Image File Types Your image file must be in either:
• JPEG format
• TIFF format in RGB color space
What's RGB color space?
TIFF files are formatted for one of two "color spaces": RGB (Red, Green, Blue) or CMYK (Cyan, Magenta, Yellow, Black). To make sure your image file is in RGB, check the file info or image settings in your image editing program.
Image File Resolution
Your image file must be at a resolution of at least 300dpi (dots per inch). For larger print sizes, higher resolution is preferred.