It’s one of the most common questions asked and with air show season now here it’s been asked by a lot of people.
There isn’t of course one correct answer to this question. It depends on a number of factors and can only really be answered by the photographer him or herself but I’ll try to give some guidance on the subject.
Let’s start by looking at some of the more common lenses out there.
Canon 75-300mm f4-5.6 USM III / Sigma 70-300mm f/4-5.6 APO DG MACRO
I’m going to bundle these two together as there isn’t anything between these two (assuming a good example of the Sigma). It’s pretty much the starter lens for everyone offering a good range of focal lengths at a reasonable price. Build quality is not great with lots of plastic but understandable at the price. AF speed and sharpness is good for the price.
Canon 70-300mm f4-5.6 IS USM
Often forgotten about and skipped over by people upgrading from the 75-300 but this is a lens you shouldn’t ignore. One of a few non L lenses to have ultra-low dispersion glass and it is a noticeable improvement over the 75-300 especially at 300mm. The AF speed is still relatively slow compared to the more expensive items in the list and Canon used the increase on the price tag over the 75-300 on the glass rather than increasing the build quality of the lens body. A good lens to bridge the gap between the budget lenses and the L class lenses.
Canon 100-400 L IS
A good range of focal lengths means you rarely miss a shot. Very good colour reproduction. It has a decent level of sharpness up to 350mm but there is a noticeable fall off after that. Good AF speed but requires a sunny day to get the best out of it. Push / pull zoom method is disliked by some. There has been some problems with the tension ring and it’s important to keep the barrel clean to try to avoid those problems. Durable and well built. Dust issues overstated and are rarely a problem. A very popular lens but many people find themselves moving onto primes after a few years.
Canon 300 f/4 L IS
Sharper, faster to focus, lighter, cheaper and a stop quicker than the 100-400 L IS. Sounds good? It is but you lose the flexibility of the zoom and 300mm can feel short for air shows but is generally a good length for photographing outside air bases. Works with a 1.4x teleconverter but there is a noticeable loss in quality and AF speed also suffers.
Canon 400 f/5.6 L
Sharper and faster to focus than both the 300 f/4 and 100-400. About the same price as the 300 f/4 and only slightly heavier. Great air show lens but too long for many other places means it is a bit of a specialist lens.
Canon 70-200 f/4 L IS
A very sharp lens but too short to be your only telephoto lens. I find most aviation photography is between 250mm and 350mm for operational flying and 400mm + for air shows. Adding on a 1.4x TC helps but requires you to stop down to f/8 limiting its use to days with lots of sun.
Canon 70-200 f/2.8 L IS II
Canon’s sharpest lens? Quite possible! Again, as with the f/4 version of this lens it’s too short. Adding a 1.4x TC helps and only requires f/5.6 making it usable in most conditions but costing you a little sharpness (you can afford to lose some!) and AF speed. A dream second lens but I wouldn’t choose it as my only telephoto.
Sigma 120-300 f/2.8
About the same price as the 70-200 f/2.8 L IS II but about 1kg heavier! Sharp with good AF speed. Gives a good range of focal lengths and build quality is also good but behind what you get from Canon L lenses. Tends to be more popular with motorsport photographers than aviation photographers (due to the weight?) but offers a fairly unique focal length range at f/2.8. It’s important to find a good example.
Sigma 300 f/2.8
Very similar to the 120-300 f/2.8 in terms of weight cost and build quality. Slightly improved sharpness (comparable with the 400 f/5.6 L) and AF speed due to being a prime.
Canon 300 f/2.8 L IS
Arguably the ideal lens for aviation photography with very good AF speed, good colour reproduction and great contrast. Sharper than the Sigma f/2.8 lenses but not as sharp as the 70-200 range. A similar weight as the Sigma 300 f/2.8 but significantly larger in size (especially the lens hood). Works well with a teleconverter as the light path of the lens was designed with this in mind but still takes a hit in both AF speed and sharpness unless in near perfect light. At almost twice the price of the Sigma 300 f/2.8 it’s far from cheap.
Prime or Zoom?
First decide between a prime and a zoom. To do this you may have to go rent one for a day to make your mind up.
As a rough overview primes tend to be sharper and have faster AF speed than zooms but at the cost of not being as flexible. With a zoom you will almost always get the shot, although that may mean cropping into the image. With a prime you either have to zoom with your feet (if possible) or reframe the shot.
You will also find it easier to quickly acquire a subject by zooming out, locating the subject then zooming in. With a prime you are looking at a small field of view and you will be scanning about trying to find the subject or having to take the camera away from your face to see the subject then redirect the lens. When you’re tracking the subject though you no longer have the distraction of having to zoom in or out, an action that can introduce camera shake, and you can just get on with framing and shooting.
To help you decide, look at your images and the EXIF information. What focal lengths do you shoot the most? Try to find a lens that meets those lengths. Also look at the range of focal lengths. If you shoot a large range of focal lengths a prime isn’t likely to be suitable (assuming you aren’t going to purchase more than one lens) but if you shoot around a relatively small focal length then it could be an option if there is a prime that fits in the focal length.
Most people start out with a zoom as it is easier to get to grips with and are cheaper. Given enough time most photographers will end up with a prime if they can afford to.