Componon-S 5.6 180mm

[john_cooper9]

I just got a barrel-mounted Componon-S f:5.6 180mm from Ebay. I have a 240 f:5.5 Tele Arton in a

compur 1 shutter. I have switched the cells. Since the Tele Arton is F:5.5, I assume the shutter markings

will work accurately for the Componon-S.

 

I seem to remember that the Componon-S and the Symmar-S were basically the same lens but the

Componon-S had slightly less/more(?) spacing between the two cells.

 

Should I add a spacer between one of the cells and the shutter and how much is needed? If the spacing

was less then how much should I take off one of the cell's flange?

 

I want to use the Componon-S 180 on 4X10. It may not cover infinity, but should provide coverage at 1:10

or less.

[ole_tjugen]

You assume incorrectly about the aperture scale. Tele lenses are wildly different beasts from more-or-less symmetrical plasmats, so your apertures are likely to be wildly off.

 

As to the rest - if you are intending to use the lens at 1:10 or less to get the necessary coverage, I can't see any reason to attempt to optimise it for infinity...

[dave_s]

(i) For a 240, f/5.5 means an aperture 44mm in diameter. For the 180, f/5.5 means an aperture 33mm in diameter. The optics might be complicated by the fact that the T-A is a tele, and we might really be talking about the front pupillary diameter or something, but I think the bottom line is you should assume the aperture markings will not be transferable from one lens to the other. (Shutter speed markings, which is what you wrote, will be the same.) One of the sages will correct me if I'm wrong.

 

(ii) You need to throw an image circle of about 275mm to cover 4 x 10. I don't think the Componon will make it, unless you're doing closeups. If it were a 180 Symmar, it would just about cover your film at infinity.

[thomas_vaehrmann]

Hi John,

 

Componon-lenses are optimized for 1:4 for the larger formats to 1:10 for the smaler ones. I use a 240mm Componon on my Linhof without any shim-rings or bothering about best ratio from close up to infinity with good results. So giv'm a try. The image circle is not as big as the Symmar one's and that seemed to be the biggest difference to me apart from the lens-arrangement which is indeed different. Concerning the f-stop scale I guess it would be one stop off if you use the 240mm scale for the 180mm lens.

 

kind regards+happy shooting

 

Thomas

[alan_rockwood]

You could have a new scale engraved by Grimes.

[john_cooper9]

How is my logic:

 

1) the 240 mm Tele Arton is a telephoto design, the opening at the shutter is 30mm at f:

5.5;

 

2) the 180 Componon-S in its barrel mount is about 26mm at f:5.6;

 

3) apertures 8 11 16 etc. are geometric progressions and are therefore independent of

lens focal length;

 

4) I can live with the difference between 30 and 26 (1/8th stop);

 

5) I will shoot with the lens using the shutter's marked aperture scale and see what

happens.

 

Too much theory, not enough "try it and see".

[peter_langfelder1]

4) I can live with the difference between 30 and 26 (1/8th stop)

 

John, the difference between 30 and 26 in aperture diameter is almost half a stop (more precisely 0.41 stop, between 1/3 and 1/2).

[john_cooper9]

Peter,

 

4) if you calculate the area for each dimension using pi.r(squared) you get an area ratio of

225 to 169 which is a ratio of 1:0.75. Where does the 0.41 figure come from?

[thomas_vaehrmann]

Hi again John,

 

if you still have the barrel-mount why don't use a ruler or caliper and transfer the f-stop to the shutter and make your own scale?

 

kind regards

 

Thomas

[john_cooper9]

Thomas,

 

A brilliant idea (why didn't I think of that!). I have the Schneider enlarging barrel so it should

be easy. The barrel aperture is 5-bladed whereas the shutter is almost circular in shape.