Global shuttering

[directore]

Here is a nice article from a German trade journal discussing a solution called "global shuttering" to the problem of geometrical distortions that is plaguing the current generation of CMOS imagers including the one in the HV20. http://www.dalsa.com/shared/content/PDFs/Photonik_CMOS_Shuttering_English.pdf The relevant message, I believe, is:

"multi-mega pixel devices operating at 60fps with true global shuttering and overall image quality that matches incumbent (but slower) CCD technology have been demonstrated."

So here is an appeal to the industry - see what you can do.
If Canadians can do it, why can't you in Korea or Japan?

The issue is important because while motion induced artifacts can be more or less successfully corrected in CCD cameras*, the rolling shutter problem responsible for intra-frame geometry distortions in the present day CMOS cameras has no solution at all.


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*post-acquisition and in software.

[mik]

that's the way to go but i don't think it'll become implemented in $1k camcorders in the next 2-3 years or even more

the v1 price range could get it much sooner

[Erik Bien]

I'm pretty sure the Dalsa Origin uses a mechanical shutter in addition to the electronic shutter to achieve this feat. That type of spinning disk shutter (used in motion-picture cameras) imposes huge penalties of size, weight and power requirements. (Sure, the Dalsa camera head looks sleek, but have you seen the recording mechanism? Personally, I don't want my next camcorder tethered to something the size of a dorm fridge!)

Directore, you're clearly not a CMOS kind of guy; for the last time, put the HV20 up on eBay and buy a Sony or a Panasonic (or a Dalsa or an Arri D-20) -- all of which, by the way, impose their own limitations.

[Ian-T]

Hey directore I have a question for you...can you name me a camera that you consider your ideal camera. Not a hypothetical cam but one out in the market right now that you would love to have. I ask because I have a feeling that no matter what your answer is...someone will be able to exploit its weaknesses. I really don't think that there is such a thing as a perfect camera. We all have are own personal favorites however and it's certainly clear that the HV20 (or anything with CMOS technology) is not one of yours. Whatever your purposes are for lambasting, critisizing, or just plain old venting about the HV20 in this forum, I highly doubt you're gonna convince all these happy users to trash theirs. Since everything you're saying about the HV20 (or CMOS' rolling shutter etc.) has been noted before I wonder what is your ultimate goal. We should be helping one another by exchanging ideas and finding ways to get around these issues, shoot better videos, better story-tellers etc.. there\s really no need to carry on like how you are. Just take Erik's advice and make yourself happy.:hv20-smilie77:

[directore]

BS, and please stop telling me what to do with my camcorders. 100g or less for a VGA+ version, light enough for you? And nothing mechanical other than your reactions to my posts.
http://www.photonfocus.com/html/eng/products/prodList.php?cat=CMOS+Cameras

Auf Deutsch:
http://www.photonfocus.com/html/de/products/prodList.php?cat=CMOS+Cameras

[Ian-T]

BS, and please stop telling me what to do with my camcorders. 100g or less for a VGA+ version, light enough for you? And nothing mechanical other than your reactions to my posts.
http://www.photonfocus.com/html/eng/products/prodList.php?cat=CMOS+Cameras

Auf Deutsch:
http://www.photonfocus.com/html/de/products/prodList.php?cat=CMOS+Cameras
Sigh......we've seen this before...know it exists....and now that dead horse is hamburger meat.....my purpose is not to offend you... so i'll leave my mechanical comments to myself...:hv20-smilie24:

[Rikki]

Q: If the Canon DSLRs can capture shots at up to 1/8000 panning for sports photography, why do those CMOS cams not have the issues that are discussed here?

[Ian-T]

Q: If the Canon DSLRs can capture shots at up to 1/8000 panning for sports photography, why do those CMOS cams not have the issues that are discussed here?Rikki, it's because we are dealing with two diferent things here. One is still photography (which CMOS technology has been using for a long time) and the other is moving pictures (where CMOS is just really getting more of a foothold). This technology is not as matured as CCD's. Someone can better explain it than I could but there are different variables going on between the two (video vs stills). Also, it's not that it can't be done (it is) but now the cost jumps up a great deal. Rolling shutter (from what i understand) is the cheapest method to implement in CMSO...that's why the price of the cam is such a steal for what it does.

[um3k]

DSLRs have a mechanical shutter. The image is read out after the shutter closes.

[angelo913]

The biggest problem with CMOS "Global" shutter is it uses space right on the imager's surface which reduces the pixel size and increase the gaps between the pixels which will cause other image issues unless the whole imager is much larger that means BIG bucks.

We can all talk about the engineering of CMOS Global shutters BUT the practicality and economics (low cost camcorders) is non-existent with todays technology. The cost effective Global shutter is still with CCD technology.

Here's an article on CCD vs. CMOS: Facts and Fiction (http://www.dalsa.com/shared/content/Photonics_Spectra_CCDvsCMOS_Litwiller.pdf).

...Angelo