Skip to main content
added 1157 characters in body
Source Link
scottbb
  • 33.3k
  • 12
  • 106
  • 192

Without knowing what strength of ND filter you were using, or under what lighting conditions, I can't give a specific answer. However, a little bit of back-of-the-envelope math can help give you an idea of the magnitude of the problem.

Assuming you were shooting a brightly-lit scene under bright midday sun, without any ND filters, the Sunny 16 rule states that at ƒ/16, a correctly-exposed shot requires a shutter time that is the reciprocal of your ISO. With an ISO of 200, the shutter speed should be 1/200.

Again, assuming you were shooting under Sunny 16 conditions, your shutter speed was overexposed by log2(2 / (1/200) = 8.6 stops. Because you were using ƒ/22, we can reduce that overexposure by one stop, down to 7.6 stops of overexposure.

Subtract from 7.6 the strength of your ND filter (I'm guessing 1 or 2 stops, probably). That is how much your long exposure shot was overexposed (again, for typical Sunny 16 exposure conditions).

If you were shooting a snow-covered landscape on a bright sunny day, you'd actually be overexposed even further, because of the light reflected from the large area of landscape. On the other hand, if there was some partial clouds, slight haze, or you subject was partially shaded, then your scene might not have been quite so overexposed by the amount calculated.

However, this gives you a rough idea of what to expect when trying to shoot long exposure shots in midday sun. You tend to need a lot of ND filter to keep the shutter open for 2 seconds. In your case, a minimum of a 6-stop ND filter: ND1.8 in Lee/Tiffen nomenclature; ND64 in Hoya/B+W/Cokin nomenclature. See also: How to read ND filter description?

For a particular scene, an easy way to figure out how much ND filter you need is set up your camera in aperture priority mode, select your aperture (in this case, ƒ/22) and ISO (200), and without an ND filter on your lens, let the camera meter the scene and determine the shutter speed. Whatever the camera meters for the scene, count the number of times you need to double the shutter speed until you get to your desired long-exposure duration.

For instance, say the camera determined that 1/125 seconds was properly exposed, and you want a 4 second long exposure to smooth some moving water and slightly blur fast moving clouds. Starting from 1/125, start doubling it:

Shutter speed:  1/125 -> 1/64 -> 1/32 -> 1/16 -> 1/8 -> 1/4 -> 1/2 -> 1 -> 2 -> 4
# of doublings:    0       1       2       3      4      5      6     7    8    9

Thus, this would require a 9 stop ND filter. But you only have a 10 stop ND filter (such as a Lee Big Stopper), either increase the ISO to 400, or open up the aperture one stop to ƒ/16. Either way, you will have the right combination of exposure settings and ND filter to correctly expose a 4 second shot in this particular scene.

Without knowing what strength of ND filter you were using, or under what lighting conditions, I can't give a specific answer. However, a little bit of back-of-the-envelope math can help give you an idea of the magnitude of the problem.

Assuming you were shooting a brightly-lit scene under bright midday sun, without any ND filters, the Sunny 16 rule states that at ƒ/16, a correctly-exposed shot requires a shutter time that is the reciprocal of your ISO. With an ISO of 200, the shutter speed should be 1/200.

Again, assuming you were shooting under Sunny 16 conditions, your shutter speed was overexposed by log2(2 / (1/200) = 8.6 stops. Because you were using ƒ/22, we can reduce that overexposure by one stop, down to 7.6 stops of overexposure.

Subtract from 7.6 the strength of your ND filter (I'm guessing 1 or 2 stops, probably). That is how much your long exposure shot was overexposed (again, for typical Sunny 16 exposure conditions).

If you were shooting a snow-covered landscape on a bright sunny day, you'd actually be overexposed even further, because of the light reflected from the large area of landscape. On the other hand, if there was some partial clouds, slight haze, or you subject was partially shaded, then your scene might not have been quite so overexposed by the amount calculated.

However, this gives you a rough idea of what to expect when trying to shoot long exposure shots in midday sun. You tend to need a lot of ND filter to keep the shutter open for 2 seconds. In your case, a minimum of a 6-stop ND filter: ND1.8 in Lee/Tiffen nomenclature; ND64 in Hoya/B+W/Cokin nomenclature. See also: How to read ND filter description?

Without knowing what strength of ND filter you were using, or under what lighting conditions, I can't give a specific answer. However, a little bit of back-of-the-envelope math can help give you an idea of the magnitude of the problem.

Assuming you were shooting a brightly-lit scene under bright midday sun, without any ND filters, the Sunny 16 rule states that at ƒ/16, a correctly-exposed shot requires a shutter time that is the reciprocal of your ISO. With an ISO of 200, the shutter speed should be 1/200.

Again, assuming you were shooting under Sunny 16 conditions, your shutter speed was overexposed by log2(2 / (1/200) = 8.6 stops. Because you were using ƒ/22, we can reduce that overexposure by one stop, down to 7.6 stops of overexposure.

Subtract from 7.6 the strength of your ND filter (I'm guessing 1 or 2 stops, probably). That is how much your long exposure shot was overexposed (again, for typical Sunny 16 exposure conditions).

If you were shooting a snow-covered landscape on a bright sunny day, you'd actually be overexposed even further, because of the light reflected from the large area of landscape. On the other hand, if there was some partial clouds, slight haze, or you subject was partially shaded, then your scene might not have been quite so overexposed by the amount calculated.

However, this gives you a rough idea of what to expect when trying to shoot long exposure shots in midday sun. You tend to need a lot of ND filter to keep the shutter open for 2 seconds. In your case, a minimum of a 6-stop ND filter: ND1.8 in Lee/Tiffen nomenclature; ND64 in Hoya/B+W/Cokin nomenclature. See also: How to read ND filter description?

For a particular scene, an easy way to figure out how much ND filter you need is set up your camera in aperture priority mode, select your aperture (in this case, ƒ/22) and ISO (200), and without an ND filter on your lens, let the camera meter the scene and determine the shutter speed. Whatever the camera meters for the scene, count the number of times you need to double the shutter speed until you get to your desired long-exposure duration.

For instance, say the camera determined that 1/125 seconds was properly exposed, and you want a 4 second long exposure to smooth some moving water and slightly blur fast moving clouds. Starting from 1/125, start doubling it:

Shutter speed:  1/125 -> 1/64 -> 1/32 -> 1/16 -> 1/8 -> 1/4 -> 1/2 -> 1 -> 2 -> 4
# of doublings:    0       1       2       3      4      5      6     7    8    9

Thus, this would require a 9 stop ND filter. But you only have a 10 stop ND filter (such as a Lee Big Stopper), either increase the ISO to 400, or open up the aperture one stop to ƒ/16. Either way, you will have the right combination of exposure settings and ND filter to correctly expose a 4 second shot in this particular scene.

Source Link
scottbb
  • 33.3k
  • 12
  • 106
  • 192

Without knowing what strength of ND filter you were using, or under what lighting conditions, I can't give a specific answer. However, a little bit of back-of-the-envelope math can help give you an idea of the magnitude of the problem.

Assuming you were shooting a brightly-lit scene under bright midday sun, without any ND filters, the Sunny 16 rule states that at ƒ/16, a correctly-exposed shot requires a shutter time that is the reciprocal of your ISO. With an ISO of 200, the shutter speed should be 1/200.

Again, assuming you were shooting under Sunny 16 conditions, your shutter speed was overexposed by log2(2 / (1/200) = 8.6 stops. Because you were using ƒ/22, we can reduce that overexposure by one stop, down to 7.6 stops of overexposure.

Subtract from 7.6 the strength of your ND filter (I'm guessing 1 or 2 stops, probably). That is how much your long exposure shot was overexposed (again, for typical Sunny 16 exposure conditions).

If you were shooting a snow-covered landscape on a bright sunny day, you'd actually be overexposed even further, because of the light reflected from the large area of landscape. On the other hand, if there was some partial clouds, slight haze, or you subject was partially shaded, then your scene might not have been quite so overexposed by the amount calculated.

However, this gives you a rough idea of what to expect when trying to shoot long exposure shots in midday sun. You tend to need a lot of ND filter to keep the shutter open for 2 seconds. In your case, a minimum of a 6-stop ND filter: ND1.8 in Lee/Tiffen nomenclature; ND64 in Hoya/B+W/Cokin nomenclature. See also: How to read ND filter description?