Invariably, the first question one asks about a camera is 'How many
megapixels?' Most people think that they should go for a camera with the
most number of megapixels. But that can actually be a bad idea.
Manufacturers don't help by advertising megapixels over anything else.
We'd like to take some time out here to talk about why more megapixels
can be a bad thing.
Try fitting a hundred people in a space
meant for fifty. They may all fit, but everyone would be very
uncomfortable, won't they? Similarly, when too many pixels get packed
into a sensor the size of a fingernail, the pixels aren't able to
capture light optimally. Of course, when the light is aplenty and the
sensor sensitivity is low (ISO 400 or less), one might get great images.
But once we hit the 'low light' stage of the day and the sensitivity
needs to be bumped up in order to capture a photo, we end up with a 'hot
mess' of red and blue pixels.
The reason for this is that
the conventional sensor in point-and-shoot cameras is of a fixed size
(with an area of just a little over 1 cm) and there are only so many
megapixels one can pack into that area without compromising image
quality. The tradeoff in the megapixel war is between detail and
quality. At the lower end of the spectrum, you get great image quality
but not enough detail. As you crank up the megapixels, the level of
detail captured goes up, but the image quality goes down. The optimal
resolution range for a point-and-shoot sized sensor lies between 9 and
More megapixels mean better detail in
images, larger prints, and also gives you greater control over image
quality when you crop it. However, camera manufacturers realize that in
order to by-pass the limitation imposed by the current sensors, only one
of two things could solve the problem - either an increase in sensor
size (something that would drastically increase the cost of cameras) or
redesigning the sensor altogether in order to make it more efficient.
a larger sensor meant venturing into DSLR territory, manufacturers felt
it best to work on the current sensor design. To this end, Sony created
their first 'backside illuminated sensor'. A conventional sensor is
designed like the human eye, with the lens in front, followed by a wire
matrix and the photodiodes at the back. This design causes some of the
light hitting the sensor to reflect off the surface, allowing lesser
light to hit the photosite (light collecting pixels on the sensor). The
backside illuminated sensor handles this problem by placing the
photosite above the wiring matrix, eliminating the reflections caused by
the same and therefore, improving light transmission by almost 40%.
bump in performance now allows manufacturers to pack in up to 20
megapixels (so far) without compromising image quality not only in
normal lighting conditions (day light, mid-day) but also in conditions
where the light levels start to dwindle (sunset, or dimly lit rooms). So
when you're out to buy a new point-and-shoot, it would be a better idea
to invest in a camera with a backside illuminated sensor (denoted by
BSI or BSI-CMOS).
Don't judge a camera or specially, a sensor by just the number of megapixels. The sensor type/ quality are much more important.
Watch out for more articles in the Photography 101 series.