PNG files must be at least 300 dpi with a transparent backround or Vector Format. If your file is not 300 dpi, you cannot just increase the resolution of the file. This is called “upsampling” and will result in a blurry image. If you are creating your file in Adobe Illustrator or another Vector-based software, just size your image to the size you want it to print.
Half Tones: Please allow us to halftone the images for you. If we do not control the halftones, we cannot guarantee the quality of the print. We do understand that some designs are complex and will require separation fees, as a client you may be inclined to try to separate or halftone the image yourself to try to keep your cost as low as possible. Unfortunately this does not work. Our computers in the art department are calibrated to set the halftones specifically for the films and screens that we use for printing. Often times if you try to separate or halftone the image yourself it may cause more art charges than you would have originally incurred.