JPEG -> PSD gives 10x size increase?

i looked around @ bunch of old threads psd size bloat , didn't clear answer.

 

if open 2.6mb jpeg in photoshop cc , save psd no changes, 26mb psd.

is normal , expected? seems bit...much.

 

(of course application little more complicated, not much. opened jpeg, masked 2 areas , applied adjustment layers. wanted save psd save workflow, information in mattered mask regions , adjustment layer settings.)

 

of course photoshop should not storing raster data lossy compression in general case, it's easy see why file size same saving lossless-compressed tiff. on other hand, lossless jpeg2000 of same file 6 mb.

 

but guess expect jpeg opened in ps no changes background layer preserve data in jpeg format file-size reasons,

at least until or unless user did transformation on layer require changing jpeg data.

 

so, what's deal? , why psd compression worse lossless jpeg2000 compression?

 

thanks!

 

p.s.: don't think matters much, image is

jpeg 4032x3024 4032x3024+0+0 8-bit srgb 2.381mb 0.000u 0:00.000 

 

p.p.s: theoretical question. don't actually need reduce file size, just…want to.

you right, compression plays big role. there more it. jpg not support layers, transparency, masks, layer effects , on. each layer added including adjustment layers , masks bloat file size.

difference between psd , tiff compression scheme. way better others.

other that, more technical answer.

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