File size misreading

[swampcollie]

I export a large file to a limited file out of Lightroom with no problem. I limit the file size to less than 2.9 mb and get files windows reports are under 2.9 mb. However I am getting server 500 errors as if I am uploading large files. I opened one of the 2 meg files in photoshop and photoshop reports it is a 57 meg file. Not 2 megs. Is this some kind of metadata bug? It is actually a 2 meg file from the upload speed. But I suspect my server is being told that erroneous number by metadata. Dead in the water in my business because of this and not very happy with Adobe right now.

[johnrellis · Accepted solution]

I opened one of the 2 meg files in photoshop and photoshop reports it is a 57 meg file.

You're probably looking at a number in Photoshop that is the number of bytes for the uncompressed photo in memory, not the size of the JPEG file on disk (which is compressed).  For example, a sample JPEG file is 2.5 MBytes on disk, while Photoshop shows the following for Document Sizes in the lower left:

"22.9M" is the number of bytes the photo uses in memory while being edited by Photoshop.  The photo is 3264 x 2448 pixel, with 3 bytes per pixel (1 byte per color channel), which is 23,970,816 bytes. Evidently, Photoshop uses the old-fashioned "megabyte" units, where M = 1024 * 1024, so 23,970,816 = 22.9M.

[elie_dinur]

Don't confuse jpg compression and image resolution. The server has to decompress the jpg before reading it into memory and a 57 MB uncompressed size indicates that it is a high resolution 20 Megapixel image (around 3600x5400), probably still at the camera's native resolution and enough to choke the server. Moreover, even on a 4K monitor any browser would have to downscale it. Do the job yourself in LR; downsizing to something more web-friendly, like 2000x3000, and applying Output Sharpening when exporting the jpg (which will then be of better quality because it won't have to be compressed so much).