One frequent question that seems to get photographers a bit confused is whether an APS-C camera (eg a Canon EOS 80D) is automatically better than a full-frame camera (eg a Canon EOS 5D IV) for wildlife photography – especially for taking photos of birds.
Some people get terribly mixed up about ‘resolution’. Some times we talk about lenses on Canon APS-C cameras having an ‘effective focal length’ of 1.6 x the actual focal length, so a 24mm EF lens would have an ‘effective’ focal length of 24 x 1.6 = 38.4mm when used on an EF-S camera.
This means the EF-S 24mm f/2.8 STM pancake lens on an APS-C camera should take an almost identical photograph (in terms of field of view) to the EF 40mm f/2.8 STM pancake lens on a full-frame camera. But unless you’re shooting ostriches up close neither of these lenses are traditionally what you’d call a ‘birding’ lens.
Let’s assume our photographer wants to take photos of birds, but doesn’t want to get too close to them. Let’s also assume he has a reasonably long lens such as an EF 400mm f/5.6L USM. What will get a better picture of the bird at a distance?
Assuming all other things are equal (and they aren’t!) the picture that we want is the one which is the highest pixel resolution when the bird is cropped out to be as big as we want it to be on our final image. For the same lens this means in general that you’d crop down a full frame image to the APS-C equivalent and then measure the resolution you get. Now what’s the one constant thing we have here? The pixel pitch. It doesn’t matter whether your camera is full-frame or APS-C. If you’re taking photos of small things far away and are likely to be cropping your pictures, the pixel pitch is the most important factor to discuss. The smaller the pixel pitch, the more pixels your bird will have in it, and therefore assuming all other things are equal (and remember, they aren’t) the quality will be better.
It therefore makes sense to try and do an ‘APS-C equivalent’ resolution on full-frame cameras to document what the resolution of a 1.6 crop would be on that particular model.
So… let’s explain this all with a handy table of some important Canon EOS cameras. Current cameras at the top, some historical models below.
|Camera||Type||Resolution||Megapixels||Pixel Pitch||APS-C equivalent megapixels|
|EOS 1DX Mark II||FF||5472×3648||20||6.5µm||7.8|
|EOS 5D Mark IV||FF||6720×4480||28.1||5.7µm||11.8|
|EOS 7D Mark II||APS-C||5472×3648||20||4.1µm||20|
|EOS 5D Mark II||FF||5616×3744||21||6.4µm||8.2|
|EOS 5D Mark III||FF||5760×3840||22.1||6.2µm||8.6|
|EOS 300D (Digital Rebel)||APS-C||3072×2048||6.3||7.3µm||6.3|
|EOS 500D (T1i)||APS-C||4752×3168||15.1||4.7µm||15.1|
|EOS 600D (T3i)||APS-C||5184×3456||18||4.3µm||18|
|EOS 700D (T5i)||APS-C||5184×3456||18||4.3µm||18|
|EOS 750D/760D (T6i/T6s)||APS-C||6000×4000||24||3.7µm||24|
The pixel pitch is the key. If you are taking photos of things far away, and are likely to crop into your image, pixel pitch is the deciding factor. The smaller the pixel pitch the more pixels your little feathery friend will have in it. A full-frame with a respectable pixel pitch (which at the moment means the 5DS/5DSR only) is a good but expensive compromise if you want a camera for taking photos of everything.
Also. I hear you wonder. Why is the 5D Mark IV listed as 28.1 megapixels, not 30? Because regardless of what marketing nonsense Canon put out, the important factor is the maximum size of image that can be saved. And a 6720×4480 pixel image is a 28.1 megapixel image. I’ve tried to recalculate the actual megapixels of each camera above from the output size rather than Canon marketing docs – however as I don’t have every camera there may be some ‘overestimation’ on the actual pixel size of some of the cameras listed. If the raw file dimensions of a camera I’ve listed above don’t match what we have in the table please let me know.
But wait… Remember how I said, at least twice, that not all things are equal? Would a 2004 EOS 20D be a better option than an EOS 6D for taking photos of birds? No. Because of course there are many other factors to take into account, focus accuracy and speed being so important, image quality, and all the other features that you care about when choosing a camera.