Bell & Howell 2 inch 1.2 projector lens

Layer-cake · Joined: 18 Mar 2013 Posts: 560 Location: Cape Town

a bit of a silly question really, I picked up one of these projector lenses and the Registration distance capable in its current design won't allow for infinity focus.

what I'm wondering is will it be possible to change the optical design of the lens to increase the registration distance possible by rehousing the lenses and either increasing or decreasing the distance between the lens groups?

Layer-cake · Joined: 18 Mar 2013 Posts: 560 Location: Cape Town

after looking at it again I think I might be able to shave enough metal off it to get infinity, but it will be snug!

Attila · Expire: 2025-11-18

I don't think so need infinity from an 1.2 projector lens, get enough working distance for half portrait should enough.

Layer-cake · Joined: 18 Mar 2013 Posts: 560 Location: Cape Town

i do agree with you, I think my need with the lens conversions to always get infinity on them has driven me to try and get it on this one!! I'll still shave off some of the metal as at the moment its infinity limit is about 1.3 meters and there is quite a bit of metal I can remove;) or I could turn it into a macro lens...??

the next issue after that is finding a helicoid wide enough to fit the lens.

Lloydy · Expire: 2022-01-01

I've chopped the back part of projector lenses off to get infinity.

Attila · Expire: 2025-11-18

Layer-cake · Joined: 18 Mar 2013 Posts: 560 Location: Cape Town

lloydy I didn't even think of that but now that you mention it I sort of understand how that could work.

Attila, the lens is a bit of an awkward design and I can't stop enough stray light hitting the sensor while holding it with my hand, I'll cut out some foam and try again to see what results I get, the dof isn't as thin as I thought it should be but that is probably me hold the lens at a slight angle.

Lloydy · Expire: 2022-01-01

This is how I used a projector lens, The camera mount is a T2 mount with the center part removed, just undo three grub screws and the mount comes apart. A short bit of sink plastic waste pipe is a good fit into the T2 mount. I taped it in place after experimenting with the length.
The lens I cut down at the back by about 1/2 inch, again by experimenting. and I built the diameter of the lens body up with wide electrical insulation tape until it slid nicely in the waste pipe. Once the lengths were right I taped the pipe to the mount.
There's nothing permanent except chopping the back of the lens off, and I think it would still work ok in a projector.

Layer-cake · Joined: 18 Mar 2013 Posts: 560 Location: Cape Town

that is pretty cool:) I think I'm going to go all out with this lens conversion, I bought a meopar 180mm 4.5 lens this morning at the market as it has a huge aperture system and I'm going to see if I can rehouse the lens elements from the bell and howell into a system with a helicoid and a working aperture!

much studying on lens design is going to be needed for this me thinks!! I really enjoy this type of thing:)

Layer-cake · Joined: 18 Mar 2013 Posts: 560 Location: Cape Town

lol it seems the 180 meopta is a large format lens that's also rather scarce!! I can't destroy something like this so I'll have to think of something else to use.