240 mm f5.6 focal lengths unavailable in copal 0

[jgsnel]

Dear photographers, I am new to LF photography. Can someone explain why larger focal length lenses with f5.6 exposure come with heavier shutters (like copal #1 or #3) supporting smaller minimum shuttertime (< 1/125 sec or < 1/200 sec) instead of 1/500 sec with copal #0?

I want to use a 240 mm f5.6 lens for portraits on location on a 4x5 inch camera using 5.6 for very small depth of fields. In bright light circumstances I expect to use 1/500 sec shuttertime otherwise I have to use very slow film. Moreover, the use of f/5.6 over for example a f/9.0 lens gives more than one stop brightness on the groundglass, which I do prefer more than the lesser weight of a f/9.0 lens.

If no such lens exists (240 mm f/5.6 copal #0), or if no such shutter exists (range up to 1/500 sec) that will support the lens, would you be so kind as to give me an advice on a good 240 mm f/9 copal #0 lens?

I read on Kerry Thalmann (http://www.thalmann.com/largeformat/future.htm) that the 240mm f9 Fujinon A is a good option.

Thank you for advising me.

With kind regards,
Jeroen Snel

[Drew Wiley]

About the closest thing I can think of would be a 250/6.3 Fujinon W with no.1 shutter.
The faster the max aperture, the bigger the lens needs to be relative to a specific
focal length. It's just part of the law of optics. And with bigger apertures at a certain
point come bigger shutters. The only thing in a zero shutter is the 240A Fujinon - a
wonderful lens but certainly not shallow depth of field due to smaller max aperture.
Also be aware that the shutters for these kinds of lenses aren't generally accurate or usable at higher speeds. You'd need flash sync.

[John Koehrer]

Just a guess here, but I'd suspect that the aperture is limited by the diameter of the shutter itself.
240/5.6=42.85mm
240/9=26.66mm

[Dan Fromm]

240/5.6 = 42.9. Maximum diameter of a #1 (Compur/Copal/Prontor standard) shutter's diaphragm = 30.0 mm.

The lens' entrance pupil's diameter, which is what matters for relative aperture, can be larger than the shutter's diaphragm -- that's why 210/5.6's can use a #1 -- but I don't think that many 240's front cells magnify the diaphragm's image by 40%.

The bigger the shutter the more force required to accelerate and decelerate the blades to get a given shutter speed. Big shutters have slower top speeds than little 'uns because of reliability and cost considerations.

[Andrew]

the g-claron 240mm f9 has a good reputation and comes in copal 1 and the specs sheet says it only weighs 330g in that shutter... which is 6g less than the fuji in the smaller copal 0 shutter !

[Drew Wiley]

Andrew - the spec sheets are off. I have both lenses and the G-Claron is a little bit
heavier, probably due to the bigger shutter. Otherwise they are similar optical formulas and both superb performers.

[ic-racer]

If you are not stopping action, most would use a ND filter for the application you suggested.

[Drew Wiley]

Andrew - just checked the spec sheets I have on file. The 250 G-Claron in Copal 1
is 330 grams, the 240 Fuji A in Copal 0 is 225 grams. This seems about right. I don't
know where you got your numbers, but I don't have time to demount my lenses and
actually weigh them. They're both very light compact lenses. Another contender,
though with much less surplus coverage, would be the 240/9 Apo Ronar.

[Andrew]

...

[Andrew]

Drew, I have the 240 g-claron too but I don't have accurate small scales to weight it and I think the exercise of nit picking over small differences is a bit silly anyway... though I can definitely see the difference between a copal 3 mounted lens and the smaller f9 lenses being discussed.

now can't find where I got the fuji weight so I gues that may have been wrong