santino
FSU gear head
This is only logical. You are saving an compressed image in an uncompressed format (file size increases, quality does not).
Coldkennels
Barnack-toting Brit.
You'd be better off saving it as a .psd if you're using photoshop - if all your modifications are on layers, you can work non-destructively unless you flatten them down/merge them.
As an experiment, I saved the same 5000 x 3500 px 8-bit greyscale image in four formats to compare file size:
JPG: 7.7MB
PNG: 7.6MB
PSD: 16.8MB
BMP: 17.9MB
The .psd file size would increase the more you add to it, but I still think it's a better move than working with bitmap files in the modern age.
Also, it's worth noting you're not actually gaining anything by converting a .jpg to a .bmp; the data lost by saving it as a .jpg in the first place cannot be regained. However, minimising the amount of times you save a .jpg is always a smart move - every additional save increases the amount of data lost until you end up with a hot mess like this:
Ko.Fe.
Lenses 35/21 Gears 46/20
I have zero issues to use cameras specific raw files. As long as lightroom is newer than camera. 
To me it means LR from 2016 v6 , last stand alone.
After 2016 cameras, except Leica made, I need to use Adobe free converter to have files as DNG.
But I got rid of cameras like this.
To me it means LR from 2016 v6 , last stand alone.
After 2016 cameras, except Leica made, I need to use Adobe free converter to have files as DNG.
But I got rid of cameras like this.
seany65
Well-known
coldkennels, I'm not using photoshop and due to the fact that neither program I have came with a manual I don't work in layers because I don't know how to and I'm not sure if the programs I have can.
I learned the hard way about saving jpegs over jpegs when many years ago I had pic I quite liked but it was rather "Pixelly", not grainy but sort of looked a bit like a mosaic, so I tried to use the clone tool clone out "wrong coloured" pixels one at a time (lol!) and due to having an 18gb hard drive with windows xp at the time I kept saving the "worked on" pic as a jpeg on top of the previous version. Pretty quickly each new version took on more of a patterned look as the pixels began to form into a sort of "square" which looked odder with each new save, not quite like your example though.
I learned the hard way about saving jpegs over jpegs when many years ago I had pic I quite liked but it was rather "Pixelly", not grainy but sort of looked a bit like a mosaic, so I tried to use the clone tool clone out "wrong coloured" pixels one at a time (lol!) and due to having an 18gb hard drive with windows xp at the time I kept saving the "worked on" pic as a jpeg on top of the previous version. Pretty quickly each new version took on more of a patterned look as the pixels began to form into a sort of "square" which looked odder with each new save, not quite like your example though.
JoeV
Thin Air, Bright Sun
When working with JPEGs using SAVE AS and appending a letter or number to the file name after each iteration leaves the original file unmolested; all the changes you made are applied to the new file name, not the original.
seany65
Well-known
JoeV, Yes, you're quite right, and I still do that with bitmaps. I save when I want a break from it, when I've made a change that I'm not sure about, when I've done a bit of work and then decide to try something I'm not sure about, or when I think I've finished working on a photo, or when I'm moving the photo to the other program which does something better. This allows me to compare each version in windows slideshow which is paused so I can go backwards and forwards, sometimes quickly, to compare versions. I can end up with a dozen different versions.