Building my own Mini-35

H

humptydude04

Guest
I'm not entirely sure in which forum I would need to post this question but Cinematography seems as likely as any other. I'm trying to build my own Mini-35 to give video a greater depth of field and more of a "film-look." So far I've procured lenses, focus screens, mounts and all the necessary accoutrement but I'm missing one thing: a biconvex lens to flip the image coming from the 35mm lens so that the image appears correctly. There are plenty of places to get the lenses but my problem arises when it comes time to choose. Is there anyone out there who knows the mathematics of lenses well enough to help me determine the size and shape I need? Also, if anyone has any pointers on construction, I'd love to hear what you have to say. Thanks!

--Jimmy
 
H

humptydude04

Guest
That surely is a possibility, but I have two reasons for wanting to go through this process: 1) I want to understand the finer points of working with different lenses, and 2) It seems it would be very disorienting/annoying to see everything upside down and reversed while you're filming. Also the fewer things I have to do in post the better. If worse comes to worse and no one can give any advice, I will have to flip everything in post.
 
H

humptydude04

Guest
I think I've figured it out! Huzzah! Thanks to the wonderful people at FSU who make this website:
http://micro.magnet.fsu.edu/primer/java/lens/bi-convex.html

I was able to figure out the relationships that I needed to know about. For my purposes the formula 1/q= 1/f- 1/p works just fine. q= distance of the image from the optical center of the lens, p= the distance of the object being imaged from the optical center of the lens, and f= the focal length of the lens. if the object is twice the distance of the focal length away from the center of the lens, then the image produce is inverted and the same size. So at 2f the object and inverted image are the same size.

I can find a lens from here:
http://www.aosa.es/Eng/Catalog/Optics/Lenses/biconvex-lenses.htm

From here, I can find the focal length in the descriptions provided, plug everything into the handy formula (assuming that I want this simple lens 2f from the back of the first lens) and place my focus screen at q from the formula.

I'm no math whiz or an expert on lenses so if anyone sees anything wrong with this please let me know! Thanks

--Jimmy
 
Top