Lens Comparison, Part Deux

In which we examine the hard choices around camera lenses.

I received to lenses recently for evaluation (from a dealer who was kind enough to let me do that!). One is a 150mm f/2.8, and the other is a 240mm f/4.5. They are longer than a normal lens for medium format (normal being about 80mm focal length), but not really L O N G for wildlife. But they came with a 2x extender, giving me 300mm and 480mm, both of which are suitable for wildlife.

This photo was taken at 480mm from about 5 feet away from our feeder:

This was about a hundred images into learning how to use such long, heavy lenses.

Here is a photo taken earlier, as I was figuring out how to use these lenses. It was taken without the 2x extender, at 240mm, and from further away:

A number of things went right and wrong here:

  • I didn’t use settings that would freeze the bird’s motions.

  • I didn’t have a useful focus setting, although it’s close—but this deep focus was part of why I couldn’t freeze motion.

  • The lens wasn’t long enough for how far away I was; even blown up, the details are not as good as I would like them to be.

  • The exposure has enough light to register details clearly

  • Not shown, but experienced: the focus on the camera was not working well hand-held. It is somewhat slow because the lens has really huge chunks of glass in it. It would hunt as my hands could not hold the camera steady enough for a full focus. About ever tenth image was focused the way I wanted it to be.

That first image was the result of taking images like the one above, and gradually figuring out what I need to have to make good pictures with this hardware. Here are the changes I made over the course of the several-hour session:

  • I got out my monopod, and mounted the camera on it. This took the weight, and I could concentrate on pointing the camera and operating the controls.

  • I added the 2x extender, to double my focal length

  • I did long sessions with each lens, instead of juggling back and forth, so I could learn the strengths and weaknesses of each.

  • I made subtle changes to my focus settings, so that I was more like to get to a good focus. Combined with the steadiness of the monopod, this allowed me to get about 75% of the images in proper focus. A big improvement, but still a fair number of lost images.

Having spent a good part of the day just learning how to use the lenses, it took several more days and several more sessions to actually get comfortable with them. I gradually reached for the right controls at the right time, and then it was time to try to decide between them. Here is what I had learned along the way over the course of about 5 days:

  • The 150mm lens, without extender, was a reasonably flexible lens. It was able to focus handheld if I was careful. (It would focus correctly about half the time.) It is a fast lens, so I had a lot of flexibility in choosing my depth of field. I could focus just on eyes, or get an entire face or bird in focus by changing the aperture.

  • The 150mm lens with the extender was a reasonable wildlife lens. The extender doesn’t allow automated focus, so I had to figure out how to set up to focus on the fly. The monopod was essential; I could not focus well without it.

  • Both lenses had better contrast without the extender. Contrast contributes to one’s sense of sharpness, even if it doesn’t affect literal sharpness directly. So for a few days, I was certain (but wrong) that the extender images were not really better. I had to work harder than I had expected to master technique in order to focus at long focal lengths manually, but in the end, once I could control focus, I finally saw the value of the longer focal lengths. I can also add in some contrast during processing afterwards.

  • The 240mm lens, with extender, was truly a difficult setup to master. Things began to become more useful for me after a long, four-hour session with just that setup. I’m glad I wasn’t using film; I took 196 images before I could say that I had enough skills to appreciate what the combination could do. Perseverance is not just for politics. :)

That said, I felt that budget-wise, if I could decide on keeping either the 150mm lens or the 240mm lens, I would. But in the end, the bare 150mm is really flexible handheld, and the 240mm is not. Similarly, with extender, the 240mm lens really is a lot more capable of capturing details than the 150mm. So it was a difficult decision about whether to keep one or the other; keeping either one would rule out important things I like to do with the other.

Part three: the evidence.