Microprism focusing screens

mtnbkr · Feb 27, 2022

Are microprism focusing screens dependent on the user's vision to properly show that the lens is properly focused? Or, does the microprism do its thing regardless of my eyes' ability to focus clearly at short distances?

I'm asking because as a recent returnee to film and manual cameras (I last regularly shot film around 2009ish), my near vision has deteriorated to the point I need reading glasses. I don't need glasses for anything beyond arm's length and my results on film with this camera, so far, seem to indicate the microprism is not dependent on my vision, but I wanted to be sure before I start using it more.

Chris

runswithsizzers · Feb 27, 2022

Have you investigated the possibility of putting a corrective diopter on your camera’s viewfinder?

mtnbkr · Feb 27, 2022

runswithsizzers said:
Have you investigated the possibility of putting a corrective diopter on your camera’s viewfinder?

I have, but the scenes I typically shoot are beyond the distance for which I'd typically need glasses. I'm not struggling to see the image or the microprism clearly, I'm just not confident what I see (clear microprism and clear image in the viewfinder) is indicative of a properly focused scene.

I would think my eye is focusing on the image on the focusing screen, so without a diopter everything should be blurry or misfocused, but my 1 roll test appear to be fine.

Chris

ciniframe · Feb 27, 2022

The eyepiece of an SLR is typically set at a certain diopter, that is, if it is not an adjustable diopter eyepiece. The cameras companies often do not publish this information but it seems that most fixed eyepieces were set at -1 (1 meter). So, if you can see clearly an object set at 40 inches from your eye you should have no problem with most older film SLR’s.
Personally I prefer a plain matte focusing screen, no micro-prism or split wedge focusing aids. In cameras that allow interchangeable focusing screens, such as my OM-1 I’ve always installed plain matte screen.

edit: If my dim memory serves, with a micro-prism focusing aid your eye needs to be centered in the viewfinder, not too far left-right or up-down. Otherwise, with a smaller aperture lens some part of the micro-prism will black out.

Paul Howell · Feb 27, 2022

I assume you are using a camera with interchangeable screens. Unless you shoot with long lens or in dim light I found a split image focusing screen to work best for me. Otherwise a plane matt screen. With long lens I'm generally at infinity so no need to be precise in terms of focus, just crank the lens to infinity and shoot.

AgX · Feb 27, 2022

Any focusing aid necessiates that one can see itself as sharp as possible.
This means seeing sharp the grain of a ground screen, the limiting lines of split wedges and microprisms and the outline of the focusing patch in a RF.

mtnbkr · Feb 27, 2022

ciniframe said:
The eyepiece of an SLR is typically set at a certain diopter, that is, if it is not an adjustable diopter eyepiece. The cameras companies often do not publish this information but it seems that most fixed eyepieces were set at -1 (1 meter). So, if you can see clearly an object set at 40 inches from your eye you should have no problem with most older film SLR’s.
Personally I prefer a plain matte focusing screen, no micro-prism or split wedge focusing aids. In cameras that allow interchangeable focusing screens, such as my OM-1 I’ve always installed plain matte screen.

edit: If my dim memory serves, with a micro-prism focusing aid your eye needs to be centered in the viewfinder, not too far left-right or up-down. Otherwise, with a smaller aperture lens some part of the micro-prism will black out.

Thanks. My vision is fine beyond about 40", so if the view on the focusing screen is based on that, then it explains why I'm able to see it clearly even though the screen is mere inches from my eye.

Chris

mtnbkr · Feb 27, 2022

Paul Howell said:
I assume you are using a camera with interchangeable screens. Unless you shoot with long lens or in dim light I found a split image focusing screen to work best for me. Otherwise a plane matt screen. With long lens I'm generally at infinity so no need to be precise in terms of focus, just crank the lens to infinity and shoot.

It's not interchangeable, but it's the sort of screen I'd choose anyway. I don't have problem with the microprism itself, I'm just unclear on whether or not it is dependent on my vision.

It occurred to me another way to frame this is this:
Is the microprism functionally coupled to the lens in the same way a rangefinder's split image is calibrated to the lens (ignoring the mechanical coupling in a rangefinder) or is it a function of my vision (and affected by diopters, correction via glasses, etc)?

Chris

mtnbkr · Feb 27, 2022

AgX said:
Any focusing aid necessiates that one can see itself as sharp as possible.
This means seeing sharp the grain of a ground screen, the limiting lines of split wedges and microprisms and the outline of the focusing patch in a RF.

That's why I'm asking the question. Even though I need glasses to read or use a computer, I can see the microprism clearly, making me second-guess how it works in relation to my eyes.

Chris

Paul Howell · Feb 27, 2022

You can test by measuring out a scene, say at 5 feet, 10 feet, 15 feet and infinity, then just look to see if the microprism center is in focus while the outside of the center is out of focus.

mtnbkr · Feb 27, 2022

Paul Howell said:
You can test by measuring out a scene, say at 5 feet, 10 feet, 15 feet and infinity, then just look to see if the microprism center is in focus while the outside of the center is out of focus.

Jeez. It didn't even occur to me to do this even though I did the same thing when I calibrated the rangefinder on my VT.

Great suggestion, thanks!

Chris

AgX · Feb 27, 2022

mtnbkr said:
Even though I need glasses to read or use a computer, I can see the microprism clearly, making me second-guess how it works in relation to my eyes.

But it does neither harms oneself or ones cameras if one checks on this: At drugstores and such you likely will be able to buy for very little money emergency glasses in plus and minus strenghts in 0.5diopter steps. Test the finder images as I described above with these on.

madNbad · Feb 27, 2022

Currently, the only SLR I own is a Nikkormat FS which like most cameras from the mid 1960s is equipped with a micro prism screen but no split image. I have poor vision and it can be a struggle to ensure proper focus. So far, the best thing that has helped is better light transmission through the lens. A sufficient amount of light falling on the finder will give a better image to focus on but still takes concentration and a lot of checking the entire screen, not just the center. My real test will come when I open the 55 Nikkor to 1.2 and see how that works.

Bill Burk · Feb 27, 2022

mtnbkr said:
Thanks. My vision is fine beyond about 40", so if the view on the focusing screen is based on that, then it explains why I'm able to see it clearly even though the screen is mere inches from my eye.

Chris

Yes it’s meant to be at a far viewpoint. That’s why I always need diopter correction because without glasses I am nearsighted and the finder is blurry.

Microprism works best with f/1.4 lenses. It’s pretty good at f/2 so that’s my main reason for wanting f/2 lenses where I can get them.

If you see a noticeable graininess changing to clear as you focus, it’s working. If it’s mostly gray all the time, the lens might be too slow or it might be stopped down.

AgX · Feb 27, 2022

Bill Burk said:
Microprism works best with f/1.4 lenses. It’s pretty good at f/2 so that’s my main reason for wanting f/2 lenses where I can get them.
If you see a noticeable graininess changing to clear as you focus, it’s working. If it’s mostly gray all the time, the lens might be too slow or it might be stopped down.

As groundscreens and split wedges, microprisms too can be designed for different lenses or different operational situations.

Bill Burk · Feb 27, 2022

Could be - I think in terms of Spotmatic which doesn’t give options. And I shoot a lot stopped down because I have a couple Super Takumar lenses (135 f/2.5 and 35 f/2) with ES-II. The juggle is real.

For all the Olympus OM screens though, I don’t think there’s “microp-matte” designed for f/3.5 lens. Instead they go to to wacky combinations of hash marks on clear, etc.

George Mann · Feb 27, 2022

You might want to investigate the magnification accessory made for the F/F2. They use the same eyepiece as the Nikkormat series.

Pieter12 · Feb 27, 2022

mtnbkr said:
I'm not struggling to see the image or the microprism clearly, I'm just not confident what I see (clear microprism and clear image in the viewfinder) is indicative of a properly focused scene.

As far as I know, if you can see the focusing screen image clearly and it is sharp the image is in focus. Now, if you can't get a sharp image through the viewfinder it is time to use some sort of correction, either glasses or a diopter.

Autonerd · Feb 27, 2022

mtnbkr said:
Are microprism focusing screens dependent on the user's vision to properly show that the lens is properly focused?
Chris

I'm in the same boat (+1.50 reading Rx). One of my favorite cameras (Pentax KX) has a microp-only screen. They're a bit harder to see than they were when I was 24, but I can generally tell when they've gone clear, and I haven't had problems getting my photos into focus. I prefer microprisms to the split-prism but for tricky situations the split is sometimes a little less ambiguous.

Aaron

eli griggs · Feb 27, 2022

You could invest in a good pocket laser rangefinder and use that to discover the distance involved, and then set your focus by Prego using with the lens AND aperture/depth of field so your shot is always in focus.

This would mean, you may no always be able to pinpoint for a shallow depth of field, but you would be getting the shot everytime you used the above method.

I've given this some thought because it's something I'd like to be able to do, but good electric pocket rangefinders are too pricey, at this moment.

Cheers and Godspeed to All.

Neil Grant · Feb 28, 2022

... I think Nikon made the widest range of focusing screens available for the F2 camera. Not only could you a have a micro prism spot, you could also get a screen with microprisms all-over. It gives a very bright image but it's not possible to judge depth-of-field when using it.

reddesert · Feb 28, 2022

As ciniframe said in post #4, the eyepiece of an SLR is usually a negative lens that makes an image of the focusing screen as if it were about 1 meter away. This is necessary since the physical distance of the focusing screen from the eyepiece is just a few inches and even a young person with good eyesight can't focus that close. So if one can focus at 1 meter and see the SLR focusing screen clearly, it should work, otherwise one needs to explore diopters (Some cameras have a built in diopter adjustment which is useful as a check).

A microprism screen has basically a bunch of small wedge prisms like mini split image rangefinders. If the image is not focused at the right plane, these offset the images creating the jagged aspect that you see. So if you can use a split image RF, then you can generally use a microprism, with the usual caveats that they black out with slow lenses or if your eye is not lined up with the viewfinder.

Microprism focusing screens

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