Reverse mounting of cine lenses with filter step-up rings?

[Planapo]

Recently, a thread opened by Harold about movie camera lenses reminded me that I have lying around a few of these with focal lengths of 16 and 25 mm which until now I have not tested since I can´t mount them onto my bellows straightaway.

I know that people around here seem more to prefer DYI solutions with drilled body caps or card board and tape/epoxy but, in this case, I am not that confident in my DIY skills that I could get it well centered and trustfully firm enough. Hence, with a DYI solution done by myself I fear that the photographic results might be deteriorated due to misalignment, or the lens could loosen and drop in an unpredictable and thus very likely unfavourable moment.

However, as they have filter threads I thought using step-up rings that get me to say 40.5 mm, 43 mm or larger might be a possible solution as from there on I have step-up rings to my reversing adapters.
Now, my lenses seem to have filter thread diameters such as 30 and 26 mm. But I don´t know if the filter threads of these cine lenses possess the same thread specifications (such as tpi etc.) as the "normal" still camera lenses. And I don´t know if and where from such small filter step-up rings are available that lead from the mentioned 26 or 30 mm to the larger diameters that then could be screwed to the reversing adapters.

Does anybody of you have more experience or information on this?

Thanks much in advance for your answers.
--Betty

[Harold Gough]

Here is one place to look for adapters or to have one made.

http://www.srbfilm.co.uk/

Harold

[DaveW]

What I found out getting a ring to step down from my Nikon 52mm reversal ring to a reversed EL Nikkor enlarging lens was contrary to what you first think you need step up rings to step down! Not as crazy as it sounds because when a lens is reversed so are the threads required on the rings to when you are fitting a filter using one conventionally on a lens normal way around.

You really have to think of things in reverse and start from your reversed lens and think that you are stepping up from that to your reversal ring not stepping down from it or you will finish up with male threads where you require female and vice versa!

Kood seem to make a lot of these sizes if you Google for step up rings of the size required:-

http://www.keene.co.uk/electronics/mult ... code=40552

DaveW

[augusthouse]

Hi Betty,
Here is an example of a 30mm to 52mm. Note the threads - male small diameter (30mm), female large (52mm). These are on eBay for US$5.99 (just to give you some indication).

Depending on your reversing-ring, the 52mm female thread of the example adapters in the images below should complete the connection.

Need to look into the thread pitch of the filter thread on your lenses. I would be assuming that they are of some 'standard' 0.75mm for eg; but I personally don't have any of these lenses.

Hope this info helps somewhat for now.

A simple DIY approach might be useful in the short-term while assessing the usefulness of the lens for your purposes.

P.S. Note - some sizes can be hard to find. I recently needed a 34.5mm (very difficult to obtain) and a 34mm just wouldn't do the job. I tend to look for adapters rather than make them myself, for the same reasons that you have clearly outlined in your post.






Craig

[Planapo]

Thank you very much for your help, guys!

Craig wrote:

Need to look into the thread pitch of the filter thread on your lenses. I would be assuming that they are of some 'standard' 0.75mm for eg; but I personally don't have any of these lenses.

Hmm, how does one measure such a thread pitch of 0.75 mm?

5,99 US$ that seems not overpriced. And another difficulty I think I will encounter is to measure the diameter correctly.
I don´t know if I will get it right with such a calliper/gauge thing to make sure whether it´s 30 mm or 30.5 mm , e. g. .
Any tips on the method how to measure this correctly with a calliper/gauge?

--Betty

[augusthouse]

Hi Betty,
Hopefully Rik will come in regarding measuring thread pitch and diameter. Have a look at the thread pitch on your EL-Nikkor filter thread and see how it compares with your cine lenses.

Do the cine lenses you own have any indication of brand or other details? This may help in determining specifications with regard to filter thread pitch and diameter, etc.

Craig