How do I choose a shutter (size) for this Petzval lens?

The width is slightly more than 5 cm, as you can see. The aperture is f4 for 152mm, which—if I understand aperture numbers correctly—suggests a maximum aperture opening of about 150/4 = 37.5 mm?

If I look here:


I'm concluding that Copal and Compound #3s will be sufficient, but I'd love to hear from experts with more experience than me.

I see some Copal #3s on eBay in great condition for 250-299.

But some of the Copals are listed with aperture numbers, which I don't understand. How does a shutter have an aperture rating? It has not absolute focal length.

Thanks for your help!

You could hang it in front of an Alphax #5 or a Compound #5. Or hang one of these shutters in front of it.

Dan Fromm said:

You could hang it in front of an Alphax #5 or a Compound #5. Or hang one of these shutters in front of it.

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Thanks. Do you think I necessarily need to go that big? The Compound #5 I was able to find was tricky to track down, and I'm saving it for my other, larger brass lens. If this one fits a Copal #3, that would be very convenient and less expensive than a #5.

Are there drawbacks to front/back-mounting a shutter rather than paying for the shutter to be integrated into the lens? Thanks.

ame01999 said:

Thanks. Do you think I necessarily need to go that big? The Compound #5 I was able to find was tricky to track down, and I'm saving it for my other, larger brass lens. If this one fits a Copal #3, that would be very convenient and less expensive than a #5.

Are there drawbacks to front/back-mounting a shutter rather than paying for the shutter to be integrated into the lens? Thanks.

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I just checked at https://skgrimes.com/shutters/ and a Copal #3 might to.

Drawbacks to front mounting? Vignetting by the rear of the tube is possible, especially with short wide angle lenses. Shouldn't be a problem with your ~ 150 mm magic lantern lens. By the way, try to measure its focal length. The result might surprise you.

Mounting the lens in shutter? Costly, and your lens isn't made for that. It doesn't seem to have a diaphragm, so you or your machinist can't be sure where the glasses should be located in relation to the shutter's blades.

I'm not sure you understand what front mounting entails. I have a small heap of lenses set up for front mounting, and a smaller heap of cup-shaped adapters for front mounting. Lens screws into adapter, adapter screws into a shutters' front tube. More lenses than adapters because some of my lenses have the same rear threads and because a few were made to screw directly into a shutter. I have no shutters dedicated to a only one front-mounted lens.

You have a Compound #5. Great, you can use it for the two brass lenses you've mentioned. Unless, that is, the longer lens is actually made of two cells that screw directly into, respectively, the front and rear of the shutter.

ame01999 said:

But some of the Copals are listed with aperture numbers, which I don't understand. How does a shutter have an aperture rating? It has not absolute focal length.

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Its likely that a bare shutter for sale once had a lens mounted in it, and the aperture numbers on the shutter related to that lens specifically. A lot of barrel lenses have their own aperture, so for them you'd ignore the shutter aperture and use the lens aperture. If you front mount a lens without an aperture, I don't know how or how well the shutter aperture would work.

You might also look at Shanel shutters. The Shanel 5 has a ~50mm max aperture, and one, the 5A I believe, was probably intended for front mounting since it doesn't have an aperture mechanism. A member here @B.S.Kumar has produced some adapters for mounting lenses on Shanel. I doubt he has sizes that would fit your Petzval, but he definitely has specs on what the Shanel needs and can provide additional info on them (he may also have some for sale, or be able to get you one in good tested condition..)

You don´t need a shutter with the calculated diameter, a size 1 shutter with a diameter of 30mm is large enough because the diameter will be optical enlarged by the front cell.
I have a Wollensak Vesta 5/180mm. It has a calculated diameter of 36mm but it needs only 30mm.
My Derogy 4.5/360mm has a calculated diameter of 80mm but it has only 65mm.

The reduction factor of the calculated diameter and the optical diameter is around 1:~1.15-1.25
So I guess a Copal 1 or Compur 1 shutter with a diameter of 30mm should be ok.
You can find a lot of lenses with this focus and speed in this shutter size, Tessar, Xenar, the Plaubel Anticomar 4.2/150mm and I have a three element lens from Steinheil with f/4 and 150mm.

Some of the size 1 shutters maybe have only 29mm diameter, please check it before. The Press shutters have 30mm. I use Prontor and Copal Press shutters, all of it having exactly 30mm.

If the lens doesn't cover more than 4x5, a Speed Graphic will work with this on it. Heck, if it does cover more than 4x5, use the FP shutter from an SG on the FRONT standard-- a 6x9 would work. It's not trivial but it would give you a lot of exposure control for field use.