Thoughts About Long Zooms and Primes and ‘Image Quality’

A lot of photographers sweat the decisions about what long lenses to purchase. Among Canon users a common decision is whether to get a high quality telephoto prime (plus one or more teleconverters) or to get a telephoto zoom. Perhaps the most common question is whether to get a 300mm L prime (f2.8 IS or f4 IS) or the 100-400mm f/4.5-5.6L IS USM.

Many seem to focus on the image quality (“IQ”) issue a lot when trying to figure this out. It is true that the primes have an edge on the basis of pure resolution compared to the zooms. At 300mm the prime will “beat” the zoom at the same focal length. But, as many have figured out, it isn’t quite as simple as determining which lens is “sharpest” – other factors can affect the answer to that question, and sharpness is not the only issue.

Beach and Bluffs, Evening
Beach and Bluffs, Evening

If you only want a lens that will shoot at 300mm, the primes have a lot going for them. The f/2.8 300mm L prime is known to be a really outstanding lens, and you’ll see it in use a lot at sporting events and in other situations. For all of its advantages, it is also an extremely expensive lens, and you need to ask yourself if the benefits are worth the costs for your photography. (This is not to suggest that the lens is “not worth the cost” in general, but to urge some caution and introspection among buyers whose photography may not take full advantage of what it offers.)

The f/4 IS 300mm L is probably more likely to be pitted against the variable aperture 100-400mm L in these comparisons. The cost difference is not that great, and for those who are mostly interested in performance at the longer focal lengths (e.g. – they may already have a 70-200 lens) it is reasonable to consider the prime plus a 1.4x TC as an alternative to the zoom since using the TC gives a 420mm focal length.

I went though this thought process recently and decided on the zoom, even though I know that the prime is capable of somewhat better IQ at 300mm. Why did I choose the zoom over the prime?

  • I don’t always shoot at 300mm. I often use the zoom at both longer and shorter focal lengths. I’ve been in situations in which being able to change the focal length quickly was critical, and if I had needed to switch lenses I might well have missed a shot entirely.
  • I did not want to mess around with a teleconverter.
  • I realized that the IQ advantage of the prime at 300mm doesn’t hold up when you have to shoot at other focal lengths. For example, If I really need, say, 370mm to frame my subject best I can get precisely that framing with the zoom and no cropping will be necessary. I could still get the shot with the 300mm lens but I’ll need to crop, thus reducing or eliminating any IQ advantage of this lens.
  • Even at 300mm the IQ difference, while measurable, is unlikely to be critical or even visible in prints.
  • While the 100-400 is probably at its weakest at 400mm is is OK there, and there is a lot of debate about the relative performance of the zoom fully extended versus the 300mm plus the TC.

So, for me the zoom has proved to be the best choice. But could the prime be a better choice for other photographers? Of course! For a photographer who really needs the best possible IQ at 300mm the prime will provide this. And a photographer who wants a lens that works at 300mm and doesn’t want to mess around with the extra variable of a zoom could be happier with the prime.

But I’m happy with my choice.

I wrote earlier about the very first time I took the 100-400 out for a spin. I ran into somewhat unique conditions in a spot I visit along the Central California coast – and managed to a few photographs (examples herehere and here) that I would not have been able to get with either my existing lenses or the prime. Nothing like that to convince me I made a good choice!

Related:

If this article helped you make a purchase decision, please considering purchasing your Canon 100-400mm f/4.5-5.6L IS lens from B&H Photo though this link and helping support this blog. Thanks!

© Copyright 2014 G Dan Mitchell – all rights reserved.

G Dan Mitchell is a California photographer and visual opportunist whose subjects include the Pacific coast, redwood forests, central California oak/grasslands, the Sierra Nevada, California deserts, urban landscapes, night photography, and more.
Blog | About | Flickr | Twitter | FacebookGoogle+ | 500px.com | LinkedIn | Email

Text, photographs, and other media are © Copyright G Dan Mitchell (or others when indicated) and are not in the public domain and may not be used on websites, blogs, or in other media without advance permission from G Dan Mitchell.

4 thoughts on “Thoughts About Long Zooms and Primes and ‘Image Quality’”

  1. Hi Dan, Thank you for your good wishes and I hope to find a new job soon too! But in the meantime, maybe I will have a little extra opportunity to get out with my camera and I can’t complain about that!

    And you definitely fixed the links and it looks like you added a third. And by the way, nice shots all! I love the compositions!

    And after reading your additional comments, I am sold on the idea of the 100-400 mm zoom. My photography is all over the place and often I wish I had more than the 200 mm I have with my 70-200 lens. And when I am out there and I see wildlife, it is always an unexpected opportunity with little chance to change lenses before the animal is gone. A zoom makes perfect sense for me and when I decide to buy, that is what I will get. Thanks!!!

  2. Cynthia, sorry to hear about your employment woes – hope you can find something soon!

    Also, thanks for letting me know about the broken links. I think I have fixed them… and I added one more while I was at it.

    Some of what I wrote in this piece is probably relevant to your question about wildlife shooting. For example, unless you shoot one type of wildlife only, and do it in pretty much the same way all the time, the flexibility of the zoom may well trump the potential slight increase in resolution from the very best primes. I shoot wildlife at a variety of focal lengths, depending upon the beast, the way I cover it, and so forth. I often shoot at FLs other than 400mm… and with the prime I’d be out of luck.

    On the other hand, if you think you would always shoot at 400mm – perhaps you photograph dangerous beasts from a distance or you photograph only very small birds – then the prime could be a fine option since the shorter focal lengths might not be that useful to you.

    For me 400mm is almost always long enough. While I do sometimes encounter situations in which something longer would be useful, they are not that frequent.

    Dan

  3. Hey Dan,

    I am sitting here unemployed (got laid off on Sept 30) and had a moment to visit your page before I get busy today. But I have long been thinking about the Canon 100-400 mm lens and your comments here make good sense to me. I do have a friend who has that lens and he is not all that pleased with it. But then he is more interested in astrophotography than wildlife or landscape photography.

    Whether I buy the lens will depend on how my finances pan out and if I can find another job. If I do find another job I’ll probably buy the new EOS 1D X and a lens like this with my severance. My 40D, as much as I like, feels somewhat limited in things I would like to do.

    Nonetheless, do you have any thoughts on how the 100-400 mm zoom would be for wildlife? Is 400 mm long enough? The zoom capability certainly sounds perfect for capturing wildlife at unknown opportunities.

    And I wanted to see your example images but the links don’t work. Can you fix them? Thanks!

    1. Hi Cynthia, I use the 100-400mm lens quite often on my Canon 40D. It is a great value for the range and flexibility that the the zoom lens offers. The one other area that I’ve found where the more expensive primes have an advantage is that they auto focus much quicker. However, that wasn’t enough for me to justify the price (and weight) difference. I think that you would be happy with the 100-400mm lens. I recently gave a presentation on wildlife photography and on slide 58 I show a comparison between the Canon 100-400mm and a Canon 600mm prime. Check it out at http://www.qnetx.com/downloads/gqwildlife.pdf

Join the discussion — leave a comment or question. (Comments are moderated and may not appear immediately.)

This site uses Akismet to reduce spam. Learn how your comment data is processed.