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Sony TRV950 / PDX10 Companion
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Old October 27th, 2003, 10:53 PM   #1
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The quest for less vertical smear

Ok, by now most of us are aware of vertical smear in high contrast and know we will just have to learn to live with it or get a new camera.

Here is my new idea for decreasing vertical smear: it has been mentioned several times that since the whole height of the CCD is not used for video, you can sometimes get smearing from light sources in areas which are not really in use. Indeed I have observed this to be true. So, I used some black electrical tape to mask or 'matte' a 16:9 rectangle over the front of the large lens hood which is included with the PDX10. To do this, I set up FCP in capure mode so I could see the whole 16:9 image field (as in 4:3, the suppied FV and LCD don't show you the full DV frame), thus I could make sure the tape was just beyond vignetting.

The result is a hood that doesn't look as cool as it used to, but actually helps you get better images ;-)

Any other ideas for reducing smear would be welcome. Somebody mentioned something about a UV-blocking filter helping reduce smear. I am skeptical, as I would think the image sensors on the cam would somehow be filtered to be non-responsive to UV and IR... but who knows what strange decisions Sony made for the sake of lowering costs, so perhaps they are sensitive to invisible light and smear can be reduced with filters. Anybody?
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Old October 28th, 2003, 01:34 PM   #2
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use a top light

less contrast = less smear
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Old November 3rd, 2003, 05:30 AM   #3
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The smear on the PDX10's chips is very shutter speed dependent. Sony obviously know this high shutter speed limitation and limit the top shutter speed in the portrait mode to 1/425th sec, but in the sports mode the shutter speed can climb to 1/3500th sec in against the light situations and it was here that multi-coloured swathes of CCD flare completely ruined my footage.

Of course the 'portrait' mode is a nonsence mode on the PDX as the top shutter speed allowed by Sony means that the camera sets f4.8 and NDs in sunshine, whereas what you want is a high shutter speed to utilise wide apertures for short DOF.

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Old November 3rd, 2003, 07:38 AM   #4
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<<<-- Originally posted by Tom Hardwick : The smear on the PDX10's chips is very shutter speed dependent. -->>>

Tom, can you clear something up for me? Does your statement mean that the smear is more likely to occur at high shutter speeds?

Just a little confused about that...thanks!

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Old November 3rd, 2003, 10:38 AM   #5
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Yes - the higher the shutter speed the more the smear. The only time I got bad smear at 1/60th was shooting at a setting sun. Other than that it's not bothered me.

I've also just installed a Century DV Matte box, and that has eyebrows that can really keep the light out of the top and bottom of the CCD that's not in the picture, especially in 16x9 mode.
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Old November 3rd, 2003, 11:00 AM   #6
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To my knowledge, there is no direct relation between shutterspeed and vertical smear. What I know is that the pixel overload which generates the smear is often reduced by diffraction spreading. Setting a higher shutterspeed opens the aperture to levels where there is less diffraction meaning that that point optical energy goes up and causes the vertical smear problem.
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Old November 3rd, 2003, 11:22 AM   #7
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For some reason the smear is very much shutter speed dependant. Set up your PDX10 with sky / horizon/ land. I used an overcast day, but whatever. Now shoot on a tripod in the manual mode and while tape is recording turn the exposure wheel to increase the shutter speed by half stops. On replay later you'll see where you reach maximum aperture and go into gain up.

All will look ok till about 1/400th sec and every click after that increases the smear hugely. At 1/3000th sec you'll be horrified. Thing is the smear is always there, it's just that the slower the shutter speed the less obvious it becomes. As you replay your film you'll see remnants of the smear in the darkest shadows even at 1/300th sec.

That's fine; at least we know. What's not good is that other folk (who don't frequent these pages) could well buy the PDX10 or 950 and want to shoot gymnastics for analysis later. What's strange is that the PD100 and TRV900 would be much better tools for that job - having bigger smear free chips and progressive scan full frame resolution. Such is progress.

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Old November 3rd, 2003, 01:02 PM   #8
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> I've also just installed a Century DV Matte box, and that has
> eyebrows that can really keep the light out of the top and bottom
> of the CCD that's not in the picture, especially in 16x9 mode.

Good. A similar approach has helped me too. Be carefull to note though that the built in LCD screen and VF are 'underscanned', they don't show you the full DV frame (the LCD eben seems to not be really 4:3) so be very carefull about chopping off parts of the image you might see later.

It is true that most TV sets underscan, but when working for web video, video CD or DVD you want to get the most out of the DV frame and not have to crop and this loose resolution.
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Old November 3rd, 2003, 01:36 PM   #9
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Do you find it vertically underscans any in 16x9 mode? I've not had the chance to find out yet.

Just been tod the .65 century wide angle has arrived so I can test that out also tonight. I'll report back with the results.
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Old November 3rd, 2003, 01:52 PM   #10
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> Do you find it vertically underscans any in 16x9 mode?
> I've not had the chance to find out yet.

Yes. I hoped it would not but it does.
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Old November 4th, 2003, 03:46 AM   #11
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And the thing that annoys me about my Sony 16:9 TV is that it masks the 4:3 frame left and right. See? I'm showing a 4:3 image in the middle of a 16:9 screen, black vertivcal bars left and right of my picture. Sony "helpfully" crop off great chunks of my picture (an estimated 80 pixels of the 720 I have to display), so that it will match what I see on a 4:3 TV. Like you say Ignacio, we're losing resolution.

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