frankencam lens help needed

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ddashk

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damian
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hi
i am trying to build a manual digital camera over at http://frankencamproject.blogspot.com/.

the main problem i am having is that the crop factor is huge. i have been rebuilding the lens in many different arrangements but i cant get the image to hit the sensor with the right size.
i was thinking that if a 2x converter is basically a macro ring with a lens to refocus the image would the viewing angle get wider is i shortened the distance between lens and sensor and added a lens like in a converter. does anyone know what shape of lens this would have to be.
if you know anything about lenses i would be really grateful if you could look at the blog. any suggestion welcome.
thanks
 
Firstly I'm no expert on these things by a long shot, but it seems to me one major problem is the focal lengths your using as they don't match the small sensors you have used.

Whilst an APSC camera (22.3mm x 14.9mm) will use say a 50mm lens, that will then result in an 80mm effective focal length when the crop factor is taken into account,however with a powershot sensor (7.18mm x 5.32) it will use a 9.5MM focal length to give an effective focal length of 140mm when the crop factor is taken into account.
Also given that you are using older lenses from manual camera's they will be designed to illuminate a full 35mm film frame so if you can get it to focus on the focal plane of the sensor only a tiny portion of the centre of field of view will be focusing and illuminating it.
Probably the best bet is to up the sensor size
 
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i wish i could afford to get a large sensor. at the moment im looking for a way to modify the lens to make it work with a small sensor.
im sure it involves bringing them closer together and changing the last lens element.
 
If you move the rear-element further away (over-step the flange distance), you lose infinity focus to gain close-up focus, as done for macro work. If you understep the flange distance, you'll lose close-up focus and gain inifinity and beyoooooond.

Thus your lens is probably too close to the sensor and, as Ian mentioned the crop factor and field of view, the target you're trying to focus on is too close. Try pointing it out of the window.

edit: I have this feeling you knew this already...
 
just had a thought. how about a lens from an 8mm film camera. would that work?
 
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