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adric22 Aug 19, 2007 1:45 AM

We have done a lot of complaining on this forum about Aiptek and others using CMOS sensors. I have read many times in various technical articles that there is no real advantage in image quality for either sensor. Yet, in my experience if a camera uses CMOS then the picture tends to be inferior. I've done quite a bit of thinking on this, and here is what I've come up with.

I think the main reason cheap cameras have CMOS images is because they are easier to impliment. Typicallya CCD requires additional circuitry to conervert the analog data over to digital. Also CMOS imagers are power efficient. THis makes them ideal for cheap cameras.

But wait! I got to thinking about something the other day. Years ago when I worked at a computer store I would have customers turn their nose up at computers with AMD processors, even if it was a high-end machine. Often they'd pay more to get an Intel computer of less performance. Why? Because they had heard that AMD systems sucked. At the time, AMD chips tended to be cheaper than Intel. Eventually it occurred to me that 90% of the computers that were designed for AMD were also of cheap, unreliable design. So they were often experiencing more problems than computers with Intel processors, but not because of the CPU, rather due to the fact the entire machine was cheaper. So even once the chips were starting to come in high-end machines, the chips had a bad name. I think the case may be similar here with CMOS imagers.

To be completely honest, I was blown away with the image performance on my Aiptek IS-DV2 when I first got it (assuming it was outdoors) Because honestly, I couldn't tell the difference between it and CCD cameras. This really did change my opinion of CMOS imagers. I also got a security camera for my house around the same time which employs a 1/3" CMOS imager. It has very good low-light performance, of course it outputs video in analog NTSC, so the sensor is probably only 640x480.

So I've seen CMOS imagers that do well in low-light, and I've seen one that takes CCD quality images outside.

I've also used about 20 low-end (under $30) cheap-o cameras that use CMOS and their image quality is poor. Of course, they have cheap lenses, bad compression, and cheap everything.

Then I found this article today:

A semi-professional camera with a CMOS imager. I've looked at the sample pictures. They are nice. However, what really struck me is the shear size of the CMOS sensor. It is HUGE compared toa comprable CCD. So that seems to be the key. In order to have good light performance on a CMOS imager, you need it to be about 3 times bigger than a comparible CCD.

This explains why Aiptek cameras generally have poor light performance. There probably isn't enough room in a hybrid-style design for that large ofa CMOS imager. Plus they keep adding on more megapixels which hurts the light performance more.

I'm willing to bet that if Aiptek could find the biggest CMOS sensor they could fit inside of a hybrid and have it only 1.3 MP (I'm sure they wouldn't mind interpolating it to like 12 MP) I bet the video quality would be excellent.

MorePixels Aug 19, 2007 4:54 PM

ardic22, I owned the D30 and that was the camera that changed my opinion of cmos. I eventually traded it for the better D60, same size sensor, more pixels, but *less noise*!

The results I get and see with the d60 is more "film like" images!

I'ver also read recently that Kodak is making their own cmos, or more likely having some onemake it for them!

All of this prior knowledge of cmos really baffled me as to why the hybrids that use them are lacking so much.

I think like any thing, quality control is very important in production. I read some where that a large percentage of sensors that fall below specs are suppose to be discarded, but some manufacturers sell them to other companies!

Also, it took Canon 2 years to really fine tune their cmos technology and firmware! They have the deep pockets needed for such R&D! Ironically they decided to stop using cmos sensors! This is very like canon. They experiement with new technology from the consumer level, and if they like it move it up to pro levels. Just the opposite of most companies like Nikon who test out new technology on the pro end first, and if they like it, move it down to consumer level market.

Where I'm going with all this is simply that I doubt we will see any remarkable improvements on cmos technology from companies like Aiptek. Probably because of the expense it would require to R&D. And there really are not too many bigger companies playing much with it. Kodak plans on using the cmos sensor on lower end consumer products, so i don't think it will be a quantum leap from what we are seeing now.

I would love to know why Canon abandon the cmos project! Perhaps the cost of producing a superior cmos got too close to CCD? Any way this is a very interesting topic!

adric22 Aug 30, 2007 3:54 PM

I just found another professional camera using CMOS. My brother just bought this camera, costs $4,000 too..

So it looks like CMOS technology may eventually be replacing the CCD.

MorePixels Aug 30, 2007 6:12 PM

Oh I agree! All this looks like a rehash from the days Canon released the D30 digital camera! And even improved on it with the D60! I still have the D60!

All those charts and diagrams with close up comparisons were shown by canon.

I just don't get why canon abandon the project, they were doing soo good!

Tebay Aug 30, 2007 6:33 PM

That CMOS is only for low-end cameras is nothing but a myth. All of Canon DSLRs are using CMOS sensors and those cameras are sold for several hundreds to several thousands dollars.

Most of Sony AVCHD camcorder, sold above one thousand dollars, are using CMOS sensors too.

The technology gap between CCD and CMOS is closing quickly. On top of that, CMOS has the advantage of lower power, faster I/O time and cheaper to build.

rgvcam Aug 30, 2007 8:53 PM

The CMOS vs CCD argument also goes hand in hand with the shutter speed myth. ie that the disadvantage of a digital camera was that it had very poor shutter speed compared to a regular film camera.

The only reason Digital cameras initially had very poor shutter speeds was simply because digital cameras were very expensive compared to film cameras and so in order to help bring the cost down to reasonable levels, they used components with poorer processing performance. This was why until recently only the highend SLR devices had good shutter performance. One only has to see the fact that sports photographers have taken to digital photography en mass to see this isn't a problem. Now that consumer digital cameras are starting to enjoy the economics of the mainstream, this problem will soon become a thing of the past.

adric22 Aug 31, 2007 8:24 AM

I think CMOS sensors also may suffer from dead pixels more often than CCDs. This is probably because each pixel contains quite a lot of extra circuitry so more chance for it to go bad. I have a bad pixel or two on several of my low-end cameras. However, it may be that the manufacturers know about the bad pixels and purposefully sold lots of them to cheap camera makers at a reduced price. The cheap camera makers know that most people won't notice or care about the dead pixels.

This was an issue with laptop LCDs for a long time during the 1990's. That is why the screens were so expensive. They had to produce 10 to 20 TFT LCD screens in order to get one that had an acceptable number of bad pixels. Getting one with no bad pixels was quite a trick. I don't see that much anymore with newer LCDs and the cost is also lower. I guess they perfected the manufacturing techniques to make sure more screens were working perfectly per batch.

But to be honest.. when my brother called me yesterday and told me he'd bought that new high-def Sony camcorder and that he paid $4,000 for it, and then mentioned it had 3 CMOS sensors (just like having 3 CCDs)I was kind of surprised. I was mostly surprised because I figured if the unit costs that much they could afford to put CCDs in there, and I figured they'd have a hard time selling it to high-end users if they knew it was a CMOS just because of the bad reputation. But I guess Sony has decided that high-end CMOS chips can actually be better than CCD.

rgvcam Aug 31, 2007 10:04 AM

The new Sanyo Full Hidef camera just out is also using a CMOS sensor:

adric22 Aug 31, 2007 11:47 AM

You're right.. an interesting note is that the actual sensor is is the same size as the CCD in my CG6. However, it actually has fewer pixels. The CG6 is a 6 MP sensor, where this new one is only 4. Which is fine with me. Most of you know my opinion that 3 MP is pretty much all one ever needs for most anything. I think only marketing has been driving the push to higher megapixels. However, in the case of this camera, I think they're banking on people being impressed with the video resolution (1080i) rather than paying attention to the megapixels.

sgspirit Aug 31, 2007 1:55 PM

Earlier in this topic people were talking in terms of companies such as Aiptek developing sensors. I don't think Aiptek, Mustek, Digilife etc. develop sensors, or the processing units or much else in their cameras. Companies such as Zoran do.

The second-tier camera manufacturers basically package components made by others, and market the results. They may do some programming of the cameras' cpu's.

At the price point and performance of the hybrids we typically discuss here, I don't think sensor type is has value as a basis for choosing a model. Ccd's have serious problems themselves, such as the vertial bars extending from very bright subject matter.

My Digilife DDV-920 and 5120A have much better low light performance than my Samsung i6. Not necessarily the fault of the i6's sensor, though.

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