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Cokin Filters question?
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I have a lot of Cokin filters and on the top of the box is COEF +1/3 or COEF + 1 2/3. I take it that COEF stands for co efficency but how do you work out the exposure compensation to be used. I know the camera will take this into consideration automatically but what if I use a hand held meter how do I work out the compensation.
Many thanks John.
John, If I remember rightly when I used to use manual light meter and set the apetture by hand that info was needed but as I became more into using the camera’s light meter through the lens, then I did not need that. Thats a while back now and a bit dusty in the brain.
BTW had a look at some of my old Cokin filters lately and they seem to be fogging a little….the plastic ones at any rate. Then I suppose they’re pretty old now. I also found a “wratten” filter in that lot which I used for infra red film……I’d probably not be able to use the Kodak Infra Red film now if I got some….it was not so straightforward to use or develop.
Stuck one of my old Infra Red B&W pics of the gable wall in my gallery from 1985.It tells you how many stops you need to increase your exposure by.
I’m trying to find out how to calculate it. For example, a 0.3 ND grad is one stop, 0.6 is 2 stops and 0.9 is 3 stops. But with yours: is 1/3 the same as 0.3 or is it a 1/3 of a stop? I’ll post again soon…..
Can’t find a definite answer. I think you’ll need to use the in-built metering facility to measure the amount of light stopped.
For example:
Put the camera on a tripod and set the priority to exposure length (tv on my Pentax)
Take a meter reading at (say) 1/125 s
Hold the filter in front of the lens and take a 2nd reading
The difference between the two is the amount of light stoppedSo, if the aperture was f/8 without and f/5.6 with, then the filter has blocked one stop’s worth of the light.
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