Tuesday, October 30, 2012

Using Enlarging Lenses with a Focusing Helicoid on Sony NEX

Unlike projection lenses, enlarging lenses have sort of a "standard" mount.  Most of them have a L39, or 39mm thread mount at the rear.  This is a good thing, because L39-M42 adapters are widely available and very cheap.  If the helicoid you have has an M42 mount on both ends, that's all you really need, if the focal length fits your helicoid.  The majority of helicoids on the market have this configuration and it makes a lot of sense.

Here are the reason why I chose something different: the helicoid with a M42 mount, and 52mm opening: 1. Some of my lenses have very large rear openings and 42mm is not large enough to accept the lens, and a 52mm opening gives me a better chance that the lens would fit.  2. I choose the M42 mount because it's interchangeable.  You can buy the helicoid with specific mounts like NEX E-mount, M43 mount, or Canon EF mount, etc.  With an M42 mount, I can use this helicoid on more than one camera system (I have NEX, M43 and EOS mount cameras), by simply screwing the helicoid onto an M42 adapter, or a c-mount adapter with M42 inner threads.  It has its compromises, of course.  For one thing, when used with enlarging lenses, I would need a M42 to 52mm step-down ring.  This would increase the thickness of the helicoid by about 3mm.

The picture below shows how I normally connect the enlarging lens to my camera.  For this particular lens (Rodenstock 50mm f2.8), it works almost perfectly, infinity focus is just slightly beyond infinity.  So, what happens if your enlarging lenses are longer than 50mm?  Very simple, just add 52mm filter rings.  The last picture shows an 80mm enlarging lens with 3 filter rings added to compensate for the longer focal length.  For very long lenses, like 150mm, it's better to buy a longer helicoid, or use extension tubes instead of filter rings.

It maybe worth mentioning that the c-mount to NEX adapter with inner 42mm thread is now hard to find.  So, it maybe be better to buy a helicoid with the mount of the camera you are using it on, instead of an M42 mount.

How the pieces are put together. Click for larger.

All connected.  In real life, the labels won't line up nicely like the picture. Click for larger.

Mounted to the camera.  Click for larger.

With extension rings (filter rings) for longer lenses. Click for larger.

9 comments:

  1. hi yu lin, i the lucid illustrations are highly appreciated. btw, would it be possible to get the link to ebay, where you got your yeenon helicoid (as a quick search in ebay leads to ambiguous descriptions).

    thanks again.

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    1. Hi Emmanuel, the link is here: http://cgi.ebay.ca/ws/eBayISAPI.dll?ViewItem&item=251163778612#ht_1561wt_1397

      Cheers

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  2. many thanks. will try looking for link in ebay hongkong which is nearer manila. maybe seller will further reduce his fixed shipping rates. good day & best regards.

    emmanuel

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    1. I believe the Yeenon adapters are sold only by it's maker. They do not have others selling their adapters. Hence they are all shipped from China. But, you can offer them a lower price.

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  3. This comment has been removed by the author.

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  4. This must be some sort of telepathy.

    This morning I bought a film lens. Yashinon 7,5-60mm F1,6. This lens has no aperture blades but can be focussed (and zoomed). I found this to be an impressive lens: heavy, well made, front glass big as the best 50mm lenses I know ... f1.6 wow fast! When I came home from the flee market I clicked for advise from wise men. Voila ... some kind of the same workaround at You-Lins blog! I didn't know that 52mm Adapters exist and I will need one for the lens has a 52mm screw mount.

    Will you please have a look at my project: I want to adapt this lens to my NEX-5 and -for I have not the slightest basics in lens making ... can you give me some tipps?

    http://www.ihobs.de/tmp/yashinon_filmlens.jpg

    - I can focus, so I will not need an helicoid adapter. Do I?
    - Have you an idea what adapter to use best? The main problem seems to be to step down from 52mm screw mount to something.
    - Have you any guess on the focus plane ... in mm ... or is it a try and error game (to achieve focus at infinty)?
    - Do I have to expect vignetting of the pictures?

    A selfmade 7,5mm lens on the NEX-5 .... this thought really thrills me. What do you think? Can I expect to get things done or can I only fail?

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    1. scalatti, I hope I am wrong, but i think the lens you have is a TV zoom lens and it won't cover even the M4/3 sensor. I have a few such lenses made by Fuji/Canon and they are pretty much unusable, in terms of sensor coverage. You can easily test this by just holding the lens near the NEX camera mount and see the image circle, which is likely small.

      1. You don't need a helicoid for this lens, but the focal flange is probably very short, like most TV lenses are. To test it, just point the lens to a strong light bulb; with the palm of you hand on the rear of the lens, move your hand to/from the lens mount until you get a clear image of the light bulb. This is the distance between the lens and the sensor, roughly.

      2. You will need a mount of sorts, depending on the lens flange. If it's very short, I would use a c-mount to NEX adapter, but the tricky part is to adjust the infinity focus. My usual method is to mount a filter ring at the rear of the lens (with JB Weld usually), and then the filter ring screws on to the adapter (helicoid usually). This method works well because I can use more filter rings to adjust spacers needed to obtain infinity focus.

      3. It's basically trial and error to measure the focus plane. See point #1 to get a rough idea.

      4. The lens is probably not usuable on the NEX. Probably good on the Pentax Q or even the Nikon V1/V2.

      So, before you begin, hold the lens close to camera until you can see a picture clearly (probably has very little contrast since light is coming from the side), this will tell you how large the image circle is, and approximately how far the focus plane is from the camera.

      If I am not making myself clear, please email me.

      Yu-Lin

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  5. Hi Yu-Lin,

    this is a really great article. I have tried to made something similar with and old lens with limited success. After I read your post I immediatly ordered a yeenon adapter. When I finally received it and I replicated your schema.
    I write a post in spanish explaining how to made this (http://blog.focomanual.com/brocofotografia-adaptador-para-lentes-de-proyeccion-a-traves-de-un-helicoide/), of course giving you al the credits and putting a backlink to your blog.

    Thank you for this clarifying post.

    Best regards,

    Manel Monguilod

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    1. Manel, I am happy this article was helpful to you. This is why I am doing this blog. Cheers.

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