Indonesia: Pulau Weh [Sumatra] - March 2010
Dear English-speaking readers, this page is an automatic translation made from a post originally written in French. My apologies for any strange sentences and funny mistakes that may have been generated during the process. If you are reading French, click on the French flag below to access the original and correct text:
Français
I had to play a bit with the video mode of Canon 7D under water.
The video
I did this at Batee Tokong, one of the dive sites accessible from Pulau Weh. And the image quality... wow!!!! It's something else than what I could get with my little compact from before.
So dive without getting wet, with this underwater mini-film. In HD (high definition), please.
Under water
Well, to tell the truth, I had a little trouble. Underwater, first. There is this damn white balance to do.
Express mini-course: underwater, you lose the colours. They are absorbed one by one, starting with the red, from 5 meters, then the orange at 10 meters, the yellow at 20 meters, etc..
The more you go down, the more everything turns blue ...
(The diagram on the right comes from the site Aqua-photo.com.)
Small parenthesis: I will always remember my astonishment as a novice, a few years ago, when, having scratched my finger on the coral, I saw a dark green liquid coming out of the small cut on my skin... Very strange.
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 turns... green!
😯
So, in a sub picture, you have to tell the digital camera which shade of "blue" underwater is equivalent to white, so that it readjusts everything accordingly and restores the colours that have disappeared.
During this dive at Batee Tokong, I make a picture of the sand on the bottom. That's what I'm doing. It has a bluish gray shade, but it's supposed to be what roughly corresponds to white underwater. The images that I will take afterwards, having this "blue-grey" as a white marker, will thus regain their reds and yellows. Long live the magic of digital!
Except that... When the camera goes back to standby, I have to go back in the multiple pictures taken in the meantime to tell it again which picture is chosen for the white balance when I want to switch back to video. (Non-divers and non-photographers friends, are you still following?)
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 ...
😀
That's how many scenes I can miss... You have to react quickly, trigger it right away. I'm still angry that I let the rippling swim of a beautiful leopard eel pass right under my nose. By the time I reactivated my settings, it was gone!
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 bit of Murene City... it's everywhere. (And not a single one on my video, grrr...) 😡
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.
Now, for HD, it's more complicated. I've been doing a lot of tests over the last few days to find the right compromise between image quality and file size. At first glance, an MP4 export, with the H264 codec, bitrate set to 5120 Kbs or 6144 Kbs, original frequency, original size, it does it pretty much... (Non-geeks and non-videographers friends, you still follow?).
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 encodes and compresses again my file, already encoded and compressed by my little hands. Result: you start to distinguish the pixels in the passages where the blue dominates and you lose fluidity. In short, not easy to restore, online, the beautiful original image.
Good. It's not too bad, either, huh. It's just for a webcast, to share my bubbles with you... (But what a job!)
🙄
