Full Frame v Crop - what's the difference?

We have already determined that the 35mm Digital Single Lens Reflex (DSLR) cameras have advantages in nature photography. If you’d like to recap click here.

These cameras are generally robust, offer good image quality, have a good battery life, have interchangeable lenses, are fast-focusing and rapid firing. They are commonly available, have good accessories, dedicated retailers and repair facilities. They are reasonably affordable and have a buoyant second-hand market.

DSLR’s offer a potent nature and wildlife photography package. Where they compromise on image quality versus the larger formats, they more than make up for it in terms of availability, cost and ease of use.

So what’s left to talk about?

Well, it turns out there are a few details to cover relating to the various types of 35mm DSLR.

A Short History

35mm is a standard that harks from the days of film, which defined the width of a negative. Modern 35mm cameras merely continue this tradition, which often allows us to use accessories and lenses from the distant past.

These days, instead of a 35mm negative we use a 35mm +/- sensor. Where the sensor is roughly 35 x 24mm the marketers got together and decided to call these cameras ‘Full Frame’.

Full Frame means essentially nothing except that the image sensor is roughly 35mm x 24mm in size.

Some DSLR’s are made with smaller sensors and these are generally termed ‘Crop Sensors’. In other words, their sensors are smaller than the 35mm standard. Many camera manufacturers produce crop DSLRs and they tend to conform to a sensor size of +/- 24mm x +/- 15mm.

There are more DSLR’s that have smaller sensors still, the Micro 4/3 standard (in which accessories can be shared across different manufacturers).

Crop v Full Frame Sensors for Nature Photography

So which of these is the best for wildlife and nature photography?

Well, as you will realise after a while, that depends…

The alternative sensor formats all have strengths and weaknesses of their own which will be useful or detrimental depending on the circumstances at the time of image capture.

Typically, Full Frame 35mm sensors offer the best quality image because the sensor is significantly larger than a Crop Sensor.

All other things being equal the battle would end right there. However, quite often (but not always) Crop Sensor cameras will also have a greater number of smaller pixels.

Here’s the rub; more densely packed, smaller pixel sensors usually offer more image resolution than larger pixel sensors. Of course, the trade-off is an inferior signal-to-noise ratio and additional noise when compared to Full Frame.

The advantage of having this densely packed, smaller sensor, is that it can offer a greater resolution in well-lit situations. Effectively, it allows us to render the same subject larger than is possible with Full Frame when photographed from the same distance.

The degree to which the image can be rendered larger all depends on the number of pixels packed into the sensor. To explain further, if one had the same pixel pitch or pixel density on a Full Frame sensor, then the subject would be rendered at exactly the same size in each body - the Full Frame would just appear to contain more background because the overall sensor size is bigger.

The trade-off is a loss in image quality in the Crop Sensor due to increased image noise. So the key with High-Density (usually Crop) Sensors is to always try to expose images with good, strong sources of light.

The advantage of this added pixel density comes when we are trying to photograph distant subjects that we cannot approach any closer. You see, if we could approach closer, the Full Frame would take back the advantage because it should have better image quality, provided we can fill the frame with the subject.

You can probably see why a high-density Crop Sensor is useful for wildlife photography. To achieve equivalent subject resolution in a Full Frame would require either, approaching the subject more closely, or utilising a longer, more powerful lens.

There is a new breed of High-Resolution Full Frame sensors, these 50-megapixel giants, include tightly packed pixels in a Full Frame sensor. They produce the same resolution as many high-end Crop Sensors, however, they still suffer a noise penalty when compared to cameras with a lower pixel density.

Change the Way you Shoot

From this discussion, we can determine that a lot of the differences between sensor types can be nullified by changing the way we use them.

For Full Frame, use longer lenses and approach more closely. If your photography is usually in murky dawn and dusk or overcast, then Full Frame will generally be an advantage.

For Crop Sensors, you do not need to approach as closely (although distant subjects will still be adversely affected by atmospheric effects). To reduce noise, use lenses with fast apertures (F2.8 - F4.0) and shoot in well lit conditions.