Counting Shutter Speeds For Filters

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jpwild

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I know all the full shutter speed counts, but I need so assistance. I use Lee GND Filters and a 450D.

Yesterday I went out to do some photos and needed to use the GND filter. So I metered the sky and then metered the ground to see the difference.

Both readings did not give me full shutter speeds. They were fractional. I've been told that I need to only pay attention to full shutter speeds like 1/500, 1/250/1/125 etc etc when using filters that have full stop measurements.

Do I round off the shutter speed to the nearest full shutter speed and do it that way? Then count the difference between the measurements and choose which strength filter to us.
 
On most cameras the standard default is to have both shutter speeds and f/numbers adjust in third stop increments. So just count three clicks for every full stop of exposure.

On the other hand, just set the meter to evaluative (best setting for most things) and shoot at whatever exposure setting it gives you. It will be very close, quite possibly spot on, but certainly a good basis for tweaking, which you will probably want to do anyway. If you don't like what you see on the LCD/histogram/blinkies, adjust from there. Note that the hardness of the grad line varies a bit with f/number - higher f/numbers make it harder, it's a depth of field effect.
 
As I use film quite a lot, and don't have the advantage of the blinkies or histograms, I tend to establish the difference between the 2 readings for sky and ground - 3 and 2/3 stops in your example - then select the ND that'll give the sky around one stop brighter than ground - so probably a 3 stopper if I had one to hand.
 
Round it off, you will be close if you are within 1/4 of a stop.

1/80
1/40
1/20
1/10
1/5 as close as you are going to get to 1/6

= 4 stops in my book

Or 3 stops if you do what BigYin said.
 
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As I said, the example is 3 2/3 stops - we're accustomed to seeing the sky slightly lighter than the ground, so I'd go for a 3 stopper ideally. For slide film i'd probably try a 4 stopper as well as the exposure lattitude is pretty narrow compared to C41.
 
jpwild said:
I know all the full shutter speed counts, but I need so assistance. I use Lee GND Filters and a 450D.

Yesterday I went out to do some photos and needed to use the GND filter. So I metered the sky and then metered the ground to see the difference.

Both readings did not give me full shutter speeds. They were fractional. I've been told that I need to only pay attention to full shutter speeds like 1/500, 1/250/1/125 etc etc when using filters that have full stop measurements.

Do I round off the shutter speed to the nearest full shutter speed and do it that way? Then count the difference between the measurements and choose which strength filter to us.
Click to expand...

You could just guess and look at what the resulting picture looked like on the screen and then correct it.

Obviously the counting and working it out is good practice...but I'd say that way is easier and probably quicker too.
 
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