Different export filesizes for simulary raw files

Just wondering: had Noise Reduction maybe been applied to some of these photos? (I don’t mean using the sliders in Detail panel, I mean the generation of a noise-reduced version of the whole photo)

If you don’t mind sharing a couple of PSDs (one large and one small), I can take look at them.
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Hi,

Thanks for your idea, but no ...all files are treated in the same way ..exported as 8bit

that was the first thing what I checked ..because the size was suspicius 

and I also checked in PS if they really open as 8bit

so I think its a bug because I didnt find any diff when I compare these pics in PS

The large files are probably 16-bit files, which are twice the size of 8-bit files.
In the Export dialog there’s an option for Bit depth – 8-bit or 16-bit.
If you’re going to edit these files in Photoshop, 16-bit is strongly recommended.
It will give you plenty of editing headroom with little risk of image degradation.

If you’re using Edit in Photoshop, you’ll find the same option in Preferences > External editing.