Reversed Zoom projection 5-7" 3.5 freelensing first sh

jamaeolus · Expire: 2015-08-20

This came in a lot of Minolta lenses. Its a generic projection zoom lens from the "zebra" era. Gorgeous hunk of metal and glass. It is VERY robust. The helical is a slotted aluminum tube nearly 1/4 inch thick with brass pegs protruding into the slots form the front lens mount assembly. The lens label bezel is also nearly a quarter inch thick. I had to clean some haze from the interior of the lens assembly so I know for a fact it is at least 5 element. The haze was a very well stuck to the glass. I had to scrape it with a wooden tongue depressor to get it loose, as repeated wipes with lens cleaner then isopropyl had no effect. My guess it was degraded lens coating material. Anyways after getting it back together I started playing with it. I could not get an image using it in the standard configuration. So on a whim I reversed it and immediately got a nice image. This is the first shot hand held free lensing. I had the a7ii set to stabilize 50mm as I have no idea how to figure the FL of a reversed lens. Light was just the ambient indoor house lighting ISO was cranked so they are bit noisy.

Another image.
[url=http://forum.mflenses.com/userpix/20173/big_7980_DSC09573es_1.jpg]

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and a crop

kds315* · Expire: 2021-03-09

jamaeolus · Expire: 2015-08-20

Thanks. I was surprised how well it actually performed. I can't wait to fab a more secure adapter and try it daylight to see what it will actually do. The EVF at max magnification looks much better than the photos which tells me I had significant motion blur in the shots I took. Anybody know how to figure the focal length on a reversed lens? It would be useful to set the IBIS to the correct setting.

jamaeolus · Expire: 2015-08-20

A few more shots. I ghettoed an adapter using a "water weeenie" foam tube and rubber bands. These were taken with a tripod and using a reading lamp for lumination. This shows how thin the DOF is on this sucker. It was relatively easy to use this way as the reversed "zoom" actually allows you to use as a focus system. A bit touchy, but much easier than shifting the tripod.

crop

kds315* · Expire: 2021-03-09

dr.volkan · Joined: 14 Nov 2008 Posts: 436 Location: Turkey_istanbul

Very good results congratulations

jamaeolus · Expire: 2015-08-20

Thanks! I was pleased with the sharpness. Trying it in any situation with much backlighting showed horrendous reduction in contrast and bad flaring. Looking through the lens at a strong light showed some residual haze, likely more degraded coating as I cleaned them carefully with alcohol. I also plan to paint the rims of the lenses elements flat black as I understand tha helps reduce flare.