Cameras and sensor sizes

I bought a 5D Mark II recently. While I love this camera (not just for its sentimental value), there are times when I wish I had something a little less bulkier to lug around. The image quality of a full frame sensor cannot be beat. I love the bokeh a FF sensor produces because of increased sensor size and shallower depth of field. Its the primary reason why I have such an expensive camera. It’s image quality is second to none. Well, we have medium format cameras but lets keep this discussion to the more “commonly” used formats.

In this article I wanted to talk about sensor sizes available today and how they affect image quality, bokeh etc. In the days of film we had 35mm sensors. Focal length was simple. 50mm meant 50mm (50mm is considered the nearest focal length to normal human vision). Then we went digital and we started having different sensor sizes for different types of cameras. The different categories (based on sensor sizes) are –

  1. Crop Cameras also known as APS-C (Crop factor 1.6x). Canon follows this and Nikon calls it their “DX” range.
  2. Micro 4/3rd format (Crop factor of 2x)
  3. Full frame (No crop factor. Same as 35mm). Nikon calls it their “FX” range
  4. Canon’s 1DX series like the 1DMarkIII (Crop factor 1.3x)
  5. Newer entrants like Nikon V1, J1 etc (Crop factor 2.7x)

So what do all these crop factors and sensor sizes mean? It means that a focal length will give a different field of view for each of these sensor sizes. 50mm on a Full Frame format camera such as the 5D Mark II or the Nikon D700 is roughly equivalent to 35mm on a crop sensor camera such as the Canon 7D or the Nikon D7000. Here is the same example with some calculations to make it easier

 

50mm, the magic focal length (multiply by crop factors)

Full Frame Camera = 50mm (50mm X 1 = 50mm)

Crop (APS-C / DX) = 35mm (35mm X 1.6 = 50mm)

Micro 4/3 = 25mm (25mm X 2 = 50mm)

and so on…

So how does all this numerical funk affect the end user? Should you be worrying about the sensor size? Before answering this, read the following information about the relation between sensor size and image quality –

 

Sensor Size is directly proportional to Image Quality

Although there are other factors involved, to keep things simple lets just go with the above statement. The reason behind this is straight. A larger sensor obviously means more light absorption. This in turn means better resolution and more information capture. If I have a larger bucket it is bound to hold more water. Another factor that inadvertently affects image noise in megapixels (resolution). If two sensors of the same size are rated at different megapixel values, the sensor with more megapixels will generate more noise. Advances in technology such as gapless microlenses defy this rule but it still is largely true. This rule is the reason why you should never opt for a higher resolution if you do not plan on using it.

 

More megapixels do not mean better pictures

Only go for higher megapixels if you want to heavily crop your image or if you want to print poster size prints. I can shoot better pictures with my old 6 megapixel Pentax K110D DSLR than most people with 15 megapixel digicams. 

Here is where the myth of megapixels becomes clear. It is a common notion that the higher the MP value of a camera, the better the “resolution” of the camera. The true resolution or resolving power of a camera is largely dependent not the lens that is used, not on how many pixels are crammed onto the sensor. The MP value of a camera is largely a marketing gimmick and is sadly still prevalent even today.

 

How to decide between Crop / Full Frame etc?

So just how does one decide what type of DSLR / Camera is suited for their need? There are many factors – money, type of photos, effect desired, end usage etc. From a financial point, Full Frame cameras are most expensive (as they are more expensive to manufacture). Full Frame cameras are best suited for portraits and landscape type of photography where depth of field and image quality are the deciding factors. APS-C or crop cameras are more suited for sports, birds etc. because of their 1.6 crop factor. A 250mm lens on a crop body will give an equivalent focal length of 400mm! The larger the focal length, the more expensive it is to manufacture a lens. This crop factor is very handy for sports, wildlife etc.

 

Portability

According to me, portability is one of the factors that influence the type of camera a person uses. What good is a $2000 camera which clicks images of the highest quality if it sits at home collecting dust? I know a lot of people who get onto the DSLR bandwagon as prices have dropped recently but do not end up making much use of their cameras.The number one excuse is that the DSLR is too bulky to carry around. Another excuse is its too complicated. By the time I have my settings ready, I’ve lost the image. Technological advances are begining to solve this problem though and we have the Micro 4/3rd format. The main idea behind the technology was getting the size of the camera down by (i) Getting rid of the mirror assembly (this is why they’re also called mirrorless cameras) and (ii) using a slightly smaller sensor than an APS-C DSLR. While the quality may not be as good as a regular DSLR, it is a whole lot better than most digicams which have tiny sensors.

 

If you’ve read this far, I hope this article gave you an idea about what sensor sizes mean and how they affect the ultimate images. All these technical details mean nothing if you aren’t out there shooting that image!

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About synapse
Programming, motorcycles and photography. Want to do more, but only have time for so much!

6 Responses to Cameras and sensor sizes

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