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45 degree prism finder questions...

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David Sw

New Member
I recently acquired my first Hasselblad and am contemplating a 45 degree finder. As an eyeglass wearer I am concerned about the eye-relief.

Which of the various (non-metered) 45 degree prism has the best eye-relief? (an issue with many binoculars, etc.)

Will I be able to see the entire area of the screen with my glasses on?

Are the various models of similar apparent brightness when viewing the screen (Acute Matte, non-D)?

I'd rather not change the eyepiece diopter to accommodate viewing without my glasses. (too big a part of my life for too many years to be whipping them on and off just to view and focus - I already change to my readers to see the ground glass on my 4x5.)

Thanks!
 
All Hasselblad 45 prisms offer correction for users wearing glasses.
The PM 45 and PME 45 have variable diopter adjustment.
The range can be expandet by fitting a different lens.

Older 45 degree prisms can be adapted by fitting a suitable lens to the prism.

Except the PME 3 all metering prisms are calibrated for use with Acute Matte focusing screens.
Please note some PME 3 prisms were later adapted for use with AM screens.

Sofar the good news.
The bad news is prisms with variable dioptre adjustment demand higher prices.
The PME 45 fetches 800-1200 USD these days.
The PM 45 can be found for 400-600 USD.
 
Thanks for this information regarding the prisms and diopter availability and the AM screen issue. Given the prices, I want to ensure I spend money wisely and not end up with something I can't be comfortable using.

I would like to ask prism users who wear glasses:

Can you see the entire screen, when using a 45 degree prism, if you are wearing your normal eyeglasses?

Or, like a lot of optical "instruments", do you have to "move" about to because you cannot get your eye close enough the the eyepiece to see the entire screen at once due to the interference (increased eye to eyepiece distance due to the eyeglasses)?

The whole issue of not enough eye relief the see the entire image at once is something many eyeglass wearers live with. It was really made apparent to me when I first had an opportunity to use a pair of (Fuji) binoculars that had a huge amount of eye relief - I could see the entire image with the bino's eyepiece resting comfortably next to my glasses, I didn't have to slide the binocular eyepieces around to see the edges of the visible field.
 
David,

After seeing your question I mounted up my NC-2 45 deg prism on a 501C. I do wear glasses (bifocal) which correct primarily my distant vision. I am able to see most of the entire focus screen with the exception of a very, very small amount of the corners. I know what you mean about having to move around behind some optics, as I have a telescope with a couple eyepieces I need to do this with. I don't find it necessary with this prism. The NC-2 has a fairly large lens to view through. I don't believe you would have any problem. I do wish it had an adjustable diopter on it though, as occasionally I like to view without glasses to reduce extraneous light.

If you live in the US, you might take a look www.keh.com for prism finders. The NC-2 I purchased from them was bargain graded and paid a mere $19 plus shipping. Aside from some paint nicks that I touched up, it works just fine.

Mark........
 
Mark, thanks for your post - that's the information I was looking for.

I shall check KEH - I'm not in the US, but I'm just across the border in the Vancouver area and have made trips across to a shipping agent to pick up purchases. I've not used KEH, but have heard many good things about them over the years.

Cheers!
 
Hi David,

I have the PM45 on a 503CW and I can see the entire screen. I too an a glasses wearer with bifocals. I believe this is the latest 45 deg. prism made and the best IMHO. I had an earlier version and was unable to see entire frame .

Hope this helps.

Ron
 
Update...

I had an opportunity today to have a view through a PM45 prism (on a body w/80mm) at a local photo supplier. It's a used "kit" and they won't separate the prism from the other two bits - a very age-mixed/colour kit on consignment. (but the fellow did mention I should check back after Christmas as someone is "renting" it for the period to try it out - they may be able to sell the bits separately if he doesn't take it)

The view through the PM45 prism was brilliant (and not just bright). With my glasses on I could see all the way to the edges without having to shift my glasses about on the rubber eye-cup. Focusing in the dimly lit store was very easy (due in part, I'm sure, to the AM screen).

I do believe I will be adding one of these to my kit if I can find one at a good price in the near future.
 
Keep in mind the dioptre value of the PM45 can be adjusted.
Look under the eyepiece to unlock the lens.
Turning the lens will adjust the dioptre.
To adjust focus on the crosshairs or other marks of the focusing screen if yours does not have crosshairs. Do not forget to lock the eyepiece after it has been adjusted.

The standard diopter range can be expanded both +/-by fitting a different lens to the eyepiece.
 
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