Bronica S2A - 2x tele extender - use?

[stephen_poe]

Just got a Komura 2x Telemore to use with my S2A - looks like a nice

piece of equipment, and will give me more use out of my 150mm

Zenzanon (= 300mm) and 200mm Nikkor (= 400mm). My understanding is

that using the 2x costs me 2 stops, so that f/5.6 is actually f/11.

And you just do the f stop "bookkeeping" in your head and remember

that you are always 2 stops less light than the lens indicates. Do I

have this right (you can tell my brain has gone to cheese using my

8008). Thanks

 

Stephen

[david_holland1]

Your bookkeeping is correct. Just multiply the f/ denominator by 2.

 

Just for the record, the 2x in your example gives you f/11 as to light transmission, but the actual aperture, which determines DOF, is still f/5.6.

 

And you are magnifying by 2 the circle of confusion along with the focused image.

 

Hence, you may very well need to use a smaller aperture than f/5.6 to get decent DOF.

 

I have the 2x for the P645N. With the 200/4 at f/8 and f/11 it is transmitting f/16 and f/22 respectively. That makes handholding marginal even in bright sunlight with 400 film, given that you're already coping with a little extra softness from the additonal glass.

 

I may be a wuss, but for me it's a tripod proposition if I want good odds to beat 35mm with a 200mm tele.

[stephen_poe]

Thanks, seems like it should not be too much trouble to keep track of the correction - and the fact that the DOF does not change is just fine with me. One of the lenses I would like to use the Komura 2x with is my Nikkor 105mm leaf shutter - I use it for portraits and it would be nice to retain the relatively shallow DOF that I like but to have a 210mm lens - seems to be no problem and I can retain shooting at f/5.6 DOF with correction to f/11, and have the ability to use the fill flash with the leaf shutter - hope I get time this weekend to try it out.