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Focal reducers: a viable option?

V

Vivek

Guest
pix2pixels, Search for FC-ENG TMW-B1 (B4 mount, I have seen those converted for Arri mount).

While the thread you link is fascinating and informative, actual use on G1 and the image quality would entirely depend on the lens used and the reducer used (the combination). Good luck with your experiments and I very much look forward to what you come up with.

Also, those who are interested in history would find what Nikon did interesting.
See: http://www.mir.com.my/rb/photography/companies/nikon/htmls/models/digitalSLRs/E2E2s/index.htm
 
R

Ranger 9

Guest
I'd be the last one to discourage experimentation, but other than for Feynman's "pleasure of finding things out" (and I certainly don't want to underrate this)...

...To get enough space behind the lens to mount the reducer on your G1, you'd probably have to start with a 35mm-format or medium-format lens. The reducer would convert this into a lens with a shorter effective focal length and a faster effective aperture.

But since there already are so many short-focal-length, fast-aperture cine lenses available, and it's so easy to use them on the G1 with readily-available adapters, it's hard for me to see the point of this exercise.

Don't let that stop anyone from trying it, though, and like Vivek, I'd love to see some pics!
 

pentacon6

New member
I am also curious about that because I also find something with a similar design of Century optics does.

Opteka 0.3x wide angle

This lens is supposed to use on Video. The comment is not bad in some forum especially the skate broad player they need wide angle to capture the fast movie shot in limited space. Have someone used it? The only question is that would this lens degrade the image quality since it is resolution may not be superior enough for still photo.
 
R

Ranger 9

Guest
Make that FW-ENG TMW-B1.
I had a go with Google and couldn't find anything relevant except a patent application for a 'telepresence' system that suggested this as a way to mount an 8mm Nikkor fisheye on a video camera. It didn't give any information about the converter.

Searching Nikon's global website didn't turn up anything either.

Any further leads? I don't need to know, but I'm curious...
 
V

Vivek

Guest
The one from Century (no idea why I kept typing "New Century" :confused:)
is this 0.65X adapter: http://www.schneideroptics.com/ecommerce/CatalogItemDetail.aspx?CID=1069&IID=1757

I bought it (new) for $50 (shipped)from Hong Kong. It works just fine with the 25/1.3 Computar-TV lens (see sample shot). There is a slight hint of a CA that can be taken care of in the post. Sharpness wise, the lens becomes sharper!

I chose that particular one for these reasons:

1. Size/weight.
2. Price.

The 0.3x is a fisheye, likely to be a very large one and heavy.
 
P

pix2pixels

Guest
Vivek,
JVC, and many other video cameras have use a trichroic beamspliter prism to divert the image formed by the lens to the 3 RGB sensors as described in this article.

The lenses (stills, movie) designed for flat field projection will cause severe chromatic aberrations if one attempts to use them in a 3 chip camera.

There are two different types of adapters:
- For using Cine, stills lenses on 3 chip cameras
- For using ENG lenses on cameras with single chip Bayer type sensor.
 
V

Vivek

Guest
Indeed. The link I gave is to show how the Nikon adapter might look like (particulalry the FW or the wide angle use one).

OTOH, the Computar-TV 25/1.3 I use is most likely made for B/W security cameras. I doubt if Panasonic's proposed 20/1.7 can better its performance and ease of handling.
 
B

borissimo86

Guest
Don't know if I should resurrect an old thread. I've been a long time visitor of these forums, but this is my first post. Specifically, this is one of the threads that inspired me, so I'm playing it forward:

YES, it is possible to use an astro focal reducer with a micro 4/3 camera. I've done it. If anyone's interested, I'll post some pictures of both the adapter and sample images, but here's the gist of it:

PROS:
+ Wider field of view, more lens coverage
+ Faster lens speed. Great for F4 lenses or slower

CONS:
- *Slightly* reduced sharpness and contrast, but not much
- Doesn't make fast lenses any faster. In fact, it makes them look terrible
 

RichA

New member
The astro stuff would be useful only with a telescope of long- very long focal length- lenses.
Well, I've seen them used on scopes from f5.9 to f10 focal ratios. The converters actually improve the image by flattening the field, producing better edge definition. Camera lenses (most of the teles) already provide flat fields. The reducers come in ranges from f3.3 to f6.3 (so your 2000mm f10 telescope becomes an f6.3 1260mm, as an example or even a f3.3 660mm!). However, except for the f6.3 from Celestron, Meade and generic sources which was made to support 35mm film formats, the others are made for smaller astronomical CCDs and might not support the whole 4/3rds field. Unlike the relatively poor quality camera converters which screw on the front of lenses, the astro units go behind the lens so they would need to be adapted from their threaded mounts. However, it might be worth experimenting with.
 
B

borissimo86

Guest
I used a Vixen 0.6x C-mount reducer. It was made for 2/3" CCD cameras but it actually covers the whole 4/3 sensor! Funny enough, it never actually worked with my C-mount lenses. The rear fit into a C-mount just fine, but the front (female part) was made for 1.25" eyepieces. It might be good for astronomy and telescoping, but pretty useless for general photography out of the box. It was expensive too, something like $185 used if I remember correctly. I know there are cheaper reducers out there, but I bought this one thinking it will work with C-mount lenses, as the name implies. I was wrong. Because of micro 4/3's flange focal distance, this reducer will only work with Nikon lenses, and even longer flange focal mounts like T-mount, and PL-mount. By the way, this particular reducer has been discontinued now and is almost impossible to find online.

I unscrewed the actual reducer from its original mount and put it through a regular C-mount to micro 4/3 adapter that I got off Ebay. I filed the adapter's opening to allow for the reducer's larger diameter. Then, I had to file the front and back "hoods" of the reducer to get the optic closer to the sensor in the back, and closer to the lens in the front. It is all held in place by superglue. When mounted, it's a very tight fit; I really can't get the reducer any closer to the sensor without hitting something or getting it jammed.

Here is how it looked like modified to c-mount :


And this is how the finished adapter looks, with the Nikon mount:



It fits my E-P1 like a glove to a hand! I calibrated it for infinity focus with Nikon lenses (actually, it goes past infinity, but only slightly). There is no blur, no tilt/shift effects, no stray light pollution, or any other outside factors affecting the image quality. Lens speed is increased, and it's pretty sharp for what it is, although contrast is decreased. Here's a test... it was shot at ISO800 to avoid blur from my handshake, but I'll have some low-ISO shots soon for you guys:


ROKINON FISHEYE 8/3.5 NO REDUCER:

OLYMPUS E-P1, F3.5, P MODE, -1.7 EV, ISO 800, 1/13 sec



ROKINON FISHEYE 8/3.5 WITH 0.6x REDUCER:

Being a fisheye, the distortion is (obviously) caused by the lens and NOT the reducer. The vignetting seen above is also not from the reducer but from the lens. The fisheye lens is DX format, made for Nikon's APS-C, so it creates a smaller circle than a lens designed for a full-frame would. I actually shaved off the fisheye's hood to get more coverage for this test! I get no vignette with other, full-frame 35mm, lenses.

Here is a vignette test for this fisheye with the reducer. This tests the lens vignette, NOT the reducer's: http://img822.imageshack.us/img822/5453/ep1reducerfisheyevignet.jpg
And here is a test with the same lens on full-frame (Canon 5D) and APS-H (Canon 1D) cameras: http://www.360pano.de/en/samyang_5D_1D.html

As you can see, the lens coverage with the 0.6x reducer is somewhere between APS-C and Canon's APS-H. This means that some of Nikon's DX lenses will vignette with this reducer.

I have a couple of more Nikon lenses to test the reducer with: Nikkor 105/2.5, Nikkor Sigma 30/1.4, Nikkor 43-86mm F3.5, and Nikkor 28/3.5. I will provide more sample images soon :happy:
 
J

jwestra

Guest
Thanks for the response. I already found this on a different forum before your update :).
Looks promising but difficult to judge with the fisheye. Do you also have some examples with a different lens (I think a full frame lens would be perfect)
 

zcream

New member
Hi Vivek. Do you have a link where you bought the Century 0.65x for 50/-

I can only see the old Sony PD150 ones on ebay. And a New Century adapter for 300/-

I assume you used a40.5mm - 37mm step down adapter for it..

Indeed. The link I gave is to show how the Nikon adapter might look like (particulalry the FW or the wide angle use one).

OTOH, the Computar-TV 25/1.3 I use is most likely made for B/W security cameras. I doubt if Panasonic's proposed 20/1.7 can better its performance and ease of handling.
 
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