Size does matter!


The retail trade would have us believe that increases in mega pixel numbers (mB) i.e. the number of pixels on the photographic chip, are directly proportional to getting better images from any new camera, whether video or stills.

This is in fact not completely true!!!

Another major attribute that affects picture quality is the actual physical size of that CCD chip (i.e. the actual size of each individual pixel), image quality is not just about the number of pixels.

My first Digital SLR camera was a Fuji Finepix S1 pro which proudly announced itself as having a 3.4 mega pixel. My mobile phone, a Nokia N95, boasts a 5 mega pixel camera. So I wandered into my garden this morning and took a picture with both.




Click to see full image

Even though the Nokia has 50% more pixels as the Fuji, the Fuji’s pixels are over 6 times bigger, spread over a chip area of 23.3 x 15.6 mm, where as the Nokia’s pixels are crammed onto a tiny chip just 4.8 x 3.6 mm.

Now I know that there are the factors of lens quality on each, but the fact remains that even though the pixel count of the Fuji is less, on picture quality the Fuji wins hands down. Each pixel has 6 times the available light to work with, therefore definition and contrast are better – especially in low light.

This is largely the reason why a digital SLR camera out perform its compact camera cousin, despite the pixel numbers being equivalent or even in some cases larger.

The same can be said of a professional video camera over a domestic or even semi professional camcorder.

So when the nice new camcorder you’re buying for your University/School boosts ‘HD’’ on the size, how much should you believe it?

I was recently tempted by an advert in my local Maplins Electronics store for an ‘HD’ camcorder for a mere £149. At that price I thought I had to try it!! After I got it home and shot a few scenes on it I transferred them to my computer for more critical analysis.

The resulting movies were quite disappointing and although the cheap lens obviously played its part, the tiny chip size simply let the pictures down. When you are trying to cram enough pixels onto a 1/3” chip to achieve HD status, you loose light sensitivity and image quality by making the pixels smaller.

You have to remember the chip in a HD video camera can be trying to create up to 150 frames of picture a second (Red, Green and Blue x 50), a stills camera has to reproduce just one frame. The more sensitive the chip and the faster it can work.

The BBC maintains that to record a ‘full’ HD picture, the bite rate (internal speed of the camera) must be above 50 megabits per second (mbs). Most domestic HD camcorders have bit rates as low as 5 mbs! Speed is another undeniable fact that contributes to better image quality.

So the bottom line is that for increased image quality of both video and still pictures then pixel numbers, though important, are far from the whole story. Overall chip size and the internal speed of the camera also have a huge effect on the actual quality. So when you see a piece of equipment labelled ‘HD’, don’t simply take it at face value, it maybe just good marketing!

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Many thanks for you patience.
Kind regards,
Mike - Media4ed.