frankenstein tlr?

[pb908]

hmm, i check the focus scale of C220 camera, and i got something "interesting" as well confusing.
this is not the same with what i wrote before with C330 scale.

here is the C220 Scale

the top one is the original picture, the bottom one is after i put a line crossing the infinity mark on the body to the lens scale, and pull it down to see the position of the bellow/lens plate
it seems that 65mm/80mm lens is at the same distance at infinity but deeper than the 55mm lens. or in another word, 55 lens @ infinity is a little bit farther (the lens plane to film plane distance) or the lens is little bit projecting out from the camera body, close with 250mm lens.

this is contradicting with the one from C330.. or did i read it wrong ?

 

[johannielscom]

Hm. Gotta admit I'm not mathematically skilled enough to figure such things out. 😱 But, I am hoping the DOF of a wider lens will cover any issues, and of course there's always the ground glass to check focus.

The 65 would likely fit better while the 55 would have more DOF to cover focus issues, dilemma... I'll just see whatever I run into first. There's the annual outdoor camera fair in Doesburg, the Netherlands in August and this might be a nice item to go look for if I haven't found one then...

 

[pb908]

Just got extra fact from real user, an old post from photo.net


1. How far is the rear element extension from the lens mount on both lenses?

I'm not exactly sure what to measure, so I measured the distance from the front(outside) of the lens mount to the end of the metal barrel that hosts the glass elements.

80mm: 13mm
55mm: 16mm

2. What are the distances from lens mounts to film focus at 10 ft.?

80mm: 73mm
55mm: 78mm

3. What are the distances from lens mounts to film focus at infinity?

80mm: 72mm
55mm: 77mm


link below :
http://photo.net/medium-format-photography-forum/00BnaX

this match with the scale on C220, that 55mm lens is "a little bit farther" from film plane.
so if this really true, both 65mm and 55mm are usable for fix lens tlr. just need a way to mount it properly.

 

[hanskerensky]

Hi Johan,

Tried to post you a return on your question about the 55 / 65 mm lens but got DNS Error reports in return for several days now.

No, alas i don't have such a Mamiya Lens :-(

Your project sounds very interesting, hope you succeed !

Regards,
Hans

 

[pb908]

Can you sink it deep enough for infinity? or a Frankenflex FW Macro is the plan?🙂

Pherdinand, sorry that i don't see your post, i'am too much concentrated on the "technical detail" of how possible is this project.

as per my finding, both 80mm, 65mm and 55mm of mamiya looks possible if we are talking infinity focus position. but after reading some spec of the lens i found some other issue.

issue:
1. infinity focus : 80mm & 65mm have the same infinity focus position, 55mm a little bit longer, all seems workable.

2. lens mount. most fix lens tlr have hole size for shutter #00 size, around 26mm diameter, while the mamiya lens is using shutter #0 size around 34mm diameter, still workable if you want to make a new plate or drill a bigger hole.

3. viewing to taking lens distance. mamiya has 5cm distance between those two lenses. i measure my yashica TLR and from center to center of the lens it measured 4cm. seeing picture of Mamiya TLR lenses, both top and bottom lens are so close, almost no space in between those two. this is the hardest part which i believe may shutdown the idea.

to adapt Mamiya 80mm taking lens only, highly possible, as normal yashica TLR is already having 80mm viewing lens.
but adapting the 65mm and 55mm, maybe not possible due to issue no3 above. best way is just to buy mamiya TLR 🙂

 

[graywolf]

One of the problems you guys are going to run into, is that the actually focal length of a lens, and the marked focal length are seldom the same. Then your viewing/focusing lens has to be, within quite close tolerance, the same as the taking lens. Then you have to have a focusing scale to match the lens.

And what you actually get for all this work is a camera that is slightly better close up at wide apertures. I would suggest going through the photos on the 120 RF Folders forum to see how much difference there is between say, an 3 element lens and an Apo-Lanthar, which is considered one of the best lenses ever.

In fact, I would suggest that anyone who wants to talk intelligently about lens got through the sticky photo thread there. Then also remember that people with more expensive camera probably have access to higher quality scans than the folks with cheaper cameras have to make do with, which narrows the playing field even more.