Digital Sensor Sizes

Toby asked, ‘You mentioned APSC recently. Not that I care, but what is that?’

I told him that there are many different sensor sizes in different cameras. The sensors in cell phones are tiny, point and shoot camera sensors were a bit bigger, then there were the ‘crop’ sensor cameras that take interchangeable lenses such as Micro 4/3rds and APS-C, then full frame sensor cameras and even larger ones called medium format.

Sony cameras with interchangeable lenses come in APS-C and full frame format. A full frame sensor is about 1.6 times larger than an APS-C sensor, 2 times larger than a Micro 4/3rds, about 3 times larger than the sensor in your basic point and shoot camera and almost 6 times larger than a cell phone sensor.

Stand at the same distance from a subject and the larger the sensor (with the same lens magnification), the more of it will be in the frame. If you move closer with a larger sensor to frame the photo the same way as a smaller sensor, you will get a shallower depth of field. The blurring of the background is called bokeh and is affected by how many blades are used to form the aperture of the lens as well as the quality and how many glass elements are in the lens. Much like wine connoisseurs arguing about one vintage or another, bokeh quality can be the subject of many arguments.

There are many discussions about noise levels between sensor sizes but in general a bigger sensor will absorb more light than a smaller one for a similarly framed scene. More light means more signal, hence a higher signal to noise ratio and finally less apparent noise. This topic can get way more complicated and generate it’s share of arguments too but the takeaway is that the bigger the sensor the better your picture will look.

Keep in mind that the larger the sensor the larger the camera body and also the larger the lens to get that light to the sensor. This will also increase equipment costs.

With many systems (to include my Sonys) you can put an APS-C lens on a full frame camera and vice-versa but the full frame body will automatically crop to the APS-C lens area and the APS-C body won’t see the extra image coming through the full frame lens.

Some will claim that putting an APS-C lens on a full frame body is like getting an extra ‘zoom’ but in effect all that is happening is your photo is getting cropped in camera rather than later. This might ‘zoom’ the picture in the viewfinder to help you frame the photo and would help a sports photographer who doesn’t want to spend time post processing, but I tend to use the full frame and crop later if necessary.

I asked Toby if that answered his question but he was already asleep again.