Tech Support: Rewinding • CMOS vs CCD • Mikin' in the Rain

Your questions answered - To Rewind or Not to Rewind (MiniDV tapes); Rolling Shutter and CMOS vs CCD; problematic sound due to continual rain

To Rewind or Not to Rewind

I have a question for you. Should I be making sure that my home-family videos (MiniDV tapes) that I have are fast-forwarded to the end after each use, according to the article in Videomaker. I know that the label on the cassette package says to rewind the tapes after each use. Is their much of a difference. Also, I've been using a MiniDV rewinder/fast-forwarder to save wear and tear on my video camera. Is that bad?
Tim Bartsch

There's no practical difference between rewinding and fast forwarding your tapes. It's a standard practice for archiving tape to take it out once and a while (at least every year or so), and fast forward it or rewind it to make sure the tape doesn't get packed together. A mini-DV rewinder is the perfect tool to use for this purpose, as any camcorder with a tape transport is a mechanical device subject to wear and tear (usually the first things to go are the black rubber pinch rollers), and so you can extend the life of your camcorder by leaving the grunt work to the rewinder, and only using your camcorder for acquisition.
-The Editors

Rolling Shutter and CMOS vs CCD

I have noticed that many of the new camcorders are using CMOS image sensors, in lieu of CCD chips. I understand that the CMOS chips consume less power, but on the downside, that CMOS sensors record images using the rolling shutter process. CCD chips have always used a global shutter for their recording process. As a wedding videographer, I am concerned about any camera movement resulting in unacceptable results, due to the image capture process. Do I have good reason to be cautious when using/purchasing any new cameras with CMOS chips?
Paul Dellarte

Rolling shutter does exist on CMOS chips, because of the progressive scanning nature of the electronics. The image is made from scanning top to bottom, much like you read a book, vs. interlaced where you would read every other line and start again. Rolling shutter occurs because something might change in the frame in the time it takes the chip to be fully scanned from top to bottom, though it would have to be something extremely fast (less than 1/30th of a second). A common culprit is photo flashes (which as a wedding videographer you probably encounter a lot), where you can end up with a frame that is half flash, and half not.

In practical terms though, it's very, very unlikely that you will ever find yourself in a situation where rolling shutter will ever be noticed by the end viewer. Even in the above example, no one will ever really be able to tell by watching that a flash occurred in one half of a frame versus a whole frame going by at 30fps. The places where rolling shutter becomes a problem in terms of wobble and skew, are generally in extreme handheld camera movements (swish pans, or heavy vibration) that would not result in viewable image anyway. We've never encountered any situation out in the field that we felt having a CMOS sensor was a detriment to the production, so we think in this case the caution is unwarranted.
-The Editors

Mikin' in the Rain

I recently had a video that was quite good visually, but the sound was very problematic due to continual rain. Do you have any good suggestions for sessions outdoors in rainy weather especially pertaining to sounds of the raindrops which interfere with the audio? Also, what do you wear, what do you use to cover equipment?
Timothy Price

Very good question, actually. The sound of raindrops (particularly during heavy or brisk rain) would be quite difficult to filter out of your soundtrack in post-production, too.

When shooting something with dialog outdoors, most Hollywood sound directors will actually reshoot dialog in a controlled studio in later and dub over the existing sound. This is called "looping". Then they trickle in a small amount of rain FX, to make it appear natural and outdoors without over-riding the dialog.

For acquiring sound, the best for most situations would be to use a shotgun, small lapel or a handheld mic, not your camera's mic, which can't get close enough to your subject to mask rain at all. Electrically speaking, it would be much safer to either go wireless or to wear gloves made of insolating material (e.g. not wool or acrylic). A windscreen helps, too. Leave the expensive mics at home, though; our experience is that water and mics really don't get along very well. Look around for a nearby awning or overhang on a nearby building. There'll probably be a way to compose a shot that has some rain in the background, but won't get you, or your gear, wet. See the Videomaker article "Shooting the Four Seasons" or our Tips & Tricks segment on our vidcast #57 for more rainy day tips.

What to wear? Rubber or vinyl would keep the rain out but also provides a surface that makes a good sounding board for all but the lightest rain. Consider some of the more advanced waterproof fabrics like Gore-Tex. As far as what your camcorder should wear, consider some of the more advanced covers (check out Porta Brace's web site, among others, for ideas.)
-The Editors

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Wed, 04/01/2009 - 12:00am