Polaroid Land Camera Lens Hacking

[planetjoe]

Here is the RF unit. It was quite easy to add the extension.

Greyhoundman: this is some very practical work; well-done. I've been looking at this idea, too - some good threads over at pnet, if you can wade through the snarkyness. There's also this thread over at APUG, which actually refers to an even older thread here; as described there, there was an issue with the "slope" of the RF with the longer lens.

You've got a 127mm on the Pola 250, so I figure you've re-aligned to infinity, but what about the RF's focus curve? Do you find that the RF tracks the focus curve of the longer lens accurately enough?

In my experience, this is the ultimate difficulty with any such project. Thanks for sharing your work, by the way. Very inspiring.


Cheers,
--joe.

 

[greyhoundman]

Chris101,
Actually it looks better when seen from a different angle. 🙂

Planetjoe,
I have had no problem with the focus. I have the RF unit moved to the top of the new film back. It is set for the 127 lens. The slightly longer focal length was perfect due to the set back involved with attaching the new back. My June 2006 blog has more pics and descriptions.
I've read the threads on pnet and apug. I didn't get involved in the arguements. Especially those started by armchair know it alls. 😉

 

[Sonnar Brian]

How did you get the RF unit set for the 127 lens? Is the metal tab arched to cover the difference?

 

[greyhoundman]

No changes to the metal arm have to be made. The unit was moved and set at the infinity focus point of the 127 as indicated by ground glass at the film plane.
A little tweaking to be right on the money, and it focuses fine down to 3-3.5 feet as indicated by ground glass.
That is why the 127 was perfect for the job. At the normal infinity position of the bellows it was right on with the added depth of my back addition.

 

[clarence]

Thank you very much for showing us what you've done, greyhoundman.

Since I don't intend to change the back, the distance between the film plane and the lens shouldn't change much; is that correct? Should I just attempt to find a lens that is the same focal length or shorter?

Thank you!

Clarence

 

[greyhoundman]

If you are just going to replace with a new shutter/lens combo, you'll need to stick to 114mm lenses.

 

[clarence]

Thanks, greyhoundman. Eastcamtech puts 127mm Rodenstock lenses on their converted cameras, without installing a new back, but it seems the rangefinder remains somewhat inaccurate:
http://eastcamtech.com/Pol250.htm

From what you've written, it seems that if I were to use a lens that is not of the 114mm focal length, I would lose infinity focus. Am I mistaken? If this is the case, I don't really mind, since I will be using this mostly for portraits.

I'm watching some auctions on tominon lenses from the Polaroid MP-3 3 / MP-4 copy cameras right now and they seem like they might work.
http://cgi.ebay.fr/Polaroid-Copal-7...hZ024QQcategoryZ30076QQtcZphotoQQcmdZViewItem
http://cgi.ebay.co.uk/ws/eBayISAPI....m=170176893617&ssPageName=STRK:MEWA:IT&ih=007

Thanks a lot, once again!

Clarence

 

[greyhoundman]

You could also go with a 101mm lens in a graphic shutter. Calibrate for the distances you plan to shoot at.

 

[clarence]

Thank you all so much for the advice. Unfortunately, a couple of unexpected things have come up in my life, and I've had to put aside this project for now, even though I'm itching to try it. This will have to wait.

Clarence