Can you explain the LUX conversion table on the back of a Gossen.

[JMC1969]

Hello,

I have a Gossen Cds Super Pilot. On the back there is a conversion chart to LUX values. It seems to be straight forward as direct translations from the EV scale, however, it changes depending on the ASA that is chosen while metering. The speed of film really doesn't have anything to do with the footcandles of a light source so I'm not sure as to how to set up for an accurate reading.

At the top of the meter (backside) it reads:

"Mit Diffusor und 18 DIN"
"Set ASA 50 and Incident Light"

I'm not sure what some of that means or if it is directly related to the chart below it. I could take this as setting the meter at ASA50, set the diffusor globe over the middle and that reading is what I use for the chart, but I am not sure. If this were the way I set up, can you tell me if this situation sounds correct?

2 - 900watt lights set across from each other, balanced at 4200k, reading a EV 9 and translated to 2800 LUX.

Also, the third column on this chart is labeled "fc appr." and I'm not sure what this is.

I downloaded a Manual for this meter and have read it, but these things do not seem to be explained.

Thank you in advance,
Jody

 

[wiltw]

'fc' footcandles = 'illuminance' or light which falls only a surface

Lux = measure of 'luminance' which is rate that a source emits light in a specific direction

 

[Anscojohn]

You CAN actually arrive at an f/stop knowing the number of foot candles and the speed of the film. IIRC, Use the ASA as a shutter speed and use an f/stop which is closest to the square root of the foot candles. But why?
IIRC. LUX is the metric equivalent of foot candles. But unless you are using your meter to determine the proper light level for your house plants, why bother?

 

[ic-racer]

Yes, to use the chart set the front to ASA 50 before reading the EV and use the incident diffuser. "fc" is Foot Candles.

 

[JMC1969]

But why?
IIRC. LUX is the metric equivalent of foot candles. But unless you are using your meter to determine the proper light level for your house plants, why bother?

It is having to do with the appropriate light levels needed to reproduce art work. I wasn't going to get too much into this as this is a Analog photography group that I deeply appreciate, but I do use a "D" scan back in a reduced 12x12 camera as part of my job. It combined with computer software, I need to know a little more info than just the F-stop, shutter speed (it claims) to discuss a problem I am having with it. Lack of light. It was soooooo much easier when we just shot 4x5 chromes. aaarrgggghhh!

Thank you for the info and "fc" = footcandles, if only I could kick myself in the head.

ic-racer: Thanks for the quick and dirty answer.

Thanks All

 

[EASmithV]

Then why don't you just shoot 4x5 chromes and scan?