Graphic Kowa f9 in barrel f6.8 in Shutter?

[Sven Schroder]

Hello All

Similar to the f9 computar does the kowa go to f6.8 in a shutter? in looking at the barrel the f9 setting is 5mm smaller than the pupil of the elements; so more glass should mean more light?

I have the 305 and matching copal 3 s (early one came with a commercial astragon) the existing scale is for f6.8 360 , measuring and comparing the kowa barrel and the shutter the apertures match only third of a stop more in the shutter (with a spotmeter on a light box).

Can I use this scale? are scales available for the early copal 3 the ones with the different colours on the levers i.e red on the cocking lever, green on the aperture.

I am aware of the sevice workshops you have in the US, here in the UK thats something we lack or can anyone recommend a UK solution.

I'll be making some test shots later in the coming week(looks great on the ground glass), so theories can be tested and thanks in advance (and for the knowledge I have gained from this forum).
Sven

[Clayton Tume]

Sven

I have one of these, I got SK Grimes to make the aperture scale for it. They can make the scale without having the lens and shutter on hand so you'd only have to tell them what you have and they'd post the scale to you.

I measured the pupil of the rear element and it came out at f8.7 which doesn't sound right but the opening is 35mm. Maybe I have my measurements wrong.

I can email you a photo of the scale if you like or give you the measurements for the f stops from the mounting screws.

By the way it's a great lens, one of my favourites.

Clayton