Occasionaly the save may leave out the Jpeg format. inconsistant results.

Question

Hi. I opne small 200K to 1meg Jpeg and Jpg images, the upsize them byt 4 to 6 times in Gigapixel. resulting in images from 25 to 50 Megapixels. Norlay i save images in Photoshop Psd format, but when i want to run them images through other programs, i Save as plain Jpeg. problem is that several times the save format options does not display ordinary Jpeg or Jpg. i get the below options only. why.?

Regards, Sandy (photoshop 27.10.0., Mac Mini M4 Tahoe 26.6.2) (I do make very large prints, up to 1 Tb as i have a large format printer, but most in the 50 to 100meg)

D Fosse · Answer

It’s very consistent: If you’re adding properties to the document that do not conform to the jpeg file format specification, jpeg is not in the list.

The jpeg specification does not support layers of any kind, 16 bit depth, transparency or alpha channels. Few people realize what a limited format jpeg is - basically anything you can do to a file in Photoshop will put it outside the jpeg specification.

Also, you do not need 300 ppi for large format prints, that’s a common myth. They will be seen from farther away, and the resolution requirement drops accordingly. A billboard can be as low as 10-15 ppi and still look perfectly crisp and sharp.

Upsampling will always degrade quality. Nowadays there is much buzz about AI resampling, but be aware that this will always produce an entirely new image, with added details that may be totally unrelated to the original. If authenticity matters, AI is not the way to go.

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