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sportysnaps

sportysnaps

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200mm f1.8 ?, 300 f2.8 ?, 600mm f4 ??

a number of us(including me)lust after such expensive heavy, hard to use objects but why?

What will a 400mm f2.8 lens at 400iso get us that a 400mm f5.6 lens at 1600iso on a maybe more expensive camera get us?
 
Extra DoF, better AF performance, ability to shoot at 2.8 at ISO1600 when light is really bad. Big lenses really are the realm of diminishing returns but sometimes you can't get the shot without them
 
The image will be sharper with a 600 set at 5.6 than a 300 with a 2x. There is a noticable drop off in image quality with a 2x on a 300. And the AF on a 1 series will still be top tracking performance since the cross sensors work at f/4 or better and the lens is wide open for focusing
 
sportysnaps said:
so is a 300 f2.8 with a 2x (600mm f5.6) the same as a 600mm f4 - set at f5.6 and if not why?
Click to expand...

grumpybadger said:
The image will be sharper with a 600 set at 5.6 than a 300 with a 2x. There is a noticable drop off in image quality with a 2x on a 300.
Click to expand...

For the 300 and 2x at f/5.6, the 300 is wide open and not at it's best even before the 2x does a little image degrading (not too much with this lens though). Knock it down a stop to sharpen it up a little and it's at f/8 (well, the combination is) whilst the 600/4 is still at f/5.6.

The costs are exponential to the benefits but life's like that.

Bob
 
sportysnaps said:
What will a 400mm f2.8 lens at 400iso get us that a 400mm f5.6 lens at 1600iso on a maybe more expensive camera get us?
Click to expand...

Ultimately, it gets you the shot where the other wouldn't.... end of, but as the focal length gets longer, the size of that front lens objective gets bigger and bigger, together with the cost of producing it. :shrug:
 
my argument to that would be you have to be more of a man to carry the weight...and hence compensation for nowt.
 
or save a lot of money and buy a 50mm f1.8 then stand a lot closer :D


(or buy a big ladder if it's moon shots )
 
I'd have loved a 300mm or 400mm prime today. It's got to happen.
 
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