Tuesday, August 26, 2008

Canon Fires Another Shot: The 50D

As was widely rumoured - and apparently leaked by Canon themselves in China last week - we now have the formal announcement of the next in the x0D series of cameras to pore over, the 50D.

I won't go through the specs in any detail as others have already dissected these in minute detail elsewhere. However, I did read with interest the new advances being touted for the sensor technology debuting here for the first time.

At the end of the day, what really matters most is image quality. Everything else is largely window dressing at this point, at least until someone gives me the only new feature I really want which is a viewfinder graphic showing available depth of field at the chosen aperture setting for the lens currently being used. (It's just maths after all, all the parameters are freely available at least to some degree of accuracy.)

The interesting thing here is that Canon appears, at least on paper, to have managed to achieve the conflicting goals of increasing pixel density (15 mp on a 1.6x APS-C chip) whilst also improving sensitivity. If this brings with it a concomitant improvement in low-ISO noise performance, as well as delivering the extra headroom they list (ISO 12,800 anyone?) then this will indeed be a major step forwards, signalling a real step forward for the company.

In addition to the pure mega-pixel count, another thing that caught my attention was the statement that the sensor features gap-less microlenses. This could by itself significantly improve image quality, especially with older pre-digital lenses, by providing a light-gathering surface that acts more like film.

Light coming in through the lens, despite being focussed onto the image plane, is still hitting the surface from many different directions, especially towards the edge of the image circle. That's not really a problem for film because it's far less sensitive to the direction of incident light than digital, being as how it presents a continuous surface after all. Up until now, digital sensors have been pits, separated by some - increasingly smaller - substrate, into which light had to penetrate to register a signal. In order to avoid the sides of this pit casting a shadow, sensors have a microlens over then to help direct incident light downwards. However, there were still gaps between each individual site driven, in large part, by separation between the microlenses rather than what the substrate minimally needed to isolate individual photodiodes. This is a problem Canon appear to have solved as explanatory diagrams show each lens set right against the next, maximising the available density of photosites, potentially increasing the light-gathering abilities of each lens and now providing much more of a continuous surface to the incoming image.

Proof-of-the-pudding and all that will be in the first images from a production camera, something we might hope to see at Photokina in September. However, I was also interested to note that Canon have included a feature on here to deal with vignetting which might lead you to conclude that the resolution of this sensor is now revealing the shortcomings of lenses in the same way that the 5D started to do when going full-frame. (With the APS-C format, lenses designed for full frame should be outstanding as only the centre of the image is covering the sensor. It's generally the edges where things get trickiest.)

Tempted? Kind of, but really things are moving so fast in the camera world right now I reckon it's worth waiting to see not only what else Photokina brings but also how quickly both the new sensor technology and the faster Digic processors tear through the rest of Canon's line up.

Can't wait to see what the next salvo brings!

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