Tamron Update

I was reading Arthur Morris’s blog today when I noticed that he was shooting with wildly different settings than I was. He seemed to be using a wide open aperture, and a relatively high 400 ISO even in sunlight, while relying on the camera to eliminate grain. This let him shoot with shutter speeds as fast as 1/2000 of a second. He had much better lenses than I did, but I still thought it might be worth a try, so I took a quick spin around the ponds at Mason Park in the late afternoon and see how this did. My lens would only open up to f/6.3 at 300mm–his could get as wide as f/4–but it did make a big difference as seen in this photo of a Western Bluebird:

Western Bluebird
Tamron 28-300 Di VC on an EOS 50D body, ISO 400, f/6.3, 1/2000s

Moral of the story: Shoot birds in Av mode with maximum aperture, and ISO 400 or greater. I’m used to thinking of f/8 as my maximum aperture but for birds I’m not as concerned with depth of field as I am with bugs. Plus the 50D can really handle the higher ISOs, even in bright sunlight. I’m still hoping for a better lens, but I now don’t feel quite such an urgent need for one.

I think what’s going on here is reminiscent of thread priorities, where one gives the highest priority to the least computationally intensive task, because it will leave plenty of room for other more CPU bound tasks. This is the exact opposite of most people’s initial intuition. In this case I cared about shutter speed so I was setting it, but I should have been setting the other parameters instead and letting the shutter speed get as fast as possible. (Also I needed to simply not care as much about ISO and aperture.)

One Response to “Tamron Update”

  1. Dolan Halbrook Says:

    Much better results than before. Indeed the 50D has wonderful high ISO as well as a high max shutter speed, so you have plenty of headroom, even on a bright day.

    I have to wonder if the 50D has a similar feature that my Pentax bodies have, which is “MTF program line”. If you want to wring the max optical performance out of a lens, it will optimize for that lens’ MTF chart (the body has a database of lenses and the lens will give the MTF info to the body). Perhaps the Canon body is already trying to so such a thing in normal program, though shooting aperture priority would bypass it. Generally lenses are not at their best wide open. f6.3 is pretty slow for wide open though so the things that kill you at max aperture (diffraction, etc) won’t have a huge effect.

    I can’t seem to find an MTF chart for that lens. Would be interesting to see where it peaks, esp. at the long end.

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