Mamiya C330 lens with dust inside and its perfomance

Discussion in 'Medium Format' started by alexey_stepanov, Oct 24, 2007.

  1. Hello, I was shooting about a year with Mamiya C330f and 80/2.8 lens (black version). A while ago I bought Contax 35mm system for fast shooting purposes. The quality of prints from Zeiss lenses impressed me a lot and I began small "research" about real performance that my Mamiya can produce. I picked up and read carefully an excellent Barry Thornton's book "Edge of Darkness: The Art, Craft, and Power of the High-Definition Monochrome Photograph". The book impressed me so much and made me in half a year change my technique. Now I'm shooting almost always on tripod and developing my HP5+ films in Perceptol 1:2. However I began to notice that my prints (and negatives) are not sharp. I read a lot about Mamiya C330 lenses and most agree that they have very good performance. I checked almost everything that can affect my negatives sharpness. Except the 80/2.8 lens. What a fool I was! After checking taking lens through the light I found out that there's a big amount of dust inside it. Can this affect the sharpness and overall performance of the lens dramatically?
     
  2. No. Something else is amiss with your C330.
     
  3. your top to bottom lens may be out od alignment.
     
  4. Let me clarify; the viewing lens shows sharp while the taking lens may be slightly off. One of the pitfalls of twin lens systems. I had this happen once. Get the C330 checked for alignment.
     
  5. Thank you both for answers. I will try out to get it checked. I suspect if it is the case, then I could test it by photographing a ruler at 45 degrees angle or so. Right?
     
  6. no. As long as you are not focusing through the taking lens, you can not be sure of accuracy.
     
  7. Sure you could. Focus with the viewing lens, see how far out the ruler is on the processed negatives. Do it fairly close and at maximum f/2.8 aperture. Often I rule a vertical line on a sheet of paper at the focus point which is easier to focus on than the rule.
     
  8. "... I found out that there's a big amount of dust inside it. Can this affect the sharpness and overall performance of the lens dramatically?" It will reduce contrast from the increased light scattering. This means details with just small tonal separations will be harder to resolve. Perhaps this is what you're seeing; dust should not affect absolute resolution at all though. Try shooting a high contrast test target like laser printed text on white paper. Shoot a whole roll with the 6th frame in focus as indicated by the viewing lens. Rack the focus ahead and behind this for the other frames. If the 6th frame develops to be the sharpest of the series, then your camera's fine mechanically. I don't like the ruler idea for TLR's because of parallax issues. I'm not sure whether even a paramender will give the accuracy of correction needed. Ummm, one last thing. You're not shooting wide open at f2.8 right?
     
  9. "Try shooting a high contrast test target like laser printed text on white paper. Shoot a whole roll with the 6th frame in focus as indicated by the viewing lens. Rack the focus ahead and behind this for the other frames." Thanks! I'll do that. Is it better to do it with 2.8 or with 5.6 for greater resolution (depth of field will be bigger though)? "Ummm, one last thing. You're not shooting wide open at f2.8 right?" No. I'm using 5.6-16 range for most of my shooting.
     
  10. Shoot f2.8 for the focus test. You want minimum DOF to reduce the amount of sharpness ambiguity between adjacent frames. "No. I'm using 5.6-16 range for most of my shooting." Sure, that's fine. It just wasn't clear from the original post whether you were expecting unreasonably sharp pictures at f2.8. As you know, most lenses are at their best a couple of stops down from wide open.
     
  11. Another thing that can affect focus is the calibration of the focusing screen to the plane of focus. The focusing screen can be adjusted with shims. One way to test whether the taking and viewing lenses are in sync, or the screen is in sync is to put the camera on a tripod, focus on a subject or object using f2.8, and open the back of the camera. Take a piece of tracing vellum cut to fit the film gate where the exposure is made, tape it in place, put a dark cloth over your head and use a loupe to examine the object. The two images (through the viewfinder) and the image you see through the vellum should be identical in sharpness. If you don't have tracing vellum you could also use a curtain of frosty Scotch tape. When using the loupe, you would have to do so gingerly so you don't press past the supposed plane of focus. I used to make a "roll" of 120 vellum/film so I could do such a test and have the vellum be pretty taut. Also examine your front standard. I have had the front standard jump a tooth on the rail that it runs on, causing blurriness on one side of the image.
     
  12. Do a seach and check the back posts. The rubber seal around the screen frame is shot, causes misalignment. Very Very seldom is a Mamiya C series lens mismatched as a set, nearly every older C 330 body has this common, common problem. Don't mess with the lenses until you do the screen surround.
     
  13. It is easy to get rid of the dust inside a C-series 80 mm (and 55mm, haven't tried this with others): the whole front lens group is removed by simply twisting it counterclockwise. The dust is on the elements nearest the shutter and diaphragm. When you have removed the front lens group, simply clean it and then set the shutter on "B", and then you can clean the dust from the lens surface behind the shutter. I have done this several times. But if you are not comfortable with this kind of stuff, leave it to someone else. Disclaimer: if you harm your lens, it is your own responsibility.
     
  14. Thanks you all for your answers! What an informative forum!
     

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