Today’s Question: I would like to use a printing service for some large metal prints. The printer will only accept a file size under 32 megabytes, but some of the images I would like to have printed are in the 38 to 39 megabyte range. The printer’s suggested solution is to change the resolution to 150 pixels per inch. Yet the same printer suggests a minimum resolution of 300 pixels per inch for metal prints. I am wondering if I should gradually lower the resolution in the Lightroom Classic export process until the file is under 32MB. Would that work?
Tim’s Quick Answer: I recommend contacting the printer directly to convince them to allow you to send larger files, or to find a different printer who doesn’t place this limitation on file size.
More Detail: Granted, you can achieve good print quality at 150 pixels per inch, especially if the final image will be displayed in a location where viewers won’t be able to get right up to the print. And in fairness, a metal print does lose a bit of detail as part of the printing process, which makes it somewhat reasonable to use a resolution of 150 pixels per inch.
However, I recommend sizing images for printing at the highest resolution supported by the output process. In most cases for a metal print, that resolution would be around 300 pixels per inch.
I consider the file size limitation of 32 megabytes to be arbitrary and frankly silly. An image saved as a TIFF file in 8-bit per channel mode would exceed 32 megabytes at an output size of a little under 13-inches by 10-inches at 300 pixels per inch. That’s not what most photographers would consider a particularly large print.
You could reduce the file size a little more by using ZIP compression for the TIFF file, which is lossless compression. Otherwise, for large prints, the only way to get the file size down without compromising on resolution would be to save as a JPEG image file, which I consider to be a bad idea especially for large prints.
So, again, I suggest having a conversation with the printer to find a way to submit a larger file size, or finding a printer that is able to accept file sizes commensurate with the output size being produced.