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by Karl Egressy on Fri Jan 29, 2021 7:53 pm
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My wife bought a 1.4 Sony teleconverter for her Sony a7RIV/100-400 Sony lens.
Works perfect. Then I tried it on my Sony a7RIII/200-600 at continuous focus. It was doing fine back and forth adjustments for about
two seconds, just enough time to loose the shot I would be about to take.
Then I tried it on the Sony a6600/200-600 and it worked perfect.
I was wondering if anybody else had this problem.
I did some other tests to eliminate other variables and it clearly pointed towards the a7RIII.
Maybe I should buy the a7RIV.
Thanks.                                    
 

by david fletcher on Sat Jan 30, 2021 5:32 am
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Hi Karl

Not the greatest knowledge on Sony, but will chip in and hope some Sony users can add some thoughts.

Re the first point on the A7RIII, was the tracking sensitivity set to 1 which will change quicker than if set at the default 3 or user selected 5, which produces less of a hunt.  Reason is that some users on other forums have said they change the tracking sensitivity when using the IV from their other bodies.  ("It was doing fine back and forth adjustments for about two seconds").

Other points being the 200-600 is a G lens with only a DDSM  Direct Drive motor whereas the 100-400 is a GM (G Master ) and has Linear Motor as well.  Could that make it better suited to later models like the A7RIV and a6600 which may have seen enhancements/tweaks on the Image Processors and AF Systems.  (The A7RIV has 567 Phase Detection points compared to 399 in the A7RII-  Both have 425 Contrast detection points).

I'm not qualified to comment on the differences in the AF use between the A7RIII and A7RIV as not a Sony user at this moment of time but hopefully a few Sony users can answer this more fully.
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by Karl Egressy on Sat Jan 30, 2021 8:49 am
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Thanks, David, I plan to sell the a6600 as a would loose little money since I bought it when it was on sale. To my greatest surprise, the a6600 not only focuses better than a7RIII but produces better quality images based on my tests results.
Thanks for the advice, I made the changes you suggested, switched from 5 to 1. Will see if it helps. The a7RTiii works better in low light, and that's what we have here in Ontario, overcast fog and pollution, LOL.
 

by david fletcher on Sat Jan 30, 2021 9:23 am
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Karl Egressy wrote:Thanks, David, I plan to sell the a6600 as a would loose little money since I bought it when it was on sale. To my greatest surprise, the a6600 not only focuses better than a7RIII but produces better quality images based on my tests results.
Thanks for the advice, I made the changes you suggested, switched from 5 to 1. Will see if it helps. The a7RTiii works better in low light, and that's what we have here in Ontario, overcast fog and pollution, LOL.
Hi Karl

I may have not explained too well, but when I mentioned the tracking sensitivity, my thoughts were that if set at 1, it may jump more frequently than if set at 5.   It appears you had it right if set at 5, and I may have caused you to change. DOH..... (5, will hold it as it provides a slower response and helps avoiding jumping around if something gets in the way).  You look to have had that set right anyway.  

My bad and apologies.

Bummer with the weather.  Not only are we stuck in lockdown, but the weather here in the South UK is wet, wet, wet...  
Make your life spectacular!

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by Scott Fairbairn on Sat Jan 30, 2021 10:05 am
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Hi Karl, it has to do with the effective aperture. With the 1.4x it becomes F9 and the A7R3 can not use phase-detect AF, contrast only. The A7R4 can phase-detect AF at f9.
 

by Karl Egressy on Sat Jan 30, 2021 9:02 pm
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Thank you all. After all I bought the a7R4 today as it is $500 cheaper right now and sold the a6600 to able to pay for the new camera.
I guess I moved to the right direction. I would never be able to afford the a1. The a7RIII will be my spare camera.
 

by Papple-Mike on Sun Jan 31, 2021 2:07 pm
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Scott Fairbairn wrote:Hi Karl, it has to do with the effective aperture. With the 1.4x it becomes F9 and the A7R3 can not use phase-detect AF, contrast only. The A7R4 can phase-detect AF at f9.
I had purchased the A7R3, 100-400 F4.5-5.6 GM lens, 2.0xTC. The aperture becomes F9 to F11.2. In the A7R3 manual it says the phase detect auto-focus works up to F8 only. The AF worked poorly on flying birds, kept hunting. I had to get the 1.4 TC instead.

I now have the A7R4, and the phase detect AF works up to F11. I hear the A1 phase detect AF works up to F22.
 

by E.J. Peiker on Mon Feb 01, 2021 10:53 am
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The 100-400 with a 1.4x is f/8, the 200-600 with a 1.4x is f/9. The AF system for the a7R3 clearly states that reliable continuous AF tracking works only to f/8. The a6600 or a7R4 has an upgraded AF system that does not have this limitation.
 

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