Iq260 dark frame - what’s it actually doing?

So I was lucky enough to be able to add an iq260 and 701 adapter to my rz67ii. I’ve started testing longer exposures using this setup and it’s a great alternative to film.

i shoot the rz/iq260 like a dumb body(orange mode) and use a wake up, cable release and the leafs shutter (t) button on the lens. This is very similar to how I’d shoot film as long exposure.

however, when I end a film exposure in this way I’d cover the lens (hat, lens cap, jacket…) and click the timed lens button to end the exposure. But then shooting the iq260 this wast I don’t cover the lens as it needs to do the equivalent time dark frame, right?

so firstly, and perhaps a stupid question, but do I need to leave the lens cap off for the dark frame? Is it reading the landscape? Actually how can it be if the shutter is closed!? I’ve been leaving it off and clicking t but worried about camera shakd in the image.

Secondly what is the dark frame/back actually doing?

The dark frame is used to digitally subtract any artifacts inherent in the sensor itself to get a cleaner image. This is done with the cover on in most digital devices.