Hello,

I've been using Holy Grail method with Qdslrdashboard on Canon R5 camera. The shutter speed increased to 20 sec and my stable interval was 22 sec with external intervalometer. I used 50 iso at the start of the lapse, and set the iso to increase to 800, but it did not change at all, so I had to change it by hand. Where could be the problem?

Can you control ISO on the camera via the qDDB ISO control when not shooting Holy Grail?
If not, there might be an issue with the specific support of that camera and you'd need to contact the developer via https://dslrdashboard.info

If the ISO control works, it might be a bad setup, for example dark time too short (Interval - Longest Exposure) so that qDDB doesn't have enough time to control the camera. Setting a lower max Shutter time then should help.

Thanks, I will try to control ISO at first without using Holy Grail. When using it I wasn't able to control ISO. You mean 2 sec dark time can be too short? Ok, I will try everything and will write if it works.

I think 3 sec dark time is working and I can control ISO now. But it's sad that there are 3sec lost between shots. Probably I need another solution to make it shorter. Is it even possible? If qDDB reads files at that speed there is no way to speed it up? Probably JPEG files that R5 brings are too huge.

Set the camera to RAW+ Jpgs (small) if possible. qDDB doesn't require large JPGs. Make them as small as possible.
With Nikon DSLR and such a setting, a dark time of 0.5 secs is possible.

I was using the largest jpeg files, so probably dark time was longer than it should be. It should be much better now. I will wait for a clear skies and will try how qDDB will read the files now.

You should do tests at home until you have everything up and running before (!) going out for any serious shooting.
Just close the window blinds to simulate day to night.

Thank you! Good idea, I will try.