Wrong shutter for Nikkor W 150/5.6

[aquinas7]

Hello everyone! The other day I discovered that my 150 mm nikkor W has a shutter for 105 mm lens. As I understand, the aperture values is supposed to be wrong in this case - I should open up the aperture about 1/3 of a stop. Now, I haven't used the thing yet and my question is do I try to use it as it is by trial and error or should I just obtain the correct shutter? Thanks in advance!

[Kirk Gittings]

or you could make or have made the proper aperture scale.

[Dan Fromm]

Um, if I calculated correctly and both of your lenses are Nikkor-Ws, indicated f/5.6 on a scale for the 105 should mean f/8 for the 150. If you're not going to shoot wider than f/8, there's no need to do much. Buf if you need to know where stops larger than f/8 are for the 150 then the best thing to do is get the right aperture scale.

It is barely possible that www.skgrimes.com can send you the right scale without having to look at the shutter. I say barely because IIRC the Copals delivered with Nikkors have apertures that move in the opposite direction to Copals delivered with other makers' lenses. Note well, I could be mistaken.

[Oren Grad]

I say barely because IIRC the Copals delivered with Nikkors have apertures that move in the opposite direction to Copals delivered with other makers' lenses. Note well, I could be mistaken.

The direction of the aperture scale matches that on other brands, but the Nikkors don't use an aperture scale plate - the numbers are printed on the body of the shutter.

EDIT: Need to correct that - I didn't inspect closely enough. The aperture scale is actually printed on a large band that runs around the entire circumference of the shutter, and includes the Nikon branding and focal length/aperture specification as well as holes for the various controls to stick through. So in principle it could be replaced with another one, but it would literally be much more of a production than just swapping the smaller aperture scale-only plates you find on other brand lenses in Copal.

[Dan Fromm]

Thanks for the correction, Oren.

[Oren Grad]

No problem. It was your caveat that sent me to look, and I've ended up learning something!

[aquinas7]

I thank you all for your valuable insights. I sort of want to try to test it and see what happens, rather than to send it somewhere, maybe alongside my Nikon W 210.Otherwise my Mamiya RB will keep me forever from real shooting. I might be able to evaluate the differences in negative density on the light table. Anyway I view the problem as an opportunity to brush up on my optics and physics :)

[ic-racer]

To support Dan's calculation above; In a Nikkor brochure, one can see the shutter speed diamond appears to be aligned with f13 on the shutter for the 105mm lens and the shutter speed diamond appears to be aligned with f18 on the 150mm lens. Since those are one stop apart, indeed, a simple calculation might be all that is needed.

[Dan Fromm]

Hmm.

105 mm lens, f/5.6, entrance pupil = 105/5.6 = 18.75

150 mm lens, f/8, entrance pupil = 150/8 = 18.75

Now that I think of it again, this is only approximate because the 150's front cell is more powerful than the 105's so it will magnify the aperture's image more.

OP, to be sure that this approximation is good enough put the 150 front cell in the shutter, set the aperture indicator to f/8, hold the lens/shutter at arm's length and measure the entrance pupil. I did this exercise once with 105 and 150 Saphir BXs, got the expected answer. ~ 19 mm.

[aquinas7]

One more thing: on the 150 mm shutter there is some space in both direction for the ultimate aperture values beyond the final numbers, that is beyond 5.6 and 45. Does that mean that the largest opening beyond 5.6 where the lever goes, is a real widest aperture for 150, that is 5.6, it should be right?

[Dan Fromm]

There's no guarantee. The Copal/Compur/Prontor/Seiko #0 shutter's maximum opening is 24 mm. 150/24 = 6.25.

150/5.6 = 26.8. This is a 150 mm lens' entrance pupil's diameter at f/5.6. We don't know the front cell's power so we don't know how much it magnifies the aperture's image. Remember, the f/# is focal length/entrance pupil's diameter, not focal length/aperture's diameter.

[Jim Galli]

The most common focal length were laid out in stops whether on purpose or by accident, long ago. 75, 105, 150, 210, 300, 420, 600 are all one stop apart from each other on a scale. Same with 90, 120, 180, 240, 360, 480 which is a 1/3rd stop from the first set. 135 and 270 are less popular 2/3 stop variants. Your f-stop scale reflects the same graduations. 105 is to 11 as 150 is to 16. Probably just confused everyone. Those relationships are constants.

If this is all boogered up, Dan will fix it. :cool:

[Dan Fromm]

Jim, you work for a gummint contractor. You're close enough for gummint work.