nimblenuts wrote:
I am wondering how to determine the file size in Lightroom Classic for JPGs. The "export as" command doesn't give me a size option for jpg files and the files it generate are huge, like 20 MB. So I have to open again in Photoshop to resave at lower file size every time.
Aside from the suggestions offered as far as specifying the file size limit in Lr's export dialog, there are two other things you can do - resize the image to a smaller dimension (in pixels) and you can also adjust the quality. A 20 mb jpeg sounds like you are exporting full size jpegs at 100% (or near 100%) quality. Specifying just a file size limit will only adjust the quality, but will keep your original dimensions intact.
You can, and probably should create a preset for exporting, that will customize the image size, quality and size in mb.
You can save an image at 12 ppi or 600 ppi (or dpi, as Adobe likes to call it), and the file size and how it displays will be identical. The ppi/dpi number in the metadata is completely meaningless, aside from giving you an image size if you were to print it at that resolution.
Here is one image saved with different parameters -
The first is the full resolution image 9683x7346 px, or 71.1mp, saved with a quality setting of 60% and 300ppi, for a file size of 15.6 mb
Next is the same image saved with a quality of 100%, file size limit of 20 mb, 300ppi. The file is slightly smaller at 15.5 mb
The next is the same image as #1, saved at 12 ppi - the file size is exactly the same as #1 - 15.6 mb.
The next is the same as #1, downsampled to 2048 px on the longest side, quality 60% - file size is 2.4 mp
And the last is the same as #1, downsampled to 3600 px on longest side, quality 60% - file size 3.2 mp
For my purposes, the last two images load faster and look fine, even when zoomed in here in the UHH file viewer. There is really no need for a bigger file.
And as you can see with the 2nd and 3rd image. the ppi the image is saved at makes no difference whatsoever.