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Mamiya C330 lens with dust inside and its perfomance

Alexey Stepanov , Oct 24, 2007; 05:27 a.m.

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?

Responses


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Mike Kovacs , Oct 24, 2007; 08:24 a.m.

No. Something else is amiss with your C330.

Mike Pobega , Oct 24, 2007; 09:58 a.m.

your top to bottom lens may be out od alignment.

Mike Pobega , Oct 24, 2007; 10:00 a.m.

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.

Alexey Stepanov , Oct 24, 2007; 10:10 a.m.

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?

Mike Pobega , Oct 24, 2007; 10:28 a.m.

no. As long as you are not focusing through the taking lens, you can not be sure of accuracy.

Mike Kovacs , Oct 24, 2007; 11:12 a.m.

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.

Robert Lee , Oct 24, 2007; 11:52 a.m.

"... 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?

Alexey Stepanov , Oct 24, 2007; 03:12 p.m.

"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.

Robert Lee , Oct 24, 2007; 04:46 p.m.

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.


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