Could you please share your insight on these questions I am having? I have tried to find answers to them by searching previous threads on this site and on other photography discussion forums, but I still have not reached the answers I seek. All of them are about the M645 1000s. 1) Does the use of extremely long exposures via cable release in the bulb setting drain the battery? I am thinking of exposures in the realm of 20 minutes and even an hour. I have done that sort of thing with my other cameras, all of which are entirely mechanical, and I would like to know if the B setting on the M645 1000s is battery-independent. The user manual offers two methods of doing long exposures, one of which involves removing the battery from the chamber(!). That makes me wonder why on earth the manufacturer would recommend such a peculiar way of going about it. Maybe it is implied that the battery might be drained by the conventional method, but it's not clear from the manual because the wording does not explicitly warn against keeping the shutter open on B for long durations of time, so I cannot settle this question on my own. 2) Is it a sign of impending mechanical failure if the film advance crank/knob randomly switches between requiring a single 360 degree rotation and two 360 degree rotations to advance a single frame? On the second-hand body that I tried, the film advance switches between these two modes intermittently with no discernible pattern. That leads me to worry that there might be something wrong with the gears inside the camera because the user manual shows only one 360 degree rotation for advancing one frame. Is this deviation from the ideal something I can safely ignore? Have other users of the M645 1000s on this forum observed the same behavior? 3) Is it still possible to buy the original Mamiya focusing screens # 2 (plain) and # 3 (grid) as "new old stock" from a reputable supplier? Did Mamiya originally sell focusing screens in a matching hard case in the way that the 120 and 220 film inserts are usually kept? Ebay at this time offers either used (i.e. scratched and dim) samples of the screens I'm looking for or seemingly brand new samples of these screens: # 1 (microprism center) and # 5 (angled split image center with microprism doughnut). I've tried the # 5 screen, and indeed it is a good screen for general use, but I would like to use the # 2 screen for extreme macro and the # 3 screen for landscape and architecture. 4) What is the length in millimeters of an "Auto Macro Spacer"? This extension tube is officially intended to be mated with the 80 mm f/4 Macro lens for use between 1:2 (half life size) and 1:1 (full life size), but the ebay prices for this little accessory are too inflated in my opinion, and KEH does not have this item currently in stock. I have the 3-piece macro tube set already, so I am wondering whether the length of the Macro Spacer is the same as the "Auto Extension Ring No. 3-S". (What does the "S" in the name signify?) I measure the length of that individual tube to be 33 mm. Also, the length of all three tubes linked together measures 70.5 mm. (As a completely irrelevant aside, the distance from the film plane indicator to the front of the lens mount of the camera body measures 65 mm.) 5) Does the "switch ring" of the 80 mm f/4 macro lens alter the inner air spacing between the two halves of the lens for better optical performance in the region 1:2 (half life size) to 1:1 (full life size)? It seems that way from using the switch ring while looking into the lens with the aperture stopped down to f/16. The extra air spacing seems to be exactly 1 mm, and the entire front half of the lens assembly (everything in front of the aperture) seems to be moved forward by that amount when switching the ring to the "spacer" mode. Does this fact complicate life when trying to use the lens for magnifications beyond full life size (e.g., twice life size)? Should one use a reversing ring in that case for best results? This is completely different from how the 100 mm f/4 Macro Takumar works in the 35 mm format. With that lens I measure the displacement from infinity focus to 1:2 (half life size) magnification to be exactly 50 mm, which makes perfect sense because 50 mm is half of 100 mm. With the 80 mm macro lens for the M645, the displacement from infinity focus to half life size magnification is only 21.5 mm, which I find surprising. I can certainly appreciate that a shorter displacement makes macro photography more manageable in 645, but I think one would be confused initially by some of the counter-intuitive consequences of that optical compression when one tries to use the lens outside of its intended design. It also leads me to wonder if this idea has been replicated by any other manufacturers of macro lenses for 6x6, 6x7 or large format. 6) Is lens separation a common fault in Mamiya-Sekor C lenses for the 645 format? I have seen three lenses that exhibit that defect. What I have seen is of a consistent pattern. Usually the separation is close to the perimeter of the optics just behind the first lens element. The separation looks like an elliptical crescent. I've compared that with sample images posted on the website of S K Grimes of other lenses that have the same defect. It looks exactly the same. It is lens separation for sure. Does it degrade image quality appreciably? One lens that has it to a worrying degree is a 300 mm f/5.6 which was classified as "LN-" by KEH. I am contemplating returning the lens, but I am still undecided about it. 7) The engraving on the right hand scale of the bellows lens hood makes no sense to me. The sequence is messed up. From right to left it reads: 300 (middle), 150 (middle), 110 (above), 210 (below), 80 2.8 (above), 70 (below), 80 1.9 (above), 55 (below). The reason I am confused by that engraved sequence is that the additional mask you have to insert clearly states that it's intended for the 150, 210 and 300 mm lenses. So shouldn't the engraving sequence look like this instead? 300 (middle), 210 (middle), 150 (middle), 110 (above) etc. And why is there a left hand scale with these markers? From right to left it reads: 2.4 X 3.6 (middle), 4.5 X 6 (above), 6 X 6 (below), 6 X 7 (middle). Why would anyone try to use this bellows hood on any other camera even if it were possible with a step-up filter adapter? The aspect ratio of 645 does not match the aspect ratio of 35 mm or of 6x6. And with the Mamiya RB/RZ67 I would expect that an entirely different bellows hood would be offered since the focal lengths used on that camera differ markedly. Nowhere in the user manual is there any explanation to clarify the intent behind these two scales of the bellows hood. What information am I missing here? Did the bellows hood originally come with a sheet of paper that explains all of this? Thank you in advance for your replies.