Hasselblad Split-Image Focusing Screen

RalphLambrecht · Nov 20, 2009

I'm a fan of the Acute-Matte D split-image focusing screen, but who can afford more than one, so, I went for it and bought a more cost-effective Chinese replacement on eBay to try it out. I did not expect too much for $37, but was happily surprised.

To check the focus, I focused with the Acute-Matte screen first, replaced it with the Chinablad screen, and... the focus is spot on, absolutely no difference and easy to focus. The screen is much darker though, and the concentric rings (not even visible on Acute-Matte) are very obvious and a bit in the way really. Still, not bad!

It's an option if precise focus is a concern. Mine has a 45 degree split-image, which proved to be a benefit with many subjects.

Just thought, I share the experience.

Kvistgaard · Nov 22, 2009

Hi Ralph,
sounds like my experience with the replacement split image screen I bought from Gevorg at araxfoto, except I did not notice any degradation of the image projected on the screen. Definitely an improvement over the original Hasselblad screen, which did not have a split image.

Don't remember the cost, but probably in the region of the $35 you paid for your Chinablad screen. Nothing outrageous.

Philippe Grunchec · Nov 22, 2009

I also use an Arax screen on my 503CW and I like it a lot!

Sirius Glass · Nov 22, 2009

I liked the Acumat D split screen for the 80mm f2.8 lens. However, I was not as happy when used with f4 lenses and downright unhappy with the f5.6 250mm lens. So I got an Acumat D screen without the split screen that has vertical and horizontal cross hairs and I am much happier.

Steve

RalphLambrecht · Nov 23, 2009

Sirius Glass said:
I liked the Acumat D split screen for the 80mm f2.8 lens. However, I was not as happy when used with f4 lenses and downright unhappy with the f5.6 250mm lens. So I got an Acumat D screen without the split screen that has vertical and horizontal cross hairs and I am much happier.

Steve

Read the first post. Who can afford an Acute-Matte Screen? What are they now >$300. Nuts! (please no eBay replies) The point was that there are cheaper options, not as convenient, but just as accurate.

Q.G. · Nov 23, 2009

There are cheaper options that are just as convenient and accurate. But you said you don't want to hear about them, so...

Nah... I can't help myself: earlier this year, i had the good fortune of paying (better sit down now) £ 9.99 for the Real Deal.
Who needs the Chinese...

ymc226 · Nov 23, 2009

Ralph, is the Chinese screen glass or arcrylic? I like the 45 degree split screen concept.

RalphLambrecht · Nov 23, 2009

ymc226 said:
Ralph, is the Chinese screen glass or arcrylic? I like the 45 degree split screen concept.

Hard to tell! I don't know how you would make the split-image out of glass. Anyway, the Chinese screen is a bit heavier than the Acute-Matte screen (18 vs 14 g) if that is any indication.

Sirius Glass · Nov 23, 2009

RalphLambrecht said:
Read the first post. Who can afford an Acute-Matte Screen? What are they now >$300. Nuts! (please no eBay replies) The point was that there are cheaper options, not as convenient, but just as accurate.

I did read the first post. I brought it new from Bel Air camera in West Los Angeles where they were dumping a large amount of Hasselblad equipment. I paid $100 for it.

Keep checking camera stores and eventually you may find that you can purchase a Acute-Matte screen.

Good luck.

Steve

Q.G. · Nov 23, 2009

You're right: with some patience, you can get the originals for much less than what they cost new.

But that's still more than twice as much as Ralph paid.
So thanks, Ralph, for giving a review of these Chinese screens! I may try a diagonal split myself.

I don't think my luck is that good that i'll be able to find another one for under £ 10.

wclavey · Nov 30, 2009

Sirius Glass said:
I liked the Acumat D split screen for the 80mm f2.8 lens. However, I was not as happy when used with f4 lenses and downright unhappy with the f5.6 250mm lens. So I got an Acumat D screen without the split screen that has vertical and horizontal cross hairs and I am much happier.

Steve

Was your unhappiness due, by any chance, to the split screen prism going dark on lenses slower than f/2.8?

Sirius Glass · Dec 1, 2009

wclavey said:
Was your unhappiness due, by any chance, to the split screen prism going dark on lenses slower than f/2.8?

Yep, especially in low light levels. You broke the code.

Steve

wclavey · Dec 2, 2009

Thanks, Steve. I tried one in my Bronica S2A but had the problem with the darkening - - all but one of my lenses are slower than f/2.8. I got one of the Arax bright screens to try too, which was very bright, but it had the same problem. Unfortunately, the Arax screens don't seem to come without the split-image prism. And while I'm willing to chip and grind on a $20 Arax screen to make it fit the Bronica, I'm not willing to do that on an Acute Matte.

Q.G. · Dec 2, 2009

The trick is to keep your eye centered above the split thingy.
Then it will work even with f/5.6 lenses (but only if it isn't too dark).

Sirius Glass · Dec 2, 2009

Q.G. said:
The trick is to keep your eye centered above the split thingy.
Then it will work even with f/5.6 lenses (but only if it isn't too dark).

I know but sometimes the darkening would get obnoxious when I did not have the time if I did not want to miss the moment.

Steve

wclavey · Dec 2, 2009

Q.G. said:
The trick is to keep your eye centered above the split thingy.
Then it will work even with f/5.6 lenses (but only if it isn't too dark).

I wonder if a chimney finder would help keep your eye centered? I use the pop-up magnifier extensively but I also wear bifocals, and I need to do critical focusing through thee bottom part of my lens... so by definition, my eye is not centered above the center off the screen... I'm looking down through the bottom of my glasses.

Q.G. · Dec 3, 2009

It will, yes.
Using a prism finder does too.

But 'don't expect miracles'. The split image rangefinder will still not work at low light levels.
It's the best focussing aid available, but has its drawbacks.

fdisilvestro · Dec 3, 2009

For critical focusing (i.e. wide open close range) you will also need to be sure that the mirror and focusing screen are properly calibrated. Older models (pre-GMS) have the mirror resting on 3 cushion foams which may have degraded and the mirror will not be where it should. The focusing screen rests on top of four screws that are used to fine tune the exact position.
This is usually something that you cannot do yourself. You'll have to send your camera to a high end repair facility.

RalphLambrecht · Dec 3, 2009

fdisilvestro said:
For critical focusing (i.e. wide open close range) you will also need to be sure that the mirror and focusing screen are properly calibrated. Older models (pre-GMS) have the mirror resting on 3 cushion foams which may have degraded and the mirror will not be where it should. The focusing screen rests on top of four screws that are used to fine tune the exact position.
This is usually something that you cannot do yourself. You'll have to send your camera to a high end repair facility.

The depth-of-focus equation suggests that focus is most critical with wide-angle lenses, at wide-open apertures, focused at infinity. Essentially, the depth-of-focus is the reverse of the depth-of-field.

fdisilvestro · Dec 3, 2009

I´m not an expert in optics, but from what i have read, the depth of focus is a function of f-stop, circle of confusion size and magnification. Wide angles in normal conditions (medium distances) give you lower magnification so lower depth of focus. At very low magnifications (infinity) the depth of focus can be approximated as a function of f-stop and circle of confusion size.
I would thank anyone clarifying if I am lost in this concept.
Anyway the possible variations due to mirror and focusing screen position may be larger than the depth of focus. Also I think than being near the extremes of the depth of focus will not translate in razor sharp images.

Sirius Glass · Dec 3, 2009

Q.G. said:
It will, yes.
Using a prism finder does too.

But 'don't expect miracles'. The split image rangefinder will still not work at low light levels.
It's the best focussing aid available, but has its drawbacks.

I use a PME and if my eye was not lined up perfectly with the view finder the split-image went half black with the f/5.6 250mm lens.

I got tired of that happening and when I saw another new Accumat-D screen without the split-image for sale at $100, I bought it;

Steve

RalphLambrecht · Dec 3, 2009

fdisilvestro said:
I´m not an expert in optics, but from what i have read, the depth of focus is a function of f-stop, circle of confusion size and magnification. Wide angles in normal conditions (medium distances) give you lower magnification so lower depth of focus. At very low magnifications (infinity) the depth of focus can be approximated as a function of f-stop and circle of confusion size...

No, you got it right. But, a small depth of focus means that an accurate screen position is more important than ever, because there is little focus tolerance left. Hence, focusing is most critical at wide-angle and infinity (where the magnification is the smallest), and of course, at wide-open apertures.

A practical test is to use your screen to focus on something near infinity and take a picture of it with wide-open aperture. Then check the negative if it rendered that something properly focused. If yes, you can trust your screen.

fdisilvestro · Dec 3, 2009

Thanks Ralph. Since it is not an issue of film plane position but instead of a focusing screen position, I usually don't pay too much attention to critical focusing with wideangles at infinity, and don't see a benefit in using them wide open at infinity too.
Where I find it critical is with the 150 or 250 sonnar, which supposedly perform best wide open, at close range (not macro).

Another issue I have experienced with split-image rangefinder with long lenses (150 - 250) is that if you have astigmatism (as I do a little) in the horizontal direction and don't wear glasses, the place where I see the image align is not the correct focus. I found out this because at one time I forgot my glasses and I though I could get away by checking only the split image, since I would never see a completely sharp image in the matte area.

Just in case, what I call horizontal astigmatism is that without glasses I can see clearly horizontal lines, but vertical lines will be blurred.

RalphLambrecht · Dec 3, 2009

fdisilvestro said:
...Since it is not an issue of film plane position but instead of a focusing screen position...

It's not an issue of one or the other; it's an issue of both and to the same degree. The focusing screen has to be in the same position as the film plane, as you stated. They both fall under the same depth-of-focus equation. If they are perfectly aligned, and the subject is out of focus on the screen, it will be out of focus for the same amount on the film plane. That's why it is a benefit to focus at wide-open aperture and take the picture closed-down. You can see out-of-focus better at large apertures, as we all know. A similar benefit can be had for the purpose of checking the screen position, by testing at infinity and not close-up, and again, by using a wide-angle lens and not a telephoto.

fdisilvestro · Dec 3, 2009

You´re right, I did not explain myself in that sentence. I was thinking that in a Hasselblad, an incorrect film plane position is a very rare problem, unless the body has been disassembled and not aligned properly.

Hasselblad Split-Image Focusing Screen

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