Unexpectedly large files after saving

[sklnner]

hi, i know this has been answered again and again but i failed to find a topic because most topics are about the reverse situation which can be described with the same set of words

so i have a jpg file with a filesize of 861 kb
i use
- Image > Map > Automatic Levels
- crop/remove a 3 pixels wide line of the top
- save as jpg

the result is 5746 kb which is more than 5x the original filesize
i get curious so i reopen the file and just save the file as jpg, no other editing
the result is 2734 kb which again is about 3x times the original filesize

why is the saved file filesize so large and what is the correct way to keep the filesize down?
thank you for your time

[cday]

Why is the saved file filesize so large and what is the correct way to keep the filesize down?

The settings used for saving are in the viewer, File > Format settings... -- Write tab

Rather hidden, I'm afraid, due to a limitation in the Qt tool set used, I understand...

[sklnner]

The settings used for saving are in the viewer, File > Format settings... -- Write tab
Rather hidden, I'm afraid, due to a limitation in the Qt tool set used, I understand...

oh thanks a lot, actually i should have seen that and not start a new thread about it

[cday]

The settings used for saving are in the viewer, File > Format settings... -- Write tab
Rather hidden, I'm afraid, due to a limitation in the Qt tool set used, I understand...

oh thanks a lot, actually i should have seen that and not start a new thread about it

It's not obvious, and contrary to normal save interface design, but I understand there is currently no solution in sight.

[Rambling Gracie]

Up until today, I've just picked a pixel size and wondered why the Output size was so large. Now, I want to understand your Write Tab discussion better. Is there a sizing rule of thumb to get best quality at smallest size?

For instance, after I crop a photo, what should determine best pixel size (I usually use either Longest or Shortest Side Mode) vs. the % Quality?

EXAMPLE: Should I go for lower pixels and Best Quality? Or higher pixels and, say, 75% quality?

And are there other settings on the Write Tab (none of which I understand) that I should learn about and consider? Like, Huffman table? Etc.

I'm sure there are endless factors to consider and countless outcomes...but a basic rule of thumb or starting point would be extremely helpful.
Thanks!