mamiya 645 pro focus problem

Discussion in 'Medium Format' started by brad_morgan|1, Jun 10, 2012.

  1. Hi.
    Ok, basically I have two mamiya 645 cameras (a pro and a super), two 80mm 1,9 lenses (both the older model sekor c and the newer N model), the 55mm and the 150mm 2.8N lens, and 3 or 4 different backs from the pro and super.. also a polaroid back.
    Now my problem is, I bought all of the cameras and lenses and parts from ebay or from private local sellers, and Ive been using my cameras for a little while on holidays, etc, and when i develop my films and scan them, I'm getting backfocus on most of my photos. I thought maybe it was my eyesight, so i bought the right diopter for my eyes, and now the focus screen is clear and crisp when I look into the viewfinder, but still it's backfocussing.
    So I decided to take print a focus test page and shoot a few photos of that with a roll of film i still had in one of my backs using both different cameras, and both 80mm lenses to see if i could isolate a problem with either one of the cameras or one of the lenses. I tried both lenses on both cameras with the same back, at about 1m distance from the test page. everything was backfocussed still (probably a good 5-10cm behind what I was actually focussing on. I focussed it by myself and then asked my wife who has much better vision than I, to double check it.
    So then I thought, maybe its the back, and I realised I still had a polaroid back with 1 last shot of instant film left in it, so i shot a picture with that, and its back focussed still.
    Now I guess my question is, what could possibly be wrong? Or what is the most common problem with these cameras that might be causing this kind of behaviour? I know that the mirror stop can move slightly, or the focussing screens can be in the wrong way around for some reason or another. But none of that makes any sense because when I set the lenses to infinity in either camera, the image in the viewfinder is sharp. The only slight abnormality I can find is that between both of my 80mm lenses, when in focus on the same point on the same camera, have slightly difference distance readings.
    I cant really afford to get my camera fixed professionally, so any help with how to isolate my problem, or maybe if I'm doing something wrong with my testing, would be greatly appreciated.
    Thanks
     
  2. When you look into the finder you are seeing the image formed on the finder screen. It needs to be positioned just so, and then that view matches with what would be occuring at the film plane. The screen may not be seated properly (upside down even, unlikely?) or it may have at one time been shimmed or adjusted for its height and no longer is.
    You need to verify if the film plane image is in focus when the viewfinder is (you have some evidence that it is not from your films). You need to arrange to have the back open and tape a piece of tracing paper, waxpaper or frosty scotch tape across the opening exactly in the plane where where the film would be.
    Focus the camera with the viewfinder, then put the lens shutter to 'B' and look at the image on the 'fake film' after the mirror flips up. It should be in focus, obviously. At that point you can play with the focus ring on the lens to see how much 'out' it really is while observing the image on the 'frosty' surface.
    My guess would be ... a mis-positioned finder screen is the culprit such that s the path length to the viewfinder finder screen (imaging surface) does not equal the path length to the film, and hence an out of focus issue occurs.
    Now, that fix may/may not be simple. If you have to go beyond this, or even have to ask the question, then the repair may be beyond your abilities to effectively accomplish (no offense implied). Some camera fixes are daunting and need special tools and techniques. Dirty Harry..."A man's gotta know his limitations." :eek:)
    That's my best guess. I use the M645 1000S, an earlier cousin of you bodies.
    Jim M
     
  3. Thanks for the reply Jim.
    I actually forgot to mention that I have tried the paper on the film plane method, but my results were kind of inconclusive because I wasnt sure exactly where the film plane is or if the paper was positioned correctly on it. When I open the back and take out the film holder, is the film plane flush on top of the rollers and unpainted exposed metal striped border surrounding the opening towards where the shutter would be?
    Ok midway through writing this I had the idea of taking the focus screen out of my 645 1000s (you mentioning that you had one kind of reminded me I had one also), and I put it in the back of my other camera flat on the rollers and tested it and everything is focussed through the finder and through the back of the camera, at the same time.
    So what can this mean? When I put film in the camera, the film isnt on the film plane? I have many different backs and inserts, but I can verify that it was back focussing on at least one back/insert, and my polaroid back.
    Im not particularly against fixing my own stuff though. Ive fixed squeeking canon A1's and siezed shut leaf shutters under, hard to remove lenses on some old rangefinders I have, and I only ruined like 1 of them... not that it means I'm awesome at camera repair, but attempting my own fix would mean if I fail I can get a replacement body for less than the cost to fix it anyway.
     
  4. Is it the same issue with both bodies?
    Does it behave the same with both bodies?
    Has the problem just started or have both bodies always done this?
    Does it occur with all lenses and always in the same direction?
     
  5. A common problem with the Mamiya 645 Super/Pro/Pro-TL series is the fragile mirror brake/rest. Check this first. It's the little "L" shaped piece of plastic with a spring around it to the bottom right of the camera body - as you look into the lens throat - that the mirror rests on. It has a tiny screw adjuster accessible through a small hole in the black baffle within the lens bayonet; or it should have! This under-engineered bit of plastic is prone to cracking and falling off completely, and if this vital little part is broken the mirror no longer comes to rest in the right place and so throws the focus out. To inspect the mirror rest/brake you'll probably have to use the Mirror-Up switch to properly see the condition of it.
    Symptoms of mirror-rest breakage are that the viewing screen shows near-correct focus at the bottom and is way out at the top. I've had this crappy plastic part break on two Super bodies so far, and it's a real pain to replace. I just hope that spares are still available.
    Brad, if that's not the problem then: a) You're lucky, and b) try removing and reseating the removable focusing screen. But be careful, the screen is delicate and can also easily be dropped onto the mirror while being removed or replaced.
     
  6. PS Brad. No, the film plane isn't across the guide rollers at the top and bottom of the gate. The image plane is on the inner pair of machined guides at the sides of the film gate. The guide rollers should actually be slightly sprung away from the body, and so don't have an exact position. However on many of the M645 cameras I've seen the springing becomes distorted and pushed hard back so that the small rollers are no longer free to rotate, but that's not how they should be.
     
  7. In repose to Philip:
    Is it the same issue with both bodies?
    I havent used the super for normal use yet, but I tested it next to the pro, using 2 different 80mm lenses, switching lenses between the two cameras, but using the same back... all test shots were about 5cm behind the target, which was less than a metre away.. it also happened with my polaroid back that I tested later

    Does it behave the same with both bodies?
    From the tests I described above, yes.

    Has the problem just started or have both bodies always done this?
    I bought them somewhat recently but I have noticed that most of my shots were out of focus... I bought the system to replace my pentacon 6 / kiev systems because I often had shots with shutter vibration... but the focus was fine on those cameras
    Does it occur with all lenses and always in the same direction?
    Both 80mm lenses I tested and it didnt change anything.. I havent tested with the 150mm or 55mm.
    In reponse to Joe:
    The mirror stop seems to be fine on both the pro and super.. they seem to be sitting in the same position.
    I also double checked the film plane today with my ground glass and made sure that it was resting perfectly on the machined guides, with the ground glass facing towards the lens.. the image in my viewfinder and on the ground glass at the film plane were both in focus.
    Honestly I'm a bit confused... if the viewfinder and film plane are both in focus at the same time, could there be anything wrong other than something to do with the back or the inserts? But when I change back the problem still seems to be there..
    I get the feeling Im going to have to blow a few rolls of film doing nothing but testing every possible thing I can imagine..
    Hopefully I managed to answer all questions aswell.
     
  8. Brad-
    Your cameras may have poltergeists :eek:)
    1. Is the film pressure plate 'springy' and able to push the film flush to the appropriate place so that it's in the right plane, i.e. same plane you imaged with your ground glass? The pressure plate when at rest should pretty much be flush with the edges of the insert, and that is a bit above the rollers. (it's the same as my 1000S inserts (same model part number for the Pro, ProTL, Super, 645E and 1000S according to B&H website)
    2. You are inserting the film insert all the way in, in the proper orientation, until it clicks into place, right? Also, you have threaded the film correctly, right? Just to eliminate any obvious issues.
    3. You are using 120 inserts with 120 film, I presume?
    Beyond these grasps at straws, I'm flummoxed.
     
  9. Brad. Thanks.

    I assume that it is focus in the viewfinder and since you know what you are doing we can probably rule out focusing
    screen issue. In addition since it is consistent and with two lenses and bodies this leaves the film back or insert. So a
    Jim says check that all is well here and perhaps check the insert is the correct one as Jim says in 3 you may have a 220
    insert with 120 film?
     
  10. Brad, let's now assume that the viewfinder and image plane are completely in alignment. For the film to be focusing more distantly than the viewfinder image, the film would have to be further forward than the image plane - i.e. closer to the lens. This rules out slack in the fixing between back and camera body, and tends to rule out insufficient pressure-plate pressure as well. The only thing left that could cause such an effect would be bulging of the film toward the lens - not likely, and I'd say pretty near impossible given the design of the film back and insert.
    Only other thing I can suggest is to take a few pictures of a really distant object, say the moon, with the lens(es) set to infinity and ignoring the viewfinder focus. This should finally rule out misalignment between viewfinder and film plane. If the pictures are sharp, then you need to examine the viewfinder alignment again. If not, then the film is bulging or otherwise misplaced in the film gate.
    Oh! One last thought. If this ONLY occurs with the F/1.9 lenses at close focus, it could be down to the lenses themselves. Many wide aperture lenses exhibit a focus shift on stopping down, especially when focused closely. The residual SA causes a spread of focus that can fool the eye into setting the wrong focus. When the lenses are stopped down by a stop or two the SA clears up leaving an incorrectly focused image. Try focusing the lenses with the A-M lever in manual atf/2.8 or f/4 and see what happens.
     
  11. I have the solution :) Please pay attention. I had the same problem but I solved it.
    Your focusing screen is wrong

    But don't worry, you don't have to replace it, a piece inside the focusing screen is inverse.
    1. Remove your view finder...
    2. Find and remove your focusing screen
    3. Carefully unscrew the pair of screws and you will notice this pieces
    -2 little plates with an screw hole
    -1 curved glass
    -1 flat glass
    4. On the flat glass, notice it has two different sides, one is matte, the other bright.
    5. reinsert the flat glass first, now inverted. The matte side has to be the one looking outside and the bright has to be in contact with curved glass.
    6. screw everything again...
    7. MAGIC... it really worked for me, I tested it using both adjustments and I finally can focus with my eye.
     

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