For my first blog, I was intending to write a piece on digital camera modes but, after visiting a camera shop recently and eavesdropping on a salesman giving his pitch to a young girl buying a new (maybe her first?) camera, I felt compelled to write and promote this article as my first blog.

The young girl was tossing up between buying two cameras, namely a camera with a 20 megapixel one inch sensor (approximately 13x10mm in size) and a DSLR with the larger 16 megapixel APS-C sensor (approximately 23x16mm).  She was obviously relying on the salesman to give her the right advice so that she could make the best choice for herself.

However, the advice the salesman gave her astounded me.  His advice was that the camera with the one inch sensor was the right choice because it had “more megapixels” than the DSLR.  Hello, where did this guy come from?  How is it that he managed to get a job in a camera shop, as his answer clearly demonstrated that his knowledge of digital cameras was clearly lacking?

So let me bust this myth once and for all that the number of megapixels is the sole determinant of a camera’s functional capability, because it is simply not correct.  In fact, it is the SIZE OF THE SENSOR and, therefore, the SIZE OF THE PIXELS on that sensor that primarily determines the capabilities of a camera and the quality of its resultant image output.  In very simple language a camera with the larger sensor will invariably outperform a camera with a smaller sensor under most shooting conditions.  However, other factors also come into play such as the quality of the lens and the camera’s image processor.  To demonstrate my point, my wife has an old Kodak DX6490 hybrid camera that is equipped with a small 1/3 inch, 4 megapixel sensor hooked up to an excellent Schneider Kreuznach lens.  Despite its small sensor size, being only a 4 megapixel camera, each pixel on this camera is quite large which results in phenomenal image resolution and detail, sometime better than what I can achieve on my Nikon full frame camera.

In the girl’s case above, in order for the camera manufacturer to fit 20 megapixels onto the smaller one inch sensor the size of each megapixel has to be smaller than the size of each megapixel on the DSLR sensor which only has to accommodate 16 megapixels spread out over the much larger APS-C sensor.  It would also be possible for a manufacturer to fit more pixels onto the larger APS-C sensor if that was a design requirement, albeit the size of each pixel would then have to be smaller than the size of each pixel under the existing 16 megapixel arrangement.

Whilst it is true that, for an equivalent sensor size, more megapixels will result in higher resolution and more detailed images (particularly in good lighting conditions), the flip side is that larger pixels on a camera sensor offer many other photographic advantages that photographers often seek, the most prominent being enhanced low light performance, higher dynamic range and reduced signal “noise”.

Having said all this, at the end of the day, the appropriate mix of sensor size and megapixel count, will depend on how the photographer intends to use their images and to what degree of enlargement.    If the maximum printed image size is 8x12 inches or less, a viewer would be hard pressed to detect variations in image quality between a photograph taken by a one inch sensor camera and a similar photo taken by an APS-C sensor camera at an ISO setting of 800 or less. 

Oh, by the way, the young girl decided to delay her decision on the camera so when she left the shop I stopped her outside and gave her my view on the relevance of megapixel count and the higher importance of sensor size.