Radiation & Pixels
Published : 6th February 2005
HD space rangers,
Anecdotal evidence suggests that radiation from airline travel causes pixel failure.
What is an effective form of radiation protection for pixels, that could be lined or woven into a lightweight carry on camcorder bag?
And something to line the lens cap or body cap?
Silver foil? Once used a copper "fabric" to screen RF, would this do?
For a scientific evaluation of this, try a NASA experiment where they flew an HD camera specifically to test the effects of radiation on the CCD:
(You'll have to follow the links and search for the relevant information. Look for the image of the HD camera on this main page!)
The salient information is this :
"In the case of HD Camcorders, the CCD chips rapidly deteriorate under bombardment from cosmic rays and other types of space radiation. In on-orbit tests, the cameras lose between 5 and 15 pixels per day..... .....Solar storms can dramatically increase the amount of radiation to which the cameras are exposed. Shielding must provide protection from space radiation or cameras must replaced every 50 - 90 days."
They still haven't posted the final results of the experiment, but in searching through the website they seem to have narrowed the cause down to alpha and gamma radiation. Alpha radiation shouldn't be a problem, as a few inches of air are an adequate shield.
Gamma radiation, on the other hand, is impossible to protect against completely - all you do is decrease the percentage that makes it through. An 8-inch thick concrete wall absorbs something like 90% of the gamma rays hitting it. Not really practical for carry-on. Lead is most commonly used, and you can certainly get it in a flexible foil (Think the lead aprons they give you when you go in for an x-ray) or incorporated into the walls of a case... …the problem is the thinner the lead, the more radiation makes it through. Unless you want to carry around a box lined with an inch of lead, you'll have to accept that a fair percentage of the gamma radiation will still make it through your shielding.
As an aside, if you're worried about bad pixels due to radiation, I've spent some time shooting within a few feet of several tons of high-grade uranium ore, which does tend to give off alpha, beta, and gamma radiation. After a week of shooting in uranium mines and mills, I experienced not a single bad pixel on the CCD.
Director/DP, Downstream Pictures
George Hupka wrote :
>In on-orbit tests, the cameras lose between 5 and 15 pixels per day..... >.....Shielding must provide protection from space radiation or cameras >must replaced every 50 - 90 days.
I wonder if Tube cameras would fare better? And I wonder how they handle this situation with their SD chip cameras, or if they consider them more "consumable".
If tube cameras were less susceptible to damage, it seems to me the extra weight would be less than the extra shielding a chip HD head would need?
>If tube cameras were less susceptible to damage, it seems to me the >extra weight would be less than the extra shielding a chip HD head >would need?
I'm guessing you've never had the pleasure of aligning a tube camera.
When we used to get new tubes from the manufacturer, they'd come in a really cool case - the tube would be suspended in a gyroscopic mount, so that it would always be facing in an appropriate direction (you would never want it facing up, because a speck of dust settling on the tube's imaging surface could damage it) and isolating it from shock.
Imagine what would happen to a tube camera on take-off in the shuttle! When I started working part-time as a news cameraman, our tube cameras were scheduled for one day in the shop every week or two, for routine alignment - and I don't think I ever put a TK-76 through anything close to a shuttle takeoff!
They also note that this shielding would be for long-term missions – the cameras' pixel-masking technology is adequate for short-term missions, but of course the memory register fills up rather quickly if pixels are lost at that rate!
SD cameras suffer the same fate as HD cameras, but I don't know that they've ever flown a regular SD television camera - I assume that the shuttle's own cameras are routinely replaced, and they're basically for live transmissions, so a few bad pixels isn't as big a deal.
One minor correction to your otherwise accurate post - the you-beaut gyro tube-shippers were designed to keep the tubes facing UPRIGHT, so that any loose particles within the tube did NOT land on the INSIDE of the business end - the target which was the orange (in the case of Plumbicon) light-sensitive coating.
BTW, does anyone recall the short-lived tube HD cameras?
I remember an HD demo tape (two double-speed C-format machines slaved to handle UNCOMPRESSED HD) displayed by I think Sony, that involved a dance routine set in a 1950's car workshop (but studio). Apart from the action the sequence was highlighted by heavy Plumbicon burns from all the shots of chrome bumper-bars. Poor choice of subject in my book.
Another tube geek,
Perth, Western Australia.
Actually the tubes in the HDC 100 were Saticons--Plums never had enough resolution.
We still have 1 HDD 1000 Digital HD VTR on line, for archival purposes. The amazing thing is that the machine looks like it is running fast forward in normal playback mode.
Executive Vice President
Director of Engineering
SMA Realtime, Inc
100 6th Avenue
New York, N.Y. 10013
>What is an effective form of radiation protection for pixels, that could be >lined or woven into a lightweight carry on camcorder bag?
Cosmic rays very well could be the culprit. That is the theory as it stands.
Yes, the higher you are the more likely that your camera will be damaged by this form of radiation. The earth's atmosphere changes the way they move for the most part so the higher you are the more you're in their path.
Did you know that time also moves slightly slower when you re in that plane 30,000 feet above the earth?
Here is the bad news, elements of cosmic radiation ain't going to be stopped by a piece of tin foil. They move at such high rates of kinetic energy that you need layers of molecules such as our atmosphere to stop them. If you can't get the pixel to fix using the Sony black balance trick, try wrapping your camera in plastic and putting it in the freezer for 24 hours. I have fixed many a pixel problem that wouldn't fix that way. Also sometimes you are just going to loose pixels because of heat, etc.
Some chips survive for longer periods and some don't. It's kind of like a pixel that is a 'lemon'. Remember the yield for chips when they are manufactured at this density is not high so the effective life of these chips mustn't be al that good either. I've known some cameras to last ten years with little to no pixel loss and some to loss grids after only a few months.
Producer, Director, Cinematographer
Hellgate Pictures, Inc.
444 E. 82 Street
New York, NY 10028
>tube-shippers were designed to keep the tubes facing UPRIGHT, so >that any loose particles within the tube did NOT land on the INSIDE of >the business end - the target which was the orange (in the case of >Plumbicon) light-sensitive coating.
Of course! Thanks for the correction, I did get it exactly backwards in my earlier post...
Director/DP, Downstream Pictures
> . . . when we used to get new tubes from the manufacturer, they'd come >in a really cool case - the tube would be suspended in a gyroscopic >mount, so that it would always be facing in an appropriate direction (you >would never want it facing up, because a speck of dust settling on the >tube's imaging surface could damage it) . . .
Almost correct, it was a very sexy multi-axis gymble mount (but not gyro) that did keep the pickup tube constantly aligned to gravity. But it was, in fact, facing "up" with the connector pins always down. The danger in shipping was tiny particles from the grid or collector knocking loose, inside the assembly, and falling down onto the back side of the photo-sensitive front end.
The mount held the tube upright so that any contaminants stayed down near the pin end. We used to use lens cleaning tissue to clean off the glass-faced front of the tubes before installation, that took care of the external dust issue.
Tomorrow, Chapter Two, "Tales of the Norelco Film Chain."
Director of Photography
Dark Street Films / VGG Systems, Inc.
Lakewood, CO USA