pdog109 wrote:
The future is now old man.
There's some comments on the SAR post that say the 600 6.3 at 2.5m MFD is too good to be true and that Sony put a TC in the lens to achieve that. Honestly i don't care about MFD, birds don't usually let me get that close.
I am sure Sony will have had to play with the optical formula considerably to get a 600mm lens in such a tiny package, a lot will be done by the lens group in the rear, not necessarily producing the best image rendering.
But they have at least (or so it seems) taken the challenge to make a lens like that, and call it GM, so I would be surprised if it turns out mediocre.
Adding a TC is adding a group of 6 (or thereabouts) lens elements at the back of a lens to force a native lens into a different focal length, I cannot see Sony doing that since they designed the 600mm f6.3 from scratch. It's a tiny lens and I don't think you can expect that much optically from a tiny lens, but being brandnew and GM, I still assume it will be special in some ways, and great to carry, and hopefully great to use with good image stabilization.
Definitely interested to see what Sony comes out with. Unless the 400mm f4.5 is about 1/2 the price of the 100-400mm f/4.5, though I have a bit of a hard time seeing many people getting the prime over the zoom. I was actually wondering recently if adapting the Sony 100-400mm f4.5 makes more sense than getting the Nikon 400mm f4.5 at this point, since for $800 more you gain a much more versatile lens. Sure, the zoom will be a bit heavier in the hand, but it makes it much easier to leave a wider zoom, like a 70-200, at home.
arbitrage wrote:
I don’t know about the IQ between the 600/6.3 and 300/2x (I think they will be close and I’d bet a slight edge to the 600). But if the 600 has 4 linear motors I bet the AF will be better than the 300/2x because that is where I feel the 300/2x suffers the most when comparing it to 300/1.4x or 600GM.
Honestly the IQ part is less important for me than the AF performance, the 300 with the 2X IQ is exceptionally good and it's basically glued to my A1II, where I find there is room for improvement is with AF performance with the 2X for fast flying birds such as swallows, Bee-eaters or kingfishers. I've been photographing Bee-eaters this Spring and early summer in Portugal and there is a noticeable AF speed/accuracy difference between the bare lens and the 1.4 or 2 converters, less so with the 1.4. This last week I spent a number of days fotographing the European Kingfishers, a small super fast flier and there is a noticeable difference in AF speed and accuracy between the base lens and the 1.4 and 2x teleconverters. If the 600 f/6.3 can match the AF speed of the 300 then I'm all in on that lens.
@MIRANDA1 agreed. A while ago I did a deep dive into how teleconverters affect autofocus speed and accuracy. It was quite a rabbit hole, and far more complicated than just the loss of speed.
For me the most educational part was that each lens autofocus servo is tuned for the relationship between the focus plane travel distance vs focusing element travel distance. Quoting Canon [1]: "larger image plane changes per focus lens unit travel distance”. My interpretation is that the AF motors are tuned to the given optical formula and introducing a TC changes that. It is an optical+mechanical problem which can't be solved with better firmware or better sensors inside a body. Based on that, I would expect the 600mm f/6.3 to have better AF performance than the 300mm f/2.8 with 2x TC despite the speed disadvantage.
old-gregg wrote:
@MIRANDA1@ agreed. A while ago I did a deep dive into how teleconverters affect autofocus speed and accuracy. It was quite a rabbit hole, and far more complicated than just the loss of speed.
For me the most educational part was that each lens autofocus servo is tuned for the relationship between the focus plane travel distance vs focusing element travel distance. Quoting Canon [1]: "larger image plane changes per focus lens unit travel distance”. My interpretation is that the AF motors are tuned to the given optical formula and introducing a TC changes that. It is an optical+mechanical problem which can't be solved with better firmware or better sensors inside a body. Based on that, I would expect the 600mm f/6.3 to have better AF performance than the 300mm f/2.8 with 2x TC despite the speed disadvantage.
old-gregg wrote:
@MIRANDA1@ agreed. A while ago I did a deep dive into how teleconverters affect autofocus speed and accuracy. It was quite a rabbit hole, and far more complicated than just the loss of speed.
For me the most educational part was that each lens autofocus servo is tuned for the relationship between the focus plane travel distance vs focusing element travel distance. Quoting Canon [1]: "larger image plane changes per focus lens unit travel distance”. My interpretation is that the AF motors are tuned to the given optical formula and introducing a TC changes that. It is an optical+mechanical problem which can't be solved with better firmware or better sensors inside a body. Based on that, I would expect the 600mm f/6.3 to have better AF performance than the 300mm f/2.8 with 2x TC despite the speed disadvantage.
Putting a TC on has no effect on the focus motors - they are linear motors and move just as fast as with no TC. They are dumb and get their move instructions from the camera so any change in performance is the cameras fault. Obviously reducing the light on the sensor will have some impact on the cameras ability to find the focus point.
And yes you can solve it with a better camera (sensor and firmware) - there is a reason the A9iii is what it is and why the A7R6 is in most situations as good as or perhaps better than the A1ii.
