400 F/2.8 and 600 F/4 AF Accuracy with TCs poll

[Steve]

I hope you can help me. I'm doing a video on 400 2.8 vs 600 F/4 and want to collect a wider breath of data for it regarding AF accuracy with TCs . NOTE - I'm not talking about sharpness, but rather AF accuracy. For the most part, TCs cause a minor loss in sharpness are still plenty sharp on either the 400 2.8 or 600 F/4 - however - where I notice a problem is with AF accuracy. In other words, when you take a series of images, do you find the number of sharply focused ones are the same with the TC or do you find that you get fewer perfectly focused shots with the TC than without it. And again, this is for the 400 2.8 and 600 F/4.

You can pick multiple choices in the poll above - and your comments are welcome as well. I can't put enough detail into the poll, so I'd like to hear about the differences you find between 1.4 and 2X TCs in regard to AF accuracy compared using the lens without a TC (with either lens).

So, here's my anecdote to get things started:

FWIW, I always have noted a drop in AF accuracy with my big primes when using a TC compared to when not using one. For instance, with my 400 2.8 lenses, I find that they are great without the TC (no surprise), good with the 1.4TC, and OK for stills but not action with the 2X (especially the Sony 400 2.8 - it's terrible for action with the 2X attached).

With my 600 F/4 it's the same thing. It';s great ton it's own, good with the 1.4X and "stills only" with the 2X.

Interestingly, I also find that the 600 F/4 is more accurate than the 400 2.8 + 1.4TC, even though the F/stops are the same and the focal lengths similar.

 

[Doug Herr]

? brand-agnostic ?

 

[Steve]

? brand-agnostic ?

Yes - feel free to post the brand, etc. in any comments. The poll just won't allow separate lines for everything possible. Thanks!

 

[bsinc1962]

Built in TC's or adapted?

 

[Steve]

Built in TC's or adapted?

Either way. I notice a drop in AF accuracy with built-ins as well as external. Just trying to give a general consensus in the video. I'm going to give my opinion on it and then mention the results I find here. I'm curious if everyone sees it with every lens or if it's more mixed.

 

[Doug Herr]

No accuracy problems with Sony a1 & 600 GM +1.4x TC for stills. No data with 2x TC or action.

 

[RichF]

For stills, results on F 600mm w/ external 1.4 is highly dependent upon the light. Good light I find little difference. Poor light and my D850 struggled w/ 600 and 1.4 TC

 

[ajrmd]

With Canon EF lenses and tc’s the effects of the tc’s were well characterized. If I recall correctly, a 1.4x tc dropped af speed by around 25% and a 2x reduced it by 1/2. This af speed reduction affected af accuracy. I’m not certain whether this has been studied with the Z-mount.

 

[RichF]

With Canon EF lenses and tc’s the effects of the tc’s were well characterized. If I recall correctly, a 1.4x tc dropped af speed by around 25% and a 2x reduced it by 1/2. This af speed reduction affected af accuracy. I’m not certain whether this has been studied with the Z-mount.

Never seen this with any Nikon body. Interesting that Canon drops speed. Wonder why? if it is due to less light than you would expect slower lens to AF slower also and I have not heard about that (then again i switched from Canon to Nikon) shortly after the R and Z6/7 were announced

 

[Steve]

For stills, results on F 600mm w/ external 1.4 is highly dependent upon the light. Good light I find little difference. Poor light and my D850 struggled w/ 600 and 1.4 TC

I find that's the case as well, which is wha makes this so tough. Every circumstance is different.

 

[Steve]

With Canon EF lenses and tc’s the effects of the tc’s were well characterized. If I recall correctly, a 1.4x tc dropped af speed by around 25% and a 2x reduced it by 1/2. This af speed reduction affected af accuracy. I’m not certain whether this has been studied with the Z-mount.

I think I might do some speed tests with the Sony and Nikon glass and see. The 400 TC + 2X seems slower to me than just the lens or lens + 1.4.

 

[Redbeard the Cameraguy]

Phew this is a very nuanced project. Steve you're the man. Good luck. A couple things that jump to mind here are these lenses native to their brand and mount? If the equipment is from a past generation will the skew your data? what about instances like a 400 tc stack 1.4 +1.4 vs 400 tc + 2x?

 

[Lance B]

As Rich states, it seems as though it might be dependent on the light, the subject and whether negative EV is dialled in. Generally, I don't notice a difference because I don't shoot all that much BIF or that much action and I either know that I will shoot at 600mm or 840mm before I take aim at the bird. Therefore, I don't know if there is a difference because I have compared the two focal lengths. on a particular scenario. You're than man for that job. Having said that, I haven't noticed that the 600TC is slower with or without the TC engaged.

 

[RikWriter]

The Sony 600 f4 AF is just as accurate with the 1.4X TC, but not with the 2X TC.

 

[JAJohnson]

I think I might do some speed tests with the Sony and Nikon glass and see. The 400 TC + 2X seems slower to me than just the lens or lens + 1.4.

Yes, my Nikon 400 TC with 2x is definitely slower to focus than without an external TC or with the 1.4x
TC. Still, I’m very happy to have it.

 

[arbitrage]

I answered the poll as stills being as accurate for both lenses and action being less accurate for both lenses.
However, I would caveat that where I feel with a 2xTC even for stills I find it less accurate.
So 1.4TC for stills I think is as accurate or close enough.
For action there is no doubt in my mind that even the 1.4TC reduces accuracy.
Most of my experience is with Sony these days but I found similar with Canon 600/4ISII, RF600 and RF400 which I've used. For Nikon I haven't used any 400/2.8 or 600/4 lenses. I had the 500/4E which I think my assessment would stand. When I owned the Z400/4.5 on Z9 I would also say the TC degraded accuracy for action and maybe a little bit for stills.

 

[Steve]

Phew this is a very nuanced project. Steve you're the man. Good luck. A couple things that jump to mind here are these lenses native to their brand and mount? If the equipment is from a past generation will the skew your data? what about instances like a 400 tc stack 1.4 +1.4 vs 400 tc + 2x?

Nah, I'm looking for a general consensus across the board. The section of the video covering AF accuracy isn't super long and it's only one of a bunch of considerations. I basically want to be able to give my take on it and mention what other users of these lens, very generally, experience with TCs. It's not a super deep dive into AF accuracy between brand A and B or this generation or the last generation of lenses

 

[Activert]

I only use the internal Tc on my 600 mm and I find in almost all the time that there is no real difference in AF accuracy with or without the tc. However in rare cases when there is mist in the air or when the light is bad or even when the subject ( with birds in action only) is very dark and the eyes are hard to be seen, then the AF would not be very accurate in few shots.

 

[fcotterill]

My responses are for a 400 f2.8E FL Nikkor with the vIII TC14 and TC2 on the D850, D5 and Z9. I set and rechecked AFFT on the DSLRs, rechecking was irregular about twice as I recall.

Experiences of AF performance over 2018-2022 were biased heavily towards stills, as I prefer a lighter rig for action (500 PF).

However it's a mixed bag. AF speed with TC2 III was slower in some situations. In comparison, the 400 f2.8E & TC14 III is an excellent pairing in all situations as a 560 f4

No experience with a 600mm

 

[John_DE]

I have the 400/2.8 TC and do not notice a difference with or w/o the TC (internal). In good light, I do not notice a difference with an external 1.4 TC or with an external 1.4 with the internal 1.4 to quickly get to 784mm. With the 2.0 external TC, think there is a slight improvement over stacking 1.4 TC’s - but have never tried to test this and only use this combo when I feel I need 800mm w/o the flexibility to switch to a lower focal length. At 1120mm things obviously take a big hit from atmospherics and I avoid using 2.0 external + 1.4 internal.

 

[ajrmd]

As I mentioned earlier with DSLR's TC's notoriously affected AF speed and accuracy. With Canon TC's the penalty was more significant than my recollection allowed. According to Canon's own admissions, "that there is an impact on autofocus performance with type II and III Extenders. Specifically, Canon suggests that AF drive speed is reduced by 50% when using the 1.4x Extender, and speed is reduced by 75% when using the 2x Extender. Canon has indicated that autofocus speed and accuracy has been improved in the type III version of the 1.4x and 2x Extenders." https://www.imaging-resource.com/articles/the-impact-of-teleconverters-on-image-quality-a-comparison

I found a suggestion that similar effects on autofocus were noted with Nikon TC's. https://photographylife.com/what-is-a-teleconverter#reduced-autofocus-performance.

Whether modern, TC's, lenses, and MILC's are as affected as prior DSLR's and equipment remains to be determined. One could postulate that the loss of aperture (i.e. light) and added processing/communication might impact af speed/accuracy. Objective testing is warranted.

 

[EJARAN]

I’m using the Sony GM 600 f4 and have NOT had ACCURACY problems with either the 1.4 or 2.0 TC. There certainly is a drop off with speed of AF, and a slight drop off in sharpness, but when the AF grabs the subject I have had no problems with accuracy. I shoot both wildlife and a little sports. Again the only thing I notice is that the AF is slower ( mostly with the 2x TC) but accuracy is fine.

 

[threesixty]

I’ve noticed no difference in autp-focus accuracy under any condition for the NIkon 400 2.8 TC.
But I’d have to make the proviso that I haven’t done a careful study of it.
I just don’t see anything that jumps out at me.
Also, I don’t use the 2xTC.

My use of the 400 2.8 is over several week-long backcountry shooting kayak expeditions.
I’ll typically engage and disangage the TC several times as I drift into or past a subject.

I’d add that I see the same in my 400 4.5 with external 1.4 TC: it’s almost indistinguishable in performance in daily use with and without a TC.
I know there’s a difference, but it’s so small that I have to look at the meta-data to see if the TC was engaged.

 

[thelordofthelight]

Nikon Z 4002.8 with 1.4TC is as good as the bare lens..even if there's any difference, I can't discern...even 2x is excellent on the Z mount and I use it often for action but is definitely not the same as bare lens or with 1.4x. My answer would be different if it was Nikon F mount glass when it comes to using 2X TC..it's a combination I'd use only for static subjects whereas Z mount works very well.

 

[KimM]

Sony 600 - only difference with TC1.4 I see is in poor light it is slower to acquire focus. Haven't used the 2.0 much on the 600.