Mamiya C220 odd focusing problem

[FlyingO]

Greetings, I have an issue with one of my two Mamiya C220 cameras. On my “problem” one, the bellows need to be racked out 25.8mm to achieve infinity focus - regardless of which lens I use. I have a functional C220 so I’ve been able to swap lenses and viewfinders to help analyze this problem. Both cameras have an identical number and placement of shims under the focusing screen, and both mirrors look identically mounted and positioned. Using a focusing screen at the film plane, I’ve affirmed that focus is the same on the film plane as in the viewfinder, so I can still confidently take photos, but the close focus range on the problem one is limited to around 3 feet compared to my “good” C220 which will focus to about 8 inches.
If the focus on the film plane had been different than that of the viewfinder, I would guess it was a mirror placement issue, but now that doesn’t seem to be the issue. There is one screw missing in the focusing screen assembly on the problem camera, so it has been opened before. The photo below is of the camera set at infinity focus. Any ideas about the cause or possible fix of this issue will be greatly appreciated! Thank you in advance.

 

[Don_ih]

I’ve been trying to figure out why a Mamiya C220 I just got needs to have the bellows racked out almost 26mm in order to achieve infinity focus

Reversed focus element? Have you tried it with multiple lenses? I doubt the mirror could be messed up enough to do that.

 

[MattKing]

Perhaps the lens mount stage is placed wrongly on one of them.
@grahamp - Graham Patterson - may have some knowledge about this, although I don't see anything on his excellent Mamiya TLR System Summary.

 

[glbeas]

Sounds like the rack and pinion of the focusing rail is misaligned. If the pinion has a stop pin on it to restrict it from coming off the end of the rack the mispositioning would do that.

 

[OAPOli]

I would think that something is wrong with the lens, like if the rear groups had been swapped. But the same issue occurs with multiple lenses, even those that focus correctly on the other camera?

 

[reddesert]

Greetings, I have an issue with one of my two Mamiya C220 cameras. On my “problem” one, the bellows need to be racked out 25.8mm to achieve infinity focus - regardless of which lens I use. I have a functional C220 so I’ve been able to swap lenses and viewfinders to help analyze this problem. Both cameras have an identical number and placement of shims under the focusing screen, and both mirrors look identically mounted and positioned. Using a focusing screen at the film plane, I’ve affirmed that focus is the same on the film plane as in the viewfinder, so I can still confidently take photos, but the close focus range on the problem one is limited to around 3 feet compared to my “good” C220 which will focus to about 8 inches.
If the focus on the film plane had been different than that of the viewfinder, I would guess it was a mirror placement issue, but now that doesn’t seem to be the issue. There is one screw missing in the focusing screen assembly on the problem camera, so it has been opened before. The photo below is of the camera set at infinity focus. Any ideas about the cause or possible fix of this issue will be greatly appreciated! Thank you in advance.

We need more clarity about what these numbers mean, because what you're describing seems impossible. If you have the same lens on two different cameras, check the focus at the film plane, and the lens has to be significantly further away from the film on one camera than the other, something is off in your test. Even if shims under the focusing screen or the mirror were different, that makes a difference of fractions of a mm in bellows extension, enough to matter for sharpness on film but not to measure wit a ruler.

Keep in mind that different focal length Mamiya TLR lenses reach infinity focus at different bellows extensions; it doesn't have a constant film-flange distance like a 35mm slr system.

So: - What lens are you using? The photo looks like a 180mm/4.5 nominally focused at 15 feet onthe focusing scale.
- What's the 25.8mm number refer to? The bellows extension at infinity (not the same for different f.l. lenses, such as 80 vs 180mm)? Or the offset of one camera to the other?
- When you say one camera focuses only to 3 feet while the other focuses to 8 inches, is that for the same lens? What focal length? That's an enormous difference. However, this is the observation that could be explained if the rack was mispositioned and one of them was hitting a stop earlier than the other, as Gary suggested.

 

[bernard_L]

On my “problem” one, the bellows need to be racked out 25.8mm to achieve infinity focus - regardless of which lens I use.

Following up and mostly agreeing with @reddesert. My emphasis added in the quoted text. This can't be; each lens has a specific bellows draw at infinity. This is clearly seen on the very picture that you show -- the curved colored lines. Only the 80 and the 65 have approx zero bellows draw at infinity. The lens on your picture is a 135 (not a 180), one of the lenses with the longest draw at infinity. Its distance curve is just starting to appear on the side panel, the blue line that crosses the distance scale on the edge of the chassis at... infinity.

This is not an issue, it's a feature. If the design had been such that all lens reach infinity for the same bellows position (at or near zero draw) a lens such as the 135 would have been a lot more bulky, with empty tubes between the rear element and the flange.

Read The Fine Manual by Mamiya to learn the specifics of the C system.

 

[Don_ih]

but the close focus range on the problem one is limited to around 3 feet compared to my “good” C220 which will focus to about 8 inches.

Is that using the same lens on each C220?

 

[Steven Lee]

@FlyingO Something is missing in your description, because as currently written it describes the impossible situation. You can't explain the same lens needing a whopping 26mm focusing distance delta by a defect in the body. And if that's a different lens, then it's a lens issue not a body issue.

 

[grahamp]

OK, if the 'problem' camera is focused in the finder, and the film plane focus matches, then the optics are correct. This does assume that the lens panel on the camera is parallel to the film plane and not buckled.

Second assertion: with the same lens pair (not another one, the exact same pair), the closest focus distance is different. Is this true for infinity?

Tests: focus on infinity with one lens on each body. Measure with a ruler the distance from the body front to the lens panel, and record. Do the same with a different focal length, if you have one. Also note the lens focal length and if it is in a black or chrome shutter (this is only likely to be an issue with 105mm and 180mm focal lengths, but let's be specific). And yes, a tripod, and measure for the minimum distance) are advised, and do the focus checks wide open.

The only way I can think that this could happen is if the focusing screen on one body has been incorrectly shimmed. If so, then the infinity extension and the minimum focus extension should be off. If we have the lens focal length and the extensions, then I, or someone else, may be able to 'tie break' the issue. We have relatively slow lenses here, so precise focus is not easy without a loupe, even wide open. It can't be too much, or the depth of focus at the film plane would not be enough to mask it.

A lens will focus at infinity at a specific distance from the film. Putting it on a different box won't affect it. There has to be something that is being missed in the description. I suspect that the lens panel is not plane parallel to the film plane, and the screen has been tweaked to compensate a bit.

Hmm, one odd thought. is the lens seating properly on the lens board and clamping down (rack fully in and operate the Lock/Unlock control to free the wire), and also check that the shutter release is on the correct side of the camera body release?

 

[FlyingO]

@FlyingO Something is missing in your description, because as currently written it describes the impossible situation. You can't explain the same lens needing a whopping 26mm focusing distance delta by a defect in the body. And if that's a different lens, then it's a lens issue not a body issue.

I’m not sure what you mean, but using the same lenses - 80, 105, 135, etc. - on both cameras results in “normal” functionality on my C220 with no issues, but on this 2nd C220 the bellows have to be racked out much farther to achieve infinity focus.

 

[FlyingO]

OK, if the 'problem' camera is focused in the finder, and the film plane focus matches, then the optics are correct. This does assume that the lens panel on the camera is parallel to the film plane and not buckled.

Second assertion: with the same lens pair (not another one, the exact same pair), the closest focus distance is different. Is this true for infinity?

Tests: focus on infinity with one lens on each body. Measure with a ruler the distance from the body front to the lens panel, and record. Do the same with a different focal length, if you have one. Also note the lens focal length and if it is in a black or chrome shutter (this is only likely to be an issue with 105mm and 180mm focal lengths, but let's be specific). And yes, a tripod, and measure for the minimum distance) are advised, and do the focus checks wide open.

The only way I can think that this could happen is if the focusing screen on one body has been incorrectly shimmed. If so, then the infinity extension and the minimum focus extension should be off. If we have the lens focal length and the extensions, then I, or someone else, may be able to 'tie break' the issue. We have relatively slow lenses here, so precise focus is not easy without a loupe, even wide open. It can't be too much, or the depth of focus at the film plane would not be enough to mask it.

A lens will focus at infinity at a specific distance from the film. Putting it on a different box won't affect it. There has to be something that is being missed in the description. I suspect that the lens panel is not plane parallel to the film plane, and the screen has been tweaked to compensate a bit.

Hmm, one odd thought. is the lens seating properly on the lens board and clamping down (rack fully in and operate the Lock/Unlock control to free the wire), and also check that the shutter release is on the correct side of the camera body release?

Thank you for this. I’ll be conducting several tests as you’ve recommended and see if I can find any pattern in the strangeness. I’ve affirmed that focus on the film plane and in the viewfinder are identical. The lens mounts are identical and lock in as they should be with no incorrect fitness to the body.
I have not yet taken measurements of the differences between the two cameras besides what I see. In addition to the amount of bellows extension, I will see if both cameras have lens panels that are parallel with the film planes. The lenses seem to be seating properly. The idea that the lens plane and film plane might not be exactly parallel in the odd camera is something I hadn’t thought of, thanks for that. I’ll be inspecting that aspect closely.
I have found that both cameras have the same two thicknesses of shims under the front of the focusing screen assembly and one has one washer on the left rear screw of the focusing screen assembly while the other has a washer on both rear screws.
I will continue with the “process of elimination” testing, using the same lenses (not copies) and taking detailed notes of all aspects - close focus and infinity distances, etc.

I do thank everyone who has offered thoughts on this. I really appreciate it!

I’m sure the cause and/or solution is here somewhere.

 

[grahamp]

If I have time today I will do some measurements with my C220 for comparison. There has to be a reason.

 

[grahamp]

Here we go. Mamiya C220 body (not C220f), original focus screen (matte with central fine focus spot. Chrome fittings, no modifications. The target was a cell tower about 1/4 mile or 450 meters away against the sky in good light. This has enough detail to resolve well, even with the shorter focal lengths.

All lenses in black Seiko shutters, except the 65mm which is an older Seikosha-S.

Lens panel extension at infinity focus by screen, measured as shown in the accompanying image.

55mm f4.5 7.5mm

65mm f3.5 1.9 mm

80mm f2.8 2.1 mm

105mm DS f3.5 22.9 mm

135mm f4.5 26.7 mm

180 Super f4.5 19.4 mm

250mm f6.3 11.2 mm

Note that the 105mm DS is a different design from the earlier 105mm lenses, and has a different back focus. I don't have an older 105mm for comparison. The 80mm f2.8 is the original version, not the late one introduced with the C330s. The camera had the bellows fully retracted and the lock/Unlock control used to exchange the lenses each time before the lens panel was racked out to get the target in focus on the screen. I have not done a check of the film gate focus, or done a minimum focus check. The Infinity measurement should be enough to show off a systematic body issue.

I have quoted to 0.1mm precision, but +/- 0.5mm is probably a reasonable measurement error, especially if a ruler is used in place of a caliper.

I measured the infinity focus on the scale side at the mid-point to try and get a standard location. I am really curious if either of the camera bodies in question have significantly different values.