CHOOSING YOUR SENSOR

Ok, so – no matter what you read online you simply can't fault the science. Firstly, ignore the swathes of people that say that Full Frame sensors are essential for achieving professional quality results. Bear in mind that full frame (35mm) is a pretty arbitrary number to begin with. Remember Medium and Large format cameras far exceeded the size of the 35mm area. These used to be considered the 'norm' for achieving professional quality results. Obviously, the needs of the professional have changed over the years, but the desire for quality results has remained.

As a rule, the larger the surface area, the more light is recorded, and the higher the image quality. However, unlike in the age of film, with digital sensors there came an additional variable to consider: sensor quality.

QUALITY VS QUANTITY

There have been huge advances in recent years in sensor technology and they are, obviously, ongoing. The comparative age of any digital camera will normally dictate how well the sensor preforms for its size. While this is not always true, it remains a good yardstick of what to expect.

The four main elements that dictate how well your sensor preforms can broadly be defined as:

  1. Light Sensitivity – ISO is the (not direct) equivalent rating to ASA from the film era and measures how sensitive to light the surface of the sensor is. Lower rated sensors (50/100/200 ISO) will always produce less noise, while shooting at a higher ISO will allow you to take images in lower light at the cost of clarity.
  2. Pixel Size- How large each physical photosite is.  A photosite can also be called a pixel in loose terms. It is the name for a single light receptor on a sensor. A larger surface area will help increase photon capacity and heat management efficiency, both important.
  3. Dynamic Range – This can be loosely described as the sensor's ability to accurately record the full colour and tonal ranges presented to it, from bright white highlights of clouds, to details in textured black surfaces. This is one particular area that has had huge technological increases in recent years.
  4. Pixel Count– This describes how many physical photosites there are on any given sensor area. These equate directly to individual pixels that comprise any digital image. Two sensors can have differing surface areas, and yet have the same number of photosites (Megapixel count). Obviously, the larger the sensor, the more information it can process. This normally results in higher image quality.

 

Crop Factor

When using a camera lens that is compatible for full frame use on a smaller sensor, the resulting image is a 'crop' of what the lens is capable of producing. The same amount of light is travelling through the lens, but as the sensor is smaller, only the middle area gets recorded. This, in effect, zooms in by an amount directly proportional to the size of the sensor. By using smaller sensors, you can really stretch the focal length of any lens, and increase your reach. Adversely, the smaller the sensor you use the less capable of truly wide-angle photography you become as the 'crop' will only allow you to record the middle section of the frame. The most common example of this is is the 1.4x crop of an APS-C sized sensor compared to full frame.

 

Conclusions

Imagine your sensor in terms of surface area for a moment. The larger the sensor, the more expensive they are to engineer and produce. This has been a constant factor since their inception, and while the particulars and costs may vary a little, it remains true to this day. This equates to larger systems being more expensive; in some cases hugely so. Larger physical sensors require larger bodies to house them and larger, heavier lenses to cover them. Simply packing such a system becomes somewhat of a endurance test. On the reverse side of this argument, smaller sensors are less flexible and are less useful for wide-angle photography as they suffer a (varying) crop factor, but are far more manageable and less cumbersome.

Now imagine your sensor's ideal resolution. Personally, I would prefer a lower pixel count, and a better dynamic range and low-light capability in a camera. Some modern camera manufacturers have released comparatively low resolution full frame sensors specifically for this purpose: to optimise image quality. Thinking the word 'megapixel' directly relates to how powerful a camera is to attach an inflated importance to its meaning. From a more cynical standpoint, this view holds its roots in the marketing apparatus of the larger camera companies. After all, the "megapixel race" over the years has fuelled sales, but it is the refinement and optimisation of each resolution sensor that is creating lasting improvements in the marketplace. As we get better at cramming more into smaller sensors, the megapixel count will become more important. Until then, it is generally true that you either choose resolution or quality as a preference. You must imagine what you are going to use your system for and then make a decision accordingly.

While I have owned comparatively high resolution systems before, I really only found it useful when the image needed cropping (especially useful in wildlife situations). Also worth mentioning is the comparatively higher storage and processing time of higher resolution images. They require more numerous/higher capacity SD cards,more battery power while shooting, and more disk space when backed-up.

A while back I realised that I would go for a higher quality image, at a lower resolution any day, but as I say, the choice is yours. It depends completely what you want to do with the images. Also bear in mind that your needs/wants may change over time as you get more and more 'into' the craft.