Dear English-speaking readers, this page is an automatic Google translation from a post originally written in French. My apologies for the weird sentences and the funny mistakes that could have been generated during the process. If you can read French, the original and correct version can be found here:
A little parenthesis: I will always remember my astonishment as a novice, a few years ago, when, having flayed a finger on the coral, I saw a dark green liquid coming out of the small cut on my skin ... Very weird .
I thought, at the time, that I had to sting myself to something unclear, which had left me a venom or a sticky deposit on the wound. It was not painful, so I did not worry more than that. It was only once on the surface that I understood.
Underwater, the bright red of the blood becomes ... green!
So, in photo sub, it is necessary to indicate to the digital camera what shade of "blue" under the water is equivalent to white, so that it readjusts everything accordingly and restores the disappeared colors.
During this dive at Batee Tokong, I make an image of the sand on the bottom. Here. It has a bluish gray shade, but it's supposed to be what roughly corresponds to the underwater white. The images that I will then take, having as a white mark this "blue-gray", will thus find their reds and yellows. Long live the magic of digital!
Except that ... When the device goes back to sleep, I have to go back, in the many pictures taken in the meantime, to tell him again what is the image chosen for the white balance when I want to go back to video. (Friends non-divers and non-photographers, do you still follow?)
I only realize that once under water, of course. I did not take the time to check, dry, how to record this kind of setting ...
This is to tell you the number of scenes that I can miss ... It must react quickly, trigger immediately. I'm still drunk to have let the swirling swims of a pretty leopard moray, which passed right under my nose. Time to reactivate my settings, she had spun!
In the future, I'll have to set the camera to always memorize the white balance for the video. Or, I may opt for an orange filter (good old technique before the digital) to place quickly in front of the lens when needed. That those who already have experience in video sub do not hesitate to give me their advice.
Other than that, Batee TokongIt's a little Murènes City ... It's everywhere. (And not one on my video, grrr ...): -x
On the computer
Well, it's not all about making pretty cool pictures in super definition. After, you have to find the right settings on the computer to encode them properly, just to have an equivalent rendering for the broadcast on the internet.
I chose HD mode 1280 × 720 on the 7D. Once my small sequences stored on the computer, then imported and mounted on Final Cut Express, comes the delicate moment of export. As long as I was in low definition with the videos of my little compact, it was not too much trouble. In most settings to choose, the rendering was consistent with the original.
There, for HD, it's more complicated. I did a lot of tests, in recent days, to find the right compromise between image quality and file weight. As you can see, an MP4 export, with the H264 codec, speed set at 5120 Kbs or 6144 Kbs, original frequency, original size, it does it about ... (Non-geek friends and non-videographers, you follow always ?)
Afterwards, you have to balance all that on the web. To simplify my life, I use the platform Vimeo, which I find much superior to Youtube and DailyMotion, although these last two also offer HD now.
Only, Vimeo encode and compress my file, already encoded and compressed by my little hands. Result: we start to distinguish the pixels in the passages where blue dominates and we lose fluidity. In short, not easy to restore, online, the beautiful image of origin.
Good. It's not too bad either, huh. It's just for a webcast, just to share my bubbles with you ... (But what a job!)