File Size versus Print Size


Today’s Question: If a TIFF file is much larger [compared to a raw capture], does that mean you can also print much larger without any loss of resolution?

Tim’s Quick Answer: No, because the file size of a TIFF is not due to greater resolution, but rather due to the nature of the file.

More Detail: Today’s question was a follow-up to a prior question about the large size of a TIFF file created by sending a raw capture to Photoshop from Lightroom Classic. As I explained in my answer to that question, a TIFF file created from a raw capture will generally be about three times larger than the original capture.

While an image with greater resolution will have a larger file size, that doesn’t mean that a larger file size automatically means there is greater resolution in the image. In other words, just because an image has a larger file size doesn’t always mean it can be printed at a larger size with equal quality compared to an image with a smaller file size.

In the case of a raw capture compared to a TIFF file, the reason the raw capture generally has a file size that is one-third the size of the TIFF image is that most raw captures don’t contain full color information for each pixel. Rather, in most cases each pixel will only have a value for either red, green, or blue, not all three. Because a TIFF file would have all three color values for every pixel, the file will be about three times the size.

Similarly, if you had added additional image layers to an image in Photoshop, such as when creating a composite image, the file size would be larger but the image couldn’t be printed any larger without degrading quality.

Another example going in the other direction would involve saving an image as a JPEG file. Even though the file size would be significantly smaller, the image could still be printed at about the same size as the source image, with the caveat that the print quality would be degraded at least slightly based on the JPEG compression.

Ultimately what determines how large an image can be printed with good quality is the resolution of the image, meaning the total number of pixels in the image. While a raw capture generally doesn’t contain full color information for each pixel, it can still be thought of as having the full resolution represented by the image sensor. The raw capture just needs to be processed to generate the full color information for all pixels.