Why CMOS?

[redsox_mark]

Whilst my own practical experience, as well as reviews of the best consumer camcorders, indicates the issues associated with CMOS may be somewhat "overblown"; it does seem to me though that the negative artifacts associated with CMOS (and it's use of rolling shutter) - that is Skew, Wobble, and Partial Exposure - are more of a concern than the Smear artifact you can get with CCDs and a global shutter.

(An overview of the issues here http://www.bhphotovideo.com/find/new...ge-Sensors.jsp )

So, why do Sony and Canon (and JVC) use them so widely? (especially Sony)? If CCD is "better", why not just use CCDs?

I don't think it is about cost; the odd thing is that the bottom of the range models use a CCD. And the new £7000 Sony EX3 uses CMOS. I know CMOS use less power, but it can't be just about that.

I'm just curious.

[glesgaguyav]

As an HV20 owner with CMOS, I must admit that I have never been aware of these issues, but that may just be me.
Could it be that CMOS is more reliable than CCD ? JVC had major problems recently with CCD's failing in certain camcorders both in the UK and US.

In the early days, camcorder users were advised to frequently "fire up" the camera just to keep the CCD usable
I guess users will always find faults with either method.

We all await perfection

[redsox_mark]

I use a CMOS camcorder and have not noticed the CMOS effects either.

I think the "partial exposure" (i.e. if lots of people are doing flash photography around you) I may have seen. But that doesn't happen often. The other effects which relate to panning I think you would have to be looking for it to notice it.

[mweb6161]

Your right Mark, as with upmarket Digital SLR's, a custom made CMOS chip will outperform a CCD chip in most areas,http://www.dalsa.com/markets/ccd_vs_cmos.asp
The current trend is that CCD is on the wane in upmarket machines, that is filtering through at lower price points too.

[redsox_mark]

I wasn't saying CMOS was better; actually I was accepting the advise of an expert that CCD is better, due to the issues with CMOS and rolling shutter. (Though I am still not convinced this is so large an issue that CMOS models like the Canon HV30 should be ignored).

My question is, if CCD is better, why use CMOS at all?

[chrishull3]

Originally Posted by redsox_mark

Whilst my own practical experience, as well as reviews of the best consumer camcorders, indicates the issues associated with CMOS may be somewhat "overblown"; it does seem to me though that the negative artifacts associated with CMOS (and it's use of rolling shutter) - that is Skew, Wobble, and Partial Exposure - are more of a concern than the Smear artifact you can get with CCDs and a global shutter.

(An overview of the issues here http://www.bhphotovideo.com/find/new...ge-Sensors.jsp )

So, why do Sony and Canon (and JVC) use them so widely? (especially Sony)? If CCD is "better", why not just use CCDs?

I don't think it is about cost; the odd thing is that the bottom of the range models use a CCD. And the new £7000 Sony EX3 uses CMOS. I know CMOS use less power, but it can't be just about that.

I'm just curious.

mark dont you listen to what i tell you cmos cams are rubbish MR D

seriously you are right why would sony use cmos on these cams if ccd is better http://www.sony.co.uk/biz/view/ShowC...=1193315635243

[Chris Muriel]

Probably because CMOS allows for more integration of digital functionality and doesn't require the use of carefully controlled CDS ( Correlated Double Sampling ).
Oldish article :
http://www.analog.com/library/analog...34-06/imaging/

or :
http://www.analog.com/library/analog...ignal_pro.html

and magazine article :
http://electronicdesign.com/Articles...992/13992.html

Chris Muriel, Manchester

[senu]

I know the physics of motion picture are different but for still photography, the very best DSLR cameras now sport CMOS ; Nikon D3 .and Canon 1DMk11s ect
Maybe there is a quiet advance on how to take advantage of CMOS technology and less of its drawbacks

I dont wish to be exposed to more opinion dished out as gospel truth but if Sony is putting these inferior things on their camcorders which cost as much as a small family car , they must know something we don't .. or are making a terrible mistake
Only time will tell if the adoption of CMOS is just a mistake in cost cutting.. or a wholesome trend is being set
I must say that my shotr exposure to the EX1 was extremely pleasurable .. not enough time to see any artifacts! but then it may be we mere mortals wont notice them even if they are served to us in a platter of ...50 " Full HD Plasma

[redsox_mark]

Originally Posted by Chris Muriel

Probably because CMOS allows for more integration of digital functionality and doesn't require the use of carefully controlled CDS ( Correlated Double Sampling ).
Oldish article :
http://www.analog.com/library/analog...34-06/imaging/

or :
http://www.analog.com/library/analog...ignal_pro.html

and magazine article :
http://electronicdesign.com/Articles...992/13992.html

Chris Muriel, Manchester

Thanks Chris; I understand some of that....
Still not sure why both are used, and there doesn't seem any logical correlation. All the entry level models seem to use a CCD. CMOS is popular with the better consumer models (e.g. HV30, SR12, etc). At the high end you have both CCD and CMOS.

[senu]

Mark it could be the concept that CCD is "tried and tested" and newer generation CMOS is by now just as good
It may just be a case of giving people a choice without the idea that one is now better than the other
The logic that "purists" would not touch anything other than a CCD but nonetheless CMOS has come of age may be the simple strategy

Im just guessing here but it does make you wonder that Sony is kitting out its high end camcorders with one or the other: the message is that they probably take the stance that they are now "interchangeable"
Panasonic do not have any AFAIK and Canon ( despite being a forerunner of CMOS in DSLRs (and not the Prosumer point and shoot which have CCD ) seem to be shy of using it on higher end kit
The question to ask is.. How many Z7 or EX1 owners are lamenting the fact that they are not CCD based?

[rhubarbe]

Originally Posted by Mr.D

I'm assuming that badly constructed first line is merely a cack handed attempt to unfairly paraphrase me rather than a malicious attempt to assign a false quotation to my user name. I'd be extremely embarrassed if someone mistakenly ascribed such incompetent usage of the English language to myself.

Right, here is something I do know about. "Myself" is only used where the verb is reflexive; as in "I shoot myself".

Here the verb being used is "ascribed" which ain't reflexive, no sir.

So, we have: "I'd be extremely embarrassed if someone mistakenly ascribed such incompetent usage of the English language to me."

[rhubarbe]

BTW, the last film we saw, something to do with Las Vegas was much better than we had anticipated. Well done!

[chrishull3]

Originally Posted by Mr.D

I'm assuming that badly constructed first line is merely a cack handed attempt to unfairly paraphrase me rather than a malicious attempt to assign a false quotation to my user name. I'd be extremely embarrassed if someone mistakenly ascribed such incompetent usage of the English language to myself.

This article was published in 2001.
The issues regarding rolling shutters on CMOS devices have not changed.

I investigated the RED One camera as a possibility for shooting effects elements for motion picture films, pyro, model work. The lack of a definitive response from RED on the available shooting speeds in 4k mode and the reported problems with the rolling shutter and moving imagery led me to reject it for the time being. The RED is regarded as being about the best behaved camera currently available with regard to CMOS rolling shutter artifacts. I know of at least one large production that is in the process of rejecting RED footage because of rolling shutter artifacts.

I assume the usage of CMOS devices in certain professional cameras is deemed acceptable because the higher capture rates (50p 60p) minimise the visibility of some of the rolling shutter artifacts and enable manufacturers to have simplified/cheaper production lines for the less component heavy circuits. However the high capture interval would render this material near useless for 24p work even if the rolling shutter artifacts were subsequently minimised: due to associated strobing if the frame rate is culled down. This was the point of the original thread that chrishull3 has dragged into this one.


http://www.dalsa.com/shared/content/..._Litwiller.pdf

you dont seem the kind of chap who likes friendly banter mr D so rather than be accused of any maliciousness i will not say more of your over the top reply.

[chrishull3]

Originally Posted by Mr.D

I'm fine with friendly banter.
I'm not fine with dragging your disgruntlement over from one thread into another and deliberately misquoting me in order to misrepresent my opinion.

Some of the newer cameras use a cmos with a rolling shutter effect rather than a CCD that captures a frame "instantly": I personally wouldn't touch one of these cmos cameras with a barge pole but not for any of the reasons touched on in this thread.[your words]

i must not understand you obviously,regarding dragging over to another thread sorry it must be due to the editing all the time.

[senu]

Guys take a chill pill. Life would be too boring if we all saw things in the same light

Mr D doesnt like CMOS.. and is entitled to that

Some of us dont care one way or another , if our eyes are happy. Interestingly, some of the folk who do like CMOS are not just lay folk but broadcast Pros.

Mark seems to be puzzled as to why inherently "flawed" technology is being adopted where cost isnt an issue ( surely with the cost of high end camcorders, saving money ( by using CMOS) and getting it wrong smacks of false economics) Sony must have faith in the technology

In a way it may not have been fair to bring the other thread up here but.. s**t happens

I guess it behoves on us as individuals to try and avoid dogma and not dig our heels in. Some are more able to do this than others ..

Disagreeing agreeably is not given to everybody.. that is life