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Author Topic: lens quiz: solution = Mamiya 7 80f4  (Read 1381 times)

chrismuc

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lens quiz: solution = Mamiya 7 80f4
« on: October 14, 2014, 12:37:38 PM »

Who can guess the lens right ?

digital back: IQ180
camera: ?
two pictures, shifted left/right +/- 13mm, stitched to 15565 x 7745 pixel
f11, no center filter, no color cast correction, no correction of geometrical distortion applied

... this to consider when guessing the focal length

pic in full resolution:
https://dl.dropboxusercontent.com/u/18437364/pictures/Pano-1.jpg

Good luck, Christoph  :)
« Last Edit: October 16, 2014, 08:39:11 AM by chrismuc »
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ErikKaffehr

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Re: lens quiz
« Reply #1 on: October 14, 2014, 12:55:32 PM »

Hi,

I may have a hunch it is Canon 24 T&S on Hartblei HCam, or even the 17 T&S, since you ask. But I am absolutely clueless.

Best regards
Erik

Ken R

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Re: lens quiz
« Reply #2 on: October 14, 2014, 01:24:06 PM »

Who can guess the lens right ?

digital back: IQ180
camera: ?
two pictures, shifted left/right +/- 13mm, stitched to 15565 x 7745 pixel
f11, no center filter, no color cast correction, no correction of geometrical distortion applied

... this to consider when guessing the focal length

pic in full resolution:
https://dl.dropboxusercontent.com/u/18437364/pictures/Pano-1.jpg

Good luck, Christoph  :)

My guess would be a lens in the 70-90mm range. My initial hunch was 90mm.
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chrismuc

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Re: lens quiz
« Reply #3 on: October 14, 2014, 02:08:53 PM »

Hi Ken: Very good guess - it's 80mm. With +/- 13mm side shift and the 54mm wide IQ180 the pic is 80mm wide equals a filed of view of 36mm focal length on 135. It's a lens with sufficient image circle for that format and excellent reputation but maybe never used with a digital back, only with film.
 ;)
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chrismuc

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Re: lens quiz
« Reply #4 on: October 16, 2014, 08:37:16 AM »

Okay I see, too difficult and too few hints.

Solution: Mamiya 7 80f4 lens on Alpa FPS (and IQ180) via customized shift adapter

Mamiya 7 lenses are always praised for their sharpness on 6x7 film, since some time I had the plan to try to mount them onto my FPS to see how they would work with a 645 size digital back.

First thing was to find out the exact flange distance to determine how much space there would be for a mount mechanism to the FPS. Luckily the head engineer of Mamiya Germany camera service in Munich was very helpful: it's 57,85 mm. Then I purchased a 6.5mm distance frame from Alpa for the FPS because my idea was to use the side rails directly for the shift mechanism of my lens mount. The whole mount is machined from a single POM (black plastic) block. From Mamiya Germany I got a Mamiya 7 camera spare part bayonet ring which I screwed on the front of the shift mount.

I searched for second hand Mamiya 7 lenses and found four nice lenses in very good condition for reasonable prices: 43f4.5, 65f4, 80f4, 150f4.5

Due to the fact that the Mamiya 7 is a rangefinder camera, the lenses have no spring loaded apertures, so the aperture ring is directly coupled to the aperture blades.
The main problem to solve was, that the Mamiya 7 lenses contain electro-magnetic central shutters which are closed without operation with the camera. Again the friendly Mamiya service was very helpful: They disassembled the lenses, removed the shutter blades and reassembled the lenses. During that proceedure we decided to leave away some "unnecessary" parts: the rear tubes of the 43 and 65 mm lenses because they restrict the shift movement and all prominent levers that stick out at the back side of the lenses because obviously nothing is coupled to the FPS camera.

After first assembly of the shift lens mount on the FPS I found out that infinity focus could not achieved: the lens mount was 1,5mm too wide. Why? Because Mamiya defines a different flange at the mount for the flange mount distance than assumed by myself. Okay, some re-machining, then the set-up worked fine.

The 43 mm lens allows about 6-7 mm sidewards shift until the back lens barrel interferes with the inside box of the FPS, the 65, 80 and 150 mm lenses can be shifted up to 13mm left and right until light would leap in between the Alpa 6.5mm frame and the shift mount.
Of course the lens mount can be turned by 90 to achieve vertical shifts.

The 65 shows little, the 43 some color cast towards the edges. I have to do some white panel compensation shots to see how severe the effect is.

Sharpness of all lenses look very promising, more test pictures to come.
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chrismuc

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Re: lens quiz
« Reply #5 on: October 16, 2014, 08:38:37 AM »

some more pics from the shift mechanism and the modified lenses
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ErikKaffehr

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Re: lens quiz: solution = Mamiya 7 80f4
« Reply #6 on: October 16, 2014, 08:41:52 AM »

I am impressed!

Best regards
Erik

chrismuc

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Re: lens quiz: solution = Mamiya 7 80f4
« Reply #7 on: October 16, 2014, 09:40:30 AM »

Thx Erik!

Enclosed another test pics with M7 43f4.5 @f11 lens, two pics stitched +/- 7mm hor. shift.
Today boring weather. This time created color cast compensation shots and applied with corner fix to the raw files before stitching. I have no experience with that procedure yet, corner fix removed quite fully any color in the sky so it exaggerated the correction a bit.

Left side not as sharp as right side, must check, seems to be an issue with my particular lens.

link to full resolution
https://dl.dropboxusercontent.com/u/18437364/pictures/Mamiya-7_43f4.5atf11_68x40mm.jpg
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