appropriate symbol.
For the multipart photo printing a coherent motive should be used, your motive must be present as a complete picture, without gaps. Avoid built up pictures for multipart formats, which are aligned to the widths of the picture parts, it cannot be guaranteed, that the gaps are accurately met, also the inner side edges of the picture parts would not match the actual motive. If you want to print several single motives, you should use the photo printing in the appropriate size for each picture separately.