DIY lens - question on image circle

Discussion in 'Camera Building, Repairs & Modification' started by m1tch, Aug 1, 2013.

  1. m1tch

    m1tch Member

    Messages:
    176
    Joined:
    Nov 26, 2012
    Shooter:
    Multi Format
    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. m1tch

    m1tch Member

    Messages:
    176
    Joined:
    Nov 26, 2012
    Shooter:
    Multi Format
    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 :smile:
     
  3. Barry S

    Barry S Member

    Messages:
    1,347
    Joined:
    Jan 28, 2007
    Location:
    DC Metro
    Shooter:
    Large Format
    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. m1tch

    m1tch Member

    Messages:
    176
    Joined:
    Nov 26, 2012
    Shooter:
    Multi Format
    The images aren't great (how ironic) but here is how far I have got:

    [​IMG]

    [​IMG]

    Attached to speed graphic to test

    [​IMG]
     
  5. Steve Smith

    Steve Smith Subscriber

    Messages:
    9,085
    Joined:
    May 3, 2006
    Location:
    Ryde, Isle o
    Shooter:
    Medium Format
    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 a moderator: Aug 1, 2013
  6. m1tch

    m1tch Member

    Messages:
    176
    Joined:
    Nov 26, 2012
    Shooter:
    Multi Format
    Thank you so much for your help on this :smile: 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. Steve Smith

    Steve Smith Subscriber

    Messages:
    9,085
    Joined:
    May 3, 2006
    Location:
    Ryde, Isle o
    Shooter:
    Medium Format
    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. m1tch

    m1tch Member

    Messages:
    176
    Joined:
    Nov 26, 2012
    Shooter:
    Multi Format
    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. Steve Smith

    Steve Smith Subscriber

    Messages:
    9,085
    Joined:
    May 3, 2006
    Location:
    Ryde, Isle o
    Shooter:
    Medium Format
    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.
     
  10. m1tch

    m1tch Member

    Messages:
    176
    Joined:
    Nov 26, 2012
    Shooter:
    Multi Format
    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)?
     
  11. Steve Smith

    Steve Smith Subscriber

    Messages:
    9,085
    Joined:
    May 3, 2006
    Location:
    Ryde, Isle o
    Shooter:
    Medium Format
    Yes, the +1 is 1000mm.

    If you are using the +2 and +4 together, you have 500mm and 250mm (so you were a factor of 10 out).

    These add together to make a +6 lens. 1/6 = 0.167m or 167mm.


    Steve.
     
  12. m1tch

    m1tch Member

    Messages:
    176
    Joined:
    Nov 26, 2012
    Shooter:
    Multi Format
    Ah sorry yes, that would make more sense! I am having a look at a few other close up filter lenses, currently using a 52mm filter size but I know you can get 88mm filter lenses so if this works I could perhaps look at getting a larger close up filter lens with the same dioptre giving me a lower f number.

    Currently with the 52mm size it would be: 166/52=f3.2
    With an 88mm filter it would be: 166/88=f1.9

    I will look into attempting to mount/free lens the setup already onto a digital camera and see what the image quality is like on it.

    I might still look into getting a single element lens or a cemented doublet lens commercially and mount it, but I will see how this performs first as the imperfections have a certain feel to them.

    Here is an example of some free lensing I did with the +10 lens (there was a gap between the camera body and lens which is why everything shines lol

    [​IMG]
     
  13. VPooler

    VPooler Member

    Messages:
    182
    Joined:
    Jun 16, 2013
    Location:
    Estonia
    Shooter:
    Multi Format
    www.surplusshed.com has everything an aspiring lensmaker could ever need - lenses! All sorts and sizes, mostly dirt-cheap.
     
  14. Sponsored Ad
  15. m1tch

    m1tch Member

    Messages:
    176
    Joined:
    Nov 26, 2012
    Shooter:
    Multi Format
    I did see that, however I am not in the US so the shipping would probably cost more than the lens :sad:
     
  16. Jim Jones

    Jim Jones Subscriber

    Messages:
    2,393
    Joined:
    Jan 16, 2006
    Location:
    Rural NW MO
    Shooter:
    Multi Format
    The main reason for having the aperture in front of a meniscus lens is for the best overall sharpness with a simple lens. The concave side of the lens faces the aperture. Some later box cameras had a simple meniscus lens in front of the aperture with the concave side of the lens facing the film. This made a more compact camera, but corner sharpness of the image suffered.
     
  17. VPooler

    VPooler Member

    Messages:
    182
    Joined:
    Jun 16, 2013
    Location:
    Estonia
    Shooter:
    Multi Format
    I live in Estonia and shipping via USPS Priority was some 10-15 dollars for a box full of goodies. Check them out, you might find exactly what you need plus the staff is knowledgeable and you can get valuable information and recommendations from them.
     
  18. m1tch

    m1tch Member

    Messages:
    176
    Joined:
    Nov 26, 2012
    Shooter:
    Multi Format
    Thanks for that, I will check them out then, due to the low cost of those lenses I would probably get a nice large selection to play with for this current lens and future lenses :smile:
     
  19. VPooler

    VPooler Member

    Messages:
    182
    Joined:
    Jun 16, 2013
    Location:
    Estonia
    Shooter:
    Multi Format
    Have fun! I plan to make some interesting if not horrible lenses for large format when I have disposable income again. Maybe even my own lomopetzval. Considering that an achromat costs approximately 4$ there, I have nothing to lose but 8$ plus shipping.
     
  20. m1tch

    m1tch Member

    Messages:
    176
    Joined:
    Nov 26, 2012
    Shooter:
    Multi Format
    I just had another play with different dioptre combinations, I have a 135mm Schneider lens so I thought I would have a look at a few wider combos, I know that for 4x5 the 35mm equivilent is 3 times smaller eg a 150mm lens is a 50mm lens equivilent on a 35mm camera.

    I had a go with the +10 lens and added on a +1 to make it an 11 dioptre lens which works out at around 90mm focal distance, so a '30mm' lens, it works ok, fair bit of distortion and I needed to bring the bellows of the speed graphic in a bit as well. I then tried a +14 lens with a +10 and +4, making a 70mm lens or a '23mm' lens eg superwide. I had to bring the bellows all the way home but it would focus, its basically a fisheye lens! Very interesting effect though, would be interested to see that stopped down. That lens would have been a 70mm f1.3 lens which is rather cool, if I had used the 88mm filter it would have been a 70mm f0.8 :D
     
  21. VPooler

    VPooler Member

    Messages:
    182
    Joined:
    Jun 16, 2013
    Location:
    Estonia
    Shooter:
    Multi Format
    Uuh, sounds cool! Take pictures of what you see on the ground glass! I am intrigued to try this when I get my Graphic. I already have a Box of Many Lenses aka a shoebox full of optical goodies I have scavenged over the years.
     
  22. m1tch

    m1tch Member

    Messages:
    176
    Joined:
    Nov 26, 2012
    Shooter:
    Multi Format
    Ok, here are some test shots, due to the dim light levels due to the time of day the camera taking the shots (Sony NEX-3 with a 35mm f1.7) was having a few issues with shutter speed (I always keep the ISO low).

    Here are a few shots anyway so you will get the idea, be aware that this is on the ground glass and looks clearer when looking at it:

    The 7 dioptre lens (3 element) (142mm)

    [​IMG]

    11 dioptre lens (2 element) (90mm)

    [​IMG]

    14 dioptre lens (2 element) (71mm lens)

    [​IMG]

    You can see that due to the fact I have to pull the bellows a long way back to focus for the 11 and 14 dioptre lens combos the rails are in view - pretty cool to see though lol but my DIY camera won't have anything sticking forward of the lens.
     
  23. Mustafa Umut Sarac

    Mustafa Umut Sarac Member

    Messages:
    4,574
    Joined:
    Oct 29, 2006
    Location:
    İstanbul
    Shooter:
    35mm RF
    Steve gave me the one of the best ideas I have ever found. At f295 was making teleobjectives for 35 mm camera with tube and collected diopters but no information on diopters and fl.

    I found it suprising , when lens designers spend years to make a lens design , your design is such simple and elegant.

    I am still looking for an answer , how cylinderical lens elemnents behave on image ?

    Umut
     
  24. m1tch

    m1tch Member

    Messages:
    176
    Joined:
    Nov 26, 2012
    Shooter:
    Multi Format
    The first lenses were simple with just a single element which had different issues where the image wasn't flat and had distortions, modern lenses remove as many of these as possible with all sorts of coatings and setups to bend the light correctly. I will be using a paper negative for my DIY camera much like the pinhole shooters, the paper will have some imperfections which is fine, I also do cyanotypes which have their own imperfections with the way the fluid is put onto the paper.

    I am just looking for a simple lens setup that doesn't cost much, maximum of 3 elements and cheap to make, I am going to get various types of lenses from surplus shed, I am interested with ball lenses, those might be interesting, or indeed experiment with fluid lenses.

    My idea with fluid lenses is to suspend a small pocket of fluid in a spherical bag of some sort and put it under pressure slightly, I can then add or remove the fluid to focus the 'lens' instead of moving the lens I just change the focal length of it lol.

    I am thinking about mounting of the lens as well, plan is to look at getting some 50mm lenses (the close up lenses are 50mm) and then put them inside a 50mm ID pipe. I can then use another small piece of 50mm OD pipe which would go inside the other pipe and keep the elements in place - this could also allow me to add some air gaps and space them out a bit.
     
  25. VPooler

    VPooler Member

    Messages:
    182
    Joined:
    Jun 16, 2013
    Location:
    Estonia
    Shooter:
    Multi Format
    I find the 14 dioptre lens rather pleasing! Good job!
     
  26. m1tch

    m1tch Member

    Messages:
    176
    Joined:
    Nov 26, 2012
    Shooter:
    Multi Format
    Yeah its quite a lot of distortion but might be interesting to shoot with, its a very wide lens on a LF camera, probably as wide as I could still use to cover a 4x5, might look to see if anything wider will work but I don't think it would be usable. I will have a look though, I have seen the travelwide camera (like pinwide camera but with an optical lens) which is basically just a double dark slide attached to a lens lol thats shooting a 90mm lens, might see if I can get away with a 70mm lens or wider as the lens is so compact.

    http://www.kickstarter.com/projects/wanderlust/travelwide-45-camera