Deciding Between Crop and Full Frame Sensor Cameras
If you decide to enter the DSLR arena then you will need to determine if you want a full frame sensor, which means the sensor is the same size as a 35mm film, or if you want an APS crop sensor, which is about half the size of 35mm film. Take note that Nikon calls their full frame cameras FX and their crop sensor cameras DX. From this point on I will refer to all full frame cameras as full frame (FF) and crop sensor cameras as APS.

One way to evaluate the FF and APS decision is to consider that there are only two disadvantages to FF, increased cost and increased lens vignetting at wide apertures (dark corners). You unfortunately can’t do much about the cost, so you are either able and willing to spend the extra cash or you are not. If you can spend the extra cash on the more expensive FF bodies and quality lenses then you will get better results by going the FF route. Keep in mind that in addition to the increased costs, the FF body and lenses will also be larger and heavier compared to the smaller APS crop sensors cameras and reduced image circule lenses. Although, some consider the greater size and weight to be an advantage as it helps reduce camera vibration and allows for easier access to controls.

As far as the second FF disadvantage, vignetting, it is simply the trade off for having shallower depth-of-field (DOF) and increased subject isolation. With top end professional glass you can shoot wide open and get very shallow DOF at f/1.2 or stop down to f/4 where vignetting is reduced and you get DOF that is similar to what an APS crop sensor camera will produce at maximum wide open apertures. So vignetting isn’t really a problem with FF bodies but simply one of the trade offs of having access to extremely shallow DOF for subject isolation.

Before continuing any further we need to discuss depth-of-field (DOF) and focal lengths as related to FF and APS bodies. The APS sensor is smaller than the FF senor, causing the APS to only "see" the inner portion of the image projected by the lens, which results in reduced DOF effect and increased apparent focal length. The exposure settings for FF and APS camera are identical at the same aperture setting but the DOF is much deeper with APS and shallower with FF at any given aperture setting. When you get into photography shallow DOF has a 3D look that makes the subject stand out from the softened background. So a FF camera offers shallower DOF but it also offer deeper DOF because at the same APS and FF sensor resolution diffraction has a reduced impact on a FF sensor at any given aperture. This means that an image taken with a FF camera at f/16 will show less diffraction blur than an image taken with a APS at f/16, thus providing the FF camera with greater DOF range, both at the shallow and deep ends of the spectrum.

The another major distinction between a FF and APS camera comes from a change in the view angle or apparent focal length. An APS sensors see 1.6x (1.5x Nikon) the lens’s stated focal length, which means that a standard full frame 50mm lens acts more like a 80mm portrait lens on APS camera bodies. So a wide angle 30 or 35mm lens is needed to have the standard 50mm view on a crop sensor. Crop sensor cameras see only the inner portion of what a lens projects on a full frame sensor. This cropping appears to increase focal length, however, this is not a true change in focal length as there is no additional telephoto compression. For that effect you still need to spend the big bucks on super telephoto lenses. Those who shoot sports or birds often prefer crop sensor cameras for the apparent focal length increase and the extra reach that it provides. In addition, crop sensor cameras use only the sharpest center portion of the lens. The main downside of this apparent focal length shift comes when you need to shoot at wider angles. Placing a very expensive and high quality ultra wide angle lens like Canon’s 17 TS-E or Nikon’s 14-24 gives you an unimpressive standard view on a crop sensor camera. In general, if you are interested in wide angle (architecture and landscapes) then a full frame sensor is by far the best way to go.

That being said, one cannot deny that the APS option provides far better bang for your buck than FF. Just keep in mind that the creative ceiling is reached pretty quickly with APS as compared to FF as a result of reduce DOF range. If the APS set up provides all the image quality and lens flexibility that you need then you’ve done very well and will save a ton of money, weight and space by selecting APS over FF. Otherwise, you will eventually hit a dead end with the APS format and then you will have to take a financial hit when selling your old APS gear to help fund the upgrade. In my experience, if you shoot subjects beyond sports/birding/wildlife, you shot RAW and finally if you have adequate funds then FF is the superior format.

Quick Recommendations:
  • Crop Sensor: Nikon D7000 w/ 16-85 VR and 50 f/1.8
  • Full Frame Sensor: Canon 5D2 w/ 24-105 IS and 85 f/1.8
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