History: SPID Underwater photography

Source of version: 2 (current)

!SPID Underwater photography
!!SPID Dealing with the loss of red light underwater 
When sunlight travels down through the water to light a fish, the reds get filtered out by the water. And when that light reflects off a fish to travel through water to the camera, the reds continue to be filtered out. You have 5 choices:
#Avoid the problem by only taking photos where the combined distance of surface-to-fish + fish-to-camera = 2 - 5 metres or less. Easy, but you will miss out on a lot of interesting stuff at deeper depths, or under shadowy overhangs.
#Add a filter that filters out the blues & greens to even up the colour balance (such filters appear red when you look at them or through them). Two problems: 
##you are reducing the amount of information coming into the camera. (But this might be a good thing: deeper than 10 m, often the highlights, which are mainly blue-green, will be too intense for the camera's pixel sensors, resulting in the highlights being whited out; by using a blue-green filter you avoid this problem.) 
##unless you have different grades of filter, sometimes you will filter too much and sometimes non enough. The pink photos you complain of are when you used the red-filter too close to the surface.
# Use Photoshop or Gimp or Dive Plus etc to reduce the blues & greens. Two problems: 
##you are reducing the amount of information in the photo, so you lose clarity, and
##you have to spend time adjusting the photos on your computer, although fiddling with holiday photos is not an unpleasant task. Dare I take my favourite notepad to a hut 3m from the ocean?
##[edit] Swmbo has installed Dive Plus on her iPhone, and with one press of the button it does a far better job than my attempts with Gimp. Limitations: it only works on a phone connected to the internet. 4 months ago they put up a huge tower on Pulau Arborek that gives good Telkomsel signal all over the island. Get a plan with enough data to feed your movies to & from Dive Plus's website. (I paid ~R300,000 for a 30 day Telkomsel plan with 10GB).
# Provide a full-spectrum (i.e. white) source of light using a torch that provides an even spread of light. (You do not want a spotlight with a parabolic reflector that provides a super intense spot of parallel light in the centre. Spotlights lights can boast an impressively high lumens rating by providing a blindingly intense tiny-angled beam that is useless for photography, and blinding for your dive buddy and perhaps even yourself if you shine it on something close.) Illuminating photo subjects with a torch should work at any depth, providing you are close enough to your subject. Note that the further the light has to travel from-the-torch-to-the-fish + bounce-back-to-the-camera, the dimmer the light top-up will be. Our experience with Swmbo's Adventurer M1000-WRA suggests that in the usually very clear waters of Raja Ampat, a combined (to + from) light distance of less than 2 metres is better. In shallower waters when 'topping up' closer subjects, it may be worth while to use a dimmer light to get a more natural look.
# Top up the amount of red light available by using a torch that provides an even spread of red light. I have yet to experiment much with red light top up, because the easiest solution is just to flood everything with white light.

btw 1: I have read suggestions that red light avoids spooking some species, and I am curious if this is sales talk or if it is a real thing. It seems reasonable, for all the species that have not already fled from a giant bubble-breathing monster – species that only live at deeper depths or only use their eyes at night (are we likely to find any?) may not have the ability to see reds, just as humans cannot see 'infra-reds'. But I suspect that if white light is dim enough not to blind smaller fish, then they may ignore me, same as they ignore most large predators, confident of their defensive manoeuvres against lumbering giants. On the other hand, if you shine a spotlight in my eyes then I will swim away from you as well, hoping that nothing dangerous happens while I remain blinded, and I suspect that fish feel the same way about spotlights. (Edit: I am ashamed to say that a Moorish Idol bumped into a bommie while swimming away from my semi-spotlight last night. Sorry fish.)
  
btw 2 Physics 101: Light reflected into parallel or near parallel beams will keep a constant intensity until water or air dissipates it. However, light radiating evenly in all directions from a camera torch will diminish in intensity according to the inverse square law, i.e. double the distance results in a quarter of the light intensity.   Our brains automatically compensate for this so that we tend not to notice variations in light intensity, but when we look at a photo with varied light intensity it looks noticeably unprofessional. So if you are fussy, position the camera and lighting so that equally interesting objects are equally far away.
!!Questions
Swmbo's camera is a Intova Sport HD SP1. The internet suggests it is good bang per buck. I am not completely happy with how it whites out the bright areas when I have not used a filter at about 10 - 20 m. Do more modern cameras have a better ability to cope with a wider range of brights to darks? 

Another question about the Intova, is that it was hard to pull ambient light shots from a movie that were not blurred by camera shake. Is the only cure to use flood lighting and/or a camera rig to slow down the shakes? Or do more modern cameras allow faster exposure times that make up for our shaky hands?
Projects
You forgot your Google ad_client number !
History: SPID Underwater photography

Source of version: 2 (current)

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