I just purchased a 150mm f9 Computar off eBay. My goal is to test this lens as a possible wide angle on 4x10. I also have a 150mm f9 Graphic-Kowa that is supposed to be the same, but maybe not (there have been conflicting reports on the coverage of these two similar lenses). I plan to tset both and keep the one I like best (if there is any difference).
In any case, unlike my 150mm Graphic Kowa that came in a barrel, this Computar came in an obviously non-original Polaroid Copal shutter. This shutter has a couple limitations compared to a standard Copal No. 1 shutter, but those may prove irrelevent in this case. First, since it is a self-cocking shutter, the top speed is "only" 1/125 sec. compared to the 1/400 sec of the standard Copal No. 1. Not an issue for me personally as I can never recall taking a single large format image at a shutter speed faster than 1/125. Second, the maximum opening of the aperture blades isn't nearly as large as a standard Copal No. 1 shutter. This might be an issue if attempting to use this shutter with a faster 150, or longer lens. However, in this case, the maximum aperture opening is a hair larger than the internal field stops of the lens cells (in other words, the diaphram does not limit the maximum aperture, the cells do). In fact, I'm told by the seller that this shutter is originally from a 75mm f4.5 Polaroid Tominon lens. In that case, it would seem I can just double the marked aperture setting to get the true aperture of my 150mm lens. In other words the f4.5 setting = f9, f5.6 = f11, f8 = f16, etc. all the way down to f45 = f90. As long as I can remember to mentally multiply by two, I don't even have to go to the expense of getting a new aperture scale engraved.
And much to my pleasant surprise, this Polaroid Copal shutter is significantly lighther than a standard Copal No. 1 shutter (115g vs. 160g). The shutter speeds all work properly and seem every bit as crisp and snappy as any other Copal shutter I own. There is no press focus lever, but the shutter has a T setting that can be used for focusing.
So, what's the catch? Is there one? The smaller max. diaphram opening (about 15 or 16mm) would limit the usefulness of this shutter for faster or longer lenses, but in this case it seems to be a good match. Am I missing something here, or did I just get a good deal on a shutter mounted lens that will cover 4x10 and weigh less than 200g?
Kerry
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