I have a Canon EF 70-300mm 1:4-5.6 IS USM lens. Will all 300mm zoom/telephoto lenses give the same magnification of the subject as mine does or, to get more magnification do I need to get a zoom or prime lens with a focal length longer than 300mm? I ask because in most of the places I photograph wading birds they are often 100+ yards away in lagoons or marshes and my 70-300mm lens doesn't really magnify them enough for a decent photo.

Please understand I am a total beginner and still learning jargon and technical terms so would appreciate if you can bear this in mind when answering

Secondary question, could someone tell me what the various elements of the lens description mean (1:4-5.6 IS USM)

  • 3
    Birds are hard because they tend to be small and far away. At least the wading ones are usually still and out in the open, as opposed to the ones bouncing about in trees. You don't say what camera body you have. Some of the ones that Canon makes have an APS-C size sensor, which increases the effective focal length by a factor 1.6. For birds and wildlife I have the camera everyone here loves to hate, the Nikon P900. The lens zooms out to 357mm, not much more than you have, but the tiny sensor makes it effectively 2000mm. That comes at a price in lens quality, but for pixels on target Aug 14, 2021 at 23:41
  • 1
    it can't be beat. The newer P950 is supposed to have a much brighter viewfinder. Mine is effectively a point-and-shoot. It has all the controls you would want, but none quite work as they should. Aug 14, 2021 at 23:47
  • 2
    I have a Canon EOS 2000D. Aug 15, 2021 at 8:20
  • 1
    Unless you're rich, get used to getting closer. Telephoto lenses longer than 300mm get extremely expensive. Nikon makes a decent 200-500mm for "cheap" (ie: $1500 range), but the difference between 300mm and 500mm is not game changing. Long primes in the 800-1200mm range will cost you thousands or tens of thousands of dollars. Wildlife photography is like hunting. You can't just sit on a bench and wait for something to come by - you need to plan your shoots, set up in advance, camouflage and have enormous amounts of patience. You will get wet and dirty. That's just how it works.
    – J...
    Aug 16, 2021 at 11:54
  • 1
    Your camera has an APS-C sized sensor, so the effective focal length is 1.6 times the actual focal length of the lens. That is a good thing when trying to photograph birds and wildlife. Aug 16, 2021 at 15:24

5 Answers 5


The only magnification difference in two lenses of the same focal length used in the same camera occur due to focus breathing, for subjects that are close to the camera. Birds are usually not so close that focus breathing would be a considerable effect.

I have written a list of requirements for bird photography kit. Your best bet at this stage would be to try to find a good quality used Canon EF 400mm f/5.6 lens (sadly not available for new anymore). It has the all-important focus limiter, the importance of which is highlighted by your low-end 2000D camera not having any kind of option to stop hunting for focus. It lacks image stabilizer so you can only use it during full daylight hours, but then again at sunset or sunrise you would be photographing only stationary birds with an image stabilizer.

If you have more money to spend, there are two paths forward from the better lens:

  • Upgrade the camera to something that has higher burst rate, more autofocus points and the option to stop hunting for focus if focus cannot be found
  • Sell the used EF 400mm lens and replace your kit with Canon EOS R6 and either 600mm or 800mm f/11 lens.

But first I recommend the EF 400mm f/5.6 lens because a used one is not that much more expensive than a 70-300mm f/4-5.6 IS USM.

Also even with the 400mm lens you'll find you usually don't get very close, so cropping is required. Fortunately the 2000D body has 24 megapixels so you can crop.

  • 1
    The big problem with cheap primes like those F/11s is that they are SLOW. Even shooting with an F/5.6 lens you're often hurting for light on an overcast day. Losing another two stops is just painful. You're forced to shoot at high ISO and the image noise at that point starts to eat into any benefit you're getting from the longer lens. Autofocus can also become sketchy at those apertures, depending on the body. Given that those cheap lenses are like $1k, it's almost a waste of money if you're serious about outdoor photography. Save the money for something better, I think.
    – J...
    Aug 16, 2021 at 11:59
  • Crop camera f/5.6 is equivalent to full frame f/9 in light gathering ability. Full frame f/11 is only two thirds of a stop slower than full frame f/9. If the said f/11 has image stabilizer but the crop camera f/5.6 (equivalent to full frame f/9) doesn't, I'd pick the f/11.
    – juhist
    Aug 16, 2021 at 13:31
  • No, crop factor does not affect exposure. F/11 does not magically let more light in on a crop sensor. In fact, a crop sensor will have smaller pixels, even at the same MP rating of a FF body, so it has an even harder time of collecting light.
    – J...
    Aug 16, 2021 at 13:39
  • 1
    Also, if OP moves from APC-C to FF, that 600mm lens will give them the same FOV as a 375mm lens on APS-C, so after all that shuffling of kit (swapping bodies, selling lenses, buying new) OP ends up with 2/3 of a stop less light and 75mm of extra reach - not even enough to consider. It's a poor plan all around. Getting more reach than they already have without sacrificing light gathering is a very expensive proposition - going cheaper is just throwing money at something that won't really pay off. OP needs to step up their fileldcraft game - this is really how you improve with wildlife.
    – J...
    Aug 16, 2021 at 14:56
  • 1
    @inkista Of course it's workable, and yes, in full African sun F/11 isn't so bad, but for the cost of the lens plus the body I'm not sure it's the smartest value proposition for an amateur enthusiast like OP. A 150-600 Tamron super-tele that opens up a bit more will be much cheaper and much more versatile and will work with the body OP already has. The glass won't be quite as nice, but at third the cost, all in, it seems rather more sensible.
    – J...
    Aug 17, 2021 at 22:20

Shooting from the same point of view will always result in the same image (in terms of magnification) with every 300mm lens you can get (zoom or prime doesnt matter). To achieve a higher magnification your only options are:

  • get closer to your subject (your best option but not always possible)
  • use a longer focal length like 400mm or 500mm (the second best option if option number one doesnt work)
  • use a different camera with a higher megapixel count or with a smaller sensor such you can crop the image tighter (rather spend your money for a longer lens since a new camera is expensive and this would only give you a minor advantage)
  • use a teleconverter which will give you a longer focal length (With your lens I strongly recommend you dont. Teleconverters are mostly meant for high end prime lenses and might not work very well)

Now let me explain the best options a little further:

  • Getting closer 30% would be equivalent in terms of magnification to using a lens with 30% more focal range. You could try to cut the distance to your subjects in half. If the birds are 100+ yards away getting closer should be quite easy. I often get down to 5 meters to birds using a 500mm lens. There are some good tips on the internet about how to get closer to wildlife. Be respectful, dont run at them and if they are offended then leave. Be quiet and move slowly and you might be lucky. You could also hide yourself using some camo and wait for them if you are up to such stuff.

  • 300mm is a relatively short lens for taking pictures of birds. It can certainly work and I did capture some nice images of birds using a 300mm lens but I would suggest you to look for something like a 150-600mm lens. Those are more or less affordable and they feature some nice reach.


[Other answers cover the meaning of the lens name]

Generally, a longer focal length is required to get more zoom. But it is worth mentioning that the maximum (and minimum) focal length of many zoom lenses varies with focal distance. Focusing close will produce a different maximum and/or minimum focal length than focusing at infinity. This is simply a tradeoff in the optical formula of a particular lens.

So when fully zoomed in, your 70-300mm lens may only be 300mm sometimes.

Practically speaking there are three methods to get more pixels on the subject.

The first is to use a longer lens. It is worth noting that here the inverse square law works in your favor. A 600mm lens puts 4x the number of pixels on the subject as a 300mm lens...a 420mm lens would put 2x as many. Generally, this is the "throw money at the problem" solution. With birds, no matter how much money you throw at longer lenses, you will always want more.

The second way of putting more pixels on the subject is to use a higher resolution camera. This is also throwing money at the problem, and only scales linearly -- a 24 mega-pixel camera puts twice as many pixels on the subject as a 12 mega-pixel camera.

Finally, the inexpensive way of putting more pixels on the subject is getting closer. With birds, that comes down to field craft and field craft is a matter of time and patience. Here again, you have the benefit of the inverse square law: cutting the distance between you and the subject in half puts 4x the number of pixels on it.

To put it another way, no matter what lens and camera you have, field craft will be beneficial when trying to photograph birds. Getting close with a long lens on a high resolution camera is the best way to put pixels on the subject. The getting close is the only part that you can practice.

It is also worth noting, that using a tripod will tend to provide sharper images. A tripod is probably the cheapest piece of gear that will improve your pictures. Using a tripod is also a sound piece of field craft.

  • 5
    A monopod is a lot lighter to carry around, a lot more convenient to handle in the bushes and almost as efficient as a tripod for this kind of photography.
    – xenoid
    Aug 15, 2021 at 7:27
  • 1
    Thanks. I'm an angler as well as a very novice birder, and watercraft trumps expensive kit every time in angling. I'm quite adept at creeping about quietly so will work on my fieldcraft rather than opening my wallet. Aug 15, 2021 at 8:30
  • 4
    Getting close to wading birds requires understanding how they move around during the day, finding a place to be where they don't care about your existence, and getting there before they arrive. I have been literally hit on the head by the wing tip of a goose flying in from behind me, landing on salt marsh and feeding 20 feet in front of me, more than once. As John Morton says, it's about fieldcraft, not technology.
    – alephzero
    Aug 15, 2021 at 11:15
  • ... and don't forget that it's much easier to get close to birds on a freezing cold day in winter when it's blowing a gale and the birds are more focused on getting enough food to stay alive till the next morning than on staying away from potential predators!
    – alephzero
    Aug 15, 2021 at 11:22
  • 3
    Its is not. But it removes three degrees freedom, and makes it a lot easier to control the 3 remaining ones since it bears most of the weight of the lens+camera. I never go in nature without one (also helps for macro).
    – xenoid
    Aug 15, 2021 at 17:24

Just to add one more way of getting more magnification that I haven't seen mentioned in other answers yet, consider digiscoping — i.e. using an adapter to attach your DSLR body to a telescope (of the kind you'd use when birdwatching without a camera) and use it like a manual-focus lens with a very long focal length.

There's an earlier Q&A thread here on digiscoping that describes some of the advantages and disadvantages of the method. The main advantage is that telescopes use different kinds of optics than most camera lenses, and can be much cheaper, lighter and easier to handle than a lens with equivalent focal length (if such lenses even exist). Also, if you're already using a telescope for birdwatching anyway, getting an adapter to attach your camera to it means that you won't have to carry around two separate pieces of heavy optics.

The main down sides are that telescopes don't have autofocus, and many tend to be relatively slow (high f-number) and thus poorly suited for use in low light conditions unless the target is stationary. Also, the optical quality of many telescopes may not be up to that of a high-end lens, so your images may end up "soft" when pixel-peeping. But the extra magnification can more than make up for that when shooting distant targets, where you'd otherwise have to crop the image. And you can always decide to invest in a better telescope if you feel you need it; for sufficiently long focal lengths, it'll probably still be cheaper than an equivalent camera lens.


"4–5.6" means aperture varies when you change focal length

"IS" means lens has Image Stabilization

"USM" means it uses USM motor for focusing

And for zooming — (short answer) — yes, all 300mm will give (more or less) the same image. And you need a lens with longer focal length. Be aware they cost money... Other solution is to crop the image.

  • 1
    "4-5.6", specifically, means that at 70mm the max aperture is F/4, and at the other end (300mm) the max aperture is F/5.6. In between falls, well... in between.
    – J...
    Aug 16, 2021 at 15:49

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

Not the answer you're looking for? Browse other questions tagged or ask your own question.