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Showing 1-13 of 13 posts in this discussion
Initial post: 16 Feb 2013, 16:49:50 GMT
ChrisJ says:
I am on the lookout for a new "always got it with me" camera. Olympus (I have their DSLR E-510 which I am very pleased with) or Canon, most probably.
They both seem to be moving from CCD 16mp sensors to CMOS 12mp sensors.
Is this change a big step forward in image quality? A sideways step? Or a backwards step and i need to wait for the CMOS 16mp sensors?

Olympus VH-410, or VR-340 or SH-21.
Canon IXUS 140, or IXUS 230, or IXUS 125.

In reply to an earlier post on 16 Feb 2013, 18:35:57 GMT
The only way anyoen here would know that is reading the reviews, I guess. Have you read up on the subject?

Posted on 16 Feb 2013, 21:34:49 GMT
ChrisJ says:
Trying to... But its not easy to make sense of all the options! Is it the sensor difference, or a different lens, or a different ISO setting, or a different JPEG sharpening that is making the difference??
And, when the reviews are often by different people, are they seeing the same things? And if by the same person, are they biased one way or another by previous good or bad cameras from the same manufacturer!

So i was wondering if there was an easy "that is why they are changing" explanation, and i can factor it into the decision making process.

Or, is it like buying a car: even a "poor" car these days is very good compared to all models from 10 years ago.

Posted on 17 Feb 2013, 11:53:41 GMT
Mark Kemmitt says:
CMOS-family sensors often produce better quality images, of course the important bit here is 'often'. Your final line has it ... and as most quality brand cameras can produce more than 'acceptable' images these days the decision should be based upon what you want to use it for and how much you're willing to pay. If you want to be taking it everywhere then I'd suggest a combination of build quality, size/weight and battery life would be the most important bits.

In reply to an earlier post on 17 Feb 2013, 13:29:07 GMT
It seems that the CCD vs CMOS argument is more of an issue with video.
Here is a good article from the Economist which is about still camera use.
"THERE is something very satisfying about using a rangefinder camera. It is all about having total manual control over focusing the image your way, rather than relying on the camera to do the focusing for you. True, digital single-lens reflex (D-SLR) cameras can be switched to give a modicum of manual control, while letting the user see a pretty good visualisation of the image that is about to be recorded. But your correspondent always feels the manual experience with a D-SLR is artificial-as if the device is providing a mere semblance of control filtered through simulation circuitry.

His love affair with rangefinder cameras started with a second-hand Leica IIIf bought 35 years ago (see "Me no Leica any more", October 17th 2008). At the time, the ultimate of all compact rangefinders, the Leica IIIg, was way beyond his means. But ever since, he has cherished the thought of owning the latest Leica one day. That nowadays would be the all-digital M9-P. Though still nostalgic about film, your correspondent has long since accepted that sensor technology has advanced so much over the decades that digital cameras do the job every bit as well as (and often a good deal better than) film cameras (see "Point, shoot, discard", December 31st 2011).

Unlike a D-SLR, a rangefinder has no mirror, nor motors to do the focusing. The rear element of the lens can therefore be much closer to the plane where the image is actually captured. As a result, both the camera body and its interchangeable lenses are far more compact. Also, with the light travelling such a short distance from the lens to the sensor, there is little room for it to diffuse. That makes the image much sharper around the edges and in the corners-a problem D-SLRs have never quite licked.

Your correspondent could wax on about the rangefinder's virtues, but he has digressed enough. What he really wanted to focus on was the choice of sensor. While drooling over a Leica M9-P in a camera shop the other day, he was surprised to learn that the full-frame sensor in this $8,000 (for the body alone) rangefinder camera still uses CCD (charge-coupled device) technology.

Though CCD sensors continue to be employed in scientific, medical and industrial equipment, as well as some high-end video cameras, he imagined that CMOS (complementary metal-oxide semiconductor) sensors had finally become good enough to replace CCDs in point-and-shoot cameras and mobile phones, as well as pricier models bought by keen amateurs and even professionals. Leica clearly thinks otherwise.

Before trying to guess why, a word or two about the differences between the two imaging technologies. Both came to prominence in the early 1970s. Both use metal-oxide semiconductors with addressable picture elements (pixels) deposited on their surfaces. And both accumulate electric charges in their pixels proportional to the intensity of the light falling upon them.

There the similarities end. In a CCD, each pixel transfers its charge sequentially to a component on the chip that converts the charge to a voltage. The signal is then transmitted off the chip for processing. In a CMOS sensor, by contrast, the charge-to-voltage conversion is done within the pixels themselves. Not having to queue to get the charges converted sequentially into voltage signals, a CMOS sensor can have lots of channels for getting the data off the chip. This difference in read-out speed has been one of the CMOS sensor's crucial advantages.

Another has been the way a CMOS chip actually functions. A pair of transistors, operating in a complementary manner, draw power only while switching between their on and off states; for the rest of the time, they effectively use none. The net result is that CMOS chips consume a hundredth the amount of juice their CCD equivalents demand. In cameras, that translates into smaller, lighter batteries with longer lives.

Within the sensor itself, low power consumption means less heat. In turn, that allows the pixels' transistors to be packed closer together. The ability to cram ever more transistors onto a chip is what made CMOS the chosen technology for microprocessors and memory devices with billions of transistors on them. With such micro-miniaturisation, the traces (ie, "wires") become shorter and thus incur less inductance, capacitance and propagation delay. All of which adds further to their speed as image sensors.

Another advantage CMOS sensors have over CCD devices is price, though it is less than most think. CMOS sensors are made using essentially the same fabrication processes as computer logic and memory chips, albeit with equipment a generation or two older and more specialised. Even so, decades of development have squeezed most of the surplus cost out of CMOS fabrication, while delivering huge economies of scale-much of which has spilled over to sensor manufacturing.

Above all, though, the CMOS sensor has the killer feature of being effectively a "system on a chip". As such, more of the digital processing that would normally be done off the device-such as analogue-to-digital conversion, noise reduction and auto-focusing-can now be integrated into the sensor itself. That speeds up operations, allows features to be added, and reduces the unit cost still further. With CMOS sensors being able to capture image data so rapidly, and perform more of the processing grunt work themselves, even pocket-sized cameras no longer just take snapshots. Some pack 20X zoom features, take 3D pictures, simulate shallow depths-of-field, and shoot surprisingly good 1080p high-definition video.

The one area where CMOS sensors have lagged is in low-light conditions. At issue has been the way the sensor's leads for collecting the pixel data run across the front of the sensor, blocking some of the light falling on it. Sony, a big supplier of sensors to phone-makers like Apple as well as the camera industry itself, solved this problem several years ago by embedding the read-out circuitry on the back of the sensor instead of depositing it on the front. These bright "backside-illuminated" CMOS sensors have now become widespread.

All this innovation, and more, had convinced your correspondent that the days of the CCD sensor were drawing to a close-or, indeed, had already gone. Today, the noise levels within both CCD and CMOS sensors is minuscule and much the same. So much so that Canon has now just about completed the transition from CCD to CMOS across its entire range of cameras that it embarked on a decade ago. The rest of the industry has followed suit.

So, why does Leica remain a holdout? Mostly, one suspects, because of the way digital shutters work, and the artifacts they create in the process. A CCD sensor uses what is called a "global shutter", which exposes the entire image simultaneously. By contrast, a CMOS sensor uses a "rolling shutter" which exposes the image from top to bottom, one pixel at a time, as it "rolls" through the picture frame-in much the same way a television set scans its screen. In either technology, no mechanical shutter actually covers, and then briefly uncovers, the sensor. Depending on the speed set by the photographer, the electronic shutter simply switches the sensor on and then turns it off after the set fraction of a second has elapsed.

Much has been written about the "smear" problem that affects global shutters. This tends to happen when the image includes a particularly bright source of light, such as car headlights or the sun. It is caused by the way the pixel charges are read from top to bottom in a CCD sensor. While a global shutter captures the whole of the image at once, it reads it out one column at a time, by shifting the charge in each pixel down its column to a read-out channel at the bottom. Pixels that have been temporary "blinded" (ie, overloaded) by a bright light will pass on their excess charge to others below them as the charges are shifted down the column. The effect is a vertical trail of white descending from the source of the bright light.

While cameras with rolling shutters do not suffer from smear, they have problems of their own. For instance, if the camera moves-whether the photographer is panning it deliberately, or because of involuntary shaking-the image can become skewed or wobbily, as different portions of the frame are exposed at different times while the motion is taking place. In a skewed image, vertical objects all appear to be leaning one way. A wobbled image looks as though it is made of jelly. Rolling shutters also suffer from partial-exposure effects when a sudden flash of light occurs-such as a bolt of lightning, a firework burst, or another photographer's flash equipment. The result is a black band across the image, caused by one part being over-exposed and the rest being normal.

Such effects can be more pernicious than smear. As a result, a widely held belief persists among serious photographers that cameras with CCD sensors are a better choice. And if the camera-maker's customers want primarily to do just one thing-take great still pictures under a variety of lighting conditions-there is little need for all those other fancy features that are now incorporated into CMOS sensors.

At least for the time being, then, Leica seems wedded to its trusty CCD design. But for how long? CMOS sensors with global shutters instead of rolling ones are on the horizon. At present, they have trouble capturing high-definition video. But no-one should ever underestimate an industry with such a track record of innovation."


Posted on 17 Feb 2013, 20:09:02 GMT
ChrisJ says:
Great find, MANY thanks, Dr G.
CMOS it should be, then. But not if the rest of the camera isn't as good!

At the moment, i am leaning towards the new Olympus XZ-10. But i will have to tell the wife it actually cost the same as the VH-10!

Posted on 17 Feb 2013, 21:14:22 GMT
Zelazowa says:
Extraordinary... Seriously where is photography headed? Myriad complexities between the photo taker and the photo and the Doc's post should be entered in the Guinness Book of Records for the longest ever Amazon Forum post!
Chris: the Olympus XZ-10 looks like a really nice camera but I bet you'd be more than happy with the images produced from any camera on your shortlist.

In reply to an earlier post on 17 Feb 2013, 21:21:05 GMT
Hi Z,
It was bit long but quite interesting I thought.

In reply to an earlier post on 17 Feb 2013, 22:15:27 GMT
You may find this interesting:

They are a bit expensive mind you.

Posted on 18 Feb 2013, 06:08:10 GMT
Last edited by the author on 18 Feb 2013, 06:08:27 GMT
ChrisJ says:
Just read that review, thanks again. Decided that for that sort of money i could get a really good lens for the D-SLR! But then, i wouldn't have the camera in my pocket all the time, so its back to square 1 again...
This time square 2 seems to have the Canon IXUS 125 on it.

Sometimes i think i like looking almost as much as shooting with the camera!

In reply to an earlier post on 18 Feb 2013, 08:00:05 GMT
Well if the Oly XZ10 has a similar performance to the XZ2 then maybe you are on to something. However, there must be some compromises if it is much cheaper?

Posted on 19 Feb 2013, 12:17:54 GMT
T.J.Byford says:
Hi, Dr. A.

An interesting explanation by the Economist writer about the technical differences between a CCD and CMOS sensor, and it is easy to see why the move to the latter is advantageous for many reasons. And I would suggest the main one is to provide video. Why else do dslrs now shoot video, and thus demand the use of CMOS?

But what wasn't explained was which has the better image quality? Has the CMOS genuinely caught up with the imaging capabilities of a CCD? I remember reading several years ago that CMOS was reserved for consumer cameras and that Canon, for one, didn't use them in their dslr's as the CMOS was inferior to the CCD in terms of image quality. The question doesn't really arise now as the CMOS has trumped the CCD in digital cameras, and the CCD is unlikely to be developed further. Even that most traditional of camera makers, Leica, has opted for CMOS in its latest M so it can shoot video.

Mentioning Leica, the correspondent got it wrong when he stated that the IIIg was the ultimate compact rangefinder. The IIIg was introduced in 1957 and was effectively a sop to Leica screw aficionados as its design was already 3 years out of date upon the introduction of the far superior M3 in 1954. It may be the ultimate III series, but not the ultimate compact rangefinder.

Posted on 19 Feb 2013, 12:59:27 GMT
Last edited by the author on 19 Feb 2013, 13:01:49 GMT
ChrisJ says:
Or, if there is little difference between CMOS and CCD, should I be more concerned with the processor? E.g Digic 4 or 5 from Canon and TruePic III or VI from Olympus?

Its hard enough keeping up with "is Windows 8 much better than Windows XP", let alone the different processors from different camera makers.

Latest thoughts: as i spend a lot of time sailing, may be a waterproof TG-2 or -830 is the right thing to get (following on the idea of "must have the camera with you to be able to take a photo").
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