Custom screw in diopters

alanrockwood · Oct 22, 2015

Does anyone know how one might have a custom made screw in diopter made without spending a fortune? What I have in mind would be something like a 0.25 diopter that would screw into the front of a 150mm lens. I don't recall the thread diameter at the moment, but it is pretty big, perhaps something like 77mm.

The form of the lens could be plano-convex, or preferably a minuscess with custom specified radii on the lens surfaces.

The purpose is to provide a bit closer focusing for a 150mm Kaleinar lens. I am not interested in getting real close, but just a bit closer than its normal focusing distance of ~2 meter.

Thanks.

Maris · Oct 22, 2015

A standard uncut spectacle lens from an optometrist is available in 75mm diameter. This fits perfectly in a photographic 77mm screw in filter after the original glass is changed out. I pay $20ea for these spectacle lenses including powers +0.25D, +0.5D,....,+3.0D. I also use a range of negative dioptre spectacle lenses to lengthen focal lengths of view camera lenses. Small adjustments like 0.25D and 0.5D have surprisingly little effect on image quality if you are prepared to stop down a bit extra.

AgX · Oct 22, 2015

I have came across large diameter close-up lenses.
If not avalaibly in your size a smaller lens and step.-down rings could be an alternative.

EDIT:
Heliopan list close-up lenses (1-4 diopters) up to 86mm filter-thread.

gone · Oct 22, 2015

Try an extension tube. It will give you less light, but no decrease in IQ.

frank · Oct 22, 2015

momus said:
Try an extension tube. It will give you less light, but no decrease in IQ.

Was about to say the same.

alanrockwood · Oct 23, 2015

I have a couple of sets of extension tubes, but the extension of the shortest tube is a little to long for my purposes, which would be to focus a little closer for making portraits.

The idea of getting an unmounted lens from an optometrist is a good one, and as luck would have it I was at a party this evening, and an optician was there. He's not an optometrist, but for this purpose an optician is even better. He told me he might be able to get me a 0.25 diopter unmounted lens for not too much money.

One issue is that the thread diameter is 82mm. I think I said 77mm earlier, but I was wrong. That's pretty big and might require a custom ordered lens.

AgX · Oct 23, 2015

As said, available from Heliopan off the shelf in four tastes.

Jim Jones · Oct 23, 2015

alanrockwood said:
. . . One issue is that the thread diameter is 82mm. I think I said 77mm earlier, but I was wrong. That's pretty big and might require a custom ordered lens.

Not a significant issue except when using the camera lens at full aperture. Step-down rings work normally as long as the smaller filter's diameter is larger than the entrance pupil at the aperture in use.

alanrockwood · Oct 23, 2015

AgX said:
As said, available from Heliopan off the shelf in four tastes.

I thought that Heliopan lenses started at +1 diopter. Can you get them in fractional diopters, such as +0.25? It is fractional diopters I want.

I am not looking for something for what would normally be called "close up" photography. My interest is just in knocking down the closest focusing distance a bit. For example rather than focusing from 2 meters to infinity it might be more like 1.3 meters to 10 meters.

AgX · Oct 23, 2015

Sorry, now I understand.

Their weakest lenses start indeed at 1diopter. You could inquire at them for a even weaker lens.
But in this case I would go the extention-tube way and "just" shorten a tube to the desired length. (Fit the cut parts together by glueing a bandage around them.)

macfred · Oct 25, 2015

There was an ANGENIEUX close up lens +0.3 in 82mm size - you can find it sometimes on ...bay http://www.ebay.com/itm/121101215610
Maybe an interesting read to subject : http://www.eoshd.com/comments/topic/2570-the-diopter-thread/

AgX · Oct 25, 2015

AgX said:
But in this case I would go the extention-tube way and "just" shorten a tube to the desired length. (Fit the cut parts together by glueing a bandage around them.)

That "just" becomes another meaning when an automatic tube is involved.

Custom screw in diopters

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