source for simple lens designs?

Discussion in 'Camera Building, Repairs & Modification' started by rippo, Nov 8, 2007.

  1. rippo

    rippo Member

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    i have built some lenses from Allan Greene's book "Primitive Photography"...heck, i built an 8x10 camera from the book too! but for the sake of convenience, i'm more interested in using the lenses with a packard shutter on my 4x5 monorail.

    i've built two, and will probably get around to building the other two described in the book. but...does anyone know of any sources for easy-to-build lenses along these lines?
     
  2. Ty G

    Ty G Guest

    If you mean actual lens elements...I sometimes get them from anchor optical. For my purposes, I used acromat.
     
  3. rippo

    rippo Member

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    thanks Ty, but i meant sources for designs of the lenses. i've bought elements from Surplus Shed. i just want some guidance on making new lenses (ones that can be cobbled together with elements and pvc pipe, that sort of thing).
     
  4. semeuse

    semeuse Member

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  5. Soeren

    Soeren Member

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    Yep
    Its an E-book containing around 1500 pages or so. I find it very good with plenty of designs covering fomats from 24X36 to 6X7. There are sample photos and how to chapters and its cheap too. I think you can easily convert the designs to cover 4X5
    Kind regards
    Søren
     
  6. Ray Heath

    Ray Heath Restricted Access

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    g'day Matt

    i've made many lenses from magnifying glasses and 90mm plastic water pipe

    check out my various posts on the subject

    i started by making a 5x8 dark slide out of MDF, then a camera to fit, then an 8x10 dark slide and a camera to fit, then i got obssesed

    i have now made 9 cameras, 1-5x4, 1-5x7, 3-5x8, 3-8x10, 1-11x14 and about 20 DSs

    plz ask if you'd like more info

    Ray
     
    Last edited by a moderator: Dec 4, 2007
  7. rippo

    rippo Member

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    Soeren and semeuse: thanks very much for the recommendation! i'm not usually a fan of doing a lot of reading at the computer, but 1500 pages...that sounds like a good thing to have. perhaps i'll get one for christmas.

    of course i was looking for something free and immediate online. :smile:

    Ray: are most of your lenses single-element types then? also, what do you use for a shutter? (bowler hat?). thanks, and i'll check some of your other posts.

    -matt
     
  8. walter23

    walter23 Subscriber

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    I'd be interested in this kind of thing too. If all else fails I'll buy the e-book :wink:

    I've been playing with diopters lately after serendipitously discovering that a Nikon +2 eyepiece diopter alone covered 4x5 and 8x10 as a 320mm f/16 to f/22. I ordered a +3 diopter for a couple of bucks and it turns out that it's about a 150-200mm lens. When I put the two together back to back the focal length becomes quite short (75-90mm?) and the coverage shrinks down to about 4x5 or less. I'd assume this arrangement is vaguely related to the asymmetric turner reich triple convertible I use.

    I don't really understand the optics here and I'd like to. Optimal spacing, focal lengths (I know there's a pretty simple compound lens focal length formula, but I'm not sure it applies), etc.

    I haven't done anything I'm proud to post with the diopters yet, but here are ugly examples / tests from 8x10:
    http://ashphotography.ca/zenphoto/albums/mishmash/homesweet.jpg
    http://ashphotography.ca/zenphoto/albums/mishmash/whymytree.jpg
     
  9. Dan Fromm

    Dan Fromm Member

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  10. Ray Heath

    Ray Heath Restricted Access

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    G’day Matt

    All my lenses are simple, single element designs made by mounting one magnifying glass in 90mm plastic water pipe fittings. Magnifying glasses are readily available and cheap. Pipe fittings are readily available at hardware stores. I use screw on pipe caps, screw in collars and push on pipe caps.

    ‘Simple’ lenses give ‘bad’ spherical aberrations which cause the image to be sharp in the centre and blurred around the edge, use of small apertures, f45-f90, cause the image to sharpen dramatically (see attached fence posts image). I like the blur and the less than perfect image quality.

    Apertures are holes cut or punched into discs made from thin black plastic sheet such as used for covers on visual art diaries. The disc is held in place with Blu Tac, this allows me to compose without the aperture then insert it for the exposure.

    Shutter is a lens cap made from a 90mm push on pipe cap. Shutter speeds of less than one second are not possible, this no restriction when using FB paper for negs as the exposure is often more than 5 seconds. For film or brighter conditions I may need to use ND filters or very small apertures.

    I have also experimented with dioptre filters. My initial experiments were with dioptres mounted in 90mm pipe fittings (see old shop image). I soon realised the diameter of the filter mounts would not allow extreme wide angle coverage.

    I neither enjoy nor understand maths so I kept the necessary calculations simple and relevant.

    To calculate focal length from dioptre number;
    fl=1000 divided by D

    To measure focal length of a simple lens or magnifying glass;
    fl=distance from centre of lens to film plane when lens is focused at infinity

    To calculate effective aperture, also called “Relative Aperture” because it is relative to the focal length of the lens in use;
    f=fl divided by diameter of aperture

    To calculate effective coverage as related to 35mm lenses;
    fl divided by diagonal of format, multiplied by 50

    e.g. what focal length on a 35mm camera will give the same angle of view as a 235mm lens on an 8x10 camera;
    235 divided by 310, times 50=37.9mm lens

    Ray
     
    Last edited by a moderator: Dec 4, 2007
  11. Dan Fromm

    Dan Fromm Member

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    "To calculate effective coverage as related to 35mm lenses;
    fl divided by diagonal of format, multiplied by 50"

    43 gives a better (closer to reality) than 50
     
  12. Ray Heath

    Ray Heath Restricted Access

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    quite right Dan

    by using Pythagoras the diagonal of a 24x36mm rectangle is 43.266615

    had you heard of this calculation before Dan? i kind of made it up, i thought

    Ray
     
  13. bdial

    bdial Subscriber

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    I've recently been looking at a copy Handbook of Photography by Henney and Dudley, copyright 1939. It has illustrations of all the clasic lens designs and a number of formulas. Plus a lot of discussion of how the elements in these designs function.
    You may be able to find a cheap copy at a used book shop, or perhaps a library sale.
     
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  15. John MacManus

    John MacManus Member

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    Hi Matt:
    Since you’ve made several lenses from the Greene bible, you are already successfully launched on a career of trial and error. Your hunt for “sources for designs of the lenses” is a pointless exercise.
    For example, you can look at http://dioptrique.info/ for all the details on lens’ composition, BUT you’ll never find the elements on the shelves of Anchor Optics or Surplus Shed or any other place that I know of. They just won’t have the correct combination of focal length, surface curvature, glass composition, etc for you to reconstruct the classic 19th century lenses, let alone anything since. Better for you to build on your experience, already knowing that a duplet is better than a single element, and see what you can build from available pieces. Try a triplet, and see what placing a negative element between two positive yields. All trial and error, but you are already a lucky guy.

    FYI the John Evans book is available on Surplus Shed under books … bend those rays … J
     
  16. Dave Wooten

    Dave Wooten Member

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    www.rolyn.com

    look at the on line catalog or ask to be sent the hard copy...
     
  17. Dan Fromm

    Dan Fromm Member

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    Pythagoras' theorem is very old, quite well-known.

    Your shortcut for comparing diagonal angles of view isn't, AFAIK, widely known but I've been using it for years. I mean, it is obvious.

    Cheers,

    Dan
     
  18. rippo

    rippo Member

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    Ray: thanks for the info!

    most of my home-mades i'll be mounting in front of a packard shutter, so i'll be able to use slightly faster shutter speeds.

    how do you mount the actual lens in the tube? since they're all different sizes. i've been using foamcore as suggested by the Primitive Photography book, although i'm not convinced it's the best way.
     
  19. rippo

    rippo Member

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    Walter: that sounds a lot like the 'portrait lens' i just built. asymmetrical duplet. the larger element goes in front, and the focal length is going to be less than either of the two elements by themselves. there's a formula somewhere for that, but i don't have it handy.
     
  20. AgX

    AgX Member

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    John MacManus,

    Thank you for that link!
     
  21. walter23

    walter23 Subscriber

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    Nikon must be using a different convention for their eyepiece diopters, because when I apply that formula I get a very different focal length from the one I measure. Eg., my +2 diopter measures as a 320mm lens, but 1/2 = 0.5 meters or 500mm. My +3 is not 333mm but rather 200mm or so.


    As an aside; this is really weird; I'm being hit by a huge dose of deja vu. I wonder if I had some conversation about diopters 3 or 4 years ago that I've forgotten all about. I have images of street photography with a diopter in my head. Maybe zombies or something too. Go figure. Must be a neurological misfire.
     
    Last edited by a moderator: Nov 11, 2007
  22. Dan Fromm

    Dan Fromm Member

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    Walter, how are you measuring? I ask because the idea behind eyepiece diopters is that the user gets a prescription from his opthalmalogist/optometrist and then buys the eyepiece diopter that fits the prescription. If the lens doesn't match the prescription the poor buyer's in trouble.

    One other possibility. Are your +2 and +3 marked +2 and +3 or are they in boxes marked +2 and +3?
     
  23. rippo

    rippo Member

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    thanks john, i do i see your point. i'm all for experimenting! but without a little guidance, i wouldn't know things like i should place the stop a certain distance before a landscape lens, but in contact with the front of a portrait lens etc. and i only have the vaguest idea why someone would stick a biconcave lens in between two positive lenses. how do i determine the proper distance between elements, etc...different building techniques other than the ones used in Primitive Photography.

    if i'm going to experiment, what do i experiment with? what's a good design to try, and how to i go about picking some interesting lens elements for it? these sorts of things.

    however that french website looks interesting, just knowing what types of elements to try...
     
  24. walter23

    walter23 Subscriber

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    They are definitely marked +2 and +3 on the rim of the diopter itself, and not on the box. No mixup here.

    Regarding my measurement methods, the fact that I can use them both on my Shen Hao which has a maximum bellows extension of 330mm speaks more of my ability to measure than my assertions to that effect :wink:

    You're right that it wouldn't make sense for Nikon to use some other weird convention though. So I don't really know what's going on.
     
  25. Dan Fromm

    Dan Fromm Member

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    Walter, thanks for the reply.

    You're right, it is impossible to focus a 500 mm meniscus with 330 mm of extension.

    This prompts an evil thought. Is y'r Nikon's finder 0 diopters with the eyepiece lens removed? I ask because y'r 2 diopter lens measures around 320 mm and y'r 3 at around 200. ~ 3 diopters and 5 respectively, total.
     
  26. Struan Gray

    Struan Gray Member

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    Wild guess: diopter for eyeglasses and close up lenses are are usually specced for light from infinity. Viewfinder diopter values are usually set to match your prescription (i.e. if you have +1 glasses you buy the "+1" diopter for your camera's eyepiece) but they are used to view a virtual image that is at a much closer distance. The shorter working distance requires a shorter focal length to get the screen in focus.