Mamiya 7 43mm lense aux viewfinder problem? perspective problem

[sserata]

I have the 43mm lense for the Mamiya 7II. It's a great lens except for a persistent problem I have had for several years. It is pretty consistent so I know it's not a one-time fluke. I think maybe the auxiliary viewfinder that slides into the hotshoe is slightly off (for those who don't know, the 43mm on the Mamiya 7 is so wide that the internal viewfinder in the camera cannot accomodate it so you have to use this additional viewfinder which is a pain) By "off" I mean I suspect it is slightly off-axis, so that when you line up the shot thru it, it causes you to skew or swing the camera slightly. I am NOT talking about the parallax error. I shoot some architecture with this lense. I need the extremely wide angle, but because it is so wide it is extremely sensitive to the film plane not being perfectly parallel with the front of the building or structure. The viewfinder has a tiny bubble level in it (and I double check that with a larger level I put on the camera) so I am not talking about tilt, I know the camera is level front to back and it is level side to side. (Ok, technically I know the camera can't do tilts or swings or shifts because it isn't a view camera but you know what I mean)

It wouldn't matter if I was shooting landscapes or something, but in architecture the front of the building/structure has to be perfectly square on the film. I know, I know, you're saying, shoot with a view camera! Yes, I also use a 4x5, but for this project I cannot use a 4x5. What I see on the film is tilted horizons, and often the film looks as though the rear standard was slightly "swung" (film plane not parallel with front of building in the horizontal axis) Imagine if I shot a square structure, the image on the film will look slightly trapezoidal in the horizontal direction. My question? Anyone else out there with the same lens/camera who has experienced the same problem? I have run 100's of rolls of film thru the camera and the problem shows up no matter how careful I am to line up the shot. I don't have the same problem with my 4x5 or my Pentax 67 or my Canon 5D, so I don't think there's something wrong with my brain!

Help!!
Thanks,
Scott



have you thought of using just a standard 3 way hotshoe mounted level? I don't have a Mamiya 7, but I have shot architecture with an RZ67, and I had no problems when using a 3 way level in the camera's hotshoe.

I'm not sure if you can fire the lens' shutter when the back is open, therefore being able to afford you the use of a ground glass on the film rails.

you might also want to try asking this same question over at www.apug.org

its for all analog users (I'm there as well). More users of the Mam 7 there than here. You should hopefully get the answer you need there.

-Dan


Dan, thanks for your reply. Yes, have tried various bubble levels including the 3way hotshoe mounted ones. I don't think this is a problem caused by the camera not being level. The camera is level. I think it is caused by the film plane not being parallel (in the horizontal axis) to the front of the structure/building. I think the film plane is slightly swung with respect to the building, causing the image on the film to look skewed horizontally, not vertically. It's as if I was shooting a 4x5 and had swung the back slightly. My only guess is that the viewfinder is off somehow and is causing me to not aim the camera accurately. Again, this is amplified greatly because the lens is so wide and I am close to the buildings.

I will take your suggestion and post this on apug.

Thanks,
Scott

 

[Reinhold]

Interesting...

I have a 43mm lens also but always do a visual check to see that the top of the camera is truly horizontal regardless of what the viefinder says.

In fact, I find that I'm often slightly off of true horizontal regardless of which lens I use. I have dismissed it as my "eye" being fooled by what it percieves as horizontal when looking thru the viewfinder (be it the 43mm accessory, or the regular finder in the camera body).

I've used M7's almost from the day they were introduced, but I always do a visual confirmation by backing away from the camera a bit and sight over the top of the camera to make certain it's truly horizontal. I have a pretty good eye for it, especially if the subject has some horizontal lines for reference...

I kind of back away and mentally/visually include the camera as part of the scene. If it's not level with the scene, I adjust it accordingly. In the medieval cities of France, I find it's sometimes better to have the camera tilted so it agrees with the subject even if it's not truly level.

As Dan says, using a ground glass to verify the film-to-viewfinder alignment is one way to see if the optics in the finder are skewed. (Yes, you can open the shutter even with the back open...)

Reinhold

www.classicBWphoto.com

 

[sanking]

I doubt very much that there is a problem of alignment at the film plane, though stranger things have happened.

In my opinion the most likely cause of the problem is that the camera is not perfectly level. I consider the viewfinder useless for verifying level and always use an external level placed on top of the camera to check. The level I use is an Ebisu Diamond and I just place it directly on top of the camera and then adjust. Before I do this I also level the camera as best I can with the buble level on my quick release plate, but the small Ebisu Diamond is much more accurate.

Sandy King

 

[sserata]

Thank you for both of your responses. I appreciate the help. Maybe I'm not being clear, or my explanation is confusing. The camera is level in every axis, that is side to side, front to back, etc. I agree with you, sanking, the little bubble level in the 43mm viewfinder is useless and I also use another level on the camera to verify level, and I also level the tripod. I have been shooting that way since I got the camera 3 years ago. But the problem persists. As I said, what I believe is happening is that the film plane is slightly "swung" (borrowing the terminology from 4x5 land) i.e. if you viewed the camera from above, you would see the film plane is not parallel with the front of the structure I am shooting. Of course, on a 4x5, when you swing the rear standard/film holder you move the plane of focus and you change the perspective/shape of the image on the film. As I said, if I'm shooting a square building, the image comes out slightly distorted, i.e. trapezoidal in the horizontal direction. This is not a case of "keystoning" i.e.vertical distortion caused by the film plane not being parallel in the vertical axis. That's what you would get if the camera was not level front to back. Does that make more sense?

Probably the problem is caused by a misalignment in the attached viewfinder and I will just have to send it in to Mamiya and have them fix it or buy a new one (ouch!)

Thanks
Scott

 

[DanielStone]

scott,

are you able to post a small picture that we could see what you're talking about in a visual sense? it would help me to see if this could be a lens issue or not. you haven't bumped or dropped/jarred the lens or body lately?

The only other thing that I could think of doing would be to say take your camera, level it on on x/y axis', and point it at a wall, or something that you can reference. If you have a ground glass, put it on the film rails with the camera set to bulb locked open. Check your framing first with the auxiliary viewfinder, frame it the way you want, then look on the ground glass, and see how far off you really are. you might want to take a super fine point sharpie and make little dots as to where the frame corners are, if the Aux. V/F is showing a wider FOV than what's on the ground glass. if you have some clear acetate, cut some and tape it over the Aux. V/F and mark on that, not the V/F glass .

after re-reading what you have wrote another 2x, i think the problem is with your lens for some reason. How much(if any, since I've never used the 43mm) distortion is there on vertical lines?

welcome to APUG btw, hope you can stay around! lots of great information on here!

-Dan

 

[AgX]

sserata,

Welcome to Apug!

You get a keystoning effect in any case of the film plane being tilted in reference to the object's plan, independent on it being perdendicular to the optical axis or not.

For me it is easier to belief that the lens tube has got a buckling due to a fall or so. However, that only would lead to misframing as long as the body is parallel to object plane. Not to keystoning.

Your problem seems only to be explained by the film plane being not (any longer?) parallel to the body's main plane. Though it is hard to belief that such could happen.

 

[John Koehrer]

Since you refer to the result being similar to a view camera with the back swung, that suggests that the film plane is not parallel to the subject. Or keystoning in a horizontal axis?
It sounds as though one of four things isn't in alignment, lens/shutter, lens mount, shoe mount of the finder or film plane.
Simple stuff first.
1)Film plane not parallel to body casting--not likely.
2) Are there screws in the bottom of the finder or the accessory shoe itself? There may be enough slop in the screw holes to have allowed the finder to have been bumped horizontally to cause a mis-alignment.
3)screw(s) in the lens mount loose?
4)lens/shutter mis-aligned?
If it's not a loose screw(I've got some) hie thee to a machine shop & ask to have all the parallel surfaces checked for parallel. That's film rails to lens mount & film rails to front edge of the lens. That should tell you if it's external damage of some sort.
Would you be able to rent either a lens/vf or body to eliminate one variable at a time?
Where are you? would you add location to your profile?

 

[sserata]

Mamiya 7 43mm lens aux viewfinder problem

Thanks again for your ideas, Dan, yes, I will try the ground glass idea but I have to get my hands on a small piece of ground glass because of course a 4x5 glass will not fit on the film rails of the Mamiya. No, the camera has not been dropped or banged around at all. Anyway it would take a major impact (like throwing it off a building!) to bend the lens tube or lens mount that much.

There is very little geometric distortion (i.e. pincushion or barrel) in this lens (that's why I bought the Mamiya 7, basically on the strengths of this lens) It is rectilinear, so straight lines stay straight. It's about as perfect a lens as can be made in this focal length.

No, John, no loose screws here! I checked. The accessory viewfinder for the 43mm is plastic with no screws. The hotshoe is solid.

I agree with you AgX that even if the lens mount or lens tube were somehow bent that would only cause misframing and not the horizontal keystoning. To use the 4x5 analogy, that would be similar to swinging or tilting the lensboard. That would cause a shift of the image or swing of the plane of focus but would not change the shape of the image. The only thing that can cause the slight keystoning I am seeing is if the film plane is not parallel to the building. I am not claiming that there is a misalignment in the camera that is causing this. That would be nearly impossible. I think it is a misalignment in the accessory viewfinder that is causing me to aim the camera slightly off and thus cause the problem. Sorry to have caused a fuss for nothing!

I'll see what I can see when I get the ground glass.

thanks again for the ideas
Scott

 

[Steve Smith]

Check your framing first with the auxiliary viewfinder, frame it the way you want, then look on the ground glass, and see how far off you really are.

Something a bit easier which you could try first. Line the camera up using the internal viewfinder making sure verticals are vertical and the horizon is horizontal, then look through the auxiliary finder. If it's not right then that's where the problem is.


Steve.

 

[sserata]

Just tried the ground glass on the back of the camera with shutter wide open and dark cloth. that must have looked funny! some guy trying to use the smallest view camera in the world! What I see on the ground glass confirms what I've been seeing on the film. Even with the camera perfectly level in all axis, if I line up the shot of a building with the external viewfinder, the image on the ground glass is slightly off, horizons slightly tilted, slight horizontal keystoning. I'll have to try more.

Scott

 

[DanielStone]

scott,

have you tried different levels to see if the level you've been using could be giving you problems as well?

I have had good luck with some levels found at the 99c store. cheap, and there's always backups in my camera box at home, or in the car

-Dan

 

[sserata]

Gentlemen, I've decided to send the body and lens and external finder into the shop for a checkup and possible re-alignment. I bought it new from Hong Kong about 3 years ago so of course it's no longer under original warranty. My question, if you've had personal experience with this, what would you recommend, authorized Mamiya service or a local camera shop (San Francisco, CA, USA area) Anyone had experience with Mamiya 7 service in the US?

Thanks again,
Scott

 

[DanielStone]

send it to MAC in NY(I believe they still do repairs in-house).

or any reputable repair house should have it fixed for you and tip-top in no time!

glad the ground glass trick worked for ya!

-Dan

 

[jlab]

Nippon Photo in NYC

I like Nippon Photo Repair in New York, they do really good work at a great price, I have found. You may have solved this issue long ago, but hopefully it will help someone else!

J