Too much blur with TRV950 when making very small movements...

[Vladimir Koifman]

Tom, yes, I understand the area that "wasted" for video is used for stills and 16:9 mode (in PDX10).
I just thought that designwise for Sony it's more beneficial to use full CCD surface in 4:3 video mode. One could get a better low light and a wider wide-angle view. Both are not very good in TRV950. I assume one needs an interpolation engine to interpolate the pixels down from megapixel to the normal TV resolution. But they already have this engine because of digital zoom, at least in TRV950. So, essentialy, this interpolation comes for free.
This is kind of rhetoric question, as only Sony could answer this for sure. It would be a nice surprise for me if anybody else can explain this.

[Tom Hardwick]

I like your argument but don't know enough about CCD technology to add anything other than conjecture. The TV screen is looking for a 720 x 576 rastor and generally bigger CCD pixels give greater low light performance so using double this amount (say) would reduce the individual pixel size to slightly less than half.

I do agree that the TRV950 has a very dissapointing wide-angle though - in fact I'd say it was contravening the Trade's Description Act to call it a wide-angle at all. It equates to a 49mm lens on a 35mm SLR and the camera cries out for a w/a converter even before a spare battery.

Not that this is so bad though as the TRV60 and lots more in the Sony current range have a 52mm focal length equivalent! Can you imagine even less w/a than the 950? Remember too that the TRV900 had a decent (almost) wide-angle of 41mm equivalent.

Of course these mega-pixel chipped camcorders do offer significantly more wide angle when used in the stills-to-Memorystick mode but this is more a by-product of the bigger chips than design intent.

One nice thing about shooting movies onto mega-pixel chips is that as the lens coverage is designed for a larger "gate", when you shoot movies you're only using the central part of the lens' image circle. This generally means that vignetting is less obvious at wide apertures and picture sharpness is improved into the corners of the frame. Soon as you shoot stills on the thing though all these advantages fly out the window.

tom.

[Nikolaj Simic]

Well, this thread has gone a bit away from the original question, but has opened some very interesting issues.

Just a small explanation about CCD: CCD is an acronym of "Charge Coupled Device" or how we called it 30 years ago: "Bucket Brigade". CCD is essentially an analogue shift register and mimicks the firemen bucket brigade that used the buckets to bring the water to the fire. The firemen have been standing in a row passing the buckets to each other. So the firemen have been standing on fixed point and the buckets travelled fast to the fire.

Same thing is happening in CCD. Each photo sensitive cell (called pixel - picture element) on the CCD chip represents a fireman. The cell accumulates a small electrical charge during the exposure time. After the exposure the shutter shuts down and the the electric charges are shifted through the shift register to the ouput of the CCD. It is important to know that the output of the CCD is analogue. This analogue signal is then converted into digital form by means of an analogue to digital (A/D) converter. The digital signal is afterwards processed in the DSP (Digital Signal Processor) and recorded to the tape or other storage device.

Knowing this we recognise that it is not essential that the pixel count of the CCD resembles the spatial matrix of the DV (720×576 in PAL). CCD can have lower pixel count and can still provide the analogue signal to the same A/D converter. Of course the quality of the picture will degrade with decreasing of the pixel count. Theoretically there would be enough to have 414,720 pixels to resemble the full quality DV picture. And most of todays better DV consumer/prosumer cameras include three CCDs each having 430,000 to 470,000 pixels (Sony VX2000, TRV900, Panasonic DVX-100E). Such a CCD can produce very good picture and still maintain good low light sensitivity by keeping the pixel size as big as possible.

But there is another effect caused by the sampling of the analogue signal. Sampling theory explains that it is possible to transfer only the frequencies up to half of the sampling frequency. And in the vicinity of the half sampling frequency the sin(x)/x function distorts the frequency response by lowering the high frequency level. That means less detail, worse colours etc. By increasing the pixel count this effect becomes less evident. Ideally the CCD pixel count would be about 1 MByte, but doubled only in horizontal direction (1440×576 pixels). That would double the sampling frequency and minimize aliasing (another nasty effect of sampling). Of course that would require much faster and complex (more expensive) electronics and nobody is doing that today. Besides, DV coding is not so simple. It utilizes 4:2:0 colour space (PAL) and spatially compresses the signal in order to fit it into 25 Mbps stream. So the coding algorhytm itself prevents the DV coded signal to be better. But still, higher pixel count above "theoretical level" of 720×576 definitely reduces sin(x)/x effect and produces better picture.

This is very evident in "megapixel" 3CCD cameras like TRV950, which produces astonishing sharp and colourful picture (when exposed correctly), using about 690,000 effective pixels per CCD. Due to the coding limitations of the DV signal there is no reason to increase the pixel count beyond that figure though.

One-chip cameras shoul be limited for the same reason to 1,5 megapixels size (red and blue colours are only sampled by half the sampling frequency).

Soooo, putting a "Megapixel label" on the camera is only partly a marketing trick, it really enhances the picture quality. Of course it also increases the still picture quality, but that is not why serious videographers are buying the camcorders for. More important would be to keep the CCD size equal or bigger than 1/4" for a consumer and 1/3" for a prosumer camera in order to increase the low light sensitivity.

Higher pixel count is usefull only when using a generic 16:9 format, like Sony PDX10. It is a pity that TRV950 doesn't use the same technology.

Nikolaj

[Mike Sanchez]

Nikolaj,

This is my first post to this forum. I have carefully read and re-read your post regarding oversampling and your reference to the fourier transform and frequency domain. Excellent post.

I had read a less detailed post on over-sampling and noise reduction wrt to the TRV-950 and that led, ultimately, to my purchasing the unit.

As long time signal processing guy I really appreciate your detailed post and your specifying the max useful resolution for 2X oversampling (and noting that nobody will do it because of the electronics issues).

I assume you work in the video image processing industry?

[Mike Sanchez]

And to the reason that this is my first topic to post on:

I had a similar blur problem making a moving video of my son on his new roller blades Christmas morning with the TRV-950. The video came out blurry even when he momentarily stopped and looked at the camera. I have owned the TRV-950 for 5 weeks now so it is still new to me.

I had sharpening turned all the way down (having discovered how much noise the SONY sharpening function adds to the image). Also, I was not able to replicate the problem later with or without sharpening and the blur problem was haunting me until I read this thread.

In future I will TURN OFF THE STEADY SHOT. I just tested panning with it on and off and the steady shot, when panning, does add blur.

Great forum.

[Tom Hardwick]

I'm most surprised to read that the OIS of your TRV950 adds blur to the image Mike, and I'm tempted to say that you may well have a fault with your unit. I've just tested the PDX10 and agree with Sony that for all intents and purposes the Super Steadyshot can be left on at all times, and only turned off if you want to conserve battery power. Unlike other manufacturers, Sony only give viewfinder warnings when the OIS is turned off, it's that transparent a technology.

Maybe you could explain in more detail what you mean by, "...does add blur". You mean the image takes on a soft focus look that isn't there when the SSSS is turned off? In theory, if a steady pan speed is maintained the floating elements will move to their bump-stops where they went when the pan was first started. When the pan decelerates to a stop the elements will again centralise in the optical path awaiting the next camera movement. As far as my tests show, having these elements out of alignment doesn't effect the resolution, but then again,in any interlaced TV system, subject or camera movement halves the vertical resolution at a stroke.

tom.

[Shawn Mielke]

I started a thread a few days ago about tracers, or, ghosting, caused by overexposure, with my PDX10. This wouldn't happen to be the same thing as your "blurring", would it? Try adjusting not only exposure, but also color levels as well and see if this affects the phenomenon.

[Ignacio Rodriguez]

Great post Nikolaj. Yes, the CCD is an analogue device. However somewhere in the camera, probably just after the AD converter, the images coming from the CCD array must be moved in real time into some kind of DSP that can do the downsampling. Presumably the video cannot be moved fast enough through this bus if the full pixel count is used. This would explain why the PDX10 can use the full size of the CCD for still pictures but not for 60i video... but it does seem to be able to use the full width, at least in my NTSC version.

This would also explain why this kind of camera, even having a high pixel count CCD, will need a lot of changes to it's circuitry and not just a realtime MPEG2 encoder in order to record in the 'almost HD' resolution of HDV.

Unfortunately the PDX10's circuits cannot be upgraded easily so this camera will never do HDV in it's current form. I wonder sometime why we put up with what they sell us... can you imagine paying $2k for a computer that will not be able to write to next year's Office? More on this in another thread...

[Mike Sanchez]

Tom,

Not sure what happened during the "blur" that occurred with my son's skating back and forth. Disturbed me for sure. Am testing my autofocus and will start a separate thread for a question on that.....could be I have a problem with my auto-focus system.

Shawn,
I definitely do get "blooming" or ghosts around white objects that are zebra striped. Have to take the exposure down a bit and they go away. Little surprised by this (and other features I am learning about).

In a separate post I will ask folks who have a TRV 950 to run a simple test and let me know what their result is.......