A question people ask me after asking “Do you shoot 4 or 4s?” is how many pixels does your camera have? I laugh to myself and then try to explain how really it is not the pixels that matter but the size of them and the sensor. This is something which a lot of people become mistaken about when it comes to digital cameras.
When we see an advert for a camera they generally tell you three things; the zoom, the price and the number of pixels. The number of pixels is really the yard stick that most people measure a good camera and even a phone by. I have seen some phone reviews stating the number of pixels being a negative.
Big is good Bigger is better.
In the early days of photography megapixels were important. I am talking of a time when 3 mega pixels was an amazing breakthrough and DSLRs were not yet a contender for the casual or semi amateur photographer. At this time every mega pixel counted, but as resolutions went up everything was looked at differently.
The easiest way to think about sensors and megapixels is to think about film. The bigger the film the better quality the images are and were. Medium format (60x60mm in differing variations) was much better than 35mm (36x24mm) while large format (5”x4” or 10”x8”) were better than both. For camera manufacturers and consumers a number of pixels are clearer and less subtle than the size of the sensor and easier to communicate.
How big is the sensor in your camera?
Manufacturers give two different figures depending o the type of camera you have. If you have a compact camera they will measure the sensor a fraction of an inch for example 1/2.5 inches. This is a strange dimension. It only gives one side of two that we would normally expect a dimension to have. This dimension is like that of a TV, measuring the diagonal. It doesn’t give us an idea of the shape except it is a quadrilateral. What is even more unclear is that the dimension does not only include the sensor that records the image but the whole chip. This means that approximately a 1/2.5 inch sensor is in fact 6mmx4.5mm inside about half the size of your finger nail.
DSLR sensors have a very different way of measuring the sensor and one people would expect. Most entry level DSLRs have a sensor size about 24x16mm give or take a millimetre depending on the manufacturer. Although there are differences these are minor when compared to; the large difference between a DSLR and compact sensor and makes a much bigger difference with major implications in the quality of the image. Most DSLR sensors are grouped as APS-C sensor which is an old film size that was half the size of a 35mm. High end DSLRS have full frame sensors that measures the same size as a 35mm film.
With the DSLRs it is easy to see the difference because the width of the sensor size in millimetres and this is a size that you can visualize. Whereas compact camera dimensions are harder to visualise how big the sensor is.
The rule of thumb when it comes to camera sensors is; DSLR have big sensors, compacts have tiny and camera phones well.
There are also large format and medium format cameras that have much bigger sensors but in the case of this article I will ignore them.
Why Small Sensors?
There are many reasons for making a small sensor for a compact and that is to make cameras smaller and the lighter. Because the sensor is smaller it is easier to make more appealing lenses as they have to produce a smaller image. With a bigger sensor the price of a compact would rocket with the bigger lens and body needed. Cost is important to a compact. The camera needs to be obtainable for the average consumer who wants to primarily take pictures of their kids’ birthdays, holidays and night outs. This commercial decision to keep an eye on cost is the same as the decision to ram up the megapixels. People associate more pixels with a better camera.
As long as consumers long for more pixels, camera makers will keep adding them without increasing the sensor size which in turn has an impact on the picture quality. DSLR buyers on the other hand, demand higher image quality and are more astute when it comes to technical differences and issues between cameras. This difference in the approach of the buyer has created a significant split in the camera market, between the compact consumer and DSLR consumer.
There are no DSLRs with a compact size sensor but there are some so called “Prosumer” cameras that that have SLR like controls but with fixed lenses and small sensors.
DSLR Sensors are good?
If the sensors in DSLR cameras are so good why do they have the two types; full frame and APS-C? The old adage from film that big is good and bigger is better. In the past there were professional SLRS and amateur SLRS and the case is the same here. For the more amateur photographer you can buy the smaller but still bigger APS-C Sensor camera that will be more affordable than the full frame version.
Professionals want bigger sensors with the quality that comes along with them and will pay for it but also they want something compatible with their old lenses. As I wrote about in a previous post; as a photographer you invest in your lenses and although a lens may be old it is still good. Using these lenses that were design for a 35mm SLR will not have the same focal length on a camera with a APS-C sensor but will have same focal length on a full frame DSLR.
All pixels are equal but some are more equal than others
If you were to look at a compact camera and a DSLR and they both had 14 megapixels, although we know the sensors are not the same size we can also say that the pixels are not going to be the same size. The pixels on the DSLR will be bigger as they have more space to be spread across than on a smaller sensor.
The size of pixels matter because they change the quality of the image. The larger the pixel the larger the light gathering area which, in turn means the light signal is stronger over the same exposure. The pixel size also improves the signal noise ratio which means that larger pixels mean less noise and smother tones and details. Less noise means the ability to shoot in lower light conditions with a high ISO. A larger pixel also has a larger dynamic range in the tones of light and dark it can capture, this means that you won’t be clipping you image and have blown out skies because your camera can’t save the detail.
Arh my brain hurts
The two most important things to remember are that a small sensor means a lower quality image and a big sensor a better quality image. There are many charts that you can find that link the number of pixels to print size, but the truth is a larger sensor will always produce a superior quality and larger output size compared to a compact camera.
Does you brain hurt too? Do you have any questions or comments, please let me know using the comment box below.