When addressing image resolution, there are a few things you need to know…
Born Digital are images created with a digital camera. We recommend that your ﬁles be kept or converted to 16-bit mode (16-bit grayscale or 48-bit RGB). If you are using a color-managed system or have a professional retoucher, you may send us the retouched ﬁle without interpolating the ﬁle to a speciﬁc ppi. We will scale the ﬁle as necessary when printing.
Scaling Your Image
Scaling your image file up is not required for our modern printers that do this internally with algorithms best matched to the printer. Some software purports to improve image quality through scaling. We do not recommend that this be used to enhance details that, in reality, were not captured in the image. There is no software that can create detail where it does not exist. The only solution is to return to the scene or event and re-photograph it in a higher resolution.
You may want to scale your images to a consistent size if you are applying special effect, grain or other filters so you achieve a consistent affect across images. Two images both printed at 20×24 inches, but one image is at 180 ppi and the other is at 240 ppi, with the same grain filter will have a different grain effect when printed. To achieve a consistent effect the ppi of the smaller file should be adjusted to the same as the larger file.
Large prints may print beautifully when they are scaled up from 72 ppi by our printers, depending on the subject matter. When the subject matter is soft with broad tones and no ﬁne details, it is more likely to meet the best visual standards, even when printed with signiﬁcant scaling. Conversely, an image with ﬁne details may not print with acceptable quality if the original resolution falls below 200 ppi for a given print size regardless of how you scale the image to 300 ppi (printing level).
Photographic Film Scans
Need higher resolution, shoot large format film. Large format film (4×5 inch or 8×10 inch) used with the proper technique and lenses can provide more detail and color quality than most digital cameras and usually at a lower initial cost. If you are planning on shooting hundreds of super-high resolution images, then the economics switches back to a super high resolution digital camera. Large format film will not be available in the not to distant future, so do this while you can.