Need advice re long telephoto lenses

Started Jan 29, 2013 | Discussions thread
audiobomber Veteran Member • Posts: 5,721
Re: Need advice re long telephoto lenses

JeffAHayes wrote:

It's a bit more than you've indicated you're want to spend, but WAY longer in focal length

A 50-500mm is not quite as long as is claimed. The Bigma is an internal-focus lens, therefore gradually loses focal length at subject distances below infinity. Here are some numbers that one reviewer came up with:

At infinity ~ 485mm

  • At 25m ~ 465mm
  • At 7m ~ 435mm
  • At 2.5m ~ 385mm

which will make it almost as slow of a lens at 420mm as the lens I'm about to reccomend

The difference between a 300mm f4 prime and 1.4X TC is 1/2 stop, f6.3 vs. 5.6, which matters to me. What I find is that I sometimes don't even have enough light for decent shutter speeds at f5.6, in the woods, or in twilight. The advantage with my 300mm primes is that I can remove the TC and I have a 300mm f4 lens again. OTOH, the Bigma is still f6.3 at 300mm, 1-1/2 stops behind. This versatility (longer & slower vs. shorter & faster) is something I need for my particular shooting conditions.

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