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Forum: Pentax Medium Format
12-08-2014, 01:03 AM
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Forum: Pentax Medium Format
01-08-2011, 08:15 PM
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I recently tested a Pentax A* 600/5.6 lens on the Pentax 645D. It worked well, but many images were blurred despite using MU and wireless remote (and a study tripod). I had an idea from the RRS (reallyrightstuff; http://reallyrightstuff.com/Items.aspx?code=LongLensPkgs&key=cat) catalog, where they describe a long lens support system. This provides a Y-support for the front of a lens.
However, the 600/5.6 has a very sturdy, and relatively short, front lens extension beyond the footplate. So I thought I'd flip the RRS design around and provide support for the body, as the body hanging off the lens can act as an oscillating mass.
I did a test with the single (standard) and the dual support setups. Items used: RRS TVC-24 Tripod, BH-40 head, CB-10 rail, B2-Duo clamp, MPR-ER (vertical bar), B2-mAS (clamp for MPR), B2-40LR (clamp for camera), and two B67 plates for the 645 body. In the upper right photo, you can see the CB-10 rail on the tripod head clamp; the B2-Duo clamp interfaces the CB-10 rail and the standard rail still on the lens's footplate (it has two nylon thumb screws). The B2-mAS is on the end of the CB-10 rail. Sliding up and down this clamp, is the MPR-ER with the B2-40LR on it's end. The 645D has two B67 plates, one seen on the side.
My readings on this forum seem to suggest that the 645 body is sensitive to vibrations in from 1/15 to 1/100 sec. I used 1/60 at f8 with MU and wireless release. I also observed a laser pointer on the set up. The dual support system had virtually no movement even when manually pressing the shutter release as the body and lens are rigidly connected.
The photos in the top row show the single support (a laser finder/pointer is resting on the handle) and the dual support setup. The bottom row shows 100% sized images taken at 7m with above setup. Not to be misleading, the single support setup did have the occasional sharp image; the dual setup was sharp every time.
This is not the first time someone has provided support for the body. The Manfrotto #359 system (reviewed here: 359) ties the body to the tripod. However, this design prevents easy re-positioning as the body is not fixed to different location than the lens. The RRS CB-10 based system is easy to re-position via the ball head (or a geared head).
This dual support setup would also work well with the Pentax 67 system. Due to the larger lenses, front lens support would be best, along with the longer CB-18 rail (8" longer than the CB-10). This front support would require adding parts at the lens end of the CB-18 rail: one CB-EC connector, one CB-YS and another B2-mAS clamp.
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