focussing anomoly with 65mm Sekor on C33 Body

[adrian_twiss]

I have recently purchased a Mamiya C33 together with a 65mm and 105mm.

Whilst doing some checks I noticed that the 65mm did not seem to be in

focus at infinity. I did an infinity check with both my 105mm and

80mm lenses and these were fine. I then mounted the 65mm lens on an

old C2 body I had lying around and dicovered that it was perfectly

sharp at infinity. This leaves me with the problem of not knowing

whether the lens or the body is at fault. I would welcome any

suggestions please. On another topic am I required to make an

exposure adjustment when using the 105mm. I notice that at infinity

the lens is racked out quite far. There is also a dial on the left

hand side of the body that gives a film speed of (for example) of

100ASA for a 105mm lens if the dial is set at 125ASA for an 80mm lens.

Please forgive me if this seems a little incoherent. I have just

finished a night shift at work.

[joachim]

Dear Adrian, for general questions on the Mamiya TLR please have a look at Graham Pattersons web page: http://www.btinternet.com/~g.a.patterson/m_faq.htm this should answer most of your questions.

 

With respect to the ones you ask specifically:

Used Mamiya TLR equipment quite often suffers from disalignment of the focusing system, camera's and lenses as well. I had problems with both and returned the equipment.

From what you describe, it seems to me, your C33 is disaligned, but I am not certain. My suggestion is to burn some film to check for that. I would use the largest and second largest

aperture with that and refocus each shoot, to average out uncertainties from you adjusting focus improperly. I would do the same with your C2 body. This way you can learn which bodies and lenses work

nicely together and which aren't.

 

On the exposure: at infinity all lenses need no exposure correction, they just need correction in close-up applications. Graham has a nice paragraph on close-up exposure as well.

I am uncertain what you refer to with the dial on the left hand side. But the ASA dial could at most be meant for memorising what film you put in. All TLR's you have to adjust shutter and aperture on the lens and that determines the exposure.

 

Hope this helps. Please come back if still unclear.

[gene_crumpler6]

Adrian:

 

I've run into this problem with a couple of lenses on my c33 body. I ended up placing a shim made from mat board on the top of the lens board to bring both the viewing lens and taking lens into alignment.

This does seem to be a problem with this used system. What you will have to do, short of employing a repairman, is to decide which body you thing is better aligned and then us it as the standard. There is info in the MFD archives about how to check the focus of the viewing and taking lens of a TLR. You may be able to adjust the alignment with shims as I have done. Be careful not to introduce light leaks around the taking lens.

 

The knob with both the film speed and the exterior pointer for the lens focal lengh are independent of each other. My film reminder is too loose to be dependable.

 

The C series camera system is aging and I personally do not plan to invest further in it because of the above problems.

[adrian_twiss]

Thank you to all those who were kind enough to respond to my question.

The problem has been traced to a deformation of the front lens panel which was preventing the bellows fully retracting. This is essential to correctly position wide angle lenses at infinity. As the panel is twisted it is highly likely that all lenses will suffer from inconsistent focus. I am putting the body in for repair.

[jon_wong]

Hi,

 

I ran into the same problem you described. I used to have extremely sharp slides from my 80mm F2.8, but I traded it in for a mint 65mm F3.5 For about two to three rolls of slides, I realised the objects in foreground are sharply in focus, but the actual object I focus on are out of focus. This usually happens to obejects from very close distance to about 10m away.

 

I dare not try the MFD method because I was worried about light leakage or bending the lens holder.

 

I sent the camera and lens in for service, and was told there was 'nothing really wrong'. The technician told me the viewing lens was 'a bit loose from the thread' but the taking lens was a bit tight. He tightened the two lenses (I don;t know how).

 

Now I have the 65mm and the 105mm both giving me sharp and satisfying pictures!