If you want to take photos at the so-called “super telephoto” range, then you have a few options. They have relative costs and relative merits. Let’s go through the main ones.
Genuine super telephoto lens
I’m a Canon shooter, so I will refer to the Canon lenses – but the same applies to Nikon, Sony and others.
If you’re doing it by the Canon book, and you want a 500mm lens, then you are supposed to go out and buy a Canon 500mm or 600mm (or longer) lens. At the time of writing the 500mm and 600mm telephoto primes are £8,280 and £10,820 respectively.
That’s a lot of cash to throw at a lens. It might pay off for a professional sports photographer, but for an amateur like me, a specialist lens like this would only see occasional use.
There are third-party options, such as the Tamron 200-500mm and the Sigma 150-500mm. These are both priced at under £1000, but do not offer the same quality as the genuine Canon lenses. The quality would be fine for my uses, but a thousand pounds is still too much for me to spend.
As I said, I don’t have any of these lenses, so there isn’t a sample picture in this section.
On the face of it, mirror lenses seem like a cheap way of getting a very long focal length. For under £100 you can buy a 500mm mirror lens.
Even on the outside of the box we can get an indication of how crude these lenses are. They are fully manual-focus. There is no electronic communication with the camera body. The aperture is fixed, and is usually quite slow (e.g. f/8). They are usually manufactured by names you’ve never heard of before. The sample I tried was the 500mm mirror lens from Opteka.
I knew this before buying, and I was happy with the risks. I have a collection of old cameras so a manual, mechanical lens is nothing new to me. In the end I was extremely disappointed with the lens for two reasons. The sharpness was very poor, and the manual focus ring was extremely sensitive. It was near-impossible to get the moon in focus.
This is the best picture I managed with it. It’s blurry and there is a lot of chromatic aberration. And this was with the moon – imagine trying to take a photo of a bird in flight with this lens. Forget it.
I wrote a post on my blog entitled “Mirror lenses: worth it?“. You’ve already had a taste of my sentiment here, but there’s more detail in that post.
Preset lenses are a sort of halfway house between mirror lenses and proper telephoto lenses. They use glass lenses rather than mirrors, but are otherwise like the mirror lenses. They are fully manual, no electronic control and either a fixed aperture, or a choice or 2 apertures that can be flipped in and out of the optical path. If you’re lucky it might have a diaphragm.
Pretty much the same conditions apply to these as to the mirror lenses. They’re slow, hard to focus and have poor quality glass. Some people online have posted surprisingly good pictures, although I think these are the exception, rather than the rule. Opteka (among others) sell a 500mm preset lens.
I don’t own a preset lens, so there’s no sample picture in this section.
Last but not least, I’ll cover teleconverters. These are small adapters that fits between your lens and your camera body, and increase the focal length, either by 1.4× or 2×.
The advantage is that you can use your existing 300mm lens, or buy one. They are common, and not too expensive. In most cases, there is a small loss of sharpness but usually this loss is acceptable.
I already owned a Tamron 70-300mm zoom lens which came as a bundle with my DSLR, but can also be bought for around £100. Almost every lensmaker sells something that can reach 300mm. Adding a £100 teleconverter has given me a 600mm lens, with autofocus (in bright light), with proper lens glass and a variable aperture. It is a far superior solution to a preset or mirror lens.
Aside from some loss of sharpness, the other main snag is that you lose two stops of exposure from your lens. For example, my Tamron lens has a maximum aperture of f/5.6 at 300mm. With the teleconverter, it’s stopped down to f/11. This isn’t enough for the autofocus to work except in very bright sunlight. Bear this in mind. Fortunately, manual focus on the Tamron is nice and the ring has enough granularity to be able to focus accurately.
While not perfect, within minutes of attaching the teleconverter I took several photos like this.
So my advice to anyone wanting to move into longer focal lengths is to buy a teleconverter for your 300mm lens. If you don’t have a 300mm lens, buy one with a teleconverter. It’s much cheaper than a Canon L-series telephoto lens, and much, much better than messing around with a mirror or preset lens.