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Sony VX2100 / PD170 / PDX10 Companion
Topics also include Sony's TRV950, VX2000, PD150 & DSR250 family.


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Old September 9th, 2002, 06:58 PM   #1
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Interesting if true

I borrowed this from rec.video.production:

If you use a camera with a "SteadyShot" function, such as the VX2000 or TRV900, you might want to disable the "SteadyShot" function, as it could result in a bunch of tiny reflections around each candle, sort of like a "firefly effect." I have a vx2000 and turn off this function whenever I am shooting around candles or similar lights.

Has anyone seen this come and go with steadyshot on/off?

I've had the phenomenon but attributed it to a poorly coated filter. Now I'll have to go back and test.


> I will be shooting Christmas Candlelight service with 2 DV this coming Christmas.
> I will be doing NLE with the footage. I have done a single camcorder shooting last year for the music service with good result.
> However I need help for all of you to help me to do a better job. For example, the light level will be very low due to the candlelight event, so how can I overcome it? Any other hint or suggestion?
>
> Ted
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Old September 9th, 2002, 07:26 PM   #2
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i have had the firefly effect happen to me while shooting at night at a local carnival all the tents had lights strung around the top that would flare i figured it was due to shaky camera work only to find out that the steadyshot could be causing the problem on another message board. i havent shot at night since but will give it a try also. shooting done with VX2k
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Old September 9th, 2002, 07:35 PM   #3
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Read this post http://www.dvinfo.net/conf/showthread.php?s=&threadid=3299 and see if there are similarities. My understanding is that Sony licenses the IS technology from Canon so they work in the same manner. I've shot candles with the IS on (XL1s, no filter) and no problems (or fireflies).

Jeff
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Old September 9th, 2002, 08:59 PM   #4
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This is a well-known quirk of Optical Image Stabilization. It's a very real effect, and I experienced it with the XL1 many moons ago at a night shoot on a well-lit football field.

OIS has its trade-offs like all other features do, and this is one of them. And it's true that Sony licenses the OIS technology from Canon, the patent holder (there's a lot of trading of technology between camera manufacturers -- for instance, all Canon camcorders have a LANC jack, which is a Sony protocol).

Any time you see Super Steady Shot on a Sony camcorder, it's actually Canon's OIS at work. The "dancing lights" effect is definitely something to look out for in certain shooting situations. The remedy is to turn off the OIS. It's not considered a defect or a problem... it's simply reflections from the vari-angle prism in the OIS mechanics. A side effect of an otherwise amazing and effective image stabilization technology.
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Old September 10th, 2002, 10:08 AM   #5
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One would think that the surfaces would be multi-coated to prevent just such an occurance. Must be something preventing the application of the coatings.
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Old September 10th, 2002, 10:37 AM   #6
 
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Most, if not all, coatings work at very specific angles of incidence. Could be that the angles involved with the OIS system are too shallow for effective AR coating to work.
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Old September 10th, 2002, 01:34 PM   #7
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The IS uses a variable angle prism. The angle will vary with the amount of shake present. Zoom in, more shake present, larger angle prism. Combine that with the angle to the specular light source and you have fireflies. The use of a filter may make the effect more pronounced. I tend to shoot specular light sources centered, out of experience. I know the center is the best corrected, sharpest part of the lens. I do it to help control flare, not realizing the added effects of the IS. Not good for composition, but combine that with the fact I don't use filters explains why I don't get fireflies.
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Old September 10th, 2002, 02:07 PM   #8
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A further thought. Thinking of 2 situations:

If the camera were locked down, then the stabilization system, though active, should not be moving its mechanism.

If the stabilization system is off, assuming it doesn't move the plates to a parallel postion and 90 degrees to the lens axis.

In both situations, wouldn't one see internal relections anyway, they just wouldn't move around?

Have to try this tonight. I have a 10:30 PM highway sightline shot for a lawsuit.
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Old September 12th, 2002, 10:03 AM   #9
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Not only that, they don't go away

After 2 successive nights of shooting traffic signals for the local PD, I can attest to the 'Fireflys' presence. Steady Shot on or off!

The fireflys simply stop moving when one turns off steady shot. They do not disappear.

This is not acceptable to me and I will pursue this with Sony through the WEVA Camera Committee.

Bill, I know you stated that coatings are only designed for a specific angle of incidence. That may be. But they are apparently effective over a wider angle as witnessed by any multicoated filter user. Surely there must be some other reason that Sony )Canon) does not multicoat the glass surfaces.
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Old September 12th, 2002, 10:11 AM   #10
 
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AR coatings are relatively inexpensive when the incident light is normal to the surface. As the angle becomes more and more oblique, the effectiveness of AR coating diminishes, and the demands on coating layers increases, as well as cost to manufacture. Each layer is VPD deposited and baked for an extended period of time. Coating ovens cost $$$ / hr to operate. The prisms used in IS systems, by design, require rather oblique angles, as well as reflections that occur internally to the glass prism. Kinda hard to coat the inner glass surface, ya know?
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Old September 12th, 2002, 02:05 PM   #11
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I'd guess the real reason they don't coat the glass is that the transmissive losses increase as the number of coatings go up?

They could certainly coat the inner surface of the glass before they assembled the module, I'd think.

Strange that I never notice the issue until the PD-150. But then the older Hi8 systems cannot hold a candle :-)))) to its low light performance.

Never more pointed out than when I tried the stop light shots with a really good Hi8 camera 2 nights ago (they wanted analog because of legal challenge issues) and I could only record the color with the aperature at a minimum. And of course, there is nothing but black and a color disk on the screen.

The 150 shows the trees, the lamp posts, the lights, the street, details in cars, etc.

About the only thing I didn't like was the fairly strong halo around the lights. But it isn't a $30,000 FIT camera, is it?
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Old September 12th, 2002, 10:57 PM   #12
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WRITE!

The more you look for them, the more deficiencies you can find w/current prosumer DV's.

But if a few convincing and succinct letters are read by the right engineering people at the manufacturers, at least maybe the problem gets addressed, sooner or later.
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Old September 13th, 2002, 06:51 AM   #13
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Actually mult-coating of optical surfaces increases the transmission of light. It was the advent of multi-coatings that help make zoom lenses less expensive and perform better (lower maximum aperatures and less flare).

I reviewed my candle footage last night and I really don't see fireflies. The scene was staged after a friends wedding. One large candle, flame dead canter, and two hands coming into frame to light the wick. I let the tape roll on the flame for maybe a minute. The camera was on a tripod, no IS, no filters. The ambient light is fairly bright, so I don't have an extremely contrasty scene. I wonder if the larger size of the XL lense allows for better baffeling in the lense. Another possibllity is the coating of non-optical surfaces. Inside a better lens the different barrels, sleeves and mechanical parts are coated an opaque black to absorb reflections. for example the aperature blades are always a dull, flat black. this minimizes reflections. I've seen some lenses with fairly reflective internal surfaces.

Now, I'm not saying the XL lenses don't produce fireflies. Chris has obviosly encountered them and they do exist. I'm going to shoot some test this weekend (lights in a parking lot at night) and see why I haven't been bothered by them. I'll also do the same shots with the 14x manual lens so I have a baseline. From all this maybe I can figure a way to minimize the firefly effect.

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Old September 13th, 2002, 01:35 PM   #14
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Yes I encountered the fireflies with the standard XL lens, but switching off the OIS eliminated the problem.
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Old September 13th, 2002, 10:06 PM   #15
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I watched the fireflys off of car headlights settle just below the headlights. Really a fine point of light so they would be hard to find if they were not moving.

Since the Sony lens are probably made by Canon, I'd guess that they are reasonably well baffled and coated. Certainly not as well as say, a $6,000 lens, but OK.
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