As some of you might have read from my Facebook page, I recently carried out some changes to my camera bag. Apart from changes to my lenses lineup*, a major change was the acquisition of a full-frame Canon DSLR, the Canon EOS 5D Mark III. This camera has now become my go-to camera of choice, replacing the Canon EOS 70D (APS-C) camera I used previously. Why? Simple really, you could call it the ‘full-frame advantage’, and that’s the subject of today’s post.
First off – let’s clarify terminology. Full-frame DSLR cameras are all those cameras that have sensors that are equivalent in size (dimensions) to 35mm film: that is, approximately 36mm by 24mm. On the other hand, APS-C sized sensors are smaller in size, with the full-frame sensor being typically 1.5 to 1.6 times larger than the APS-C sensor. This is called the ‘crop factor’, and in simple terms it refers to the ratio between the full-frame sensor’s dimensions when compared to the APS-C sensor. Therefore, a Canon APS-C sensor with a 1.6 Crop Factor would be 1.6 times smaller than its full-frame brother. In fact, APS-C sensors on a Canon are approximately 23mm x 15mm, whilst those on Nikon models are slightly larger, given the smaller Crop Factor of 1.5. Do note that, nowadays, you can also find full-frame digital cameras that are mirrorless (such as the Sony A7R II), so this post is not exclusive to DSLR cameras but to all cameras featuring a full-frame sensor.
“OK, it’s a bigger sensor – so what…”, you might say. Here’s what: size does matter (please excuse any innuendo there). In particular, it provides a couple of advantages to your photography, as follows.
Please note, I will spare you the technical detail and focus on simple terminology, as is my style. For more detailed (read scientific) explanations, I will post a couple of links at the end which you could follow later.
1. Image Quality
The full-frame advantage, here, is improved image quality, particularly increased sharpness, better colour reproduction and lower noise. This all ties down to the size of the pixels, which are generally larger due to the bigger surface area of the sensor itself.
To explain this in simple terms, imagine the sensor as being an array of buckets all lined up next to each other to cover the entire area of the sensor. Assume you have to cover both an APS-C and a full-frame sensor with exactly 200 buckets each. What you’ll soon realise is that you can use bigger buckets on the full-frame sensor due to the physically larger sensor size. Or, put the other way round, the buckets on the APS-C sensor would have to be smaller than those on the full-frame sensor, as otherwise they wouldn’t fit. Replace “buckets” with “pixels” and you would have cracked the first advantage of full-frame.
Bigger pixels on full-frame sensors, just like bigger buckets, capture more image information from the light rays falling on it. This translates into improved sharpness, better colour accuracy and lower noise. Ergo, better image quality.
Note: The above argument applies for two sensors with the same amount of pixels, for instance 20 Megapixels (MP). If one had to compare a full-frame sensor of 12 MP with a crop-sensor of 18 MP, one might find that the advantages mentioned might not be across the board. For instance, the image might appear sharper on the 18 MP crop sensor, but it could also be noisier at the same ISO setting when compared to the full-frame image.
2. Focal Lengths: WYSIWYG
When it comes to focal lengths, the WYSIWYG rule applies with full-frame sensors (What You See Is What You Get). Let’s assume you are using a 50mm prime lens on both a full-frame and a crop-frame camera. Whilst the lens will output the same “image circle” on both sensors, only the full-frame sensor is big enough to translate that image circle into an image with an EFFECTIVE focal length (EFL) of 50mm. The smaller sensor would not be large enough to capture all the image circle output by the lens, and would thus result in an image composed only of the central part of the image circle. This translates into an image that seems to be a result of ‘zooming in’ on the original 50mm image. In fact, lenses on a crop-sensor camera produce images with a different EFL than that stated on the lens, for instance, a 50mm prime on an APS-C sensor would result in an image with an EFL of 75 – 80mm (depending on crop-factor). This translates into more simplicity for full-frame cameras, whereas with crop-sensor cameras you need to compute the EFL for each lens you wish to acquire to fully determine its usefulness.
This also links to a third advantage: Depth of Field.
3. Depth of Field
Consider the two photos below.
I shot the photo on the left using my 5D Mark III (Full-Frame) using a 24-105 lens set at approximately 80mm and f/4.0. The image on the right was shot using my 70D (APS-C) using a 50mm lens also set at f/4.0. Although the images are composed in such a way to look as identical as possible, one can immediately notice the more substantial blurring on the 5D image, coming from a shallower depth of field. (Notice, for instance, how the heart shapes on the furthermost pot are barely recognisable in the 5D image, whilst clear enough to be made out on the 70D photo).
The reason behind this is tied to the principle of effective focal lengths explored in (2) above. Basically, on the crop-body (70D), the 50mm was providing me with an angle of view similar to an effective focal length of 80mm, however the depth of field it provided me was that of a 50mm lens. Given the same aperture, (f/4.0 in this case), depth of field will become shallower as you increase focal length. Therefore, a shallower depth of field would be available to you if you shoot at 80mm f/4.0 than if you shoot using a 50mm at f/4.0, (regardless of sensor size).
As a result of this, full-frame sensors offer you shallower depth of field (hence better blurring of background) over crop-sensor bodies when comparing like-with-like image situations (e.g. shooting mug shots with a blurry background). Although remember, the extent of background blurring is NOT the result of sensor size exclusively; other factors are also at play (e.g. aperture, physical distance to subject, focal length, lens quality).
So there you have it: three key advantages of full-frame cameras over crop-sensor bodies. These advantages give full-frame shooters an edge in several aspects, but it’s not all rosy on this side of the camp! There are always two-sides to a coin and that second side will be the subject of my next blog.
*Recently I sold my Canon EOS 600D, its kit lens the EF-S 18-55 IS II; as well as the EF-S 10-18 STM and the EF 50 f/1.4. These were replaced by the EF 24-105L f/4, the EF 17-40L f/4 and the EF 50 F/1.8 STM.