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  1. #1

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    DIY lens - question on image circle

    Hi all,

    I am going to be building a large format 4x5 camera and use some paper negatives, I have a few large format lenses already for my speed graphic, however I want to make my own (simple) lens and use waterhouse stops to stop the lens down to make it as simple as possible.

    Anyway, I am looking into the lens and am having difficultly working out what I need, I am thinking I would need a lens that has a focal lenth of around 150mm which work be a 'normal' lens on a large format camera. Would any 150mm focal length lens work ok or is there a program I can use to work out what lens I need to get? An example is that I can easily get a 50mm diameter 150mm focal length lens, but how do I know that the image circle will be ok?

  2. #2

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    Just created a DIY lens using those macro filter close up lenses, made a negative meniscus lens from a +4 and +2, then reversed a +1 to create a triplet lens which seems to focus at around 150mm or slightly wider, so its an f3 or f2.8 lens

  3. #3
    Barry S's Avatar
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    Image circle won't be a problem with your DIY lens--unless you physically vignette with a barrel. Don't expect much edge sharpness, but it should easily light up a 4x5. BTW, adding positive meniscus lenses doesn't create a negative meniscus lens. You might want to find a copy of Primitive Photography--it has some good info on DIY lenses.

  4. #4

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    The images aren't great (how ironic) but here is how far I have got:





    Attached to speed graphic to test


  5. #5
    Steve Smith's Avatar
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    Most lens elements you can buy singularly will be listed by their Dioptre* value. A Dioptre is 1 divided by the focal length in metres. So a 1000mm lens is 1D, a 500mm lens is 2D, 333mm is 3D, and so on.

    150mm is 6.667D. To make it easier, 167mm (close enough) is about 6 Dioptres. To combine lenses, all you have to do is add their Dioptre values.

    So you can create a 167mm lens using two 3D lenses or three 2D lenses or a 2D and 4D.

    If I was doing this, I think I would do it with two 3 Dioptre lenses with the waterhouse stop exactly in the middle keeping it symmetrical.



    Steve.

    (* or Diopter for some reason if you're American)
    Last edited by Steve Smith; 08-01-2013 at 03:52 PM. Click to view previous post history.

  6. #6

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    Quote Originally Posted by Steve Smith View Post
    Most lens elements you can buy singularly will be listed by their Dioptre* value. A Dioptre is 1 divided by the focal length in metres. So a 1000mm lens is 1D, a 500mm lens is 2D, 333mm is 3D, and so on.

    150mm is 6.667D. To make it easier, 167mm (close enough) is about 6 Dioptres. To combine lenses, all you have to do is add their Dioptre values.

    So you can create a 166mm lens using two 3D lenses or three 2D lenses or a 2D and 4D.

    If I was doing this, I think I would do it with two 3 Dioptre lenses with the waterhouse stop exactly in the middle keeping it symmetrical.



    Steve.

    (* or Diopter for some reason if you're American)
    Thank you so much for your help on this I think I kinda get it, I will have a look for that value when purchasing, I guess I could also make it from 6 1D lenses for example?

  7. #7
    Steve Smith's Avatar
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    Quote Originally Posted by m1tch View Post
    Thank you so much for your help on this I think I kinda get it, I will have a look for that value when purchasing, I guess I could also make it from 6 1D lenses for example?
    That would work. One Dioptre is a common size for supplementary close up lenses (it looks like that is what you are using already) the most common being the Canon +1 lens with a 58mm thread.

    They seem to be available in 1, 2 and 4 Dioptres but not 3.

    The adding of Dioptres method technically only works for lenses very close together but I think all of yours will be close enough for it to be a good approximation.

    Something I learned here was that if you put a positive and negative lens together, you can create a degree of zoom by moving them apart.


    Steve.

  8. #8

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    Quote Originally Posted by Steve Smith View Post
    That would work. One Dioptre is a common size for supplementary close up lenses (it looks like that is what you are using already) the most common being the Canon +1 lens with a 58mm thread.

    They seem to be available in 1, 2 and 4 Dioptres but not 3.

    The adding of Dioptres method technically only works for lenses very close together but I think all of yours will be close enough for it to be a good approximation.

    Something I learned here was that if you put a positive and negative lens together, you can create a degree of zoom by moving them apart.


    Steve.
    Ah, the close up lense I have are +1, +2, +4 and +10, could those be the Dioptre values? I wanted to keep the lenses together for ease of focus, however I could look at having a front element and then move the back elements for focus rather than the whole assembly.

    With regards to stopping the lens down, I had a Kodak autographic brownie which had the aperture iris in front of the lens rather than behind, I might look into this option as it would allow for the DIY camera to be set up slightly easier than having stops in the middle of the lens.

  9. #9
    Steve Smith's Avatar
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    Quote Originally Posted by m1tch View Post
    Ah, the close up lense I have are +1, +2, +4 and +10, could those be the Dioptre values?
    That's exactly what they are.

    Quote Originally Posted by m1tch View Post
    With regards to stopping the lens down, I had a Kodak autographic brownie which had the aperture iris in front of the lens rather than behind
    Whilst that's easier to keep it all light proof, I don't think it's optimum.

    Some of the early cameras only had one lens element so there wasn't the option of putting the stop in the middle.

    I have read that if you keep it symmetrical, any errors are cancelled out.

    However, please don't think I'm an expert in this, I am just repeating things I have learned from others on this forum who are more expert than me!


    Steve.

  10. #10

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    Quote Originally Posted by Steve Smith View Post
    That's exactly what they are.



    Whilst that's easier to keep it all light proof, I don't think it's optimum.

    Some of the early cameras only had one lens element so there wasn't the option of putting the stop in the middle.

    I have read that if you keep it symmetrical, any errors are cancelled out.

    However, please don't think I'm an expert in this, I am just repeating things I have learned from others on this forum who are more expert than me!


    Steve.
    Awesome, I always wondered how they would quantify the figures, in that case is the focal length of that +1 filter 1000mm?

    So am I correct in saying that I have added a 50mm lens with a 25mm lens to produce a 166mm lens (negating the reversed +1 lens)?

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