Solar cells in a Leicameter MC

[dennersten]

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This guy:

 

Leicameter MC med solceller

 

Claims he had put "solarcells" instead of the Selencells. Could that actually be true? How does it work? Are there anybody who had done the same thing out there?

[lars_bergquist]

The EU hates selenium, which it regards as a poison. So selenium meters cannot be sold anymore. Seconic took their classic selenium Studio Deluxe meter and replaced the selenium cell with a large silicon cell, the same kind that is used in pocket calculators and the like. So it can be done. Selenium and silicon cells have in common that they output quite a lot of milliamps, so they do not need electronic amplification, and hence no battery.

 

But I would surmise that the two types of cells have quite different light input--current output curves, so the trimming circuits that are supposed to give us a reasonably linear readout must be a bit different. There are a number of internal micro trimming pots in a Leicameter MR, and probably a couple in the MC too. A Leicameter MR needs some tweaking even to convert it from mercury cells to Wein cells. But heck, I never met a selenium meter that was even approximately linear!

 

The old man from the Age of No Meters

[brianv]

Silicon Cells are sensitive to Infrared light out to 1.1um. To get the same spectral response as Film, or a "normal Digital Camera, an IR cut filter needs to be placed over it.

[dennersten]

The EU hates selenium, which it regards as a poison. So selenium meters cannot be sold anymore. Seconic took their classic selenium Studio Deluxe meter and replaced the selenium cell with a large silicon cell, the same kind that is used in pocket calculators and the like. So it can be done. Selenium and silicon cells have in common that they output quite a lot of milliamps, so they do not need electronic amplification, and hence no battery.

 

But I would surmise that the two types of cells have quite different light input--current output curves, so the trimming circuits that are supposed to give us a reasonably linear readout must be a bit different. There are a number of internal micro trimming pots in a Leicameter MR, and probably a couple in the MC too. A Leicameter MR needs some tweaking even to convert it from mercury cells to Wein cells. But heck, I never met a selenium meter that was even approximately linear!

 

The old man from the Age of No Meters

 

So Silcon cell is a "solar cell" ??

 

And it seems to me that you are slightly doubtful it will work?

[dennersten]

Silicon Cells are sensitive to Infrared light out to 1.1um. To get the same spectral response as Film, or a "normal Digital Camera, an IR cut filter needs to be placed over it.

 

That seems to be problematic. I guess the advertized meter don't have that. So what you are saying is that i should avoid silicon cell meters?

[giordano]

That seems to be problematic. I guess the advertized meter don't have that. So what you are saying is that i should avoid silicon cell meters?

 

Only ones that don't have filters to compensate for the near-IR sensitivity ... and then only if it's important to have precise metering in incandescent light. I doubt whether an unfiltered silicon cell would be much worse in this regard than a CdS photoresistor.

[brianv]

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Going on memory here- but CDS cells are not sensitive into the near Infrared past 0.8microns or so. The silicon cells have 1/2 of their sensitivity in the Infrared. Which is good news if you want to convert a digital camera to infrared, but no so good for film.

 

Now- using a Silicon cell for general purpose light reading in regular daylight would be bad. Do not forget the Chlorophyl reflects IR and will give poor readings to a silicon cell. The Selenium, CDS, and Blue SPD cells will not see the Infrared reflected by chlorophyl.

 

[brianv]

Above shot is using a first-generation Digital Infrared camera. Monochrome Silicon based CCD, sensitive to 1.1uM.