cmos vs. ccd for underwater HD

[Shari Coleman]

I am curious about the differences between cmos and ccd sensors when it comes to underwater videography. I am thinking of purchasing a prosumer camcorder, and am seeing that sony is making some of their camcorders (v1u, etc) with cmos sensors. I thought that cmos produced inferior quality compared to ccd? Is this not true? Any thoughts would be appreciated.

[John Miller]

One thing that disappointed me with my first DV underwater system (with a CCD) was that very bright scenes such as looking up at the sun from, say, 60 feet, take on a green/turquoise color. I thought at first that this might be to do with the DV compression but when I reviewed some of my older analog footage, it seemed to be present there, too. I hadn't noticed it because most of the footage was made in the colder, greener waters of around the UK(!)

With my CMOS-based HDV system, this problem is much, much less. I can't say if any green occurs because I haven't recorded enough. That will change in a few weeks...

Whether all of this is simply a CMOS vs CCD thing, I can't say.

[Rick L. Allen]

Originally Posted by Shari Coleman

I am thinking of purchasing a prosumer camcorder, and am seeing that sony is making some of their camcorders (v1u, etc) with cmos sensors. I thought that cmos produced inferior quality compared to ccd? Is this not true? Any thoughts would be appreciated.

Shari, CMOS has come a long way and the chips are equal to or better than CCD's in some situations. Purchasing your camcorder should come down to what features and format you prefer. CCD's vs. CMOS isn't really an issue. John's observation is probably more related to improved white balance circuitry and isn't related to chip type. All of the Sony prosumer cameras will produce great pictures if you have good technique.

[Shari Coleman]

I've just been trying to do a little research about hd broadcast-quality camcorders, and this cmos/ccd thing has just been sticking in my craw. It's good to hear that it's not really an issue or that when it comes to underwater videography, there may be no difference. I haven't really read any complaints about cameras with cmos, but I thought I'd ask that question anyway.
Thanks.

[Tom Hardwick]

Originally Posted by Shari Coleman

I haven't really read any complaints about cameras with cmos, but I thought I'd ask that question anyway.

Then you haven't been doing much reading here then :-)
But for underwater videography CMOS chips will be fine, and I'd have no hesitation in recommending them. As John says, the CCD chip smear (when you film directly into the sun from below) will be absent.

tom.

[Jonathan Shaw]

You will actually get great images with both CCD and CMOS, I would say the most critical things are:
Chip size and number to assist you in the low light
Your knowledge of the camera and it's limitations
A decent WA adapter which does not distort or produce chromatic aberation.

Jon

[Tom Hardwick]

Originally Posted by Jonathan Shaw

A decent WA adapter which does not distort or produce chromatic aberation.

The wide-angle adapter I used under water had quite severe barrel distortion but I didn't find this a problem at all - in fact with no straight lines down there it's very hard to spot.

But breaking the surface the barrelling becomes much more noticeable because a) you've suddenly got a horizon which gives the game away, and b) the wide-angle lens is far more powerful when working in air. So much so that above water my housing vignetted the image - under water all was well.

tom.

[Jonathan Shaw]

What camera / housing WA adapter combo were you using? I have had issues with 'wet' wide angle lenses and would never go there again for decent quality video.
It the vignette problem is also fairly common and normally occurs when not using lenses that are specifically designed for underwater use. Normally zooming in slightly will solve the problem.

[Ron Chau]

Fathoms. Expensive, but probably the best UW wide angle lenses for consumer/prosumer housings.

[John Miller]

Here's an example of the problem I described earlier re. bright areas around the sun (typically) looking very turquoise instead of the bluer surroundings. It doesn't seem so bad on a PC display (LCD or CRT) but looks absolutely dreadful when watched on a CRT TV yet doesn't show up on the camcorder's display. In reviewing footage from my c. 1993 Video8 Handycam, I notice that it doesn't suffer this problem at all. I originally put it down to my using a first generation DV camcorder but I see it a lot on places like Discovery. Just last night I saw a trailer for an upcoming series that shows exactly the same behavior. To me, it completely destroys the video. I'm surprised it is permitted for broadcast.

[Jonathan Shaw]

You have actually got a few things going on in that frame, firstly the halo effect is a reflection of the camera lens and front edge of the cam. If your camera is silver at the front one thing you can do is make it black, whether with a permanent marker pen of black tape (depending on how neat / permanent). Secondly the vignette, to solve that zoom in slightly, this is a reasonable common problem, if the lens was designed for the housing then it shouldn't do it. As Ron said Fathom ports are fantastic and do not have this problem. Unfortunately U/W gear is bloody expensive and it does come down to the more you pay the better it gets.

Also when shooting into sun any blemish or bit if dust will show on the port you will need to be careful of that.....

It's funny you mention about broadcast, heaps of crap gets through and in the U/W world it's who you know and your name probably more than your shooting ability. If you actually look closely at the "Blue Planet" a very highly regarded underwater BBC production there are lots of very average shots. Don't get me wrong I think it's great but there are some really bad (technically) shots in it.

[Dave Allen]

I have seen remarkable footage shot with both CMOS chips versus CCD's.

I personally wouldn't spend much time giving it any thought.

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