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General HD (720 / 1080) Acquisition
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Old March 1st, 2005, 08:23 AM   #76
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> The other thing about still cameras is they have
> a lot more flexibility in shutter speed -- you can, in
> some circumstances, reasonably take the camera to
> shutter speeds exceeding a second. You can't do
> that with moving images.

Exactly. Which is why consumer digicams can make do with a single small sensor. Video doesn't have the advantage of stopping time, so it's either 3 sensors or larger sensors to get enought light at 1/50 or 1/60 and above. Thus, if we want single sensors for video, they have to be big, especially for HD, otherwise we will end up with noise pictures and lousy low-light performance like the JVC HDV experiment.
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Old March 1st, 2005, 10:51 AM   #77
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I have been quiet for awhile, but I now would like to say a bit more.

First, it seems to me that the size of the imager would have NOTHING to do with sensivity. Imagine shooting some ISO 100 film with a particular lens at say f/4.5 at say 1/200 sec on a piece of 35mm film. We now take scissors and cut out a piece of the film to say a 16mm image. Is not the smaller image exactly the same exposure as the larger one? Certainly it is! it's PART of it! Will not ISO 100 film give an identically exposed image at f/4.5 and 1/200 sec (and under the same conditions) REGARDLESS of the focal length of the lens and the size of the film? It's just that you need a shorter focal length lens to give the same field of view with a smaller imager - film OR CCD. Aperture is always given in terms of the focal length (f/4.5 means that the actual aperture is focal length DIVIDED by 4.5). This all means that ISO 100 film will always give the same exposure results with a particular f-stop and shutter speed, regardless of the size of the piece of film you are using, or the focal length of the lens. The same would hold true for CCD imagers.

Let's go to the 3 CCD thing. It is certainly true that 3 imagers (RGB) are more sensitive than one (all else being equal). Though there is a little loss in the prism, 100% of the green light gets to the green imager, 100% of the blue light to the blue, and 100% of the red light to the red. On the other hand, a single imager filters the light at the surface of the imager. That means the minute green filter on top of a green pixel THROWS AWAY the red and blue light hitting it. The same is true for the other color filters. That's why the single CCD camera starts the sensitivity race behind the 3CCD.

Luminance is not equally divided among the three colors. Green has something over 60% of the luminance, blue only about 11%, with the rest going to red. This is why I thought the JVC approach with a white filter (throws away nothing), a green filter (throws away less than 40% OF THE LIGHT HITTING THAT FILTER), a yellow filter (throws away only about 11% OF THE LIGHT HITTING THAT FILTER). It has one other filter, but I forget what it is. And by NOT using a blue filter, which throws away 89% of the light hitting it, JVC was able to improve S/N considerably over the typical RGB filtering. At this point some high school algebra is used to get red, green, and blue. (R+G+B=Luminance)

And time marches on. Improvements continue to be made. And there is a balance between, cost, size, weight - and a ton of other factors. I find it interesting that no one has seen fit to make a 3CCD still camera (anyone know of one?).

Keep those cards and letters coming!
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Old March 1st, 2005, 02:04 PM   #78
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<<<-- Originally posted by David Kennett : First, it seems to me that the size of the imager would have NOTHING to do with sensivity. Imagine shooting some ISO 100 film with a particular lens at say f/4.5 at say 1/200 sec on a piece of 35mm film. We now take scissors and cut out a piece of the film to say a 16mm image. Is not the smaller image exactly the same exposure as the larger one? Certainly it is! it's PART of it! Will not ISO 100 film give an identically exposed image at f/4.5 and 1/200 sec (and under the same conditions) REGARDLESS of the focal length of the lens and the size of the film? -->>>

Right, but with a loss of resolution. If you're trying to duplicate the resolution of the original 35mm piece of film in the 16mm swath, you need to pack the "sensors" closer together. The tighter you pack them together -- whether you're talking about film or CCDs/CMOS, but especially the latter -- the less light every individual sensor can gather -- because the smaller it is, the less light it receives. (Or, more accurately, the less surface area it has to gather light.) So the only way to maintain the same light sensitivity at a smaller size is to not pack the sensors, i.e. lower the resolution.

As for why there aren't 3-CCD imagers in still cameras: one, I think the size/weight additon would be somewhat prohibitive. And the move is away from CCDs at all, and toward CMOS imaging, in the high end. The new 11+ megapixel cameras from Canon and Kodak are rather large, 35mm, which -- see above -- has its own benefits.
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Old March 1st, 2005, 03:13 PM   #79
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Colin,

I guess I'll have to think about that size of pixels thing. Fine grain films are less sensitive, so maybe you have something. In any case, sensors seem to be getting smaller AND more sensitive over time. I've never seen anything that says that BECAUSE an imager is larger, it is more sensitive either. So many other variables too!
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Old March 2nd, 2005, 12:35 AM   #80
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Area sensitivity + Color %

<<<-- Originally posted by David Kennett : First, it seems to me that the size of the imager would have NOTHING to do with sensivity. ......

Luminance is not equally divided among the three colors. -->>>

David,

1) more area = more photons. It is law of phisics

2) you are totally right and this thread is plenty of wrong math.
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Old March 2nd, 2005, 06:46 AM   #81
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> more area = more photons. It is law of phisics

This is true. It's the reason why the cameras usually used for broadcast video will usually have larger sensor than the ones we can buy for home or prosumer use.

It is true that advances in electronics, specifically in the low noise signal amplifiers and analog to digital converters have allowed more usable gain, thus smaller sensors appear to be more sensitive. But there is a limit to that, which is being approached noways with CCDs. The limit is noise. Even though your average Handycam can capture video at 7 lux, the quality of a broadcast camera at 7 lux will be like the quality of the Handycam in full daylight. At 7 lux most small single sensor cameras will exhibit high levels of noise, cameras with multiple sensors will show less noise and the cameras with multiple large sensor (i.e. 2/3") will show almost no noise at all.
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Old March 2nd, 2005, 10:44 PM   #82
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Didnt really think of that...

Yeah didnt ever think that but your right,

makes a lot of cents

ccd's harder to produce than silicon chips

smaller ccd's+cpu for gain correction cheaper then big cdd's

and offcourse big ccd's+cpu gain correction=$10,000+ equip
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Old March 3rd, 2005, 01:49 AM   #83
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Re: Didnt really think of that...

it is hard to integrate individual amplifiers in CCDs. It is done in CMOS and one of the uses is to increase a better dinamic range. Other use to reduce noise.

Everything is relative but I predict that prosumer cameras with 3CCD will go away and if they stay it's only for marketing reasons. All the pro photocamera don't have 3 CCD, results are asthonishing.

The Panavision movie camera uses only 1 CCD:

http://tinyurl.com/5glds

All this advantage of 3 CCD is really a bit funny.

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Old March 25th, 2005, 01:09 AM   #84
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add on... 1ccd NAB 2005

CAN SOMEONE MAKE IT???

a prosumer 1ccd monster with xlr and a high quality color prism

3ccd might be a marketing thing... but how do so many people get duped?

why can't a pana or sony or canon come with a 1ccd big bad cam

***NAB 2005 PRIDE AND JOY***

*THE CANON PANASONIC SONY HYBRID*

2.3" SONY cmos chip with
a high quality CANON glass prism for color

CANON 24x optical zoom + canon wide + tele adaptors

MATSUSHITA(HITACHI) 80gig 2.5" harddrive
+ wifi wireless G built in

SONY 5" lcd and lithium battery system for power

packed into a PANASONIC DVX type body with XLR inputs

with an isreali vegitarian leather KATA bag

$6999 M.S.R.P.
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Old March 25th, 2005, 01:28 AM   #85
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"why can't a pana or sony or canon come with a 1ccd big bad cam"

No one at this point in time will attempt to market from this angle. The masses are far to focused on three chip hype for the last 6 years. Marketing suicide. Thank god for JVC for showing that one chip is possible. It will take the perfect, and I mean PERFECT cam to ever make 1ccd a market dominating product. Even then it will be a massive up-hill battle.
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Old March 25th, 2005, 07:22 AM   #86
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Actually JVC demonstrated that --at least at a small size and price-- the single-sensor concept for video is not there yet. Sensitivity and noise were really bad with their first HDV-type camera.

The only way single-sensor will work well is with LARGE sensors, and those are still expensive, for similar reasons that large LCD panels are expensive. The larger area makes for a higher chance of dead pixels, so to get a good 35mm CCD or CMOS the manufacturer needs to make and discard a large number of units, hence the exponentially higher cost related to size.

Yes, many digicams have large sensors, but they are SLOW, most digicams cannot go past 10 fps. And even slow sensors are expensive at large sizes. The Canon digicam with the 35mm-sized chip is a good example. They are slow because the photo market needs much higher resolution than the video market, and it takes time to process a frame with all those pixels.

The sensors required for good, fast 1920x1080 video do exist, but are not yet made in quantities that bring their price down to prosumer levels. Pretty soon the offerings will probably exist but be expensive. Actually they already do but are far from the prosumer pricing we would all want. Time will fix that. But by the time it is fixed, we will all want something else, like chaotic optics or 120p or 4k or who knows what. It is just human nature, to want more and more.

So what does a professional do? Learns how to work with the available technology, pushes it to the limit and saves money for the upgrade, or rents on a project by project basis.
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Old April 7th, 2005, 07:27 PM   #87
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Things that make you go hmmm

I definately agree that 3CCD's aren't needed anymore. Most of my experience is with the Jyhd10, however recently I've been shooting with my XL2. I did a controlled shoot the other day, and I was blown away with the results from the JVC. I actually had to do color correction on the Canon in post. Granted I'm way more familiar with the JVC, the XL2 is a way better camera to use, but I wish (at times) that it shot as nice as the JVC. I'm sure as I get more and more familiar with XL2 my opinions might change. For a camera (JYHD10) that has taken alot of abuse, it never stops amazing me. I scrinch when I say this, but if you know how to use it and can put up with it's many inperfections it actually holds it's own with the DVX100a and Xl2. Once I get some hosting space I will post samples.
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Old May 1st, 2005, 12:59 PM   #88
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3 CCDs cameras are not needed right now or in the future. In the world of high-end High Definition, the Arriflex D-20 hybrid camera is a reality. It can record film or video. It only uses a single 6 megapixel CMOS sensor. It can shoot in 35mm, super 35 or High Definition.

So the fact that high end cameras are already using only ONE CHIP is a reality right now.

Not only this, but this advanced camera is also made future proof. Arriflex designed this camera to never get obsolete so fast. When a more advanced CMOS chip is available, let's say a 25 MP, with more resolution, better chrominance, more latitude, etc., you do not need to upgrade the camera. Just remove the old chip and insert the new one. Fantastico !!!

Read more here:

http://www.arri.com/prod/cam/d_20/d_20.htm




Quote:
Originally Posted by Robert Silvers
When Canon came out with the EOS-D30, I said "Whatever, a digital still camera will never look good because it has a single CCD -- or maybe it will look good when it has 20 million pixels which can be downsampled to look good."

Well, look where we are now with digital still cameras. The EOS 10D, 20D, etc -- look amazing with their single-CMOS. Would we not be happy if it captured motion at 60 frames per second? Would we complain the color is bad, or the noise is too high? No way! But 5 years ago I would not have thought this possible.

I predict we will soon see a single CCD camcorder, perhaps from Canon, which has a single CCD and produces EOS quality images. So if you hear of such an annoucenment and it is from Canon, don't be too quick to snob it like people did to the JVC.
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