# ND106 filter question

#### rocketatw

##### Senior Member
i know this filter will helps to take smooth water surface, but want to know how it benefits us? Can i say we can take at a faster shutter speed and yet still achieve the desire exposure for smooth water surface.

take for example without filter, at f5.6 pointing at a clear water surface, i half press the exposure timing shows 1/4s, so now if i put on the ND106 filter, at the same f5.6, what will the exposure timing be? can i say ND106 is 6 stops, so the exposure timing will be 1/256s base on the below 6 stops calculation.

1/4s, 1/8s, 1/16s, 1/32s, 1/64s, 1/128s, 1/256s

i am looking to buy a ND106, or ND110 filter, but just want to clear some doubts

#### CamInit

##### New Member
I think you got it the wrong way. A 6-stop ND filter reduce the amount of light that passes through by 2^6 = 64 times, so to get the same amount of light, you need to open your shutter for 64 times longer. A 1/4sec exposure becomes 16sec to get the same exposure with the filter, all other settings being equal.

#### rocketatw

##### Senior Member
I think you got it the wrong way. A 6-stop ND filter reduce the amount of light that passes through by 2^6 = 64 times, so to get the same amount of light, you need to open your shutter for 64 times longer. A 1/4sec exposure becomes 16sec to get the same exposure with the filter, all other settings being equal.
thanks for the clarification, so now if my exposure is 1/4s, with filter on it will be 16secs right? i always thought we can take smooth water surface with nd filter at a shorter exposure, hence no need tripod. i am wrong.

so what do we achive here with all setting the same, except with nd filter. the water surface will be smoother? i still dont see the reason to get the nd filter since i can set to TV mode and set to 16sec exposure, i believe i will still get smooth water surface. correct me if i am wrong, just want to know the adavantages of the filter.

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#### CamInit

##### New Member
thanks for the clarification, so now if my exposure is 1/4s, with filter on it will be 16secs right? i always thought we can take smooth water surface with nd filter at a shorter exposure, hence no need tripod. i am wrong.
Yes. To get smooth water surface requires a longer exposure which will accumulate the spread of water disturbances across time. A stable support is a must.

#### rocketatw

##### Senior Member
Yes. To get smooth water surface requires a longer exposure which will accumulate the spread of water disturbances across time. A stable support is a must.
but i can also set to TV mode and set to 16sec exposure? i believe i will still get the same result right, since both ways still require a tripod. with both method at 16secs, which will get a better picture.

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#### catchlights

##### Moderator
Staff member
i know this filter will helps to take smooth water surface, but want to know how it benefits us? Can i say we can take at a faster shutter speed and yet still achieve the desire exposure for smooth water surface.

take for example without filter, at f5.6 pointing at a clear water surface, i half press the exposure timing shows 1/4s, so now if i put on the ND106 filter, at the same f5.6, what will the exposure timing be? can i say ND106 is 6 stops, so the exposure timing will be 1/256s base on the below 6 stops calculation.

1/4s, 1/8s, 1/16s, 1/32s, 1/64s, 1/128s, 1/256s

i am looking to buy a ND106, or ND110 filter, but just want to clear some doubts
you counter the wrong way..

1/256s is shorter, faster shutter speed than 1/4s

#### CamInit

##### New Member
so what do we achive here with all setting the same, except with nd filter. the water surface will be smoother? i still dont see the reason to get the nd filter since i can set to TV mode and set to 16sec exposure, i believe i will still get smooth water surface. correct me if i am wrong, just want to know the adavantages of the filter.
You use ND filter when you cannot increase the shutter opening duration without getting over-exposure. Let's say your camera recommends an exposure of f/5.6, ISO100 and 0.25sec. To increase exposure timing, you set to an equivalent exposure of f/22, ISO100 and 4sec. You can't get decrease your aperture size any more. ISO is at the minimum. Going beyond 4sec will over-expose your picture. Your waves are still not smooth enough.

What to do? Adding a 2-stop ND filter will drag your exposure from 4 to 16sec. A 3-stop will further double to 32sec. This is one way. Then again, for some reason, if you prefer the look of f/5.6 rather than f/22, then you still need a 6-stop ND filter for a 16sec exposure. This is another way.

#### rocketatw

##### Senior Member
You use ND filter when you cannot increase the shutter opening duration without getting over-exposure. Let's say your camera recommends an exposure of f/5.6, ISO100 and 0.25sec. To increase exposure timing, you set to an equivalent exposure of f/22, ISO100 and 4sec. You can't get decrease your aperture size any more. ISO is at the minimum. Going beyond 4sec will over-expose your picture. Your waves are still not smooth enough.

What to do? Adding a 2-stop ND filter will drag your exposure from 4 to 16sec. A 3-stop will further double to 32sec. This is one way. Then again, for some reason, if you prefer the look of f/5.6 rather than f/22, then you still need a 6-stop ND filter for a 16sec exposure. This is another way.
i think i understand now, thanks for the clarification.

#### daredevil123

##### Moderator
Staff member
but i can also set to TV mode and set to 16sec exposure? i believe i will still get the same result right, since both ways still require a tripod. with both method at 16secs, which will get a better picture.
Yes, but you will be forcing the aperture to be too small. When aperture is too small, you actually lose sharpness due to small aperture diffraction. On a D90 it is advised not to go smaller than F/16. Not sure what camera you are using though.

#### Octarine

##### Moderator
Staff member
but i can also set to TV mode and set to 16sec exposure? i believe i will still get the same result right, since both ways still require a tripod. with both method at 16secs, which will get a better picture.
No. Tv is a half-automatic mode and will set the aperture to something that might not be suitable. Your initial example was good: fix the aperture in Av or M to achieve the desired Depth of Field. Then add the filter and set the shutter speed according metering (in M) or let the cam set (Av). Tripod is a must.