I am new to posting here. I am shooting a film this upcoming week in winter conditions in South Dakota. I am using my own Eclair ACL camera with 400' magazine, a 10mm Switar lens and a set of Minolta MD mount lenses. I know this camera is very finicky. I have had to overcome light leak and flicker issues, problems that I believe I have solved in the latest test.
The test did have one major issue though. On the test, I used a cheapo MD to c-mount adapter and though we measured the focus in each shot (using measuring tape and focus pulling according to the markers on the lens barrel), the focus was often somewhat off (the focus often went in and out of correct focus on follow shots or was slightly off on non-moving shots). I was expecting a professionally made adapter from a camera tech, but it will not be ready in time for the shoot. My main question is, because the focus is not correct on the lens barrel, should I try focusing the shots by eye, that is through the viewfinder, or by the barrel on the lens somehow?
I've also done more testing to determine where the focusing could have gone wrong. I used the 10mm switar lens as a control (since it does not need an adapter) and compared the viewfinder image focus to the technically correct, measured focus. The focus that I was able to get by eye with this lens was almost exactly the same as the correct measured focus. (i.e. I measured a subject 1 meter in front of the lens, set the correct focus and turned the focus back in forth until it looked in focus in the viewfinder; the viewfinder focus was the same as the correct measured focus). I did this for a series of measurements with the lens and found that the viewfinder focus was always correct. I should also note that the diopter was locked down during the entirety of the test.
I then tried to determine to what degree the markings on the lens barrels was set off because of the adapter. Before testing the lenses on the adapter on the Eclair ACL, I tested that the focus markings were correct on my Minolta X-700 still camera. All of the lenses were correct except for the 24mm where the focus markings were set off before the measured focus (i.e. actual focus: 6 ft.; on lens barrel: 3 ft.). When testing the lenses on the Eclair ACL, the 24mm lens had the same incorrect variation that I had expected but the other lenses had unexpected results. The 35-70 mm zoom and the 75-210mm zoom had correct focus in viewfinder and on the focus markings, which seemed to indicate that the adapter did not set off the focus on the barrel. But the 50mm and 50-135mm zoom lenses' focus markings on the barrel were after the measured focus (i.e. actual focus: 30 ft; on lens barrel: 40 ft).
So from this test, I have a few questions: how could the adapter create different levels of variation in the correct focus on the barrel for different lenses? Is setting the viewfinder to the correct focus on the 10mm lens, not enough to determine if the focus is correct on the 35mm MD lenses? Is the viewfinder not reliable to determine the correct focus?
I am sorry for writing such a long-winded comment here but I also have a few more questions and concerns. I also have a Super 8 camera. If there is no way to determine the correct focus for the ACL should I use that camera instead? Also I have not loaded 400' cores on my camera before, only 100' daylight loads. Loading a practice roll in a changing bag was quite easy and it ran smoothly when I attached it to the camera. There is only one step in the loading process that I am concerned about. Should I gaffer tape up the feed side of the mag before taking it out of the changing bag or is it okay to tape up that side of the mag outside a changing bag or in a somewhat darkened room?