a finder for the Koni Omega 135mm

sanmich

sanmich

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I like my KO quite a bit, and have recently put my hands on a decent 135mm.
The only problem is that the frame for it is simply awful: four little dots in the frame corners, getting lost between all the other frames.
Any suggestion for an external finder?
A 40mm FOV finder for 35mm is not an option because of the frame ratio, but maybe a finder for 4x5 could be close enough?
 
Try a Tewe with an external mask - a couple of strips of tape will do it. Another option (big!) is a Linhof or MPP finder.

It wouldn't be 40mm, though. On 6x7cm, 135mm is about like 65mm on 35mm. That's the advantage of a zoom finder: you can set it exactly.

Cheers,

R.
 
Or a Nikon (Nippon Kogaku) Varifocal. They go from 35mm to 135mm (without the extortionately expensive WA adapter). Parallax corrected, nice build quality and looks good as well. I rather like mine. I use it for the 90mm Hexanon on my R-D1. (90x1.5=135)
 
" On 6x7cm, 135mm is about like 65mm on 35mm."

That claim is based on equating the diagonals of the 6x7 and 135 formats, which in this case makes little sense (if indeed it ever does, for this sort of purpose).

If you're going to use an external VF designed for 135 format, equipped with an external mask (say, tape) to reshape the 2:3 aspect ratio of 135 format to the 4:5 aspect ratio of 6x7cm format, then the obvious place to start is by equating the short sides.

For a KO, the short side has length about 56mm, while for 135 format the short side is 24mm. So the conversion factor is equivalent to 56/24 = 2.333... . That translates to about a 58mm lens on 135 format. Locate a finder intended for a 58mm lens on 135 format, mask the ends of the long side to force 4:5 aspect ratio, and you're there [ignoring things like parallax, etc.].
 
JRG said:
" On 6x7cm, 135mm is about like 65mm on 35mm."

That claim is based on equating the diagonals of the 6x7 and 135 formats, which in this case makes little sense (if indeed it ever does, for this sort of purpose).

If you're going to use an external VF designed for 135 format, equipped with an external mask (say, tape) to reshape the 2:3 aspect ratio of 135 format to the 4:5 aspect ratio of 6x7cm format, then the obvious place to start is by equating the short sides.

For a KO, the short side has length about 56mm, while for 135 format the short side is 24mm. So the conversion factor is equivalent to 56/24 = 2.333... . That translates to about a 58mm lens on 135 format. Locate a finder intended for a 58mm lens on 135 format, mask the ends of the long side to force 4:5 aspect ratio, and you're there [ignoring things like parallax, etc.].
Click to expand...

Funny, I would have said it was closer to a 60mm lens in 35mm photography. But then math never was my strong suit.
 
sanmich said:
Of course,
I had the 90mm in mind...
thanks for the correction, Roger
Click to expand...

On a 6x7 rangefinder, I wouldn't think the difference between 90 and 100 would be much to worry about. But I don't know if you have 100mm frame lines on the KO. I do on my Super Press 23.
 
JRG said:
" On 6x7cm, 135mm is about like 65mm on 35mm."

That claim is based on equating the diagonals of the 6x7 and 135 formats, which in this case makes little sense (if indeed it ever does, for this sort of purpose).

If you're going to use an external VF designed for 135 format, equipped with an external mask (say, tape) to reshape the 2:3 aspect ratio of 135 format to the 4:5 aspect ratio of 6x7cm format, then the obvious place to start is by equating the short sides.

For a KO, the short side has length about 56mm, while for 135 format the short side is 24mm. So the conversion factor is equivalent to 56/24 = 2.333... . That translates to about a 58mm lens on 135 format. Locate a finder intended for a 58mm lens on 135 format, mask the ends of the long side to force 4:5 aspect ratio, and you're there [ignoring things like parallax, etc.].
Click to expand...

Sure, that's a much more accurate calculation. But as I said, with a zoom finder, you can zoom to exactly the right focal length. Either way, it's not 40.

Cheers,

R.
 
Finder said:
This finder may work out for you:

http://cgi.ebay.com/Viewfinder-4x5-...ewItem&pt=AU_FILM_CAMERAS&hash=item3f0070dd9e

The 4x5 masks would be close to 6x7. You could even cut your own. The company also makes a "zoom" finder using an adjustable mask. I use a zoom finder with my 6x12 camera--not as nice as my Horseman finder, but not as expensive either.
Click to expand...

This one seems a very good solution indeed.
Now, just to check my calculation: the equivalent FOV for 4x5 (of a 135 in 6x7) would be about 240mm, and my best bet should be the 250 mask?
 
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