need some technical data on Mamiya Sekor 500mm f8

<p>Hello all,<br /> I have just acquired the beastly Mamiya-Sekor 500mm F/8 for my rb pro-sd for a song. However, it came with an aftermarket bracket, which is too short and too inconvenient to use while focusing. The original bracket prices range from 200 to 400 USD, which does not quite make sense, since it is a pretty straightforward piece of equipment. Thus, an idea was born to make a DIY bracket. And for that purpose I need your assistance.<br /> From what I have found on the net, there seem to have been several versions of the bracket (for rz/rb) and I am thinking of the simplest one pictured below (there is also a "curved" one, presumably for an rb, but i do not really see the difference). Image taken from *bay, solely for the purpose of illustration :<br /> <img src="http://www.kamera-boerse.com/store/image/data/_1010858.JPG" alt="" width="879" height="659" /><br /> ©Kamerabörse<br /> I would appreciate if someone owning such lens/bracket combination would be so kind and provide me with several measurements, mainly:</p>

<ol>

<li>The length (from end to end), height and width of the bracket.</li>

<li>Distance from the center of camera tripod screw to the near end of the 'cradle' or support ring. </li>

<li>Distance from the center of camera tripod screw (where the body goes) to the bottom tripod screw (where tripod QR plate goes).</li>

<li>Thickness of the 'cradle'/support ring.</li>

</ol>

<p>Thank you!<br /> ps if you have experience with this lens and have any thoughts or comments to share - I'd appreciate that too:)</p>

<p> </p>

<p>1) Overall length, end-to-end, just shy of 13 inches (12" 15/16ths of an inch).<br /> ...Width of flange at body: 2" 3/4 inch, with a fore and aft measurement of flange, 1" 5/8ths inch,<br /> ...Bar stock of main rail: 3/8ths" thick, by 1" 5/32nds inch wide,<br /> 2) For teeter balance, the tripod mounting hole is located 4" 7/8ths inch from body flange end of the bar,<br /> ...or 8" from center of tripod hole, to center of lens cradle mount holes.<br /> 3) 3" 29/32nds inch<br /> 4) Thickness of the ring is just shy of 3/8" inch all around, except where a 'flat' is ground at the point where the ring mounts to the bar. At that point, thickness is just shy of 1/4" inch.</p>

<p>The rollers (there are two) that support the lens, are located at 4:30 and 7:30, clock face positions, (Aprox).<br /> Inside diameter of the ring is 4" 3/8ths inch.<br /> For DIY bracket, it really wouldn't be necessary to fabricate a completely circular cradle ring; a stubby sling-shot frame, or "Y" bracket would suffice. (see link)</p>

<p>The bracket in the link below is for use on both, RB or RZ bodies, and for use with either the newer 350mm lens, or older 360mm lens. Notice there is 'step' cut at the cradle end. This step enables the cradle to be moved for use on RB or RZ. Cradle is mounted on the high step for RB, on the lower step for RZ.</p>

<p>The RB body is just slightly larger then the RZ body, (center of lens throat to tripod mount is greater on the RB).<br /> Most re-sellers list replacement brackets for the 500mm lens separately; a bracket for RB, and another for RZ.</p>

<p>http://www.usedcameraexchange.com/HAM1506/1.JPG</p>

<p>A Manfrotto 293 lens support might be worth checking out</p>

<p>AS a DIY project, all you are concerned about is taking the weight off the bellows rack. So any type of support to the body via tripod mount will do as long as it rides the lens for the full travel of the rack. Also remeber the camera still has to be able to mount on a tripod... such a long lens needs all the support you can get, even shooting at 1/500th.<br>

.</p>

<p> </p>

<p>The Manfrotto bracket could be an option, but only after some DIY additions of two small wheels on the front support, allowing bellows focusing. I do see how this could be an economical alternative to the dedicated brackets from Mamiya.</p>

<p>Marc, thanks for your time and detailed info. That's all I could ever need to build the bracket.<br /> Gareth, I was thinking about the Manfrotto 293, but it somehow doesn't seem solid enough for a heavy outfit like this. And it does not differ too much from the bracket that came with the lens (Marumi MAS 1174 PRO) which would be pretty useable, albeit too short for the 500mm. <br /><br /> Paul, sure, taking the weight off the bellows rack is one concern, along with the requirement that the supporting cradle/ring must remain under the front part of the lens that moves parallel to the bracket while focusing. <br /> Thanks again for your contributions. I have just done some quick test shots with a polaroid back - the lens performs very nicely, even "wide open". all it needs is a solid and convenient support bracket:)</p>

<p>If you still have the lens- I found constantly bolting the bits together a complete pain so I bought a cheap tripod shoe for a nikon zoom with an 82mm diameter aperture (see Amazon} and wrapped a slim band of sticky velcro round the narrowest part of the lens. This ensured a tight fit and prevented any scratching. The lens can now be fitted directly on the tripod and when the hood is attached together with the RZ, waist level and back it balances really well. I would not add the prism or winder though as the extra weight might harm the mount. The complete lens is now a doddle to put up and fits conveniently in my big bag- hope this helps you and anyone else with one of these beasts.</p>