VLUX-1 & Lumens, Lux and Foot-Candles

[leica dream]

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I am a keen orchid grower and most cultural books tell us that those plants grow best in certain light conditions which are always quoted in Foot-Candles.

Does anyone know if there is a way that I use an exposure reading from my VLUX-1 which can be converted to foot-candles? I only need a reasonable approximation.

My research revealed that 1 foot-candle equals 10.764 Lux, so if I can get Lux I can calculate from there.

Richard

[SJP]

Also a novel application for an M8, but the VLUX-1 should work fine:D

 

Anyway what I think you need is the table shown here.

 

So if you know the foot.candle or lux value you can convert that to the appropriate EV.

 

The EV value can then be transformed to shutter, iso and aperture stuff via this:

Exposure value - Wikipedia, the free encyclopedia

[leica dream]

Thank you, Stephen, that is most helpful and I shall give it a go. I am sure once I get the hang of it I shall be able to create an alogorithm for quick PC Conversion.

Richard

[leica dream]

Stephen, I have given your idea a try but sadly on the VLUX-1 one cannotascertain the value of the EV, only adjust the "given" abstract value by up to + or - 2 depending upon your image improvement in the view finder.

I guess I'll keep looking!

Thanks anyway

Richard

[SJP]

If you take a picture of something (an orchid for example, combine business with pleasure) then that gives you information on ISO, aperture and shutter speed. On the other hand maybe using a white sheet of paper would be better.

 

Using the wikipedia page you can then convert that to the EV of the scene.

 

Example, assume you have 1/125 sec, f/5.6, ISO 260 (random choice)

 

Then the wikipedia table 1 gives EV = 12 but you need to reduce that with 2log(260/100) = log(2.6)/log(2) = 1.38 for the camera ISO setting, so EV = 10.6 in this example.

 

Then the seconic table gives 336 fc.

 

If you can lock ISO to 100 then it just involves looking up the EV value in the tables for the shutter speed and aperture.

 

Hope this helps.

[leica dream]

That is great, Stephen, thank you so much.

I was at fault last time because I did not read to the end of the Wiki entry but just took one table. Now I have a table matrix so can read off EV values against exposure times and F nos all at 100 ISO then go to the foot candles table to get my values, which is great as I usually keep my VLUX-1 set at 100 ISO for general images.

Richard