If using the 150-600mm on a crop sensor camera.... 300mm is a very long telephoto... 400 to 500mm is extreme... and 600mm is bordering on insane! Adding any teleconverter to a 600mm lens would be.... um, what comes after insane?
If using a FF camera... get a crop sensor camera.
If that's still not enough, get closer!
300mm lens on a mere FF camera...
300mm lens on a crop sensor camera...
Okay, gotta admit, sometimes I add a teleconverter to a 500mm prime (500 + 1.4X for 700mm equiv.)...
... on a crop sensor camera, all supported with a very sturdy tripod!
But, seriously, extreme focal lengths make it a lot more challenging to get a steady shot, even with stabilization. Your friend should plan to use a quality tripod or at least a monopod and still will need to keep shutter speeds fairly fast. Also, shooting small subjects at greater distances through more atmosphere is another important factor that can significantly effect image quality.
Amfoto1-
Alan- thanks for your input- yes I agree- perhaps a Sony 77-ll would be a good move for her- she may have already thought of that but I will mention it.
I have a nikon TC-14EII and a nikon TC-17EII. Neither one will fit the Tamron 150-600.
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