Today’s Question: After photographing with my iPhone I would like to post-process the image in Photoshop. The only way I know to do this is to export the image from Apple’s Photos application which gives me two options: “Unmodified Original” or simply as JPEG, TIFF, or PNG. Which do you recommend if extensive post-processing is intended? The unmodified file was JPG at 1.8 MB and the TIFF file was 34MB, but all other characteristics were the same, such as pixel dimension, and color mode.
Tim’s Quick Answer: In this type of scenario I suggest exporting as a TIFF image, since you will likely want to save the final result from Photoshop with various layers intact. Also note that choosing a file format rather than “Unmodified Original” will also ensure that adjustments you’ve applied in Photos will be included as part of the exported image.
More Detail: In this scenario the original capture was a JPEG image, rather than the newer HEIC format or an Adobe DNG file (such as for images captured using the Lightroom CC mobile app). That means you are starting out with 8-bit per channel data, and pixel data that has been compressed to reduce file size. In other words, you aren’t starting out with an image that was optimized for image quality.
In concept that means you could continue working with a JPEG image, since that is what you started with. However, applying significant adjustments and possibly re-opening the image several times to make revisions can have a further negative impact on image quality.
If you are going to process a JPEG capture there isn’t a significant benefit to converting to the 16-bit per channel mode, because you have already started with 8-bit per channel data. However, you will likely want to take advantage of adjustment layers and perhaps additional image layers in Photoshop, which would require a TIFF or PSD file format.
In addition, converting to something other than a JPEG image will ensure you are applying additional image compression when the image is modified and re-saved. That additional compression can further degrade overall image quality.
So, since you would likely want to save the final result as a layered image in Photoshop, to me it makes sense to convert to a TIFF file right from the point of exporting the image from the Photos app. Note, however, that you can choose to have that TIFF image in the 8-bit per channel bit depth, which will provide a TIFF image that is half the size it would be in the 16-bit per channel mode.