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underwater_videography_with_gopro [2025/05/01 20:17] – qlyoungunderwater_videography_with_gopro [2025/05/07 22:44] (current) – include percent sign qlyoung
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 where *I₀​* is the initial light intensity (at the surface), *I(z)* is the intensity at depth, *z*, and *k* is the absorption coefficient that varies depending on the medium characteristics (for water, things like clarity and particle content). where *I₀​* is the initial light intensity (at the surface), *I(z)* is the intensity at depth, *z*, and *k* is the absorption coefficient that varies depending on the medium characteristics (for water, things like clarity and particle content).
  
-For air *k* is around 0.0001. For seawater *k* is more like 0.1. That gives us roughly the following:+For air *k* is around 0.0001. For seawater *k* is more like 0.05. That gives us roughly the following:
  
-| Depth (m) | Light Intensity (%) | +| Depth (m) | Depth (ft) | Light Intensity (%) | 
-|-----------|---------------------| +|------------|------------|---------------------| 
-| 0         | 100.00%             | +| 0          | 0          | 100%                | 
-| 5         | 60.65%              | +| 5          | 15         | 78%                 | 
-| 10        | 36.79%              | +| 10         | 35         | 61%                 | 
-| 15        | 22.31%              | +| 15         | 50         | 47%                 | 
-| 20        | 13.53%              | +| 20         | 65         | 37%                 | 
-| 30        | 4.98%               | +| 25         | 80         | 29%                 | 
-| 40        | 1.83%               |+| 30         | 100        | 22%                 | 
 +| 35         | 115        | 17%                 | 
 +| 40         | 130        | 14%                 | 
 +| 45         | 150        | 11%                 | 
 +| 50         | 165        | 8%                  | 
 + 
 + 
 + 
 +It's much more complicated than this - absorption is wavelength dependent, seawater is not uniform, there are scattering effects, etc - but this is a decent approximation for this discussion.
  
 The upshot is that the diving environment is low light as far as cameras are concerned. This is why underwater photographers have kit that looks like this: The upshot is that the diving environment is low light as far as cameras are concerned. This is why underwater photographers have kit that looks like this:
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 ## Sensor size ## Sensor size
  
-A full frame camera sensor is ~43mm on the diagonal. The Hero 11 has a 1/1.9" sensor size, roughly 13mm diagonal. That is over 3 times smaller.+Generally speaking the larger the sensor, the more light it can collect and the better its dynamic range. Smaller sensors struggle more in low light. 
 + 
 +To put in perspective how challenging it can be to use an action cam underwater: 
 + 
 +A full frame camera sensor is roughly 36x24mm for an area of 864mm^2. The Hero 11 sensor is 6.74x5.05mm for a sensor area of 34.04 mm^2. That is ~25x smaller than full frame.
  
-Wasn't sure where else to put this information.+If you are wondering why 6.74x5.05mm does not correspond to the 1/1.9" figure published by GoPro, that is because that figure is in {{wp>optical format}}.
  
 ## Color ## Color
  
-Water is blue because it preferentially absorbs wavelengths of light other than blue. The deeper you get the more light is absorbed and the bluer the scene.+Water is blue because it preferentially absorbs wavelengths of light other than blue. The deeper you are the further light has to travel through water, the more red light is absorbed and the bluer the scene.
  
 {{:absorption_coefficient_of_water.png?600|}} {{:absorption_coefficient_of_water.png?600|}}
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underwater_videography_with_gopro.1746130629.txt.gz · Last modified: 2025/05/01 20:17 by qlyoung
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