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Lachlan 717
19-Jul-2010, 23:28
I got this lens today. Cheap.

Not much to go on. It is marked "6 IN. EF." and has the serial number V58633.

It is a 6" focal length (tested on camera). The front element is 75mm/3" wide, making it around an f2 lens.

It is very, very, very heavy!! It comes in around 3kg/6.6lbs.

Anyone know anything about this lens?

Tiny DOF; looking forward to testing it!

Thanks in advance,

domaz
20-Jul-2010, 07:58
If it has no aperture my guess would be a projector lens of some sort. Maybe a Petzval but more likely a triplet. Can you disassemble the lens easily to take a look at it's configuration?

Mark Sawyer
20-Jul-2010, 13:02
It is a 6" focal length (tested on camera). The front element is 75mm/3" wide, making it around an f2 lens.


Is the front element 3" wide, or is the minimum diameter of the barrel measured through the front element 3" wide? The latter is how one determines the f/stop.

If it has a lower f/stop, f/6.3-ish, I'd guess it's a Metrogon aerial lens in an odd barrel. If not, I'm with Domaz's guess.

Lachlan 717
20-Jul-2010, 13:39
If it has no aperture my guess would be a projector lens of some sort. Maybe a Petzval but more likely a triplet. Can you disassemble the lens easily to take a look at it's configuration?

I don't know the terms for particular designs (except for the Petzval; it's not one if those); however, it has 2 forward elements (front, flatter one and inner, thick one). The rear seems the same design.

Lachlan 717
20-Jul-2010, 13:44
Is the front element 3" wide, or is the minimum diameter of the barrel measured through the front element 3" wide? The latter is how one determines the f/stop.

If it has a lower f/stop, f/6.3-ish, I'd guess it's a Metrogon aerial lens in an odd barrel. If not, I'm with Domaz's guess.

Thanks, Mark.

3" maximum diameter through the lens. Should make it f2, but it measures around f2.4 at the ground glass. Test shot at f2 are a bit underdone, supporting the slightly slower speed.

One thing is not open to ambiguity: it is built solid!! Very, very thick brass case.

EdWorkman
20-Jul-2010, 13:44
The Metrogon I have is very deeply curved, the pictured lens is not????
Should the aperture be measured at the exit pupil, rather than the front?
Or does it appear to be the same from either side? In any case, Mark is right, measure the hole not the element.
What do those knob thingies do? IS there an iris to vary the aperture size?

Mark Sawyer
20-Jul-2010, 14:10
I think we're back to a projection lens, but it might be an aerial lens from that heavy housing. To fast for a process/graphic arts lens. Still a mystery! But at f/2 or f/2.4, it should be an interesting lens to work with.

Lachlan 717
20-Jul-2010, 15:30
The Metrogon I have is very deeply curved, the pictured lens is not????
Should the aperture be measured at the exit pupil, rather than the front?
Or does it appear to be the same from either side? In any case, Mark is right, measure the hole not the element.
What do those knob thingies do? IS there an iris to vary the aperture size?

Ed,

When you mention the Metrogon having a deep curve, what are you referring to? The front element? This one is fairly flat. The second element, on both the front and back, is very thick (I would estimate it is at least 2/3 as thick as the element is wide) and quite deeply concave on the rear.

The hole is 3". No iris.

As for the knobs, they're the tightening screws for the iris lens clamp I had this mounted in. In turn, the clamp is mounted on a Sinar board.

Lachlan 717
20-Jul-2010, 15:36
I think we're back to a projection lens, but it might be an aerial lens from that heavy housing. To fast for a process/graphic arts lens. Still a mystery! But at f/2 or f/2.4, it should be an interesting lens to work with.

Mark,

Here's the test shot from last night. Not a very willing subject, but so be it! As I mentioned, I think that this is going to be closer to f2.8 than to f2.

Unbelievably bright on the GG, which is a good thing given its DOF...

EdWorkman
20-Jul-2010, 16:20
Nice shot- well done.
Deeply curved as in the outside appears to be a sphere front and back.
So what do you figure is the image circle?
Congratulations.
regards
Ed

Lachlan 717
20-Jul-2010, 16:36
Nice shot- well done.
Deeply curved as in the outside appears to be a sphere front and back.
So what do you figure is the image circle?
Congratulations.
regards
Ed

Thanks, Ed.

I'll post a couple of additional photos a little later, including the lens broken down into its parts.

Jim Galli
20-Jul-2010, 17:19
I've got one just like it but 7 inch focus. Gigantic and heavy. I've been saving if for breaking out store front windows the next time we have a riot in Tonopah. Yes, it's a projector lens. It's a modern and fairly complex anastigmat.

Lachlan 717
20-Jul-2010, 17:27
I've got one just like it but 7 inch focus. Gigantic and heavy. I've been saving if for breaking out store front windows the next time we have a riot in Tonopah. Yes, it's a projector lens. It's a modern and fairly complex anastigmat.

Thanks, Jim.

How are you going to lift the thing to throw it?

It's a strange lens. Clearly marked as a 6", yet its draw is significantly less than my 150mm Fujinon. Not knocking that; in keeps the mass well back.

I'm thinking of mounting it on a Sinar board as I think the weight on the iris clamp could be too much over time. Just need to add a thread and retaining ring. Not too difficult given the thickness of the brass!