JPEG image of 4MG ending up as 300 MB after photoshop edit

[jackiev44588623]

I use LR for initial edit (jpeg), then export into PS from there. The resulting files end up as 300MB psd's? Does this for all files.

[davescm]

JPEG uses agressive (and lossy) compression to reduce filesize. It is great at reducing filesize in order to send files over the web, but should never be re-opened and re-edited as the image losses and artifacts from that lossy compression are cumulative and unrecoverable. Jpeg also only handles one layer.

PSD files handle multiple layers and the compression, if used,  is lossless i.e. all image information is recovered on re-opening. It is therefore a good format for master files that may need to edited later. You can choose whether PSD uses any compression in Preferences>File Handling. The other choice in there is Maximise compatibility which saves a flattened version of the image in teh PSD file which is used by Lightroom. Personally I choose not to compress PSDs as the larger files open faster as no decompression is needed. Disk space is cheap , my time is not.

Dave

[Stephen_A_Marsh]

Helpful information would include:

Color Mode (such as RGB)

Bit Depth (such as 16 bpc)

Pixel Width (such as 1920 px)

Pixel Depth (such as 1080 px)

Number of Channels (such as 3)

[jackiev44588623]

5472px x 3648 px

240ppi

16 bit

sRGB

So here is an example of what happens: JPEG file is 4M. Will use' Edit In' from LR into PS 2020. (if I save STRAIGHT from there back as jpeg for experimentation, it doubles in size without anything being done to it)

If I run an action and end up with 6 layers and save as psd the file will save as 300M. If I flatten, it ends up around 120M.

I am a fairly experienced photographer and have been using the software for many years. I do understand that psd's end up much bigger than jpeg and how and why but I think 300M for a single file is a bit excessive is it not?

[Test Screen Name]

Doesn't sound at all excessive. Lets see, you have six layers, so you need 7 copies of the data stored in the PSD. Compression is minimal, so we have 7 x 5472 x 3648 x 3 x 16 / 8 bytes = 838,397,952 (800 MB). To its credit, it is much smaller than that. As people have said, JPEG is GOOD at this. Your original 5472 x 3648 RGB 8 bit image will use 5472 x 3648 x 3 = 59,885,568 bytes = 57 MB. The JPEG at 4 MB has been compressed to 7% of that, rather much for best quality I think.