Resizing pics with thumbnails/previews.

[Mk1st]

I take loads of pictures for my work as an energy auditor, mostly of the same routine things in new houses and like to keep them as small as possible, both for storage/transmission purposes and to keep my pdf reports small. They only need to be large enough to view on a small computer screen, huge zoom-in detail not required.

I take the pics using a canon G12 point/shoot camera set at it's lowest resolution (1600 x 1200 @ 180x180 dpi),

then when I transfer them to my computer I resize them down to 800 x 800 @ 30x30 dpi

with this first resizing a folder of 48 average pics from the camera will go from about 20MB down to around 4MB. Great,

UNTIL.... I add the thumbnails and previews, when the size of the folder then becomes 83MB!!

This is the same whether I use the native Finder commands in an Automator script or by using the Graphic Converter "create thumbnail & preview" command.

My question is...why does the resulting file and folder sizes end up being 4 times as big??? and, is there a way to reduce it? I've not found any settings for these, except a few in GC but changing these has no effect.
I know in this day and age of endless cheap storage it seems weird that this should be an issue to me, but I'm into efficiency (my job!) and want to keep from filling up storage unnecessarily. Plus I do take thousands of pics and processing them is just that much faster when they are smaller.

thanks!

[forum_adm]

Thumbnail/previews in the resource fork are not required since many years. The Finder and also the GraphicConverter browser creates temporary previews for the preview.

So, just do not create legacy previews.

Which macOS do you use?