OK, tried to attach this to the other thread but its closed. I can solidly confirm this has NOTHING to do with ACP. I've been in touch with Andor in Belfast today and they duplicated what I'm seeing too. Turns out that if the subframe is less than about 100 by 100 pixels no data is being sent. They had me go through ever larger subframes until data was received and at 100 by 100 I'm back in business. I sent them a huge pile of data and am awaiting their response and or solution to this. This is not a problem with the Alta series as I used a U 16M for years no problem. I must say this was a very big surprise and I would NEVER EVER EVER have diagnosed this without Bob's superior knowledge and even better customer service on a SUNDAY to boot!!!!!!!!!!!! Thank you Bob Denny