Calculating exposures for a 12 stop filter. How?

mickledore

mickledore

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I calculate that my welding glass is approximately a 12 stop filter. Google is not my friend in this instance, so does anyone have, or know of, a conversion chart for adjusting exposure for 12 stops? 10 stop charts seem widespread, but I can't find a 12 stop one. Anyone know where there is one?
 
darren.lewis1984 said:
If you have an iPhone, try the free app Long Time Exposure Calculator. It's nice and simple to use
Click to expand...

Sorry, don't have an i-phone. Only have the most basic P&G possible!!!

Here's the one I use
Click to expand...

I looked at that, but found it damned hard to read with all the small, blurred print and confusing colour schemes.

I finished up using DD's formula and wrote up my own version.

Thanks everyone for all your help.
 
So it would be: Normal Shutter Speed x 2^No.Stop Filter. ?
For an exposure at 1/60 with 10 Stop Filter...
1/60 x 2^10 = 1/60 x 1024 = 17 Seconds.

Slightly different from the chart as it doesn't round off the numbers for each stop.

Edit for original Question:

Shutter Speed * 2^12 = Shutter Speed * 4096.
 
Last edited:
That's what seems to be the rule, although I'm no mathematoot trawling the interweb comes up with that formula, which can of course be tweaked for every different filter stop.

OOPs we posted at the same time. That PDF is much better. Many thanks.
 
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