Simple compund lens design

[Joshua Brown]

Ok, so I've got this old film Camera, it's got a 60mm single meniscus lens on it and it shoots to 120mm film. I want add a wide-angle to it but all the ones I've seen only cover portion of the frame. it's just a circle exposed on the film. I want to make a wide angle big enough to cover the whole frame.

Why hasn't this been done before? (at least I can't find it) Is it technically too hard?

I figure I can use an oversized bi-convex lens fitted onto the barrel to pick up the wider fov. What do you think? Plausible? Too expensive?
Anyone know how to do calculations for this sort of thing?
i.e. size of lens, fov of lens needed when coupled with a 60mm single meniscus lens, back focus distance... etc.

-Josh

 

[Joshua Brown]

bump.

p.s. I'm not too worried about quality with this project. It doesn't need to be amazing. Just some way to get a good wide angle that coveres the whole frame.

-Josh

 

[Dan Hudgins]

lateral chromatic aberration

lateral chromatic aberration

If you use a bi-concave lens and a Dioptre in a reverse Galilean Telescope design you will get barrel distortion and lateral chromatic aberration.

You really need to use 4 lenses to get correction. You can probably find a larger wide angle adapter that will cover. If not you can maybe replace the lens on the camera with a better wide angle 2 1/4 camera lens or a short focus view camera lens.

You can also use a field lens and then use a wide angle SLR lens, like an 18mm, if you focus your camera on the field lens with a close up achromat the image in the camera will be upsidedown but you should get better quality that way. That would also let you change the SLR lens to get any angle of view or to use a zoom lens on your 120 film.

 

[Joshua Brown]

If you use a bi-concave lens and a Dioptre in a reverse Galilean Telescope design you will get barrel distortion and lateral chromatic aberration.

You really need to use 4 lenses to get correction. You can probably find a larger wide angle adapter that will cover. If not you can maybe replace the lens on the camera with a better wide angle 2 1/4 camera lens or a short focus view camera lens.

You can also use a field lens and then use a wide angle SLR lens, like an 18mm, if you focus your camera on the field lens with a close up achromat the image in the camera will be upsidedown but you should get better quality that way. That would also let you change the SLR lens to get any angle of view or to use a zoom lens on your 120 film.

Hi Dan, thanks for your detailed responce. I'll admit though, after looking up words and viewing diagrams, I am still pretty much in the dark about what you were saying there. I should point out, the camera I'm using is a very cheap camera with no pro-features nor a slr mount. So I don't think thats quite what I'm looking for. Now, if your saying I need to pirate some inner lenses from a SLR style lense, I get it.

What I envisioned is a, say, 2" or so bi-convex lens set into a cardboard tube or something (again, not going for quality on this one). That tube can then be taped onto the fixed lens of the camera (think disposable camera size lens that shoots to 120 film). I don't care if the image is upside down or anything. So long as it has a fish eye style that covers the whole plane of the film (minor barrel distortion is fine, I don't expect it to be perfect). I simply don't want to see a round punchout on my square film. I'd like it to cover the whole thing.

-Josh :couch:

 

[hunterrichards]

I have a 3" magnifying glass that throws a huge image circle, have you tried playing with some of the older glass kind? Its a surprisingly sharp image for something that was never made to be used photographically.

 

[Joshua Brown]

I have a 3" magnifying glass that throws a huge image circle, have you tried playing with some of the older glass kind? Its a surprisingly sharp image for something that was never made to be used photographically.

Actually thats not a bad idea. I'll see if I can find a big magnifying glass lens and figure out where the focus point is. See what it does. Thanks.

-Josh

 

[chuck colburn]

Here's a good source for glass to fool around with.

http://www.surplusshed.com/