Sony 400-800 Poor AF accuracy at 800 f/8
p.4 #1Sony 400-800 Poor AF accuracy at 800 f/8
icantbebigwill wrote:
I just returned my third copy of this lens. It is the perfect focal length range for birds, but I never managed to get any images I was really happy with - although if all you want is something to post to social media, it's an okay lens.I also went through 3. I've been quiet in my own thread because I gave up and went back to Nikon. I have the Z9 now, and bought a new copy of the 600PF. 95% tack sharp pictures again like I'm used to. In a car, handheld, etc. Again, I've shot the Canon 200-800, the Canon 800 f/11 and never had these problems. Maybe I don't possess the skill to use the 400-800. I learned an expensive lesson, the grass isn't always greener.
I was never really impressed with the Nikon 600mm f6.3 - I thought my Sony FE 300mm f2.8 with a 2x TC was sharper than the Nikon lens on its own. I also see a lot of used Z 600mm f6.3's for sale on the used market, so perhaps there's some sample variation with that lens - like there apparently is with the Sony 400-800.
Cliff L. wrote
Jemini wrote
I didn't get a single shot thst I was happy with. Two pieces in a raw. So I'm reluctant to try it again even though 400-800 is THE bird photography range.I was never really impressed with the Nikon 600mm f6.3 - I thought my Sony FE 300mm f2.8 with a 2x TC was sharper than the Nikon lens on its own. I also see a lot of used Z 600mm f6.3's for sale on the used market, so perhaps there's some sample variation with that lens - like there apparently is with the Sony 400-800.
Aug 28, 2026 at 08:33 AM
p.4 #2Sony 400-800 Poor AF accuracy at 800 f/8
At f/8 or f/9 you need good light and if the sun is too high then atmospheric disturbances ruin most shots unless you can get pretty close up. You might have to download and view with a native viewer at something less than 100% unless you have a Retina display. The one was taken in aps-c mode.
Aug 28, 2026 at 08:39 AM
p.4 #3Sony 400-800 Poor AF accuracy at 800 f/8
icantbebigwill wrote:
I just returned my third copy of this lens. It is the perfect focal length range for birds, but I never managed to get any images I was really happy with - although if all you want is something to post to social media, it's an okay lens.I also went through 3. I've been quiet in my own thread because I gave up and went back to Nikon. I have the Z9 now, and bought a new copy of the 600PF. 95% tack sharp pictures again like I'm used to. In a car, handheld, etc. Again, I've shot the Canon 200-800, the Canon 800 f/11 and never had these problems. Maybe I don't possess the skill to use the 400-800. I learned an expensive lesson, the grass isn't always greener.
Since my last post I've done some unscientific testing of when I miss focus or back focus with my 400-800mm and it has come down to this for me: Tracking sensitivity set too high on stationary objects.
On perched or stationary objects, if I am in one of my "birding modes" that I set up like User1 on my dial, where I have tracking on and tracking sensitivity set high, like anything above 3, ( like AF Tracking Sensitivity 5 (Responsive)) the A/F will "hop" back and forth to the background and when you depress the shutter, there is a 50/50 chance you will land on the back focused hop. If I lower tracking sensitivity it locks more consistently on stationary objects.
So, I have the custom AF-ON button set where I switch from Tracking wide with a custom Hold, to turn it off to Tracking Spot and lowers my sensitivity from 5 down to 1, and I get a two-fer from it...
one, I can track birds in clear sky with tracking on, and when they land in the branches and busy bush I thumb hold the button and it now stays locked on the perched birds eye and ignores the branches,
and two, it doesn't back focus on stationary objects when my thumb is on the AF-On button because of the lower sensitivity setting.
Another alternative might be to use AF-S instead of C for stationary objects... I think that is probably the only setting change you can make that will force the camera to ignore your sensitivity setting.
I dunno... like I said, I don't have the time or motivation to really lock it down or publish with more solid testing, but its an easy enough thing for anyone out there who is having trouble to try for themselves.
I would be curious to hear back from anyone who tries/has tried this and if it worked for them.
For what it's worth, I bought my 400-800mm used here on the forum, (they did not say they were unhappy with anything about it, but you always wonder) and I'm getting sharp shots with it consistently now, even wide open.
Eric
Edited on Aug 28, 2026 at 09:34 AM · View previous versions
Cliff L. wrote
Jemini wrote
I didn't get a single shot thst I was happy with. Two pieces in a raw. So I'm reluctant to try it again even though 400-800 is THE bird photography range.Since my last post I've done some unscientific testing of when I miss focus or back focus with my 400-800mm and it has come down to this for me: Tracking sensitivity set too high on stationary objects.
On perched or stationary objects, if I am in one of my "birding modes" that I set up like User1 on my dial, where I have tracking on and tracking sensitivity set high, like anything above 3, ( like AF Tracking Sensitivity 5 (Responsive)) the A/F will "hop" back and forth to the background and when you depress the shutter, there is a 50/50 chance you will land on the back focused hop. If I lower tracking sensitivity it locks more consistently on stationary objects.
So, I have the custom AF-ON button set where I switch from Tracking wide with a custom Hold, to turn it off to Tracking Spot and lowers my sensitivity from 5 down to 1, and I get a two-fer from it...
one, I can track birds in clear sky with tracking on, and when they land in the branches and busy bush I thumb hold the button and it now stays locked on the perched birds eye and ignores the branches,
and two, it doesn't back focus on stationary objects when my thumb is on the AF-On button because of the lower sensitivity setting.
Another alternative might be to use AF-S instead of C for stationary objects... I think that is probably the only setting change you can make that will force the camera to ignore your sensitivity setting.
I dunno... like I said, I don't have the time or motivation to really lock it down or publish with more solid testing, but its an easy enough thing for anyone out there who is having trouble to try for themselves.
I would be curious to hear back from anyone who tries/has tried this and if it worked for them.
For what it's worth, I bought my 400-800mm used here on the forum, (they did not say they were unhappy with anything about it, but you always wonder) and I'm getting sharp shots with it consistently now, even wide open.
Eric
Edited on Aug 28, 2026 at 09:34 AM · View previous versions
Aug 28, 2026 at 09:07 AM
p.4 #4Sony 400-800 Poor AF accuracy at 800 f/8
I’m wondering if the magnified 800 FoV sees so much small detail that it has issues locking on a now relatively lager and smooth surface eyeball? I too am hoping there’s a FW fix. The resolution and detail are definitely there when focus is nailed. But even at f8 or 9, DoF is super shallow at typical bird distances.
Aug 28, 2026 at 09:23 AM
p.4 #5Sony 400-800 Poor AF accuracy at 800 f/8
I’m sure there is. My new copy of the 600 PF is better than my first and I would have considered the first a 10/10. Just given the slots they occupy in their respective lineups I’d expect the 400-800 to have more inconsistency but who knows. I’m 2 for 2 on PFs and 0 for 3 on 400-800s.
Cliff L. wrote:
I just returned my third copy of this lens. It is the perfect focal length range for birds, but I never managed to get any images I was really happy with - although if all you want is something to post to social media, it's an okay lens.I also went through 3. I've been quiet in my own thread because I gave up and went back to Nikon. I have the Z9 now, and bought a new copy of the 600PF. 95% tack sharp pictures again like I'm used to. In a car, handheld, etc. Again, I've shot the Canon 200-800, the Canon 800 f/11 and never had these problems. Maybe I don't possess the skill to use the 400-800. I learned an expensive lesson, the grass isn't always greener.I was never really impressed with the Nikon 600mm f6.3 - I thought my Sony FE 300mm f2.8 with a 2x TC was sharper than the Nikon lens on its own. I also see a lot of used Z 600mm f6.3's for sale on the used market, so perhaps there's some sample variation with that lens - like there apparently is with the Sony 400-800.
Cliff L. wrote:
icantbebigwill wrote
Cliff L. wrote
Jemini wrote
I didn't get a single shot thst I was happy with. Two pieces in a raw. So I'm reluctant to try it again even though 400-800 is THE bird photography range.Sep 03, 2026 at 04:45 AM
p.4 #6Sony 400-800 Poor AF accuracy at 800 f/8
I'm seeing more posts about problems with this lens. I have been pleased with mine. Picked it up when it was first released to replace my 200-600. I've used it with the A1 and A7RVI. No issues. Is your copy still made in China? When the lens was first released it was US $2899, then shortly after due to tariffs, went to $3299. Then, it dropped pretty quickly to $2699. Wonder if anything was changed to get it down to a lower price. Manufacturing location? Design change?
Sep 22, 2026 at 04:38 AM
p.4 #7Sony 400-800 Poor AF accuracy at 800 f/8
AtomicPunk wrote:
I'm seeing more posts about problems with this lens. I have been pleased with mine. Picked it up when it was first released to replace my 200-600. I've used it with the A1 and A7RVI. No issues. Is your copy still made in China? When the lens was first released it was US $2899, then shortly after due to tariffs, went to $3299. Then, it dropped pretty quickly to $2699. Wonder if anything was changed to get it down to a lower price. Manufacturing location? Design change?
Solely based on my hunch, the price drop is more due to the announcement of 2 light-weight primes in the Sony lineup...
I'm seeing more posts about problems with this lens. I have been pleased with mine. Picked it up when it was first released to replace my 200-600. I've used it with the A1 and A7RVI. No issues. Is your copy still made in China? When the lens was first released it was US $2899, then shortly after due to tariffs, went to $3299. Then, it dropped pretty quickly to $2699. Wonder if anything was changed to get it down to a lower price. Manufacturing location? Design change?
Solely based on my hunch, the price drop is more due to the announcement of 2 light-weight primes in the Sony lineup...
Sep 22, 2026 at 05:54 AM
p.4 #8Sony 400-800 Poor AF accuracy at 800 f/8
Just to add my 2 cents. I no longer own the lens but this is the post i had made on the facebook page.
"Hey guys, I posted about the focusing issue i've been having with A1ii and 400-800 lens. I tested this extensively now with many different combinations of focus settings including what's on sony's website and suggestions here.
Nothing has helped. Then i turned off the AI autofocus and voila, all sharp photos again. See below where the left photos are AI/subject detection on, and right photos are AI off. Now keep in mind the subject detection DOES see the eye, draws a box, but ultimately its not in focus. all photos were taken at 1/2500 ss. The photos were a burst, so this behaviour was consistent across. I also tested on my wife and a similar issue happened so it is not just bird AI
Then I tested on my 70-200 GM 2 with 2x TC and it was accurate, sharp and no difference between subject detection on or off.
My guess is that the lens is not responding well to the Subject detection/AI algorithm. There seems to be a software incompatibility between this lens and my body. The lens is actually sharp, I thought it was just soft on the 800mm end but it is just not focusing precisely, it is inprecise just enough so you think its focused but its not.
I can confidently conclude that it is the lens and not the body now. I do recall back in the A7RIV days and 200-600mm lens, some 200-600mm lenses and A7RIV just did not like eachother. The same 200-600 could be used on a different A7RIV body and it would be fine. The same A7RIV could be used with a 200-600 and it would be fine. My pairing never had issues but this was quite wide spread. I am guessing as more people use the 400-800 they'll start finding out about incompatibilities like this.
Again, the LEFT photos are AI on, RIGHT photos are AI off. "
"Hey guys, I posted about the focusing issue i've been having with A1ii and 400-800 lens. I tested this extensively now with many different combinations of focus settings including what's on sony's website and suggestions here.
Nothing has helped. Then i turned off the AI autofocus and voila, all sharp photos again. See below where the left photos are AI/subject detection on, and right photos are AI off. Now keep in mind the subject detection DOES see the eye, draws a box, but ultimately its not in focus. all photos were taken at 1/2500 ss. The photos were a burst, so this behaviour was consistent across. I also tested on my wife and a similar issue happened so it is not just bird AI
Then I tested on my 70-200 GM 2 with 2x TC and it was accurate, sharp and no difference between subject detection on or off.
My guess is that the lens is not responding well to the Subject detection/AI algorithm. There seems to be a software incompatibility between this lens and my body. The lens is actually sharp, I thought it was just soft on the 800mm end but it is just not focusing precisely, it is inprecise just enough so you think its focused but its not.
I can confidently conclude that it is the lens and not the body now. I do recall back in the A7RIV days and 200-600mm lens, some 200-600mm lenses and A7RIV just did not like eachother. The same 200-600 could be used on a different A7RIV body and it would be fine. The same A7RIV could be used with a 200-600 and it would be fine. My pairing never had issues but this was quite wide spread. I am guessing as more people use the 400-800 they'll start finding out about incompatibilities like this.
Again, the LEFT photos are AI on, RIGHT photos are AI off. "
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Sep 22, 2026 at 10:44 AM
p.4 #9Sony 400-800 Poor AF accuracy at 800 f/8
I have just done a test with my 400-800 to check the sharpness at f/8 with manual focus and it seems to be just as sharp as at f/9.
These were taken with manual focus and from the first f/9 image until the end I set the focus on the fur and did not change it while those images were taken. Settings for each at the bottom.
I used my iPhone app as a bluetooth remote to take short bursts of images.
The f/8 images are very very close to the f/9 image in terms of sharpness and much much better than anything I can get when using Autofocus - even with subject detection turned off.
So it seems the lens is quite capable of extremely sharp images at f/8 but when using autofocus something goes horribly wrong as there is not a single image that is sharp and they all look as if they have a small amount of motion blur on them.
Seems like I might have to send the lens back to Sony to ask them to look at it - no doubt they will just turn around and say it is within spec but there seems to be no good reason why the lens shouldn't be able to produce the exact same image quality with AF as with MF.
Curious as to whether others have focus problems at f/8 also find their lens is sharp with MF and it is only when AF is used the f/8 images become blurry.
Compare the first f/9 image with the f/8 images that follow - to me the f/8 images look slightly better than the f/10 images.
https://duncangroenewald.com/pages/collections/2026-09-23-FE400800-MFTest.html
These were taken with manual focus and from the first f/9 image until the end I set the focus on the fur and did not change it while those images were taken. Settings for each at the bottom.
I used my iPhone app as a bluetooth remote to take short bursts of images.
The f/8 images are very very close to the f/9 image in terms of sharpness and much much better than anything I can get when using Autofocus - even with subject detection turned off.
So it seems the lens is quite capable of extremely sharp images at f/8 but when using autofocus something goes horribly wrong as there is not a single image that is sharp and they all look as if they have a small amount of motion blur on them.
Seems like I might have to send the lens back to Sony to ask them to look at it - no doubt they will just turn around and say it is within spec but there seems to be no good reason why the lens shouldn't be able to produce the exact same image quality with AF as with MF.
Curious as to whether others have focus problems at f/8 also find their lens is sharp with MF and it is only when AF is used the f/8 images become blurry.
Compare the first f/9 image with the f/8 images that follow - to me the f/8 images look slightly better than the f/10 images.
https://duncangroenewald.com/pages/collections/2026-09-23-FE400800-MFTest.html
Sep 23, 2026 at 01:48 AM
p.4 #10Sony 400-800 Poor AF accuracy at 800 f/8
AGeoJO wrote:
Solely based on my hunch, the price drop is more due to the announcement of 2 light-weight primes in the Sony lineup...
That price drop to $2699 happened well before the announcement of the 2 new primes. It was almost a year ago when it dropped.
AtomicPunk wrote
I'm seeing more posts about problems with this lens. I have been pleased with mine. Picked it up when it was first released to replace my 200-600. I've used it with the A1 and A7RVI. No issues. Is your copy still made in China? When the lens was first released it was US $2899, then shortly after due to tariffs, went to $3299. Then, it dropped pretty quickly to $2699. Wonder if anything was changed to get it down to a lower price. Manufacturing location? Design change?That price drop to $2699 happened well before the announcement of the 2 new primes. It was almost a year ago when it dropped.
Sep 23, 2026 at 04:50 AM
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p.4 #11Sony 400-800 Poor AF accuracy at 800 f/8
My 4-800 is sharp at 800 on an A1II; however, if the subject is far (even twenty feet is far in turbulent air) or the atmosphere is turbulent, sharpness goes down the tube. I always look at the highlight in the Birds Eye; if it is perfectly round, then atmosphere isn't an issue but if it looks nervous or has a lot of spikes, then turbulence is high.
Sep 23, 2026 at 07:32 AM
p.4 #12Sony 400-800 Poor AF accuracy at 800 f/8
aryanenzo wrote:
Just to add my 2 cents. I no longer own the lens but this is the post i had made on the facebook page.
"Hey guys, I posted about the focusing issue i've been having with A1ii and 400-800 lens. I tested this extensively now with many different combinations of focus settings including what's on sony's website and suggestions here.
Nothing has helped. Then i turned off the AI autofocus and voila, all sharp photos again. See below where the left photos are AI/subject detection on, and right photos are AI off. Now keep in mind the subject detection DOES see...Show more →
You might be right. I don't have the lens anymore. But what you showed on the left hand side is what I was seeing in all images. I took some shots on tripod with timer. But I don't remember if I had AI on or OFF.
Just to add my 2 cents. I no longer own the lens but this is the post i had made on the facebook page.
"Hey guys, I posted about the focusing issue i've been having with A1ii and 400-800 lens. I tested this extensively now with many different combinations of focus settings including what's on sony's website and suggestions here.
Nothing has helped. Then i turned off the AI autofocus and voila, all sharp photos again. See below where the left photos are AI/subject detection on, and right photos are AI off. Now keep in mind the subject detection DOES see...Show more →
You might be right. I don't have the lens anymore. But what you showed on the left hand side is what I was seeing in all images. I took some shots on tripod with timer. But I don't remember if I had AI on or OFF.
Sep 23, 2026 at 07:56 AM
p.4 #13Sony 400-800 Poor AF accuracy at 800 f/8
duncangr wrote:
I have just done a test with my 400-800 to check the sharpness at f/8 with manual focus and it seems to be just as sharp as at f/9.
These were taken with manual focus and from the first f/9 image until the end I set the focus on the fur and did not change it while those images were taken. Settings for each at the bottom.
I used my iPhone app as a bluetooth remote to take short bursts of images.
The f/8 images are very very close to the f/9 image in terms of sharpness and much much better than...Show more →
I wonder if it's because that Sony didn't use the XD linear motors on the 400-800mm.
Sony claimed that they used "Precision Linear Motors" but not their XDs. So with the current algorithm it might be doing something weird with the focusing, especially with AFC because AFC is predictive, so there might be a "vibration", say overshooting the error of focal plane constantly between each of the PDAF samples. Like a vibration or delay spike that can happen in many close loop feedback control systems...
I have just done a test with my 400-800 to check the sharpness at f/8 with manual focus and it seems to be just as sharp as at f/9.
These were taken with manual focus and from the first f/9 image until the end I set the focus on the fur and did not change it while those images were taken. Settings for each at the bottom.
I used my iPhone app as a bluetooth remote to take short bursts of images.
The f/8 images are very very close to the f/9 image in terms of sharpness and much much better than...Show more →
I wonder if it's because that Sony didn't use the XD linear motors on the 400-800mm.
Sony claimed that they used "Precision Linear Motors" but not their XDs. So with the current algorithm it might be doing something weird with the focusing, especially with AFC because AFC is predictive, so there might be a "vibration", say overshooting the error of focal plane constantly between each of the PDAF samples. Like a vibration or delay spike that can happen in many close loop feedback control systems...
Sep 23, 2026 at 08:22 AM
p.4 #14Sony 400-800 Poor AF accuracy at 800 f/8
hotellonely wrote:
These were taken with manual focus and from the first f/9 image until the end I set the focus on the fur and did not change it while those images were taken. Settings for each at the bottom.
I used my iPhone app as a bluetooth remote to take short bursts of images.
The f/8 images are very very close to the f/9 image in terms of sharpness and much much better than anything I can get when using Autofocus - even with subject detection turned off.
So it seems the lens is quite capable of extremely sharp images at f/8 but when using autofocus something goes horribly wrong as there is not a single image that is sharp and they all look as if they have a small amount of motion blur on them.
Seems like I might have to send the lens back to Sony to ask them to look at it - no doubt they will just turn around and say it is within spec but there seems to be no good reason why the lens shouldn't be able to produce the exact same image quality with AF as with MF.
Curious as to whether others have focus problems at f/8 also find their lens is sharp with MF and it is only when AF is used the f/8 images become blurry.
Compare the first f/9 image with the f/8 images that follow - to me the f/8 images look slightly better than the f/10 images.
https://duncangroenewald.com/pages/collections/2026-09-23-FE400800-MFTest.htmlI wonder if it's because that Sony didn't use the XD linear motors on the 400-800mm.
Sony claimed that they used "Precision Linear Motors" but not their XDs. So with the current algorithm it might be doing something weird with the focusing, especially with AFC because AFC is predictive, so there might be a "vibration", say overshooting the error of focal plane constantly between each of the PDAF samples. Like a vibration or delay spike that can happen in many close loop feedback control systems...
I posted my findings on AFC missing focus on stationary objects earlier in this thread and I have yet to see anyone confirm if they have tried it (though one user said they tried AFS and the problem went away for them, same thing really, so that is a form of confirmation).
Setting AFC Tracking to 5, Responsive will make the lens miss a lot on stationary objects, turning down AFC to anything less than 3 sensitivity seems to improve it drastically.
I'd love for someone here to corroborate or replicate my findings. And it shouldn't just happen with the 400-800mm, but it's probably more obvious because of the narrow DOF and other factors with this lens.
Eric
duncangr wrote
I have just done a test with my 400-800 to check the sharpness at f/8 with manual focus and it seems to be just as sharp as at f/9.These were taken with manual focus and from the first f/9 image until the end I set the focus on the fur and did not change it while those images were taken. Settings for each at the bottom.
I used my iPhone app as a bluetooth remote to take short bursts of images.
The f/8 images are very very close to the f/9 image in terms of sharpness and much much better than anything I can get when using Autofocus - even with subject detection turned off.
So it seems the lens is quite capable of extremely sharp images at f/8 but when using autofocus something goes horribly wrong as there is not a single image that is sharp and they all look as if they have a small amount of motion blur on them.
Seems like I might have to send the lens back to Sony to ask them to look at it - no doubt they will just turn around and say it is within spec but there seems to be no good reason why the lens shouldn't be able to produce the exact same image quality with AF as with MF.
Curious as to whether others have focus problems at f/8 also find their lens is sharp with MF and it is only when AF is used the f/8 images become blurry.
Compare the first f/9 image with the f/8 images that follow - to me the f/8 images look slightly better than the f/10 images.
https://duncangroenewald.com/pages/collections/2026-09-23-FE400800-MFTest.html
Sony claimed that they used "Precision Linear Motors" but not their XDs. So with the current algorithm it might be doing something weird with the focusing, especially with AFC because AFC is predictive, so there might be a "vibration", say overshooting the error of focal plane constantly between each of the PDAF samples. Like a vibration or delay spike that can happen in many close loop feedback control systems...
I posted my findings on AFC missing focus on stationary objects earlier in this thread and I have yet to see anyone confirm if they have tried it (though one user said they tried AFS and the problem went away for them, same thing really, so that is a form of confirmation).
Setting AFC Tracking to 5, Responsive will make the lens miss a lot on stationary objects, turning down AFC to anything less than 3 sensitivity seems to improve it drastically.
I'd love for someone here to corroborate or replicate my findings. And it shouldn't just happen with the 400-800mm, but it's probably more obvious because of the narrow DOF and other factors with this lens.
Eric
Sep 23, 2026 at 08:37 AM
p.4 #15Sony 400-800 Poor AF accuracy at 800 f/8
Jemini wrote:
"Hey guys, I posted about the focusing issue i've been having with A1ii and 400-800 lens. I tested this extensively now with many different combinations of focus settings including what's on sony's website and suggestions here.
Nothing has helped. Then i turned off the AI autofocus and voila, all sharp photos again. See below where the left photos are AI/subject detection on, and right photos are AI off. Now keep in mind the subject detection DOES see the eye, draws a box, but ultimately its not in focus. all photos were taken at 1/2500 ss. The photos were a burst, so this behaviour was consistent across. I also tested on my wife and a similar issue happened so it is not just bird AI
Then I tested on my 70-200 GM 2 with 2x TC and it was accurate, sharp and no difference between subject detection on or off.
My guess is that the lens is not responding well to the Subject detection/AI algorithm. There seems to be a software incompatibility between this lens and my body. The lens is actually sharp, I thought it was just soft on the 800mm end but it is just not focusing precisely, it is inprecise just enough so you think its focused but its not.
I can confidently conclude that it is the lens and not the body now. I do recall back in the A7RIV days and 200-600mm lens, some 200-600mm lenses and A7RIV just did not like eachother. The same 200-600 could be used on a different A7RIV body and it would be fine. The same A7RIV could be used with a 200-600 and it would be fine. My pairing never had issues but this was quite wide spread. I am guessing as more people use the 400-800 they'll start finding out about incompatibilities like this.
Again, the LEFT photos are AI on, RIGHT photos are AI off. "You might be right. I don't have the lens anymore. But what you showed on the left hand side is what I was seeing in all images. I took some shots on tripod with timer. But I don't remember if I had AI on or OFF.
What is this AI autofocus you guys are talking about - I have an A9iii, A1ii and A7R6 and none of them have any AI menu option that can be turned on or off.
Are you referring to turning off Subject Detection ?
If find that doesn't help at all - I have to turn off AF using the lens button MF/AF to switch to MF in order to get consistently sharp images.
aryanenzo wrote
Just to add my 2 cents. I no longer own the lens but this is the post i had made on the facebook page."Hey guys, I posted about the focusing issue i've been having with A1ii and 400-800 lens. I tested this extensively now with many different combinations of focus settings including what's on sony's website and suggestions here.
Nothing has helped. Then i turned off the AI autofocus and voila, all sharp photos again. See below where the left photos are AI/subject detection on, and right photos are AI off. Now keep in mind the subject detection DOES see the eye, draws a box, but ultimately its not in focus. all photos were taken at 1/2500 ss. The photos were a burst, so this behaviour was consistent across. I also tested on my wife and a similar issue happened so it is not just bird AI
Then I tested on my 70-200 GM 2 with 2x TC and it was accurate, sharp and no difference between subject detection on or off.
My guess is that the lens is not responding well to the Subject detection/AI algorithm. There seems to be a software incompatibility between this lens and my body. The lens is actually sharp, I thought it was just soft on the 800mm end but it is just not focusing precisely, it is inprecise just enough so you think its focused but its not.
I can confidently conclude that it is the lens and not the body now. I do recall back in the A7RIV days and 200-600mm lens, some 200-600mm lenses and A7RIV just did not like eachother. The same 200-600 could be used on a different A7RIV body and it would be fine. The same A7RIV could be used with a 200-600 and it would be fine. My pairing never had issues but this was quite wide spread. I am guessing as more people use the 400-800 they'll start finding out about incompatibilities like this.
Again, the LEFT photos are AI on, RIGHT photos are AI off. "
What is this AI autofocus you guys are talking about - I have an A9iii, A1ii and A7R6 and none of them have any AI menu option that can be turned on or off.
Are you referring to turning off Subject Detection ?
If find that doesn't help at all - I have to turn off AF using the lens button MF/AF to switch to MF in order to get consistently sharp images.
Sep 23, 2026 at 02:00 PM
p.4 #16Sony 400-800 Poor AF accuracy at 800 f/8
Erictator wrote:
These were taken with manual focus and from the first f/9 image until the end I set the focus on the fur and did not change it while those images were taken. Settings for each at the bottom.
I used my iPhone app as a bluetooth remote to take short bursts of images.
The f/8 images are very very close to the f/9 image in terms of sharpness and much much better than anything I can get when using Autofocus - even with subject detection turned off.
So it seems the lens is quite capable of extremely sharp images at f/8 but when using autofocus something goes horribly wrong as there is not a single image that is sharp and they all look as if they have a small amount of motion blur on them.
Seems like I might have to send the lens back to Sony to ask them to look at it - no doubt they will just turn around and say it is within spec but there seems to be no good reason why the lens shouldn't be able to produce the exact same image quality with AF as with MF.
Curious as to whether others have focus problems at f/8 also find their lens is sharp with MF and it is only when AF is used the f/8 images become blurry.
Compare the first f/9 image with the f/8 images that follow - to me the f/8 images look slightly better than the f/10 images.
https://duncangroenewald.com/pages/collections/2026-09-23-FE400800-MFTest.htmlI wonder if it's because that Sony didn't use the XD linear motors on the 400-800mm.
Sony claimed that they used "Precision Linear Motors" but not their XDs. So with the current algorithm it might be doing something weird with the focusing, especially with AFC because AFC is predictive, so there might be a "vibration", say overshooting the error of focal plane constantly between each of the PDAF samples. Like a vibration or delay spike that can happen in many close loop feedback control systems...I posted my findings on AFC missing focus on stationary objects earlier in this thread and I have yet to see anyone confirm if they have tried it (though one user said they tried AFS and the problem went away for them, same thing really, so that is a form of confirmation).
Setting AFC Tracking to 5, Responsive will make the lens miss a lot on stationary objects, turning down AFC to anything less than 3 sensitivity seems to improve it drastically.
I'd love for someone here to corroborate or replicate my findings. And it shouldn't just happen with the 400-800mm,...Show more →
My post above basically does that - it confirms that the lens can be very sharp at f/8 but to achieve that I have to use manual focus. When using autofocus (subject detection off or on) the images appear to have motion blur of some sort - as if from moving lens elements. f/9 improves things a bit and f/10 seems a lot better.
I am going to send mine back to Sony to see what they have to say about it. It's not really acceptable for the lens to not work properly with autofocus on static subjects - after all it is primarily a wildlife lens.
hotellonely wrote
duncangr wrote
I have just done a test with my 400-800 to check the sharpness at f/8 with manual focus and it seems to be just as sharp as at f/9.These were taken with manual focus and from the first f/9 image until the end I set the focus on the fur and did not change it while those images were taken. Settings for each at the bottom.
I used my iPhone app as a bluetooth remote to take short bursts of images.
The f/8 images are very very close to the f/9 image in terms of sharpness and much much better than anything I can get when using Autofocus - even with subject detection turned off.
So it seems the lens is quite capable of extremely sharp images at f/8 but when using autofocus something goes horribly wrong as there is not a single image that is sharp and they all look as if they have a small amount of motion blur on them.
Seems like I might have to send the lens back to Sony to ask them to look at it - no doubt they will just turn around and say it is within spec but there seems to be no good reason why the lens shouldn't be able to produce the exact same image quality with AF as with MF.
Curious as to whether others have focus problems at f/8 also find their lens is sharp with MF and it is only when AF is used the f/8 images become blurry.
Compare the first f/9 image with the f/8 images that follow - to me the f/8 images look slightly better than the f/10 images.
https://duncangroenewald.com/pages/collections/2026-09-23-FE400800-MFTest.html
Sony claimed that they used "Precision Linear Motors" but not their XDs. So with the current algorithm it might be doing something weird with the focusing, especially with AFC because AFC is predictive, so there might be a "vibration", say overshooting the error of focal plane constantly between each of the PDAF samples. Like a vibration or delay spike that can happen in many close loop feedback control systems...
Setting AFC Tracking to 5, Responsive will make the lens miss a lot on stationary objects, turning down AFC to anything less than 3 sensitivity seems to improve it drastically.
I'd love for someone here to corroborate or replicate my findings. And it shouldn't just happen with the 400-800mm,...Show more →
My post above basically does that - it confirms that the lens can be very sharp at f/8 but to achieve that I have to use manual focus. When using autofocus (subject detection off or on) the images appear to have motion blur of some sort - as if from moving lens elements. f/9 improves things a bit and f/10 seems a lot better.
I am going to send mine back to Sony to see what they have to say about it. It's not really acceptable for the lens to not work properly with autofocus on static subjects - after all it is primarily a wildlife lens.
Sep 23, 2026 at 02:06 PM
p.4 #17Sony 400-800 Poor AF accuracy at 800 f/8
duncangr wrote:
These were taken with manual focus and from the first f/9 image until the end I set the focus on the fur and did not change it while those images were taken. Settings for each at the bottom.
I used my iPhone app as a bluetooth remote to take short bursts of images.
The f/8 images are very very close to the f/9 image in terms of sharpness and much much better than anything I can get when using Autofocus - even with subject detection turned off.
So it seems the lens is quite capable of extremely sharp images at f/8 but when using autofocus something goes horribly wrong as there is not a single image that is sharp and they all look as if they have a small amount of motion blur on them.
Seems like I might have to send the lens back to Sony to ask them to look at it - no doubt they will just turn around and say it is within spec but there seems to be no good reason why the lens shouldn't be able to produce the exact same image quality with AF as with MF.
Curious as to whether others have focus problems at f/8 also find their lens is sharp with MF and it is only when AF is used the f/8 images become blurry.
Compare the first f/9 image with the f/8 images that follow - to me the f/8 images look slightly better than the f/10 images.
https://duncangroenewald.com/pages/collections/2026-09-23-FE400800-MFTest.htmlI wonder if it's because that Sony didn't use the XD linear motors on the 400-800mm.
Sony claimed that they used "Precision Linear Motors" but not their XDs. So with the current algorithm it might be doing something weird with the focusing, especially with AFC because AFC is predictive, so there might be a "vibration", say overshooting the error of focal plane constantly between each of the PDAF samples. Like a vibration or delay spike that can happen in many close loop feedback control systems...I posted my findings on AFC missing focus on stationary objects earlier in this thread and I have yet to see anyone confirm if they have tried it (though one user said they tried AFS and the problem went away for them, same thing really, so that is a form of confirmation).
Setting AFC Tracking to 5, Responsive will make the lens miss a lot on stationary objects, turning down AFC to anything less than 3 sensitivity seems to improve it drastically.
I'd love for someone here to corroborate or replicate my findings. And it shouldn't just happen with the 400-800mm, but it's probably more obvious because of the narrow DOF and other factors with this lens.
EricMy post above basically does that - it confirms that the lens can be very sharp at f/8 but to achieve that I have to use manual focus. When using autofocus (subject detection off or on) the images appear to have motion blur of some sort - as if from moving lens elements. f/9 improves things a bit and f/10 seems a lot better.
I am going to send mine back to Sony to see what they have to say about it. It's not really acceptable for the lens to not work properly with autofocus on static subjects - after all...Show more →
I anxiously await your result from Sony, if you are the first in line to get a definitive answer from Sony on it, you could be doing everyone a favor...
...though I have to tell you, it's a known issue on Sony bodies, and I don't really believe it's a lens problem, it's just more apparent on an 800mm with such a shallow DOF.
My 200-600mm did it, just not as annoyingly obvious. I often shot it stopped down because that is where I thought peak sharpness was, but some of it was the micro adjustments the CAF was constantly racking back and forth with CAF with responsiveness set too high.... with AF-S it's not an issue on either lens.
So, while it could take a combination lens FW update and body FW update to fix it, I'm still not so sure it's really a lens-centric issue as much as a body CAF issue, if you get my drift?
Eric
Erictator wrote
hotellonely wrote
duncangr wrote
I have just done a test with my 400-800 to check the sharpness at f/8 with manual focus and it seems to be just as sharp as at f/9.These were taken with manual focus and from the first f/9 image until the end I set the focus on the fur and did not change it while those images were taken. Settings for each at the bottom.
I used my iPhone app as a bluetooth remote to take short bursts of images.
The f/8 images are very very close to the f/9 image in terms of sharpness and much much better than anything I can get when using Autofocus - even with subject detection turned off.
So it seems the lens is quite capable of extremely sharp images at f/8 but when using autofocus something goes horribly wrong as there is not a single image that is sharp and they all look as if they have a small amount of motion blur on them.
Seems like I might have to send the lens back to Sony to ask them to look at it - no doubt they will just turn around and say it is within spec but there seems to be no good reason why the lens shouldn't be able to produce the exact same image quality with AF as with MF.
Curious as to whether others have focus problems at f/8 also find their lens is sharp with MF and it is only when AF is used the f/8 images become blurry.
Compare the first f/9 image with the f/8 images that follow - to me the f/8 images look slightly better than the f/10 images.
https://duncangroenewald.com/pages/collections/2026-09-23-FE400800-MFTest.html
Sony claimed that they used "Precision Linear Motors" but not their XDs. So with the current algorithm it might be doing something weird with the focusing, especially with AFC because AFC is predictive, so there might be a "vibration", say overshooting the error of focal plane constantly between each of the PDAF samples. Like a vibration or delay spike that can happen in many close loop feedback control systems...
Setting AFC Tracking to 5, Responsive will make the lens miss a lot on stationary objects, turning down AFC to anything less than 3 sensitivity seems to improve it drastically.
I'd love for someone here to corroborate or replicate my findings. And it shouldn't just happen with the 400-800mm, but it's probably more obvious because of the narrow DOF and other factors with this lens.
Eric
I am going to send mine back to Sony to see what they have to say about it. It's not really acceptable for the lens to not work properly with autofocus on static subjects - after all...Show more →
I anxiously await your result from Sony, if you are the first in line to get a definitive answer from Sony on it, you could be doing everyone a favor...
...though I have to tell you, it's a known issue on Sony bodies, and I don't really believe it's a lens problem, it's just more apparent on an 800mm with such a shallow DOF.
My 200-600mm did it, just not as annoyingly obvious. I often shot it stopped down because that is where I thought peak sharpness was, but some of it was the micro adjustments the CAF was constantly racking back and forth with CAF with responsiveness set too high.... with AF-S it's not an issue on either lens.
So, while it could take a combination lens FW update and body FW update to fix it, I'm still not so sure it's really a lens-centric issue as much as a body CAF issue, if you get my drift?
Eric
Sep 23, 2026 at 03:02 PM
p.4 #18Sony 400-800 Poor AF accuracy at 800 f/8
For predicative focusing algorithms, yes there's always going to have a local optima problem. It's trying to optimize the results with a set step size, but the size can be too large for some situations. And when all the stars align you might encounter something like what happened on the original 100-400GM, the 200-600G and 400-800G: A slightly less responsive linear motor + a default step size too large + potentially lack of vertical features for the PDAF pixels to grab on = perfect storm.
Sep 23, 2026 at 08:24 PM
p.4 #19Sony 400-800 Poor AF accuracy at 800 f/8
I got rid of my FE 200-600mm for the same reason. Now I own an FE 400-800mm with much better results.
Sep 24, 2026 at 03:37 AM