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Is Tamron 200-400mm f/5.6 LD a worthy upgrade?

Started Feb 5, 2015 | Discussions thread
John Sheehy Forum Pro • Posts: 26,698
Re: Is Tamron 200-400mm f/5.6 LD a worthy upgrade?

I, John Sheehy accientally wrote:

The maximum aperture on the 250mm is 44mm, so the Tamron gets more light at f/8 than a crop of 250mm gets at f/5.6, so don't think for one minute that you are compromising light using 400/5.6. 400/5.6 gives an aperture (71mm) unavailable on the 55-250.

Sorry, that should have been "don't think for one minute that you are compromising light using 400/8". The Tamron is 50mm at f/8 and 71mm at f/5.6, while the 250 at f/5.6 is only 44mm. So, with the same shutter speed and distance, the Tamron get more subject light (photons), even at f/8.

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