Front-mounting a Berthiot Perigraphe

[ntenny]

This is a followup on an earlier thread in which Dan Fromm pointed me to an Ilex #3 shutter as a suitable mounting platform for a Berthiot f/14 Perigraphe. (Mine happens to be the 120mm No. 3, but several focal lengths use the same barrel in my understanding.)

After a little bit of searching and an unfortunate misadventure with an Ilex #3 *Electronic* shutter (you know why they're so cheap? BECAUSE YOU CAN'T TRIGGER THEM MANUALLY!), I scored an Acme #3---it actually came with a decent-looking 215mm Acutar---and confirmed that the Perigraphe is a nice fit. I shimmed the threads with a little strip of cardstock to get a more secure fit, and the result is attached.

I'm mostly posting this for the benefit of future searchers, since these little lenses are reasonably abundant and cheap. Hi, future searchers; go get yourself an Ilex #3. (Acme or Universal should work, but not the Kodak versions.)

When the lensboard arrives, hopefully in the next few days, I'll try it out for performance.

-NT

 

[David A. Goldfarb]

If you front mount it on an Ilex #3, it probably won't cover 8x10". Mine was mounted by S.K. Grimes (when he was still around) in an Ilex #3 in the conventional way, using the shutter's iris, and it does just cover 8x10".

 

[ntenny]

If you front mount it on an Ilex #3, it probably won't cover 8x10". Mine was mounted by S.K. Grimes (when he was still around) in an Ilex #3 in the conventional way, using the shutter's iris, and it does just cover 8x10".

The rear threads will cause vignetting, I suppose? I think Dan said he had done some surgery on his shutter to prevent that---if I get really excited about this project, maybe I'll get a dedicated front-mounting shutter and do the same thing, but I expect I'll use it more on 5x7 anyway, where it isn't *so* absurdly wide.

-NT

 

[David A. Goldfarb]

Yes, the rear threads will vignette. I'm not sure how much surgery can be done to give you enough room. Even the conventional mounting cuts it close.

 

[Dan Fromm]

Nathan, the quick way to check is to hold the shutter in front of you and rotate it slowly until the rear tube just starts to occlude the lens' exit pupil. Estimate or measure the angle the shutter's been rotated. Do the exercise with the lens wide open and at your likely shooting aperture. Stopping down will help a little, not enough.

David's right, an Ilex 3 truncated like mine will give you around 270 mm before mechanical vignetting bites. A truncated Alphax #3 should just do it for you.

David, I use a similar triangles model to predict mechanical vignetting with front-mounted lenses. (tube ID/tube length) * lens focal length = diameter of the circle that can be covered without mechanical vignetting. If, that is, the lens has that much coverage.

 

[ntenny]

Well, with a conventional lensboard and the front mount I can't bring it to focus further than about 18" in front of the lens on my 8x10, and on the 5x7 it won't quite reach infinity. I'll need to get my wife to fire up the wood shop for a recessed board, but I can sanity-check its performance at portrait distances on the 5x7 this evening.

The good news is that at the point-blank range where I *can* focus the 8x10, I don't think I've hit the mechanical vignetting from the shutter. It may actually work as it is for macro use, although I don't know that its performance in that role will be too exciting. Dan, have you tried it for macro work in, say, the 1:1-2:1 range?

-NT

 

[Dan Fromm]

Well, with a conventional lensboard and the front mount I can't bring it to focus further than about 18" in front of the lens on my 8x10, and on the 5x7 it won't quite reach infinity. I'll need to get my wife to fire up the wood shop for a recessed board, but I can sanity-check its performance at portrait distances on the 5x7 this evening.

The good news is that at the point-blank range where I *can* focus the 8x10, I don't think I've hit the mechanical vignetting from the shutter. It may actually work as it is for macro use, although I don't know that its performance in that role will be too exciting. Dan, have you tried it for macro work in, say, the 1:1-2:1 range?

-NT

Re your focusing problems, what are your cameras? I ask because as I calculate it 18" in front of the lens is ~ 4.5 focal lengths, so on your 8x10 extension must be ~ 1.25 focal lengths, i.e., 160 mm, of which ~ 25 mm will be due to the shutter.

I have smaller cameras than you, but even my 4x5 Cambo and the CC-401 I sold early this year have minimum extensions much shorter than 135 mm. Given the shutter's thickness, you'll need minimum extension of around 95 mm to make infinity with a 120.

I haven't tried either of my f/14 Perigraphes (60, 90) closeup. I haven't felt the need to use them for closeup since I have other more luminous lenses that do very well closeup.

 

[ntenny]

Re your focusing problems, what are your cameras? I ask because as I calculate it 18" in front of the lens is ~ 4.5 focal lengths, so on your 8x10 extension must be ~ 1.25 focal lengths, i.e., 160 mm, of which ~ 25 mm will be due to the shutter.

Don't take my estimate of the distance as too exact, but both cameras are Eastman 2-Ds, which have pretty hefty standards front and back. I have a 111mm lens for the 5x7 that *just* focuses at infinity with the standards together---but it's in a Rapax shutter and conventionally mounted, which accounts for the extra few mm. The Perigraphe doesn't look like it misses by much on that camera, but on the 8x10 it's much more drastic.

-NT

 

[E. von Hoegh]

Was the original lens a 215 Acutar? That's a damn good lens!

 

[Dan Fromm]

Was the original lens a 215 Acutar? That's a damn good lens!

PMFJI. If you look closely at the shutter's aperture scale, you'll see that it is scaled for a convertible lens. The combined lens' maximum aperture is f/4.8.

Ilex' Acutar was a tessar type, said to be a clone of the f/6.3 Commercial Ektar.

Tessars aren't convertible, some plasmats are. The likely convertible plasmat was Ilex's own 215/4.8 Acuton, said to be a good lens.

Which were you thinking of? Oh, and by the way, I find Ilex' nomenclature nearly as confusing as Graflex'.

 

[ntenny]

My mistake---it is an Acuton. Just as well; I already have a good tessar type in the same range, but the larger coverage and convertibility put mean this one fills a different niche.

-NT

 

[ntenny]

Well, I shot a couple of smoke tests, and the results ain't bad, at least in terms of the lens's performance. You can't fault it for sharpness, and considering its vintage the contrast seems acceptable; also, the perfectly round apertures are a nice little bonus. The shot of the peppers is quite strongly backlit, and I think the amount of veiling is reasonable considering.

Both of these are negative scans, and I seem to have had the sloppiest day of my life for tray development---the scratches are outrageous, and there are even some fingerprints around the edges, which is pretty hard to achieve when you're wearing gloves! I don't think the lens can be blamed for that part, though.

-NT

 

[E. von Hoegh]

PMFJI. If you look closely at the shutter's aperture scale, you'll see that it is scaled for a convertible lens. The combined lens' maximum aperture is f/4.8.

Ilex' Acutar was a tessar type, said to be a clone of the f/6.3 Commercial Ektar.

Tessars aren't convertible, some plasmats are. The likely convertible plasmat was Ilex's own 215/4.8 Acuton, said to be a good lens.

Which were you thinking of? Oh, and by the way, I find Ilex' nomenclature nearly as confusing as Graflex'.

That one.

 

[Dan Fromm]

Nathan, re vintage. Per P-H Pont's Berthiot chronology, between 1900 and 1905.