Hasselblad PME3 issue with longer focal lengths

McDiesel · Apr 19, 2022

@Photomultiplier sorry, looks like most of the comments are not addressing your original problem. Personally, I think it's quite bizarre what you're seeing. Can't think of anything even hypothetically plausible and I'll be watching this thread with great interest.

I do have an interesting experiment in mind though. What happens if you mount a waist level finder and measure light directly off the focusing screen using your Sekonic? Obviously the reading won't be accurate or even meaningful, but at least you can repeat this procedure for different lenses and see if the pattern persists. This way you'll isolate one variable (prism meter).

etn · Apr 20, 2022

"Older" Hasselblads tend to dim part of the image in the waist level finder with longer lenses. This (non-) issue has been corrected with the introduction of the Gliding Mirror System in 501CM and 503CW cameras. Maybe this plays a role here? although I would expect the effect to be opposite of what you are observing.

Photomultiplier I see you are in Austria: are you from time to time in Munich? if yes I'd propose you to test your lenses + body + prism against mine. I have a 503CW and PME45. Contact me in pm if interested.

Photomultiplier · Apr 20, 2022

@etn: I know, the GMS system solved this problem in newer bodies. But this effect would further decrease the reading while i am observing EV values +1EV higher than they should. Also when using the Flexbody which has no mirror.
I am indeed thinking about a visit to Munich. The Alte Pinakothek Gallery is on my list, as i am really into renaissance art
Thank you very much for the offering.
Your gear works as intended, i suppose? No need to set a different max aperture? Automatically compensates for bellows extension?

@McDiesel: Good idea! I think i dabbled around with those kind of things in my despair some time ago but after your comment, i built a proper setup with stray light protection, two tripods and my spotmeter and i made some very interesting
observations.

The Sekonic was pointed perpendicularly onto the screen and everything was shielded with cloth against stray light. When i closed the aperture in full stops, the reading did not change accordingly but in about 0.5stop increments or even less.
About at f5.6 and smaller, the reading changed in full stops.
When pointing at the screen slightly off axis and off center, things changed and i was able to obtain more like 1EV increment when closing down from 2.8 to 4, but going just a few degrees too far, the optical artifacts of the screen became obvious.
Rainbow pattern and so on.

Maybe that is the reason why the prisms have their sensitivity zone slightly above the center? To avoid some peculiar optical effect like the light of the exit pupil additionally illuminating the screen?
The 55mm tube also did not alter the reading by more than a fraction of a stop.

I even examined the internals of the PME3 again and everything seems to be in place where it should be.

Sirius Glass · Apr 20, 2022

etn said:
"Older" Hasselblads tend to dim part of the image in the waist level finder with longer lenses. This (non-) issue has been corrected with the introduction of the Gliding Mirror System in 501CM and 503CW cameras. Maybe this plays a role here? although I would expect the effect to be opposite of what you are observing.

Photomultiplier I see you are in Austria: are you from time to time in Munich? if yes I'd propose you to test your lenses + body + prism against mine. I have a 503CW and PME45. Contact me in pm if interested.

All the GMS does is eliminate the disappearing in the viewfinder, not on the film, of a sliver of the top of the image when using the 250mm lens or longer. I do not have the GMS and long ago stopped noticing the sliver.

McDiesel · Apr 20, 2022

@Photomultiplier interesting! I wouldn't read too much into EV values not changing by full stops, as I said the results obtained this way are hard to interpret, but at least you can compare lenses this way. If the camera is facing a big enough flat grey-ish surface (the sky is actually perfect) the readings should be the same regardless of the focal length.

etn · Apr 21, 2022

Photomultiplier said:
@etn: I know, the GMS system solved this problem in newer bodies. But this effect would further decrease the reading while i am observing EV values +1EV higher than they should. Also when using the Flexbody which has no mirror.
I am indeed thinking about a visit to Munich. The Alte Pinakothek Gallery is on my list, as i am really into renaissance art
Thank you very much for the offering.
Your gear works as intended, i suppose? No need to set a different max aperture? Automatically compensates for bellows extension?

As far as I can tell, everything works fine, although I admit I did not run extensive tests like you did. All I can say is that my pics come well exposed.
I need to change max aperture on the meter when swapping lenses, but not to compensate readings. And yes, it compensates for bellows extension, which is -as you mentioned- one of the main advantages of using a metered prism vs. handheld meter.

If I can, I will join you at the Alte Pinakothek. Haven't been for several years. My little boy is passionate about trains, therefore we currently go more to the train museum (Deutsches Museum Verkehrszentrum) than to art museums but even before he was born, my partner and I were more into 19th / 20th century art.

Coming back to your problem, maybe your meter is reacting differently to different angles of incidences of the incoming light?
Are you using a polarizing filter or color filter for B&W?

etn · Apr 21, 2022

Sirius Glass said:
All the GMS does is eliminate the disappearing in the viewfinder, not on the film, of a sliver of the top of the image when using the 250mm lens or longer. I do not have the GMS and long ago stopped noticing the sliver.

Yes, but the metering is taken in the viewfinder, therefore it might have an influence - although as noted, the expected influence would be opposite to what Photomultiplier is observing.

Sirius Glass · Apr 21, 2022

etn said:
Yes, but the metering is taken in the viewfinder, therefore it might have an influence - although as noted, the expected influence would be opposite to what Photomultiplier is observing.

Except GMS does not change the exposure. Talk to a Hasselblad repair person and they will tell you the same thing.

MattKing · Apr 21, 2022

Sirius Glass said:
Except GMS does not change the exposure. Talk to a Hasselblad repair person and they will tell you the same thing.

It would change the exposure if the meter reading is taken off the affected section of the viewing screen.

Photomultiplier · Apr 21, 2022

Please be reminded that the effect of the shorter mirror in cameras without GMS is not the original topic.
The shorter mirror causes a darkened band on the top of the focusing screen with longer lenses and it has absolutely nothing to do with the image projected onto the film.
Further, no manual of the prism mentions this effect (there are also older meter models where GMS did not exist yet) and lastly any darkening would yield lower readings, not higher as in my case. This has been already pointed out.

The question is: Why does my PME3 behave the way it does while it should do otherwise and others do not observe this behavior.

I will, for sure, not give up until i have the solution to this riddle and i will let you know as soon as i came to any conclusion

The best way will be a direct comparison and cross check with a known-good set of components.

Sirius Glass · Apr 21, 2022

MattKing said:
It would change the exposure if the meter reading is taken off the affected section of the viewing screen.

The effected section is a thin sliver at the top of the mirror and no where near where the light meter takes its reading.

McDiesel · Apr 21, 2022

Feature request: the author of a topic should automatically get moderator privileges for it, so they can remove noise and close it down when the solution is found.

MattKing · Apr 21, 2022

Sirius Glass said:
The effected section is a thin sliver at the top of the mirror and no where near where the light meter takes its reading.

Apropos to the OP's original question, where on the focusing screen does the meter take its reading from?
And is that reading affected by the change of focusing screens in ways that are unpredictable?
I can see how the addition of a fresnel lens in the screen could bring into play issues concerning the directionality of the light through the lens - something that is affected by the addition of extension tubes.

Sirius Glass · Apr 21, 2022

MattKing said:
Apropos to the OP's original question, where on the focusing screen does the meter take its reading from?
And is that reading affected by the change of focusing screens in ways that are unpredictable?
I can see how the addition of a fresnel lens in the screen could bring into play issues concerning the directionality of the light through the lens - something that is affected by the addition of extension tubes.

The metering prisms take the light from zones on the center of the screen. One has to look at the manual for each type. But none take readings from the top edge of the view finder.

itsdoable · Apr 23, 2022

It's the weekend, so I have some time to dig up some equipment I don't use much (like my 55mm extension tube, which took me a while to locate!).

The main difference is I have the PME51, which has updated electronics from the PME3. The rest is similar, acute matte 42165, 2.8/80CF, 4/150C, 5.6/250CF, and the a fore mentioned 55mm extension (original C version).

The PME51 reads within 1/2 EV between the 80mm and 250mm, which accounts for the difference in transmission (T stop) that is typical of telephoto lenses.

The PME51 showed a reduction of more than 1 stop (EV) when the 55mm extension tube is added to the 80mm. In fact as you focus the 80 to MFD (without the extension tube), you can see the meter drop a 1/2 stop, depending on if the meter is close enough to the threshold to change.

The meter reads and behaves the same on a GMS body, as expected.

It also reads and behaves the same with an acute matte II. I did not test it with a pre-acute matte screen.

Photomultiplier · Apr 24, 2022

One question for clarification: The readings within 1/2stop between the 80 and 250 were obtained with adjusting the max aperture according to the lens? (2.8 and 5.6)

Does the bottom view of my PME3 look reasonable? Especially the "vertical" position of the photodiode. There is a ~1mm gap visible between the plastic frame and the plastic bracket that holds the
diode.

Maybe the diode got displaced over time?

itsdoable · Apr 24, 2022

Mine is more crooked than yours!

And yes, I set the max aperture on the meter to match eash lens, otherwise the reading would be that many stops off.

McDiesel · Apr 24, 2022

I finally got around to trying this at home. My prism is PME51 designed for AcuteMatte D screens, matching what's on my camera. I have pointed the camera at a giant green screen which I use for videoconferencing occupying 100% of the viewfinder area. I measured with 3 lenses, each time adjusting MAX parameter on the prism according to the lens maximum aperture.

60mm Distagon CFI - 8EV
150mm Sonnar CFI - 7.5EV
250mm Sonnar CF - 7EV

Using external light meter:

Ambient 7.5EV
Reflected 8EV

Not sure what to make out of this. Generally, I've been quite happy with the photographs metered via the prism.

Hasselblad PME3 issue with longer focal lengths

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