Rear-element wide angle adapter + 72mm Vest Pocket Kodak possibilities?

[will_frost]

<p>So, here I'm going to show my ignorance of optics: Is there a way to mount a lens group behind a 72mm lens to widen the effective angle of view?</p>

<p>On a Vest Pocket Kodak, a f/6.8 72mm achromatic meniscus lens puts a huge image circle down for a 4cm x 6.5cm frame. Could I insert something behind it to shrink the image circle down to something usable on a small digital sensor?<br /> I'm interested in:<br>

a. putting the sensor inside the camera<br>

b. not altering the outside appearance<br>

c. using the original lens<br>

d. keeping something similar to a normal angle of view, (which on the VPK is around: 31° horizontal, 49° vertical, 56° diagonal)<br>

Is this impossible, or merely difficult?<br>

Will</p>

[sumo_kun]

<p>I don't think you will have enough space in the camera for the lens element. Shrinking down your 6.5cm diameter circle to something like a compact camera sensor size will probably require a huge RI for the glass or whatever material for the space you are trying to stuff it into.<br>

"Impossible" is also a constantly shifting boundary. For the most part, if you need to ask this question then it will probably be impossible :)</p>

[will_frost]

<p>Thank you, that is probably the best definition of impossible I've yet seen. :) Perhaps I'd be better off waiting for cheap large-size sensors!<br>

Will</p>

[tom_cheshire]

<p>There used to be wide angle and telephoto accessory lenses for some of these cameras. They were single element glass like a filter. Kodak made them. Zeiss made them. I recall they were named Telek and Distar or something like that. They slip on the front of the lens. If you can't find those then any negative or positive diopter glass will work the same. </p>

[sumo_kun]

<p>Don't give up yet. Try slapping it on a scanner or something ;)</p>

[will_frost]

<p>Hum! I <em>do</em> have an old flatbed scanner. It's not as though the world isn't awash in those...some are even relatively small and portable. Alright, you've given me another direction to explore, thanks!<br>

I did see <a href=" on flickr, where someone mounted an extension tube onto a plate that attaches to the back of a vpk. (In place of the film magazine.) It's a clever, non-destructive solution.<br>

Tom Cheshire, thanks for reminding me to look for accessory lenses. I have some positive diopter lenses on order, perhaps I can experiment with those too.<br>

I'm beginning to think that another tack I should try is to see if I can find a meniscus lens that already has the right focal length, and attach one to an existing point-and-shoot as a prototype.<br>

Will</p>

[will_frost]

<p>Ah! I did have an idea that might help - I could focus a point-and-shoot in macro mode onto a ground glass back on the VPK. If I could move the focal plane into the camera (toward the lens) even an inch or so, it might be fairly manageable. And certainly faster and more portable than mounting a scanner. I'm thinking a sheet of acetate film, roughened with 0000 sandpaper might work pretty well for a ground glass, provided I can tension it adequately.</p>

[sumo_kun]

<p>Are you suggesting mounting a digi P+S camera set on macro behind the KVP with a GG on the film gate? That will work as in you will get images but the quality might not be what you are after. An image on a GG is not clear. You will always see some sort of grain. Also, the P+S mounted in macro at that distance will not be able to take in the whole 6x4.5 frame probably.</p>

[will_frost]

<p>Yes, that's what I was thinking about. I don't know that I'm after terribly good image quality - I have cameras that can do that. It's always appreciated - but a low quality solution beats no solution at all :)<br>

I also doubt that the P+S would be able to take in the whole frame, so I'm still poking around for a reducing element that I can mount behind the lens. Shrinking the image circle even by a centimeter or so would be helpful. I'm also doing some testing of the P+S's that I have to see what size rectangle they can cope with.</p>

[yuri_sopko]

<p>Might be easier to replace the lens up front. If you want the look of the original lens then you can just disassemble it and reinsert a new lens in the old lens barrel assembly that does what you want. Maybe an old enlarger lens that has a long throw. That will work. Maybe a 16mm movie lens or something. IIRC some of those lenses had a really long throw behind them.</p>

<p>But, nothing says that you can't experiment on your own. If you can safely remove the lens, do so, and then insert in lenses in between your P&S camera and the original lens in hopes of finding one that will work. People have used this for the purpose of macro shots so maybe using a wide angle lens as the lens in between might work. Image will not be pretty but it might be possible.</p>

[steve m smith]

<p>You can put a positive (convex) lens in front of or behind the lens. This will reduce its focal length and will require you to move the whole lens assembly closer to the film/sensor.</p>