Using aperture scale (Copal 3) on 210 mm Angulon

[billkantor]

<p>Attached is a close up of the aperture scale on a Copal 3 housing my 210mm Angulon.<br>

Question is where do you place the aperture pointer to achieve the desired settings? I have been using the midpoint of the numbers. E.g., if I want f/22 I set the pointer in between the first 2 and the second 2. This is only possible up to f/32. Then it appears that for f/45 there is a marking with a line showing where the pointer should lie. Mysteriously there are two unlabeled dots after f/45. What do these mean? f/64, f/90.<br>

Can anyone clarify?<br>

Thanks,<br>

Bill</p><div></div>

[vick_vickery]

<p>I've always used the midpoint, too, but I think that it is really a purely academic exercise...anywhere in that area is so close that you couldn't tell any real difference in the exposure.</p>

[vick_vickery]

<p>Oh, I forgot the last part of your question...senior momert :) ...f/45 would be at the line, and, yes, I would assumme that the two dots would be f/64 and f/90 although the spacing of the dots makes me a little suspicious. I would probably not stop down past f/45 anyway since the performance of most lenses suffers when stopped down that far.</p>

[billkantor]

<p>Agree. I am not so worried about this up to f/32. Up to this point I can even reasonably guess at 1/3 stop positions. But after this things get very close together. I can't set 1/3 stops between 32 and 45. (OK, I can work around that.) But I am wondering what those mysterious dots after f/45 are intended to represent.</p>

[leicaglow]

<p>Yes, you're doing it correctly. If the aperture continues to close as you go after f/45, I would say they are the mysterious f/64 and f/90. They probably don't have numbers because the spacing is too small.</p>

[User_503771]

<p>I agree, I think that the dots represent additional aperture markings. Lucky you!</p>

<p>I do believe, though, that you won't know how the lens performs at those apertures until you actually try them. You might be pleasantly surprised.</p>

<p>I say this because the Angulon would be a fairly old lens, and old lens design. It's a well proven design, to be sure, but who knows how that particular lens measures up to the standard for that lens?</p>

<p>Some of the older designs actually do either show improvement at very small apertures, or at least don't suffer too much.</p>

<p>In any event, the proof will be in the pudding, when it comes to accuracy of the markings.</p>

<p>If you have a roll film back, you could run a test of the aperture-shutter speed relationship and accuracy without burning up a bunch of sheet film. Shoot wide open, then stop down/adjust shutter speed, etc. and so on. If the exposures all look about the same, you've got it made.</p>

[friedemann_pistorius]

<p>Yes, those dots are f64/f90 marks. Unlike modern scales, where the numbers are evenly spaced, the numbers on your aperture scale are set in a logarithmic manner, which you can recognize by the spacings between the numbers - they're gettings closer and closer, as the numbers grow. The two dots follow exactly that pattern.</p>

 

[billkantor]

<p>Thanks everyone for the explanation/confirmation.</p>

<p>Friedmann,<br>

So if the scale is log then where would the 1/3 and 2/3 stop marks fall (on a linear basis)? (I know I can calculate this but it sounds like you probably know.)</p>

[friedemann_pistorius]

<p>Bill,</p>

<p>well, to be honest, I'm everything else but an expert in math's.</p>

<p>Obviously, the spaces on the scale between f22 - 32 - 45 etc are so small that one can only guess where 1/3 and 2/3 lies, in my opinion it is useless. Between 8 - 11 - 16 - 22 the 1/3 and 2/3 stops are logarithmic, too.<br>

But, please don't ask me how to calculate that :-)</p>

<p>I would just guess where to set the pointer for 1/3 and 2/3, trying to follow the logarithmic "rhythm" of the full numbers.<br>

Of course, a third of an f-stop can make a difference especially when shooting transparencies. But with the fact in mind that shutter speed tolerances up to 30% are normal (as far as I know, however), I've learned to trust my guessings over the years. Men's eyes accuracy is better than one would believe!</p>

<p>This is not a very scientific answer, I know...</p>

<p>Friedemann</p>