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newindustar
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, March 27, 2006 - 01:39 pm: | 
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I received a clean working S2 and ran a roll of slide film through it to give it a challenging test in automatic. It was a roll of Astia 100, older version. There was a stong underexposure. Probably a third of the frames were too dark for the scanner to deal with, another third the scanner was able to extract the image with maxing out the exposure control, the rest were dark but passable. They were mostly outside in the daytime so I was stuck with 125-500 shutter. I was careful to make sure I was in metering range for the automatic mode.
I am running the Radio Shack alkaline 625 with no adjustments to the metering. I was expecting better results because I compared it to matrix metering on my Nikon F100. At very low EV (lowest shutter speeds)the Konica was asking for up to 2 stops additional light than the Nikon. At mid ev they were very close. At high ev (shutter at 250 or 500 with iso 100 the Konica was asking for less light than the Nikon by one or 2 stops. This test was not facing high contrast, mostly indoors and using late afternoon sky. My actual test run with the slide film had to face more challenging higher contrast situations.
I have a roll of print film in the lab I haven't seen yet. Normally I would probably be using Fuji Reala 100. If the camera was tending towards overexposure I would be better off with print film but I am in the undesirable underexposure realm.
Do these cameras tend to underexpose heavily in high-contrast situations.
I am unlikely to invest in special hard to find and expensive replacement batteries. The automatic mode would be mandatory most of the time.
Do you think the Alkaline 625 is causing this? The shutter and apeture do not seem to be sticking as far as I can tell. I read somewhere they never achieve a true 500 but most of the shots were at 250.
If it recommended to adjust the metering circuit for the alkaline 625 how is this acomplished?
Any insights would be appreciated. |
charlie
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, March 28, 2006 - 06:13 am: |
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Hearing aid batteries, #675 zinc/air, 1.4 volts, are about $1 each. They are small in size and may require some spcers to fit but would give you a chance to test the camera with the proper voltage before deciding on your next step. |
Stuart Willis
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, March 29, 2006 - 07:55 am: |
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The discharge curve of Alkaline batteries is a gradual downslope from the moment of first use- whereas the original (now unobtainable) mercury cells provide a virtual horizontal line discharge pattern and they maintain their rated voltage until their very last gasp. The metering needs to "see" that full rated voltage and that's why mercury cell chemistry is used.
So you can expect the metering of the Auto S2 to shift into under-exposure as the Alkaline cell voltage drops.
You can compensate by using the Auto S2 in manual metering mode and opening up a Stop or so - but the required compensation is non-linear as the cell discharges - so it is just a huge guessing game.
The issue of using hearing-aid zinc-air cells has been done to death on this forum. I can give you some rock solid reasons why your should not use them - but others who think they know better, will offer contrary views. So suffice to say that your safest solution is to adapt the battery compartment to accept Silver Oxide cells which have the same discharge pattern as mercury cells.
If however you Auto S2 metering does not initially come good as with a brand new Alkaline cell - then the metering error is due to something else.
That something else will inevitably be black wire corrosion of the hot lead from the cell compartment to the metering circuit. Black wire corrosion is typical of mercury-call powered cameras of many decades old. The copper cores of the wire deteriorate into high ohms and then ultimately into open circuit black powder. The aforsaid wire needs to be replaced.
However - you might first thoroughly clean the battery compartment contacts - and pay special attention to the chassis "Ground".
It is possible that this will restore your Auto S2 to consistently reliable metering - at least for a while.
The other possibility of course - is that the mechanical coupling between meter and iris, is gunked up and causing under-opening of the aperure. |
Jan Dvorak
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, March 29, 2006 - 11:07 am: |
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Just to add to Stuart's excellent post's last sentence - the aperture system in the S2 is controlled by a very weak spring. The aperture blades and its mechanism have to be perfectly clean and oil free for everything to work properly.
Set the camera to manual f-stop selection and move the aperture dial. The aperture blades should move evenly, without any binding. Generally, if there is dirt in the system, the blades will stay closed - this would result in underexposure.
Good luck,
Jan |
newindustar
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, March 30, 2006 - 06:03 pm: |
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The battery was new. I should put a voltmeter on it to see where it is at now.
With a new 625 alkaline have you gotten good exposures with a normal camera? How well do they normally meter with the right battery? I bought this camera for the Automatic mode and the lens. If they really don't meter well even with print film and I am running in manual I probably would shoot a medium format camera instead. How do they respond to high contrast?
I had the other post on repairing a S2 with the sheared meter wire. I ended up completly dissambling that one. I could't not finish the repair because of a broken retainer post for the brass plate in the lens barrell so I got a very good idea of what is under the hood including the shutter and apeture. That experience of a stuck shutter and how they feel when free after cleaning is why I was able to feel they were free on this new camera. The apeture definitely opens and closes fully every time. It can be hard to know if the shutter or apeture linkage is dragging a little. I know it is not sticking altogether because the I shot it exclusively in Auto.
I got a roll of print film back at it had a lot of underexposure grainy prints also.
The hard part is that when compared with Nikon Matrix it was over at one end and under on the other end so trying to adjust it across the range might not be possible. Of course adjusting it to a Nikon might be inappropriate.
Possibly adjusting to Nikon at the high ev side might work out. Of course if that meter is so sensitive to falling voltage it may be a waste of effort using the alkaline.
There is one thing odd. The manual says (I think) the the battery test should make the needle move DOWN to the orange mark. My battery test pegs the needle off the TOP of the scale. What is normal here? |
Kendra
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, June 07, 2006 - 07:09 pm: |
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I'm hoping to get my old Konica Auto S2 working again and need a battery. I see from an earlier post that silver oxide cells are recommended. I'm going to try the #675 zinc/air hearing aid battery, but if that is successful, which silver oxide cell would be recommended? |
Winfried
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, June 08, 2006 - 02:29 pm: |
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You should not use plain silver oxide cells on cameras designed for mercury cells, since silver oxide cells have a higher voltage (1.55V instead of 1.35V).
You might use them if you manage to solder a Schottky diode (BAT46 or similar) into the battery wire. There is plenty of room for an additional diode under the bottom cover of the S2.
I think there are silver oxide cells with same or similar size as PX675 cells (I think the designator is SR44). IIRC the S2 battery compartment has an outer contact so you cannot use plastic rings to fill up space. Maybe a "ring" formed from aluminium foil would work. |
