Fitting Correction Lens to NC2 Prism

[jrsmith]

I have a -1 dioptre correction lens which I wish to fit to a Hasselblad NC2

prism. Snag is, I don't see how to get the original eyepiece out. Can anyone

help?

 

Many thanks

 

John

[q.g._de_bakker]

John,<br><br>My NC2s have a retaining ring in the eyepiece, with two slots, that unscrews to accept correction lenses.<br><br>However, i had an optician swap the original lens, instead of adding a correction lens. Perhaps the only option if the correction lens retaining ring is no longer on your prism eyepiece.<br>To do that, you take off the entire eyepiece (it too unscrews as a unit). When you do, you'll see that underneath, the original eyepiece too is held in place by a retaining ring with two opposing slots.<br><br>You need a special adjustable wrench to unscrew the ring. An optician might have such a thing. But when in a pinch, you can also use one of these sliding vernier callipers (the inner measurement 'tongues' will fit nicely. But mind that you do not use one you might want to use again to get precise measurements. I use an old, worn one for this purpose. You can also get one of the cheaper ones that are found in all hardware stores. They are not good for their intended purpose anyway.)<br>But make sure, whatever tool you sue, that you do not slip and scratch the glass!

[q.g._de_bakker]

P.S.<br><br>Using an -1 correction lens, you must not take the original lens out, but add it to the original one.<br>The -1 lens alone will be no good.

[jrsmith]

QG

 

thank you very much. I will have another look at this tonight - my correction lens is a genuine Hasselblad part, and is set in a threaded mount. So this should screw in above the standard eyepiece?

 

John

[q.g._de_bakker]

John,<br><Br>What you have is meant for later prisms (the NC2s were discontinued long before Hasselblad started selling replacement eyepieces, instead of the correction lenses alone).<br>I do not know if, and how, it will fit the NC2.<br>The idea of these later correction eyepieces is indeed that you remove the original eyepiece, putting the new one in its place. Perhaps it will fit the NC2 when you take the original eyepiece off entirely.

[jrsmith]

Aha, mystery solved - wrong correction lens. Well, I suppose if the threads are the same, we might be able to do something. Otherwise it's one for the spares box. Bother. Thanks again, QG.

 

John

[q.g._de_bakker]

Yes. We won't know if it indeed is the "wrong" one untill it has been tried. Might well fit anyway!

[jrsmith]

QG

 

you were absolutely right. The lens I had bought replaces the original eyepiece, and is not added to it. I had to dimantle the prism to get at the rear of the eyepiece, when I could unscrew the lockring and remove the lens. There are two screws on the rear casing below the eyepiece, and two more hidden under the leather cover. The actual glass lens in the Hasselblad -1 dioptre ring was exactly the right diameter, and then was a straight swap. Job done!

 

John

[q.g._de_bakker]

Excellent!<br><br>It shouldn't have been necessary to dismantle the prism though (but a fun thing to do anyway). The NC2's eyepiece is threaded, and should come off as a whole. When it does, it of course allows acces to both its sides.<br>But i understand that it wouldn't come off. I would have loved to know whether the thread on the NC2's original eyepiece is the same as that on the much later replacement eyepieces.

[jrsmith]

Yes, Q.G. I couldn't test that out. I think the thread probably is the same, but the eyepiece was really tight and my soft tools wouldn't shift it. You can understand that I didn't want to resort to a hard vice or Mole grips to get it out and damage it in the process. By the way, my NC2 has a date stamp inside, on the prism glass itself - September 1974. Anyhow, I can now use the prism wearing my computer/reading glasses, which was the object of the exercise.

 

John