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Old March 24th, 2015, 06:45 PM   #1
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HPX500 sensitivity increase in SD?

I read somewhere that the HPX500 will gain low light sensitivity, since it uses SD CCD's. Is this true, same chips as the SPX800, so it would be a stop faster in Standard Def mode?

Paul
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Old March 28th, 2015, 07:03 PM   #2
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Re: HPX500 sensitivity increase in SD?

As a generalisation, then HD must mean smaller photosites than SD for the same size chip, so if all else equal, expect higher noise figures.

But it's not quite that simple. Come display then even if the s/n ratio is worse, the pixels are smaller, so the noise on each pixel is less visible. The effects tend to balance out....... That's the theory, anyway!
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Old March 28th, 2015, 10:01 PM   #3
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Re: HPX500 sensitivity increase in SD?

I believe the HPX500 uses the SDX900 series CCD's, that they interpolate to create a fake HD image, hence the SD size photosites, but the interpolation induces a loss in sensitivity. At least that was what I was under the impression was going on?

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Old April 1st, 2015, 03:44 PM   #4
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Re: HPX500 sensitivity increase in SD?

All I can say from experience is the HPX 500's fewer pixels did have more sensitivity when compared to an HPX 3000 with more pixels when shooting Warhorse in a multicam shoot for Lincoln Center a few years back. Same amount of light through the lens hitting fewer pixels was the explanation. Signal to noise and other parameters could be more important. I believe the chip block was 720 not 1080 but the camera could record either way. The one part of the camera which was clearly SD was the viewfinder output.
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Old April 1st, 2015, 04:53 PM   #5
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Re: HPX500 sensitivity increase in SD?

Quote:
Originally Posted by Paul Anderegg View Post
I believe the HPX500 uses the SDX900 series CCD's, that they interpolate to create a fake HD image, hence the SD size photosites, but the interpolation induces a loss in sensitivity. At least that was what I was under the impression was going on?

Paul
The HPX chips are each 960x540, with the red and blue pixel shifted from green. Hence it's easy to derive a 1080 signal (though not 1080 resolution!), and the pixel shifting gives a resolution increase of about 1.2x on each axis for luminance only - so expect luminance resolution of about 1150x650. (Pixel shift gives an improvement of about 1.5x overall, if it's split between H & V then each axis is improved by about the sq rt of that - so about 1.2x.)

So large photosites, and likely quite good sensitivity - but at the expense of resolution, not even quite up to 720p.

For SD cameras it was nearly always the case that the photosite count was the same as system resolution, so for NTSC pretty certain to be 480 vertically (576 for PAL variants). Not so sure about the horizontal as the SDX900 was 16:9/4:3 switchable, but I'd think the most likely was 960 for the 16:9 frame, hence 720 for 4:3 crop.
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