To have the test be meaningful, both camera light meters must be calibrated by the same laboratory.
Following this lead, I checked my two camera backs, and they do differ. I made some observations by setting both backs to the same ISO, fixing the lens aperture at f11, and then metering an indoor scene under constant illumination. I noted the speed indicated in the AE display for each exposure compensation setting, for both backs. The metered shutter speeds for one back were consistently slower than for the other back. The differences ranged from from 1/3 stop to 1 full stop, with the larger differences at higher shutter speeds.
This after cleaning the gold-colored hemispherical contacts at the upper right of the back, and on the lower right of the finder.
I noticed two pin-type connectors at the lower inside surface of the back, with complementary features on the camera body. One near the ISO dial, the other not. Does anyone know what these connectors are for?
Following this lead, I checked my two camera backs, and they do differ. I made some observations by setting both backs to the same ISO, fixing the lens aperture at f11, and then metering an indoor scene under constant illumination. I noted the speed indicated in the AE display for each exposure compensation setting, for both backs. The metered shutter speeds for one back were consistently slower than for the other back. The differences ranged from from 1/3 stop to 1 full stop, with the larger differences at higher shutter speeds.
This after cleaning the gold-colored hemispherical contacts at the upper right of the back, and on the lower right of the finder.
I noticed two pin-type connectors at the lower inside surface of the back, with complementary features on the camera body. One near the ISO dial, the other not. Does anyone know what these connectors are for?
There was one camera body, two film backs attached thereto (serially).To have the test be meaningful, both camera light meters must be calibrated by the same laboratory.
Could you post a photo of the side of the back that mates to the body? It is intuitively odd there would be two sets of electrical contacts on the back...the only electrical data should be the ISO setting for the film which is loaded.
There is a mechanical interlock...
The fact that you do not get same metering result when switching backs is pointing to some issue of uncertain origin.
- which should prevent the shutter from being released when the film has not been advanced to the next frame (unless there is a multi-exposure switch set on the body of Bronicas with that feature), and
- there might be an interlock on Bronica backs (depending upon vintage of back) which prevents shutter from being released if the dark slide has not been removed.
Thanks reddesert. So the ISO and exposure compensation settings are passed to the AE finder via the two gold hemispherical contacts at the upper right of the film back ...?The two mechanical pin connectors between back and body on a Bronica ETR, SQ, or GS, as wiltw said, communicate whether the back and camera are wound, and whether the darkslide is in or out to prevent shutter firing when the darkslide is in. They don't have to do with metering.
All Bronica backs of these systems prevent the shutter firing when the darkslide is in, I believe. However, only the later generation of backs prevent removing the darkslide when the back is off the camera, I think that's the generational difference wiltw was thinking of. You can tell the difference because the later darkslides have a little notch near the bottom, and the backs have a little sprung metal piece that engages the notch. (On the ETR and SQ, the later darkslides with the notch have a gray handle. On the GS, I think all the darkslides have the notch and a black handle. That's real Bronica trivia.)
Thanks reddesert. So the ISO and exposure compensation settings are passed to the AE finder via the two gold hemispherical contacts at the upper right of the film back ...?
For a while I had only one dark slide between two backs - which at first was a problem. Turns out (file this under more Bronica trivia) that there is a tiny metal nubbin (maybe your 'little sprung metal piece'?) on the bottom of the film back, near the dark slide handle, which when pressed allows the dark slide to be removed when the back is off the camera. To insert a dark slide into a loaded, off-camera back, press the nubbin in and insert the slide. Maybe this is common knowledge - but it took me a while to catch on.
Well .... it turns out my GS-1 metering scene is pretty erratic. I got inconsistent results comparing the stock and Oleson screens, in a composed and artifically lit scene. Using the same lens, film back, ISO, aperture, lights and position. So - no help here on comparing screens.Let me know how it goes with the Oleson screen! I was actually thinking of getting a Maxwell split image screen for my P67II, but while chatting with Bill (a very long chat indeed, haha), he checked out the genuine P67II split image screen on eBay and saw that they're going for astronomical prices - around $700 for a split image screen! Anyway, he said that his would cost me around $500, to which I had to politely decline. :/
I checked out Rick Oleson's screens and it's nice to know that there are other focusing screens out there for sure.
Using an external meter obviates the need to repair my LED display and sensor, so that's a plus. And not really an inconvenience, given that external metering is de rigueur for large format cameras, folding cameras, etc.
reddesert, I followed up on your excellent idea, on my three GS-1 6x7 film backs. They do show some variability, which would account for some of the metering inconsistency I've been experiencing. A plot attached, showing resistances that I measured at ISO 100, for exposure compensation settings -3 to +3, for three backs (red, blue and black lines). Your measurements would fit in nicely with the data for my three backs.The two electrical contacts at top are how the back passes film speed to the meter prism. I think it's just a variable resistor but don't know exactly. To put some numbers on it, I measured and with one back I get a resistance of about 1000 ohms when set to ISO 100 and 0 exposure comp. For every stop you change the film speed or exp comp, the resistance changes by about 200 ohms. You could measure your two backs with an ohmmeter and see if there is a difference. I don't know what the "correct" value is, although a repair manual would likely say. I don't have a GS meter prism.
Good luck with that kit! I selected the 65 and 150mm lenses, along with the G-36 teleconverter, as it gave me a good range in focal lengths and only 72mm filters.A nice Bronica GS-1 kit has shown up today at home. My Pentax 67II still does not know it yet in case she gets jealous. The kit matchs very well my usual set of lenses with the Pentax (55, 105 and 200 mm).
View attachment 347126
Some thoughts after playing a little bit:
- Focusing screen: Dim, very dim compared to the Pentax and without any focusing aid. It is ok for the 100 mm but not for the 50 mm and 200 mm. If I keep it I will buy a Rick Oleson's.
- AE lock button: It is in a very uncomfortable place, perhaps I will get used to it.
- Filter diameter: Three lenses, three diferent filter diameter (72, 82 and 95 mm). Not cool.
- Double strock advance: With the grip. Seems it needs one for film advance and another for cocking the shutter and mirror return, both feel very smooth. Not really a problem but it slows down a bit compared Pentax 67 single stoke.
- Shutter operation: Quiter (still noisy) and smoother than the Pentax.
- Weigth and size: With AE prism and grip Bronica weight is very similar to a Pentax 67II, and with worse mass distribution. Both are similar in total width and height, Bronica has more length than the Pentax due to the modular design (body+back).
I am a big fan of Bronica SQ-Ai but this GS-1 clearly falls behind in terms of usability, at of course the same compared to a Pentax 67II. I did a quick test roll to be developed tomorrow to validate the working condition and more will come if there is no unpleasant surprises. At the end of the day image quality and reliability is what I care the most.
- Filter diameter: Three lenses, three diferent filter diameter (72, 82 and 95 mm). Not cool.
One thought: you got unlucky with the lens selection though. It just so happens that these 3 all have different filter diameters. Have you gone with the 65, 100 and 150 trio, the filters would have been the same.
You won't be disappointed by the Oleson screen BTW.
As you might glean from earlier thread entries, the AE system gets mixed reviews. I'm curious to hear your impressions.
It is equally dim than Bronica original [...] Did the Oleson screens changed or I am missing something else?
I found the Oleson MPD screen dramatically superior to the matte screen supplied with my GS-1, for focusing purposes. The central area of the Olesun is much brighter than the matte screen, as is the Oleson microprism annulus. Outside the annulus, I don't recall that the difference was that pronounced. But I went from more or less guessing that the focus was close with the matte screen that came with my camera, to feeling that I could nail it with the Oleson.I put today Rick Oleson's Brightscreen MPD (split and microspism) in my GS-1 and I am surpised. It is equally dim than Bronica original and it doesn't need any exposure compensation (not required either in Oleson page). I got exactly the same AE prism readings with both screens.
Did the Oleson screens changed or I am missing something else?
I found the Oleson MPD screen dramatically superior to the matte screen supplied with my GS-1, for focusing purposes.
Something else is going on here. Maybe the Pentax is just out of this world in terms of focusing screen brightness? I never used one, I don't know but I own 7 medium format cameras and none of them sport a brighter screen than the GS-1 native screen or Oleson's screen. Hasselblad AcuteMate, Mamiya TLRs, or the latest Rolleiflex FX/FW - none of them are brighter. The reason I recommended Oleson screen was their focusing aids.
I have taken out the Pentax 67II for peace of mind and it is definitely and without any doubts much brighter than GS-1 with AE prism.
Is that at the same f-stop? The P105 is a stop faster than the GS 100, so the image on the same screen would be ... twice as bright.
There is about 6 years between the two, so the screen technology probably did not change that much. There is a balance between brightness and focus-snap for manual focus, and that depends a lot on the designers preference at the time. I had the P67, but never tried the P67II, I did not find the older P67 screen any better than the GS1.The comparison was done with Zenzanon PG 200 mm f/4.5 and Pentax 67 SMC 200 mm f/4, both closed to f/5.6.
We use cookies and similar technologies for the following purposes:
Do you accept cookies and these technologies?
We use cookies and similar technologies for the following purposes:
Do you accept cookies and these technologies?