Sharpness of Mamiya RB67 lenses

[paul_ong1]

<p>Hi,</p>

<p>I have been constructing a digital 4x5 using a Toyo 45G and Nikon D70. I am using the hybrid to learn technical control, plus I like to tinker in my workshop.</p>

<p>While the Schneider lenses are nice for 4x5, they are not very good for the attached DSLR, and I cannot get the 90mm Schneider to focus at infinity on the hybrid. I have now moved to using Mamiya RB67 lenses because of the considerable flange-to-focal-plane distance of 112mm. To reduce weight of an old broken non-C 90mm, I remove the existing mount, the housing, and the broken shutter. I save the aperture, and the final result is about the same size and weight as the Schneider. You can see the hybrid at<br>

http://www.flickr.com/photos/9476880@N02/sets/72157623319405313/<br>

I have been able to modify a non-C 90mm and started testing with it. In the above set are several shots along with 100% crop. The photo with the sharpest image is "Mamiya_Toyo_Nikon_test4_cr". Don't look at the autos, but look instead at the sign.</p>

<p>My question is about the relative sharpness of the non-C 90mm versus the 90mm KL. I have a broken 90mm KL that I have to replace the aperture before it can be used. (I have been able to modify the mechanism for the floating lens to work on the 4x5.) For those who have used both lenses, how much more sharpness can I get?</p>

<p>I will also eventually get a Mamiya 50mm lens when I can find a broken one. (If anyone knows of where I can get one, let me know. I regularly check KEH and ebay. I don't want to dismantle a good working one.) For those who use the non-C 50mm, how does it compare to the non-C 90mm in terms of sharpness? Also, how much sharper is the C 50mm?</p>

[john_cooper9]

<p>Paul, how old is your 90 SA? Schneider had quality control issues in the 70's and 80's. Make sure you have a modern one or at least an old one marked "TECHNIKA". My SA's are Technika versions and are very sharp. Looks like you need a sunken lens board for your set up. I have one I tried to adapt to my Linhof Kardan - you can have it if you like. Let me know, John.</p>

<p>PS: I just got rid of an ugly but working Mamiya 50 non-C at the Largo camera show (sorry!) and I found a Mamiya 50 6.3 (biogon copy) for the Universal that is reputed to be very sharp on 6X9 film.</p>

[ondebanks]

<p>Cool! I have done something quite similar. Last year I bought a complete Toyo 45G for €150, added an original Toyo bag bellows for €20, and rigged up a Mamiya 645 camera-mounting lensboard. The latter consists of a Toyo lensboard with a hole for a Copal 3 shutter, through which a Kiev60/P6 62mm reversing ring passes, which is locked on the other side of the lensboard by threading on a 77-62mm filter step-down ring; this ensemble makes a lensboard onto which a P6-mount camera could attach. Then my Mamiya 645 attaches via a P6/Kiev60 to M645 adapter, and it has enough clearance for the metering prism. In other words, this is a complete M645 tilt-shift bellows system, with standardised LF lensboards and lenses. Can do incredible macro and special lens-movements effects. Pretty much any glass ever made could be mounted on a front lensboard; the camera provides the shutter and the 45G provides the accurate bellows R&P focussing. You were obviously thinking the same!<br /> <br /> I like your clever makeshift bellows between the standards - but you should look for a Toyo bag bellows, as this can allow the standards to come so close together, they almost touch. It might allow you to use lenses with shorter registration distances than the RB67 ones - I have had good experiences with similarly mechanically-broken Bronica SQ PS lenses.</p>

[paul_ong1]

<p>John,<br>

Thanks for the reply. Sorry that did post earlier about needing Mamiya 50mm, but hope you like your new 50mm. Do you happen to know the distance from the flange to focal plane for the Universal? Don't know how old the Schneider is. It is a Super Angulon, f/8, serial number 13 273 xxx, and no "TECHNIKA" marking. Even with a better version, I may have the same problem, which is that the rear of the lens hits that DSLR mount before it can focus at infinity. I have a custom mount that allows me to put on a filter to protect the DSLR and allows it to rotate freely for alignment. It sticks past the lens board on both sides. So, my next steps are to play with the 90mm KL to see if I can get better sharpness and look for a Mamiya 50mm.</p>

<p>Yes, a sunken board would be nice. Is it for a Toyo or some other brand? If not a Toyo, I probably can adapt it. Thanks again for your generosity.</p>

[paul_ong1]

<p>Ray,<br>

Sounds like you and I are on the same page. There is another person who created a Toyo-RB67 hybrid. Like your idea about using a reversing ring. I will have to give that a try when I get a Mamiya 50mm.</p>

<p>My hybrid builds on those done before by expanding the hybrid into a three parts: Mamiya RB67 lens in front, the Toyo 45G in the middle for technical controls, and a Nikon D70 DSLR in back for capturing digital images. Going digital allows me to experiment with many photos on the cheap and get faster turn around time, thus shortening the learning curve to learn technical controls.</p>

<p>I also am considering Bronica lenses as an option to RB67 lenses. The Bronca SQ's register length is not as long as the RB67, but appears to be sufficient.</p>

<p>I have a Toyo bag bellows, but it is harder to use than my custom bellows. I amy give it another try as I refine the hybrid.</p>