File size changing??

[elsa hoffmann]

Something strange though which I have no explanation for -
A friend sent me a photo (converted in LR from NEF to Jpeg) - transferred the file to me thru Skype - and it is 4.6MB (I checked where I downloaded the file to - clearly says 4.6MB.
I then opened the file in Photoshop, and saved it to my desktop  without touching it or changing the name - now it's 15.1MB.
Another frienf mine checked -
his comments: I have noticed that PS saves a bigger file, I just rechecked and opened a 6.8 MB Canon 80D file in CS2, changed the file name only when "saved as" and now it 8,4 MB. Don't know why PS does this. I'v also noticed similar changes when Exporting the same file, full size, from raw to jpg from LR and Canon's DPP, LR saving the larger file size.
Explanation? any compressing somewhere?
I dont use LR so I cant check any settings

[Bjørn Rørslett]

Sounds like one set of specifications is for the nominal, uncompressed, file size. The typical 'jpg fine' setting tends to give 1/4 actual file size.

A file read into Photoshop will report the same pixel dimension whether it started its existence as a highly compressed or non-compressed file, but the sizes of the corresponding disk files can vary greatly.

[elsa hoffmann]

Thank you Bjørn

[Akira]

I consider this phenomenon rather normal.  whenever I process a jpeg file in Photoshop and save it as jpeg of the maximum quality, the file size will be more than twice as large as the original.

[elsa hoffmann]

I have never noticed as I almost never look at file sizes. It's not that it makes a difference to me unless I resize for the web. Thats th eonly size that matters.

[Bjørn Rørslett]

if your computer uses an expensive SSD for main storage, file size on disk becomes pretty important it seems.

[elsa hoffmann]

Bjørn yes - how "fast" SSD will become really cheap is another story.
My 2.5 year old Mac still doesnt have SSD - so I dont "feel" that part ($$$)
But if you work with images from a 96MP camera - I bet we would WANT that SSD 

[David H. Hartman]

I consider this phenomenon rather normal.  whenever I process a jpeg file in Photoshop and save it as jpeg of the maximum quality, the file size will be more than twice as large as the original.

This is my general procedure also. I feel this reduces the loss of saving a JPG to a JPG. I will make an additional more deeply compressed JPG for special purpose.