720, small cameras, and sensitivity

[infocus]

A paragraph from "High Definition" magazine got me wondering.

"It (720) is likely to become the format associated with small cameras and that isn't bad. The smaller cameras like FX1 and new Panasonic need small size CCDs to keep size and weight of lens low and overall package dimensions to a minimum. The smaller the CCD the smaller the pixels and so the less sensitive. As users of FX1 will tell you it is 2 stops slower than a PD150. Expecting a true 1920x1080 imager in these cameras in the near future is unrealistic unless the manufacturers can come up with a way of improving sensitivity."

Firstly, can anyone confirm or deny the statement comparing the FX1 to the PD150? The basic premise I find interesting, and it would help to define and distinguish market segments - something manufacturers like to do. On the other hand, manufacturers do seem to have nailed their colours to one mast or the other, so I can't see it happening.

[mooblie]

Surely the FX1 is native 1080i?

[Alan Roberts]

FX1 is native 960x1080 ccds. They use the industry-standard process of offsetting G from R abd B by a half-pixel to get the effective resolution up.

As far as I'm concerned, FX1 is about a stop less sensitive than PD170, but it's hard to measure accurately since we're comparing apples and pears.

The final goal is 1080p at 50 or 60 fps with no image repetition (i.e. smooth motion). But that's a few years away, so the battle is to decide which is the best way to get there, 720p to have smooth motion, or 1080 to have better resolution. Personally, I don't give a hoot which is used as long as it's not to the exclusion of the other, 720p's great for sport/news, 1080i's great for LE/news, 1080p preferred for serious drama (although I hate the film-look, even though I earn a decent living showing people how to get it).

[infocus]

Surely the FX1 is native 1080i?
Most certainly it is! The way I read the initial quote, the author is stating his belief that 1080 from 1/3" chips is a step too far (hence his negative comments about the FX1s sensitivity), and a better compromise for small chip cameras would be 720 - the JVC approach.

I posted it because I find it an interesting idea, not because I think it likely. Sony seem to be 1080 only as a matter of policy, as with the FX1, and his point is that that may not be for the best. Personally, I'm in two minds.

[Alan Roberts]

But Sony have just announced a 720 camera, that's a first. So they've come to terms with the "mixed economy" view that I've been pushing for a decade or more.

[StevenBagley]

But Sony have just announced a 720 camera, that's a first. So they've come to terms with the "mixed economy" view that I've been pushing for a decade or more.

Is that the one that is switchable between 720p, 1080i and 1080p and uses 1080p60 native CCDs?

Steven

[infocus]

But Sony have just announced a 720 camera, .....
I had forgotten that, but if it's output is switchable 720/1080, both originated with 1080 chips, that's not quite what the original author is getting at. His point is more that native 1080 chips are fine if they're 2/3", but at 1/3" a better resolution/sensitivity compromise may be achieved with native 720 chips. What gets output from the camera is another matter again.

Sort of acknowledging that a 1/3" camera won't have the resolution of a 2/3" (but will be smaller, lighter, etc) but making the best overall compromise, rather than going for "resolution is everything".

[StevenBagley]

His point is more that native 1080 chips are fine if they're 2/3", but at 1/3" a better resolution/sensitivity compromise may be achieved with native 720 chips. What gets output from the camera is another matter again.

But the 1/3" HD cameras that do 1080i (the Z1 and the A1) all have bigger pixels than a lot of the other consumer camcorders currently do. E.g. compare the Z1 to the PDX10 where the area of the pixels in the Z1 is still twice the size of that in the PDX10. The DVX100 has 1540x990 pixels (going by information gleaned on http://www.reel-stream.com/andromeda) on it's 1/3" sensor compared to 960x1080 on the Z1.

Also remember that the interlaced cameras will be line-pairing to read out interlace which reduces noise and increases sensitivity (remember the DVX100 is less sensitive in progressive mode than interlace) where as 720p camera won't be able to line pair.

And isn't being a stop less sensitive a good thing? It should reduce the depth-of-field without needing an ND filter on the front of the glass :)

Steven

[infocus]

And isn't being a stop less sensitive a good thing?
No! Because you may not be in control of the general illumination level, and there may not be enough! To control DOF it's very easy to cut down the amount the light entering the lens with an ND filter, but I've yet to see a filter that increases it. (I suppose you'd call such a thing "gain", but that comes at a penalty. ;) )

[Alan Roberts]

The pixel size issue is interesting. We're now seeing 1"/6 single ccd cameras at SD, so a 1"/3 single ccd HD camera should have the same sensitivity because the pixels are the same size. And so on...

[infocus]

The pixel size issue is interesting. We're now seeing 1"/6 single ccd cameras at SD, ..........
Indeed, but I seem to remember some reviews being less than glowing about the quality of these offerings. (Tom?) OK, they're small, and have their place, but just because something is possible is not the same as saying it's desirable, is it?

[Alan Roberts]

Never mentioned desirability, only sensitivity :)