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simopane
Participant
May 19, 2023
Question

Saved Jpg is much smaller after editing a original jpg

  • May 19, 2023
  • 1 reply
  • 714 views

photoshop 24.4.1 - windows 10 
Hi all.
I have a friend that asked me to remove some spiderweb from a bird's photo.
He gave me a jpg file 150dpi , of about 10mb.

I removed the web, and I started to save as a copy.

I got the usual slider that ask me what size from 1 to 12.
Set on 12, I saved and the new file is 5.6mb .
I tried of course to save NOT as a copy, but is the same.
I tried to export - web - setting at 100 and I got a 6.7mb.
Not sure what's going on.
To be fair, I shoot my shots only in raw, and I process till to save in Jpg, so I don't have idea if the jpg I retrieve from my file should be bigger (heavier). 
Anyone can shoot some suggestions? 
Simone

This topic has been closed for replies.

1 reply

D Fosse
Community Expert
D FosseCommunity Expert
Community Expert
May 19, 2023

Jpeg file size depends on a number of factors. Compression level is just one.

 

The jpeg compression algorithm is much more effective on flat, smooth areas than it is on busy high-frequency detail. So image content and pixel structure has a huge impact on file size. These two are the same size and have been saved at exactly the same settings. The first one is 601 kB, the second is 77 kB:

 

 

When you open a jpeg it is decompressed back to full native size (if not exactly the same state). When you resave, the compression algorithm runs all over again from scratch. It doesn't "remember" the last compression. If you have made any changes to the image, it's unlikely that it will be the exact same size.

 

In short, jpeg file size means precisely nothing. It indicates nothing. All you know is that it will be dramatically smaller than the native size (at a price), but it's pretty much impossible to predict how much smaller.

    S
    simopaneAuthor
    Participant
    May 20, 2023

    Thanks for the answer, first of all.
    I hink I understood what do you mean, but still I find strange that, if photoshop decompress to the native size, a file that at the start was 10mb, I remove one line of  spider web, and I save with the max quality , why that file is not going to be : lets say 9mb... 8.5mb... 
    It is 5.6mb.
    Half of the native size saved at the start.
    What I'm trying to say, there is no dramatic removing or dramatic editing. Is just a clone tool on 1 line of web.  

    cheers 

    D Fosse
    Community Expert
    D FosseCommunity Expert
    Community Expert
    May 20, 2023

    The two sizes you're comparing are both compressed sizes. The native size will be up to tens of times bigger.

     

    I don't know how and in which software the first jpeg was saved. Maybe Photoshop's jpeg encoding is slightly more aggressive.

     

    This is nothing to worry about. Jpeg file size is by nature totally unpredictable and seemingly random.

     

     

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