Mamiya C330 focusing

[Sully75]

Hi there,

I'm on Mamiya C330 no.3, it's been a challenge to get a working one. This one is a bargain KEH body and an excellent KEH 80mm lens.

I'm wondering about the focusing. It seems like it comes in from blurry and slowly gets sharper and sharper, and then becomes blurry again, without ever getting perfectly sharp in the ground glass. It gets really close but it's still a touch soft, and then begins to get blurry again.

Is this normal? It seems to be less of a problem in close up shots than in shots a couple of feet away.

 

[wobsy]

Generaly these are not a problem but you could check the following
1) When you fitted the lens, did you cock it first? If not the cocking lever on the lens fouls with the cocking lever on the body which stops the lens sitting squarely on the body.
2) Turn the body upside down and check that the lens panel has not been knocked out of true of the body. Both body and base of the lens panel should be square to each other at all sides, top, bottom and sides.

 

[BobD]

Hi there,

I'm on Mamiya C330 no.3, it's been a challenge to get a working one. This one is a bargain KEH body and an excellent KEH 80mm lens.

I'm wondering about the focusing. It seems like it comes in from blurry and slowly gets sharper and sharper, and then becomes blurry again, without ever getting perfectly sharp in the ground glass. It gets really close but it's still a touch soft, and then begins to get blurry again.

Is this normal? It seems to be less of a problem in close up shots than in shots a couple of feet away.

The image on the ground glass isn't produced by the taking lens but rather
the upper viewing lens. I wouldn't worry about it unless the resulting images
on film are not sharp.

 

[fotch]

It should be sharp, something is wrong.

 

[grahamp]

Step 1, make sure that you can focus on the boundary of the central focus spot with your finder. Use the flip-up magnifier on the waist level finder. I am assuming that you are using a microprism screen. If the flip-up finder won't let you do it, take the finder off and use a loupe.

2. focus the camera so that both the focus spot boundary and the image are in sharp focus. Use something with clear edges for the test.

It does help to keep stray light out of the finder. If you cannot get the focus aid edge sharp, then you need to adjust your eye correction somehow. Either with the finder or with glasses.

You can do a sanity check with a piece of translucent tape taut across the film guides with the back open. Lock the shutter open on B with a cable release and verify the focus of both lenses.

It is not uncommon to rack lenses back and forth to find the peak of focus, but you should be convinced that there was a point of focus as you go past it.

 

[Christiaan Phleger]

The screens can be a bit lacking in snap, a good way is to start from infinity, pull in just past the point of focus, then rack back out just past the point, then fine tune on the back in. An old shooter taught me this, if you have a slight mis-focus due to operator error using this technique then the point of focus is slightly closer, which visually speaking seems less abrupt and jarring to the viewer. Also consider the most common Mamiya TLR focussing problem, search the web, over the years I've posted the same info about this camera. The foam surround on the focussing screen frame gets compressed and sticks, causing a very minute error. This leads to a very wrong 'mismatched lens pair' diagnosis, and all the incorrect ways to fix that 'problem'. I've 'repaired' soft lenses that had a non-factory shim placed on the threads of the viewing lens, removed the shim and magic, lens is sharp on a properly foamed body. I've posted how to do the fix many times. As a matter of course I refoam my 2 TLR's if I haven't used them very often, probably once a year.

 

[Smudger]

There is another thing you should try. I had a 180 Super lens that was optically disappointing. As a last resort I swapped the front lens groups. Result :a great improvement.

 

[steven_e007]

Have a look at the mirror, easiest by looking through the front with the lenses off.

It can get dusty or covered in age film, giving a poor ground glass image, but can also be damaged easily by clumsy cleaning...

 

[Sirius Glass]

Have a look at the mirror, easiest by looking through the front with the lenses off.

It can get dusty or covered in age film, giving a poor ground glass image, but can also be damaged easily by clumsy cleaning...

It is front surfaced, so be very careful cleaning it.

 

[unclemack]

Also check that the mirror hasn't been flipped. People have been known to do this to improve the appearance of a mirror with cleaning marks/foxing but it throws the focus out.
As Sirius Glass says the mirror is front-silvered - or should be!

 

[PeterB]

In the hope that someone already subscribed to this thread has an idea, I have tried numerous things already to fix my C330f focusing problem only to be stumped. You can see my question here.
thanks
Peter

 

[Loren Sattler]

Does the problem exist with multiple lenses, or just one. I once owned a 55mm lens that was simply soft for unknown reasons. I replaced it with a different one that is sharp.

 

[PeterB]

I only own the 80mm lens. The image is VERY sharp once it is focused. The problem is that the when the viewing screen is in focus, the image isn't in focus on the film plane.

 

[Smudger]

I had the same problem you describe. For some reason,the magnifier in the waist-level finder finder did not focus properly on the ground glass. I had to do some surgery to bring the two into alignment.
Very strange,because the finder was in excellent shape,and not damaged in any way.
My dual-magnification chimney finder needed a similar adjustment to bring the swing-in second element into alignment.

 

[PeterB]

Thanks smudger. Your description of the problem is the first I have encountered in any forum (and I've been combing them for solutions for weeks now) and I'm sceptical about the explanation. It doesn't make sense that if the original magnifier in the waist level finder (WLF) is not positioned correctly that it would prevent one from focusing. Sure the image viewed through the WLF won't be sharp, but at least when it is as sharp as it can get then that is the right point. I can't see a need to add a second lens in the WLF. Please try and convince me otherwise.

 

[MattKing]

Has someone installed an accessory diopter correction lens in your WLF magnifier?

 

[PeterB]

Has someone installed an accessory diopter correction lens in your WLF magnifier?

Not AFAIK. I will check tonight though, BUT even if they had how is that going to make a difference to the optimal point of focus ?? I have glasses that I sometimes wear to sharpen things in the distance. The problem I see with my C330f's mismatched focus is identical (to within limits of repeatability) whether I put my glasses on or not. Therefore if the WLF lens' diopter isn't the original default, and I swapped the default back in, this is identical to me focussing with my glasses on or off.

Sure things will come to a sharper focus with my glasses on (or with the default WLF diopter viewed by somebody who doesn't use glasses), but this shouldn't change the actual optimal position of the main lens assembly on the track/rail.

Matt, your suggestion is based on the same false premise as smudger which I attempted to counter in my above reply to him.

 

[MattKing]

Peter:

I agree that an incorrect diopter would merely make it more difficult to determine visual focus. I guess I was responding more to the OP's description of his camera.

 

[PeterB]

Peter:

I agree that an incorrect diopter would merely make it more difficult to determine visual focus. I guess I was responding more to the OP's description of his camera.

Yes, your reply makes sense now Matt. I think I might need to purchase the camera's service manual to determine the cause of my focus discrepancies.

 

[Ryuji]

Depending on the screen, the sharpest point doesn't look that sharp. Mine is C3 with old fashioned ground glass, which is easy to reach the optimum focus point, but the image is rather dark and coarse.

 

[PeterB]

Depending on the screen, the sharpest point doesn't look that sharp. Mine is C3 with old fashioned ground glass, which is easy to reach the optimum focus point, but the image is rather dark and coarse.

I totally agree Ryujii. However even though the image on my viewing screen isn't razor sharp, it is very easy to determine the point that it is the sharpest it can be (as one turns the focus knob). That point by definition is when the object is in focus.

My problem isn't that the image in the viewing screen (via the viewing lens) isn't sufficiently sharp. My problem is when that image is as sharp as it gets, the corresponding image in the film plane (via the taking lens) isn't as sharp as it can get. I have to move the main lens assembly back and forth by about 0.6mm (focus knob turns about 2mm circumferentially) as I switch between looking at the film plane and the viewing screen to ensure each is at its sharpest.
I'm impressed that TLR camera manufacturers were able to manufacture their cameras to sufficiently high precision to ensure appropriate lens and image alignments in the first place.

 

[Ryuji]

PeterB, when your viewfinder is in focus, does the focus of taking lens come near or far from the point in focus in the viewfinder?

 

[PeterB]

PeterB, when your viewfinder is in focus, does the focus of taking lens come near or far from the point in focus in the viewfinder?

Good question Ryujii as I'm sure the place to look for the problem will differ depending on the answer. I've switched back and forth between lens plane and viewfinder so many times that I can't remember which direction was positive or negative. I can find out in about 5 hours when I test it again. Let me know if there's anything else I should check for while I'm at it.

Peter

 

[MattKing]

Seen as we are making suggestions about what you should check for ....

How does the focus discrepancy manifest itself at different subject distances.

 

[PeterB]

How does the focus discrepancy manifest itself at different subject distances.

From about 1.5m to infinity it is the same (within limits of repeatbility) - about 0.6mm linear movement of the lens assembly (perpendicular to the film plane). I haven't tested sub 1.5m for a few days after making the changes to the viewfinder foam and swapping back the front halves of the viewing and taking lenses.

Peter