IMEC codevelops 4k/2k CMOS 12 bit sensor w/Panasonic for 2/3 inch
 

Looks set to launch in 2014, Panasonic joins the 4k party


Imec news-imec

Re: IMEC codevelops 4k/2k CMOS 12 bit sensor w/Panasonic for 2/3 inch
 

I read the article, but where does it say the chip will be a 2/3"?

Re: IMEC codevelops 4k/2k CMOS 12 bit sensor w/Panasonic for 2/3 inch
 

The pixel pitch is 2.5 microns, less than one quarter that of the BMCC and BMPCC.

Re: IMEC codevelops 4k/2k CMOS 12 bit sensor w/Panasonic for 2/3 inch
 

Really what is likely to be crucial is the implementation - whether they get used in a 3chip fashion, or as a single chip, with something like a Bayer filter.

Smaller photosites compromises sensitivity, adding Bayer filtration to a single chip compromises it even more (relative to the same basic chip used as a 3 chip design with beamsplitter).

If used as the foundation of a 3 chip design this could be very interesting, if used with a Bayer filter as single chip I'd say much less so.

Compared to an s35 chip with similar photosite count, the resolution, chroma aliasing, etc will be almost identical - but at an eighth the area the native sensitivity will be down by at least three stops!

The other issue comes down to something Alister brought up in another thread - http://www.dvinfo.net/forum/digital-...ml#post1808242 - diffraction limiting. That already causes severe limitations in 1/3" HD cameras, and 2/3" at 4K is likely to be comparable to 1/3" at 1080.

Re: IMEC codevelops 4k/2k CMOS 12 bit sensor w/Panasonic for 2/3 inch
 

At 4000 pixels and a pixel pitch of 2.5 microns, that's 10mm, which is basically a 2/3 inch sensor. 2/3 inch sensors are 9.587mm x 5.393mm

Re: IMEC codevelops 4k/2k CMOS 12 bit sensor w/Panasonic for 2/3 inch
 

Thanks. I have no idea what formula you used, math never being my strong suit.

So...4K, 2/3" 3-chip cameras? Perhaps a single chip camera, like the HPX600?
Go ahead, David, tear it a new one.

Re: IMEC codevelops 4k/2k CMOS 12 bit sensor w/Panasonic for 2/3 inch
 

I agree.

I think diffraction limiting is not affected by size of the photosites, it is the phenomenon of light bending as it passes around the edge of an object (iris). The amount of bending depends on the wavelength of light and the size of the opening. As the opening gets closer (i.e. smaller) relative to the size of the wavelength, the bending is more. It doesn't care how small or large the photosites are. So at 2/3 inch, diffraction limiting would be the same as for a regular 1080 panel of the same dimension.

Re: IMEC codevelops 4k/2k CMOS 12 bit sensor w/Panasonic for 2/3 inch
 

I *THINK* that whilst the first part of your argument is correct, (that the actual amount of diffraction is a function of the size of the iris) then the finer the photosite array, the less is the level of diffraction that can be got away with before it becomes objectionable.

That's why 1/3" chips were never seen to have any large diffraction limiting problem when they were SD, but did come HD. In each case, at a given aperture, there's the same amount, but whilst it may have visibly softened an HD image, it may have been still better than fundamental SD resolution.

Hence for 1/3", diffraction may only have become a problem stopped down below about f8-f11, with HD it's more like f4-f5.6.

Glen - you seem to find the physics inconvenient. I'm sorry, I don't write the laws.

But with everything else equal, a single chip camera can't perform as well as one with three of the same chip, but beamsplitter instead of Bayer filtration. It will be over a stop down in native sensitivity. Doesn't matter who makes it, what the chips are, that's fundamental to camera design.

Same with the diffraction argument above. Tom has raised a very sensible point and I hope I've answered it. I still think that for 4K, and a 2/3" sensor, then diffraction limiting will start to become an issue at similar f stops to we currently see with 1/3" and HD, typically f4-5.6.

If you think the theory of my argument is flawed, then please explain why you think it to be the case.

Re: IMEC codevelops 4k/2k CMOS 12 bit sensor w/Panasonic for 2/3 inch
 

Sorry, David, couldn't resist.

So, can we use the JVC HMQ10's performance as a barometer for a 2/3" chip 4K cam?
The HMQ10 has a single 8.3 million active pixel 1/2.3" CMOS chip. Smaller than a 2/3" chip, but I think it's the closest we have for a comparison. I understand the HMQ10 operates under a very tight F-stop range to get usable 4K (or quad 4K) video. Plus, I've heard it's not the best camera in low light conditions.

Re: IMEC codevelops 4k/2k CMOS 12 bit sensor w/Panasonic for 2/3 inch
 

That makes sense, I see that now. In other words, the light is being bent a finite amount, but for the same amount of deflection means 2 pixel error on a 4k panel that would be only a 1 pixel error on a 1080 panel.

Re: IMEC codevelops 4k/2k CMOS 12 bit sensor w/Panasonic for 2/3 inch
 

The HMQ10 chip is a bit less than half the area of 2/3", and if 8.3 million pixels that's about the same count - 3840x2160.

Hence a 2/3" 4K should be expected to perform something like a stop better.
Well, I've always understood the limit for 1/3" at HD to be about f4-f5.6 before noticeable softening, and theory gives that to be the figure for 4K with 2/3". Hence theory also then predicts about f2.8 for the HMQ10. Since max aperture is only going to be around f2, you can see why it may be said to have a limited usable f-stop range! So theory backs up what you say.

Go the other way, and s35 is about 8x the area of 2/3". So by the same logic, expect diffraction limiting there around the f11-f16 point for 4K.

Re: IMEC codevelops 4k/2k CMOS 12 bit sensor w/Panasonic for 2/3 inch
 

The one thing that caught my eye was native 60p right off the bat.

However... This will still come with the consequence of the rolling shutter. Remember the HPX300? Let's all hope that the incredibly high amounts of skew of that first gen CMOS cam does not carry over to this first gen sensor.

One thing we're guaranteed to not see coming out of anyone is affordable Global Shutter sensors anytime soon.

Re: IMEC codevelops 4k/2k CMOS 12 bit sensor w/Panasonic for 2/3 inch
 

I'd have been surprised if it had been any less. Current thinking is that 4K needs at least 50/60fps, otherwise the static resolution is being largely wasted.

As far as global shutter goes, then the F55 gets it's global shutter by virtue of a drop in sensitivity (compared to the F5). That may be reasonable on larger sensors with much higher native ISOs to play with, but far less feasible the smaller the sensor.

Re: IMEC codevelops 4k/2k CMOS 12 bit sensor w/Panasonic for 2/3 inch
 

And the current pricing on Global Shutter sensors is prohibitive. The big camera manufacturers will only take it seriously when it can be produced cheaply and in mass quantities, while still maintaining decent sensitivity. Who knows, this hurdle may not be overcome for the 1080 generation...

Re: IMEC codevelops 4k/2k CMOS 12 bit sensor w/Panasonic for 2/3 inch
 

Might be an interesting camera for those needing to shoot 4K run and gun, but sensitivity is likely to be an issue, you really want a small aperture for run and gun for a deep DoF but diffraction effects will force you to use larger apertures. My bet would be for a single chip bayer design. I don't know what the practicalities of creating a high enough quality prism are? Might be too expensive.

Re: IMEC codevelops 4k/2k CMOS 12 bit sensor w/Panasonic for 2/3 inch
 

Getting 4K with deep depth of field is going to be a problem, period, and the sensor size is irrelevant if you work it through. For a given resolution and angle of view, the ONLY factor that is relevant to dof is the physical size of the aperture (not the f stop, but actual dimensions).

A given size of aperture will be equivalent to (say) f4 for 2/3", f11 for s35. And in each case the dof will be the same. Start then to stop down in each case, and they will both start to diffraction limit the same no of stops down - when they are both the same physical size.
I commented on whether it will get utilised in a single or 3 chip form early on in this thread, and well, we'll have to wait and see.

If it is 3 chip, then this is a way this (2/3" 4K) could have a definite unequivocal advantage over a single chip 4K s35 sensor, at least in terms of low light performance, and the reasoning follows on from the above.

For a given size, weight etc of lens then we'll assume the physical size of the aperture is the same whether it's used for 2/3" or s35. As regards f stop, the s35 version must then be 3 stops lower - but the sensor will be 3 stops higher intrinsically, so performance should be the same, the factors cancel each other out.

The only way to improve the performance of either is to either increase the physical size of the lens - or go from single chip to 3 chip. Put another way, for a given size of lens, a 3 chip 2/3" camera will have at least a stop advantage over a single chip s35. (I'm assuming that 3 chip s35 is out of the question.)

Re: IMEC codevelops 4k/2k CMOS 12 bit sensor w/Panasonic for 2/3 inch
 

A prism is a non starter at s35 as the flange back would be too deep for DSLR or PL lenses. Any wide lenses would need to be retro-focal to accommodate the very deep flange back. Even at 2/3" with a prism to get a wide FoV the lens must have a retro-focal design (one of the reasons 2/3" zooms are expensive compared to DSLR zooms). This is one of the reasons why I think the Pana 4K will be single chip, the lens will be simpler and much cheaper, the lens design for this camera will be a challenge.

I'm not arguing against David's science on the lens size for sensor size sensor/aperture argument, but there is also the signal to noise ratio to be considered, which with smaller pixels will most likely be higher than with the large pixels on most s35 sensors. So the camera will be less sensitive for any given SNr. Even if the camera is a 3 chip prism design, that alone only brings around a 1 stop advantage (prisms are not loss less they normally include absorption filters for passband trimming).
The reality is that right now you can easily get f1.8 primes and f2.8 DSLR zooms that are neither large or bulky for s35. To get the same on a 2/3" sensor your looking at f0.6 and f1.0 lenses and I have yet to see a decent f1.0 zoom, so in practice s35 will remain the better performer in low light. My guess would be f1.8 as is typical of most normal 2/3" B4 lenses. So you won't get as much light on to the sensor and the sensor will have a higher noise floor, so overall I think s35 will still remain a much better performer in low light.

Re: IMEC codevelops 4k/2k CMOS 12 bit sensor w/Panasonic for 2/3 inch
 

And there's the HPX600 with a single 2/3" chip design. Interesting.
I wonder....

Re: IMEC codevelops 4k/2k CMOS 12 bit sensor w/Panasonic for 2/3 inch
 

Yes, as a rule of thumb, for the same sensor size, a 3 chip design will have an advantage of about a stop compared to an equivalent single chip design.
The lenses you describe are likely to either be prime or short zooms, which may be just what one market sector (let's call it the "digital cinema" market) wants and needs. I agree with what you say above, so yes, here s35 is best suited for the reasons you say.

BUT let's think about another market sector, of which live sport etc may be one example. The type of work traditionally where 2/3" cameras have been seen to be best. Here the expectation is that long range zooms are the norm, and cost/size/weight dictate the max aperture - to say nothing of cost. For a given size of lens, it may be f1.8 when designed for 2/3", but 3 stops down when designed for s35. Comes to the same thing, same performance, as the s35 chip is likely to have an ISO 3 stops higher - it's not true to say long range zooms are prohibitive for s35.

THEORETICALLY, it may be possible to design a long range s35 zoom with max aperture of f1.8 - but the cost is likely to be prohibitive, to say nothing of size and weight!

The implications are that if both sensors (s35 and 2/3") are single chip, the only way to get better low light performance is to make a lens with a bigger front element - hence bigger, heavier, more expensive etc. OR to go 3 chip - which will give a stop improvement for the same lens. And since (as Alister says) that is not practical for s35, then if implemented for 2/3" would immediately give such a camera a benefit relative to s35 for such lenses.

And that's why whether this sensor gets implemented in single or 3 chip form is so important. If in single form, it gives no benefit over 4k s35 sensors for use with long range zooms - and lacks the versatility of being able to be used with fast primes or short zooms. But if in 3 chip form it immediately gives the camera an edge if the primary usage is seen as with long range zoom lenses. For comparable lens sizes, it will give it a stop sensitivity advantage compared to s35, AND will give true 4:4;4 full 4k resolution, better than a 4k bayer can manage.