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10-03-2011, 08:14 PM   #1
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ND Filter shutter speed example

I may (and probably am) be missing something quite simple, but I'm trying to work out what 1 f-stop equates to in terms of shutter speed. This has been driving me nuts, I've looked for ages with Google, but I think I must be searching for the wrong thing. Can someone please give me an example of what would happen to the shutter speed if you say too a photo at f10 1/100 if you then put on a ND4 filter and left the aperture the same and took the same photo.
Thanks and sorry if I've just missed something.

10-03-2011, 08:27 PM   #2
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There's been a lot of questions about ND filters lately...

Shutter speed is simply slowed by the number of stops of the ND filter. So an ND 6 stop will slow a shutter down by 6 f-stops. So if you're getting 1/60 without an ND, then with the ND you'll get a shutter speed of 1 second (1/60 * 2 ^ 6).

The problem is knowing how many f-stops your ND filter is. A 6 stop could be refrered to as an ND64, ND 6-stop or ND 1.8.

QuoteQuote:
Can someone please give me an example of what would happen to the shutter speed if you say too a photo at f10 1/100 if you then put on a ND4 filter and left the aperture the same and took the same photo.
I'm going to assume this is a 2 stop filter, so your shutter speed will be 1/25 (1/100->1/50 for 1 stop -> 1/25 for 2 stops). There's very little use for a 2-stop ND filter to be honest, a CPL will serve as one anyway.
10-03-2011, 08:29 PM   #3
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Ok, thanks that help quite a bit, I think I'm going to get a 3 stop ND8 filter to play with.
10-03-2011, 08:36 PM   #4
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Shutter speed is time and therefore VERY predictable (unlike f stops). For an ND4 (assuming a density of 1.20), the change from 1/100 sec. will be:
1/100 to 1/50 (twice the time, twice the light) - 1 stop change
1/50 to 1/25- 2 stops
1/25 to 1/12 (about) 3 stops
1/12 to 1/6 = 4 stops. Round it to 1/5 of a second or 1/4 and it will probably still work.

Remember, changing stops (f2 to 2.8 to 4 to 5.6 etc.) is a one stop less light change for each. Changing from 1/30 to 1/60 to 1/125 to 1/250 are one stop less light changes also (a little more between 1/60 and 1/125, but close enough for photographic work).

Simple E=IxT basic exposure stuff. Does this help?

10-03-2011, 08:44 PM   #5
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A 1 stop filter will cause your shutter duration to double with using the same apeture. The filter will cut the light by half
Or you can open up the apeture by 1 stop (doubling its size) and keep the shutter speed the same.

eg say you have f5.6 and 1/250 sec
fitting a 1 stop filter means to get the same exposure you will set to f5.6 and 1/125, or you could do f4 and 1/250 to get the same.

An ND4 filter reduces the light to 1/4 of the original and this is called a 2 -stop filter.
using my example say you had f5.6 and 1/250. then you fit a 2 stop filter (ND4) this will cut the light to 1/4 soo.
this becomes f5.6 and 1/60 by reducing the shutter speed or it could be f2.8 and 1/250 by increasing the apeture size
Of course you can alter both by 1 stop each. eg f4 and 1/125

In any of the auto modes like P, Av, Tv etc the camera obviously sets to the lower light level automatically and in M mode the meter bar graph also indicates.


I think the most commonly bought ND filter is an ND8 which gives a resonable change to the settings to acheive lower shutter speeds or larger apetures in bright condtions.


In you example f10 and 1/100. then put an ND4 on this would change to f10 and 1/25 if you we just changing the shutter speed.


Edit: Oh.... I guess i am the slowest typist of the guys above.
10-03-2011, 09:10 PM   #6
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Man it's hard to find an ND10 filter at a store.. I've checked around whenever I go out of town.. I guess I'll have to ORDER one
I'm just glad my K-5 has it's nice EV meter in the viewfinder and on top.. so when I use my CP + ND8 on my 43mm or 18-135 (which can get down to f40 @ 135mm) I don't waste 3 or 4 shots getting the EV right.
10-03-2011, 09:44 PM   #7
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Thanks for all the replies, you guys (or girls) rule. You ask a question and you get decent answer quickly, none of the "learn how to google" replies you can get other places.

Another quick question or two, if I got a ND4 and an ND8 filter, and combined them what would that then by equivalent to? Also if doing this I understand that you can have issues with vignetting on wide angle lens, would this be a major issue at 16mm (on DA 16-45mm). Should I be looking at getting larger filters and a step up ring?
10-03-2011, 09:59 PM   #8
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putting a ND4 and ND8 filter together will reduce the intensity of light by around 5 stops - but I do not recommend stacking filters on top of each other because it raises the chances of wrecked images because of the increased potential for filter flare.

QuoteOriginally posted by Smilesy Quote
I understand that you can have issues with vignetting on wide angle lens, would this be a major issue at 16mm (on DA 16-45mm). Should I be looking at getting larger filters and a step up ring?
I would not recommend using step up rings - due to the FOV of most wide angle lenses the extra space between the filter and the filter thread often makes vignetting much worse.

Just be careful when you buy your Nd filters some of them can have some pretty nasty colour casts, I would not recommend mixing filters from different manufacturers:



10-04-2011, 03:26 AM   #9
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Nice graphic there. I wish there were a comprehensive test of filters showing exactly that.
10-04-2011, 05:32 AM   #10
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QuoteOriginally posted by Jodokast96 Quote
I wish there were a comprehensive test of filters showing exactly that.
there probably is one out there somewhere, colour casts become a big issue with the ultradark ND filters that reduce the intensity of light even more than ND8 filters can. Unfortunately I do not have the B+W ND 10 or either of the Singh-ray vari-ND filters, some of which are said to be able to reduce light by as much as ten stops. Personally I prefer the Lee big stopper - because it's solid glass and it can be used on practically any lens.
10-04-2011, 06:25 AM   #11
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QuoteOriginally posted by Chex Quote
Man it's hard to find an ND10 filter at a store.. I've checked around whenever I go out of town.. I guess I'll have to ORDER one
I'm just glad my K-5 has it's nice EV meter in the viewfinder and on top.. so when I use my CP + ND8 on my 43mm or 18-135 (which can get down to f40 @ 135mm) I don't waste 3 or 4 shots getting the EV right.
Why not try a variable ND filter? I see a lot of them rated for ND2 to a crazy ND400. I haven't used one, so there may be very valid reasons not to, but it sounds like it'd be just the ticket for what you want to do.
10-04-2011, 08:22 AM   #12
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Neutral density IS additive (ND4 + ND8 = ND12) However the density (neutral density) increases just a slight bit more because of the additive nature of the two filters. There is a concern as has been mentioned, of reduced image quality. This can be attributed to inter-reflections between the filter surfaces. Unless the filers have a good multicoating on them, these inter-reflections can be a problem. This manifests as reduced sharpness even ghost imaging. And I have found it seems to be worse for digital cameras and some lenses than with film cameras. If someone could explain why, I would certainly like to know!

Regards,
10-04-2011, 08:48 AM   #13
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QuoteOriginally posted by BigDave Quote
This manifests as reduced sharpness even ghost imaging. And I have found it seems to be worse for digital cameras and some lenses than with film cameras. If someone could explain why, I would certainly like to know!
I think it's due to the reflective nature of the sensor? Not sure on that, but it seems logical.
10-04-2011, 09:00 AM   #14
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Regarding the OP, one thing to be wary of is that there are various different ND 'scales'. So for example you may see the infamous ND110 also referred to as ND 3.0, and even ND1024 or, as here, ND10. Kind of nuts if you ask me.
10-04-2011, 10:21 AM   #15
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Any experience with variable nd? What about stacking a nd with a polarizer?
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