A Curious Thing - Lens-hack Question

[nelsonfotodotcom]

SO, I purchased a JML 6.5" f/8 from Don Bryant. It's a nice chunk of metal and glass, holding it now having received it moments ago in the post.

I'm eyeballing this thing, opening and closing the diaphragm, when the question pops into my head: Wide open, there's still a lot of opening to be had... is it possible to have a lens like this tweaked to open beyond f/8? If not, why not? What is prohibitive? I'm even thinking it might be fun to yank the diaphragm out of it altogether....

Now, I'm new to the LF lens racket, so pardon me if this is an elementary issue and one which might draw a roaring "STUPID!" from many, but I figured I would ask. I've picked up quite a bit thus far just by reading these forums, so, hoping to learn another thing or two about a thing or two.

Danke!

C.

[Dan Fromm]

Craig, manufacturers usually limit apertures to protect users from themselves and to preserve their reputations. It is often the case that forcing a larger aperture than the manufacturer intended just kills image quality far off axis. But since your lens more than covers 4x5 and you're shooting 4x5 this may not be a major problem.

In other words, since you own the lens now there's no reason why you shouldn't remove the diaphragm or break it (or maybe not) trying to get it to open wider.

[nelsonfotodotcom]

Dan, howdy!

I've got a query into Grimes' crew to see what it would cost me to have mounted in shutter or at least to have it placed in a decent board for its size and weight. I'm not the least bit mechanically inclined, so the hacking would not take place by my hands, but at some point it might be interesting to have it altered, if possible, to see what happens.

Thanks for the input. Seems on par with Rick Oleson's advice over on my board.

Best,
Craig

[nelsonfotodotcom]

Also occurs to me that these process lenses would have been set for sharpest output, hence the high minimum aperture. I love the look of the old, fast lenses, the wild OOF, etc., so that's what got me to wondering about the potential in this one.

Again, thanks.

[Jim Galli]

Actually the JML process lenses are sought after for that. Machine whatever is stopping the diaphragm so that it can open all the way and then you will observe a very softish performance from a normally super sharp lens. Or so I've heard.

[nelsonfotodotcom]

Jim - you wouldn't happen to know what potentially could get FUBAR if I open this thing up, or what exactly would be needed? The cells unscrew from the diaphragm, leaving the center free to disassemble. Worried I'd end up when tension devices and/or aperture leaves all over the place.

Single locking screw, by appearances, on the threaded portion which would take a retainer or flange. I'm assuming once the is removed, the rest will unscrew, revealing another screw that is visible within the diaphragm barrel. I image that might be a stop of some kind, perhaps the key to opening the diaphragm, fully.

Ideas? I'd be willing to shoot some images if needed as examples.

C.

[Jim Galli]

No I haven't done one and truly don't know. OK, just went out and looked at both my 6" and my 8 1/4". The 6 inch you take the front group out of the barrel and then the aperture ring slides right off. You can see the slot that would have to be enlarged to make it open wider. The 8" is similar but there is a retainer behind the aperture ring that comes unscrewed and then the rign slides off. Same thing, expensive machine work. That slot would have to be milled.

[nelsonfotodotcom]

The ring is locked in on the 6.5" - must come out like the 8".

I might tinker with it later. In the midst of assembling some Dremel stuff in order to make a board for the JML so I can at least see what it does at f8.

Thanks, Jim, for checking.

C.

[lenser]

You might also check with Carol Miller at Flutot's Camera Repair in Whittier, Ca. She does some truly amazing things at extremely reasonable prices:

www.Flutotscamerarepair.com

[nelsonfotodotcom]

Thanks.

After a little work with the Dremel, the lens squeaked its way into that old lensboard I had. Had to sand a bevel into the back of the board to allow the rear element room to bolt down, and had to remove the bottom lensboard nut to get the assembled lens and board into the camera. Once everything screwed back into place, she's a-ready to go, I do believe. Looks sharp to me. Will shoot a sheet or two past her tomorrow. Time for bed.

[nelsonfotodotcom]

Miller's page keeps resetting. Won't load. Will try later on today. For now, I need sleep.

[Dan Fromm]

Dan, howdy!

I've got a query into Grimes' crew to see what it would cost me to have mounted in shutter or at least to have it placed in a decent board for its size and weight. I'm not the least bit mechanically inclined, so the hacking would not take place by my hands, but at some point it might be interesting to have it altered, if possible, to see what happens.

Thanks for the input. Seems on par with Rick Oleson's advice over on my board.

Best,
CraigCraig, there's a reason why most people buy used lenses in shutter instead of used process lenses in barrel and have them remounted. $$$. I get away with hanging process lenses in barrel in front of a #1 because coverage really isn't an issue for me. If I went up in format from 2x3 to 4x5 or larger, I'd be in trouble.

On the whole, inexpensive process lenses are dangerous temptations.

Why don't you just put the thing on a board for your Speed Graphic and use the Speed's shutter for short exposures?

I don't believe your JML too heavy for your Speed's front standard. If it is, well, make a support for it. Yep, a crutch. I have one for my 12"/4 Taylor Hobson telephoto; the crutch goes between the lens' barrel and the front cross-piece of my 2x3 Speed's front bed rails.

[Nick_3536]

Even the 8" JML isn't that heavy. It's big and impressive looking but it ain't heavy. If you want heavy I've got an OEM Brown 19". At almost 7lbs that's heavy -)

OTOH I can't imagine having a 6" JML mounted in a shutter. Maybe in front of a packard. The cost of just the shutter will exceed the cost of a used 150mm lens. Then you'll still face the cost of machining the JML to fit the shutter. You're now looking at the price of some new 150mm.

Stick it in front of a 5x7 with maybe some lith film behind it. Won't even need a shutter.

[nelsonfotodotcom]

As I concluded in this thread, early morning hours, I ripped out an old board to fit the JML. It's mounted, now, and heading out with her after I finish chow, and get some film holders loaded. Need to fashion a cap right quick, too.

And yes, it's clear to me that attempting to have this mounted in shutter would be pointless by way of expense.

Thanks,
Craig

[Mark Sawyer]

Just a note that a similar modification is very frequently done to the Wollensak 159mm f/12.5, getting them to about f/5.6 or so. A wonderful modification for composing the image, regardless of performance if you exposed at that aperture. (And as Jim indicated, "performance loss" is not always a bad thing.) But watch out for focus shift if you focus wide then close down...

[nelsonfotodotcom]

Thanks, Mark. I was also thinking it might be worth altering the opening for the sole purpose of being able to preview above f8.

I need to read some more on the possibilities of focus shift, however.

Film in the soup now. Headlights from a car blew through my bathroom window covering that at first seemed light tight. That said, the effect was mild, and I hurried up to finish loading. Hoping all comes out ok.

Will know in a bit. Shot 6 sheets total past the JML.

C.