This picks up from a previous post about carrying heavy gear.
So how close, in terms of focal length, can I get? It’s a perennial problem especially when you balance weight of lenses against getting close enough for the shot without intruding on the animal’s world. I would suggest that a lot of amateur photographers use a maximum focal length of 300mm for two main reasons: cost and weight. I’ve previously said that big lenses have one major disadvantage: they can be mighty heavy. But there is the other factor that often governs what we use: price. Make no mistake big glass often costs big bucks. Even pre-owned. So lets assume that, for whatever reason, you use a 300mm. How do you get that distance shot that seems beyond the reach of your lens? Two answers I think ( assuming you don’t get disturbingly close to the subject). First off you use a crop sensor camera. This seems to give more reach than a full frame but in reality it’s an illusion: There are lots of forum threads about this issue and I quote just one from DPREVIEW, ‘A telephoto lens like a 200 may give the impression of a 320 on a crop, but it’s just that the edges of the image ( that would be seen in full frame) fall outside the smaller crop sensor giving the illusion that your reach has been extended.’ Sure, this is a controversial issue and will continue to be debated as long as crop and full frame sensors exist! That said there is a way that you can realistically extend the focal length of you lens without adding much weight and keeping price down. Back to the 300mm lens.
Let’s assume that you’re using a crop sensor camera with a 300mm lens attached. The apparent reach you get is calculated thus (I use Canon as an example): Canon DSLRs with APS-C sensors have a 1.6 crop factor therefore multiply the focal length of the lens by the crop factor (300 x 1.6) which give the ‘illusion’ of 480mm reach. What this means is that for a full frame sensor you’d need a 480mm lens to get the equivalent ‘reach’. Now I don’t want to get into things like pixel size and density and low-light performance, rather I’m trying to show how a shortish lens (300mm) can have it’s reach extended beyond that of the ‘illusory’ crop factor.
Extenders/Teleconverters: These are readily available and effectively and realistically extend the reach of you lens. Simply put they give you:
- A longer focal length
- A better focal length/weight ratio
- A better focal length/price ratio (with a few exceptions)
- Double the compositional options
- A way to get to focal lengths that aren’t achievable with a prime lens on its own
If you’re going to buy one of these brilliant bits of kit I would strongly advise you to buy one that matches the brand of both lens and camera. But bear in mind that you will lose one or more stops of light and your auto focus may run a little slower and be limited to fewer focus points. However, I think they can be worth their weight in gold to get that shot you might otherwise not consider. Canon offer 1.4xiii and 2xiii teleconverters and as an example using a 2xiii on a 300mm lens will give you 600mm reach on full frame, so you can easily work out what that looks like on 1.6 crop sensor!
One final point, a lot of photographers, when they first use teleconverters, complain that their images are not a sharp as those taken without the converter. This is simply down to the photographer…Arthur Morris (probably the premier bird photographer of the 20th century and one of the first Canon Explorers of Light) tells of a fellow world class bird photographer who experienced the same problem using teleconverters for the first time. Arthur’s advice was simply to keep practising with the extender, and within a couple of weeks he received a call from said photographer confirming that his images were now tack sharp. Moral?: Practice makes perfect.
If you’ve not tried a teleconverter then do so. You might just surprise yourself.
Do I use them? Of course I do. Do I use a crop sensor as well as full frame? Of course I do.
Stay safe my friends.
Meter the Light 