I just received my CDS metered prism for my RB67! can't wait to try it but I have no clue what batteries it takes. Does anyone here have one of those meters, if so, what battery am I supposed to use? Also, I noticed it has a dial on the side with what appear to be speed and aperture numbers. Does this mean I have to match up aperture and speed on the meter prism then manualy adjust on camera?
RB67 CDS Metered Prism Help
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You got it.
I can't verify it because I don't have my camera with me at work, but I did a quick search on the web and found that it uses two MS-76 batteries
t_nunn said:
Thaks for the info! I tried a couple of these batteries and they worked perfectly. Now if I had only spent more time in the gym so I could lug the RB67 with this CDS prism...
Be careful with the use of CDS cells. They display memory problems when quickly changing from brightly lit to dimly lit areas. Wait a minute before proceeding from on type to another. I have not used this particular meter. I have a RZ67, for which I had a meter prism. The meter worked very accurately.
Claire Senft said:
Is this memory problem a temporary thing or will it ruin the meter permenantly? I only tried it once to check if it was working properly and compared it to the meter in my Nikon F2A. It seems to be pretty accurate, although somewhat slower.
It di\oes no harm to the meter. You just have to wait a minute before taking a reading when changing from brightly lit to dimly lit.
Nothing is permanent except taxes
snegron, the cds issue is temporary, and can be "balanced" out quicker and more reliably by placing a lens cap or hand over the lens for a few seconds. The alternate is to point the lens toward something in the shadows and wait about 10 seconds or more. In our photo world, there are two types of device that are of interest to us: photoconductive and photovoltaic. We see these commonly as CdS and Silicon cells, respectively.
Let's tackle the photovoltaic silicon cell, which is the more common and modern of the two. When photons strike the cell surface, they are absorbed by the silicon semiconductor strata and electrons are displaced creating a voltage potential and current flow. These cells actually generate electricity, and is why they are used to power outdoor landscape lights, alternative electrical generators, and mundane calculators. They need no battery to make them operate. In a camera, the increase in voltage produced by light striking the cell registers on the cell. A silicon semiconductor is very stable, accurate, and has a very fast response and recovery state time due to being a single substrate layer.
A CdS cell (cadmium disulfide) is a photoconductive device. This means that it does not generate voltage on its own; instead it regulates the amount of voltage traveling through it as provided by a battery or power source according to the intensity of the light falling on the cell. These sorts of cells are comprised of two "bands", a conduction band and a valence band. Sandwiched in between them is what is known as a doner and acceptance level.
In darkness, the ratio of electrons and "holes" is very high and dense. This creates a state of high resistance, and little voltage can flow through to something like a metering needle in the camera. When light strikes the CdS crystal, electrons located in the valence band are driven toward the conduction band. This decreases the number of electrons, increases the number of holes, and lowers resistance so that more voltage can flow.
The acceptor level can capture an excess of free holes and lower the potential for recombination (what was called here "memory"). This state changes more slowly because the return to the N state is not dependent upon the change in light, rather a return to steady state. Sulfur, being the ionic constituent of this process degrades over time. This is why many of these cells become inaccurate, intermittent, or faulty. Returning to a dark state returns the cell to its pre-excitation, high resistance state.
Clear as mud?
snegron, the cds issue is temporary, and can be "balanced" out quicker and more reliably by placing a lens cap or hand over the lens for a few seconds. The alternate is to point the lens toward something in the shadows and wait about 10 seconds or more. In our photo world, there are two types of device that are of interest to us: photoconductive and photovoltaic. We see these commonly as CdS and Silicon cells, respectively.
Let's tackle the photovoltaic silicon cell, which is the more common and modern of the two. When photons strike the cell surface, they are absorbed by the silicon semiconductor strata and electrons are displaced creating a voltage potential and current flow. These cells actually generate electricity, and is why they are used to power outdoor landscape lights, alternative electrical generators, and mundane calculators. They need no battery to make them operate. In a camera, the increase in voltage produced by light striking the cell registers on the cell. A silicon semiconductor is very stable, accurate, and has a very fast response and recovery state time due to being a single substrate layer.
A CdS cell (cadmium disulfide) is a photoconductive device. This means that it does not generate voltage on its own; instead it regulates the amount of voltage traveling through it as provided by a battery or power source according to the intensity of the light falling on the cell. These sorts of cells are comprised of two "bands", a conduction band and a valence band. Sandwiched in between them is what is known as a doner and acceptance level.
In darkness, the ratio of electrons and "holes" is very high and dense. This creates a state of high resistance, and little voltage can flow through to something like a metering needle in the camera. When light strikes the CdS crystal, electrons located in the valence band are driven toward the conduction band. This decreases the number of electrons, increases the number of holes, and lowers resistance so that more voltage can flow.
The acceptor level can capture an excess of free holes and lower the potential for recombination (what was called here "memory"). This state changes more slowly because the return to the N state is not dependent upon the change in light, rather a return to steady state. Sulfur, being the ionic constituent of this process degrades over time. This is why many of these cells become inaccurate, intermittent, or faulty. Returning to a dark state returns the cell to its pre-excitation, high resistance state.
Clear as mud?
Support.
Welcome to the Mamiya M/F World Snegron, although regular workouts help, I always thought a most useful addition to the available accessories in the Mamiya system would be a truss !!snegron said:Thaks for the info! I tried a couple of these batteries and they worked perfectly. Now if I had only spent more time in the gym so I could lug the RB67 with this CDS prism...
Pragmatist said:snegron, the cds issue is temporary, and can be "balanced" out quicker and more reliably by placing a lens cap or hand over the lens for a few seconds. The alternate is to point the lens toward something in the shadows and wait about 10 seconds or more. In our photo world, there are two types of device that are of interest to us: photoconductive and photovoltaic. We see these commonly as CdS and Silicon cells, respectively.
Let's tackle the photovoltaic silicon cell, which is the more common and modern of the two. When photons strike the cell surface, they are absorbed by the silicon semiconductor strata and electrons are displaced creating a voltage potential and current flow. These cells actually generate electricity, and is why they are used to power outdoor landscape lights, alternative electrical generators, and mundane calculators. They need no battery to make them operate. In a camera, the increase in voltage produced by light striking the cell registers on the cell. A silicon semiconductor is very stable, accurate, and has a very fast response and recovery state time due to being a single substrate layer.
A CdS cell (cadmium disulfide) is a photoconductive device. This means that it does not generate voltage on its own; instead it regulates the amount of voltage traveling through it as provided by a battery or power source according to the intensity of the light falling on the cell. These sorts of cells are comprised of two "bands", a conduction band and a valence band. Sandwiched in between them is what is known as a doner and acceptance level.
In darkness, the ratio of electrons and "holes" is very high and dense. This creates a state of high resistance, and little voltage can flow through to something like a metering needle in the camera. When light strikes the CdS crystal, electrons located in the valence band are driven toward the conduction band. This decreases the number of electrons, increases the number of holes, and lowers resistance so that more voltage can flow.
The acceptor level can capture an excess of free holes and lower the potential for recombination (what was called here "memory"). This state changes more slowly because the return to the N state is not dependent upon the change in light, rather a return to steady state. Sulfur, being the ionic constituent of this process degrades over time. This is why many of these cells become inaccurate, intermittent, or faulty. Returning to a dark state returns the cell to its pre-excitation, high resistance state.
Clear as mud?
So, how can we tell when the cadium disulfide cells are about to die?
No expiration date
Well, just like any other electronic device there is no way to determine that. Generally though, they do not age extremely well. Often rather than just "croaking" outright, CdS cells will begin to behave erratically or become inaccurate. I would check the calibration against a known good metering standard and periodically re-check to see if consistance is being held. Likely though, you will get a lot of use out of the one you have.
snegron said:
Well, just like any other electronic device there is no way to determine that. Generally though, they do not age extremely well. Often rather than just "croaking" outright, CdS cells will begin to behave erratically or become inaccurate. I would check the calibration against a known good metering standard and periodically re-check to see if consistance is being held. Likely though, you will get a lot of use out of the one you have.
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