Going Long with Telephoto Lenses

In this article we consider the sore spot of most photographers' existence: the telephoto lens. Why is it a sore spot? Because there's a good chance that what you need is big, heavy, and expensive; or that Nikon doesn't make it; or you can't get one because it's out of stock. Yuck.

Let's start at the extreme. Probably the most extreme telephoto use is for birding. Short of being in a blind (and sometimes even then), bird photographers tend to gravitate to the longest lens they can afford and handle. Generally wildlife photography doesn't fall much behind the birding photographer: you don't want to be shooting a grizzly bear with a 105mm lens unless it's at the zoo and there's something between you and the bear ;~). 

Unlike wide angle, where a small difference in focal length number seems to make large differences in angle of view, at the telephoto end the opposite seems to happen: large jumps (100mm or more) of focal length seem to garner only small changes in angle of view. That "little bird" viewed at distance with a 600mm lens seems to look only a tad bigger than it did with the 500mm. Hmm. Maybe an 800mm?

  • 200mm — FX 10°, DX 6.75° (all numbers are horizontal angle of view)
  • 300mm — FX 6.9°, DX 4.5°
  • 400mm — FX 5.2°, DX 3.4°
  • 500mm — FX 4.1°, DX 2.7°
  • 600mm — FX 3.4°, DX 2.3°
  • 800mm — FX 2.6°, DX 1.7°

Someone recently asked me how to calculate subject size to angle of view. Your geometry instructor at school was right: geometry knowledge is useful in real life! 

Believe it or not, Google can do the heavy lifting for you. Let's say we have an FX sensor, 50mm lens, and want the horizontal angle of view. The sensor is 36mm wide, so half that is 18. The formula you want is 2*arctan (half_sensor/focal_length). So just type "2*arctan(18/50) in degrees" into a Google search bar (the words "in degrees" at the end is important [otherwise you get the answer in radians, which you probably don't think in]) and you get your result (~40°). 

Now how do we get the distance to a fixed size subject or the size of a subject at a fixed distance? That's tan(A) = subject_size/distance. We now have calculated angle A, which will be half of the value Google generated in the previous equation. 

So if the distance to the subject is 20m, we want to be calculating tan(20) = a/20, which gives us half the subject size. A calculator will give you "tan 20 in degrees" as ~3.6. So now we multiply both sides by 20 and get 20*3.6 = a. If instead you wanted the distance to a subject that's 20m wide, take half the 20 and you get 3.6 = 10/c. Divide each side by 3.6 and multiply each side by c and you have c = 10/3.6. (For these distance calculations, you can use any units, as long as they are consistent.)(Update: Google no longer directly caculates tan 20 in degrees, thus I've changed the wording in this paragraph slightly.)

Or you could have asked your teenager who's taking geometry ;~). But I've gotten away from lenses.

I have one suggestion to those who are into true wildlife photography, especially where smaller animals are concerned: just bite the bullet and get as long and as fast a lens as you can afford and handle from the start. If you can't afford it, rent one for critical trips. It's sort of like my famous tripod article suggests, only with a twist: you can buy a series of lenses hoping that you can sneak up on the goal and maybe find something "usable" that's less expensive and smaller, but it ain't going to happen. 

You'll buy a 70-300mm VR. Replace that with a 300mm f/4. Replace that with a 200-400mm f/4. Replace that with a 500mm f/4. And eventually decide that maybe the 600mm f/4 is what you really need (all the while wondering how it performs with teleconverters ;~). By the time you're done, you'll have spent a small fortune on lenses and still wonder if you have the right one. 

Since the exotics keep going up in price, trying to sneak up on the final answer has a cost penalty, too: what you can buy today for US$11,000 probably cost US$7000 back when you bought your first 70-300mm. While you might be able to get much of your money out of the telephoto lenses you bought as you work your way up the focal length ladder, it is by no means assured. 

Yes, I understand that not everyone can afford to just go out and buy the "right kit" from the start. Plus spousal buy-in is usually necessary. But trying to sneak up on "the right lens" is just an exercise in frustration and perpetual credit card abuse. The problem with wildlife photography, and especially bird photography, is that the same opportunity you saw this morning might not occur again. So if you didn't have the right lens this morning, you'll never get that shot.

If you have to compromise at the extreme end, compromise on features, not quality and focal length. It's long been my suggestion that if you can't afford a 500mm f/4 VR, for example, that you look for a used 500mm f/4P. Yep, you lose autofocus and VR, but you'll pay US$2500-3000 for a lens in excellent or like new condition versus $8500 for the latest and greatest version. And as I note in my article on VR, you're already turning VR off when you're on a tripod or shooting at over 1/500. Are you really sure that autofocus and VR is worth US$6000? 

So, for those of you thinking you have to save up for or sneak up on the exotics, consider these options instead:

  • 400mm f/5.6 AI-S. Small, convenient, sharp.
  • 500mm f4P. Basically as good as the current lens without the Nano, VR, or autofocus.
  • 600mm f/5.6 AI-S. Smaller and lighter than the 500mm f/4, but hard to find.
  • Any of the AF-I or AF-S previous versions of the 400mm f/2.8, 500mm f/4, or 600mm f/4. You won't get VR, but all these lenses have autofocus capabilities that pretty much match the current exotics, will take the current TCs, and product image quality on par with the current versions (only small differences).

Three other things you can consider if you don't have the extreme focal length requirements of the birders and dedicated wildlife users:

  • 70-200mm f/2.8E with the TC-20e. Looks pretty darned good for a TC'd lens. Certainly an arguably better choice than the 80-400mm to shoot at 400mm f/5.6 right now. 
  • 300mm f/4E PF with the TC-14e. Gets you to 420mm at a reasonable price.
  • 300mm f/2.8G with the TC-14e. Starting to get into the pricey range, but still a reasonable alternative if you're not really trying to get to 600mm (Note: I haven't yet tested the 300mm f/2.8 with the new TC-20e; it might actually be usable, but I don't know yet). 

These options still deliver decent image quality. Though not quite at the level of the dedicated focal length exotics, these last three options tend to be better than the 80-400mm and 150-500mm options that tempt the "long shooter." But they're also bigger and more expensive than those popular telephoto zooms. 

Still, I put image quality at the top of the list always when it comes to sports, wildlife, birding, and the other types of uses you need these lenses for. Again, that's because many times the "great picture" opportunity you encounter only occurs once (or at least rarely). You won't be able to duplicate what happened today a few years from now when you can afford the exotic telephoto. Thus, always buy image quality first and foremost for very long telephoto lenses. All features are window dressing.

Update: Nikon's 200-500mm f/5.6E changed things. This is a lens I can recommend even on a D850. Optically, it performs well out of its modest price range. The one drawback to the lens is that, while it is a zoom lens, zooming is fairly inconvenient due to the way the zoom ring works (or doesn't ;~). Still, Nikon rarely offers us bargains. This is one you shouldn't overlook in your quest for the right long lens.

Of course, you can also consider renting. You can rent a 500mm f/4 for a week's use for about US$500. If your budget is US$2500 and you're only shooting three weeks a year where you need such length, you might be able to get by with just renting for a couple of years. Of course, you won't own anything at the end of that period (other than great pictures, that is!).

So, if you need a really long lens, the bottom line is that you should never compromise the wrong thing. You need a long focal length with high image quality. You may not need a zoom, autofocus, or VR. 

Most users just want a solid telephoto lens that's a little more modest. The 80-200mm range is something almost every photographer needs covered. Nikon has two excellent choices here: the 70-200mm f/2.8E VR, and the 70-300mm f/4-5.6 VR AF-P. Both are quite good lenses (and you'll find reviews of them elsewhere on this site). Every Nikon user should have one (or both) of those lenses in their kit, in my opinion. 

Better still, with a close-up lens set (usually the Canon 500D) or the right extension tube, the above two lenses can also provide some reasonable macro capability. For the 70-200mm, any of the TC teleconverters can give you an impromptu focal length boost without sacrificing much, if any, performance. (That's true of the VR II and E FL versions of the lens with the latest TCs. The oldest 70-200mm is a little less capable with TCs, especially the older TC-20e.)

text and images © 2020 Thom Hogan
portions Copyright 1999-2019 Thom Hogan-- All Rights Reserved