Focus Weaknesses: A9, A7R III, A7R IV

[Ziggy]

I've documented my experiences and others have chipped in theirs over at Fred Miranda.

Sony AF weaknesses - A9, A7R III

www.fredmiranda.com

I encountered my first disappointment on my first day out with the A9 and FE 100-400mm, and that was poor performance with Small Spot on small static birds.

Another one has come up and that's back focussing with the 400/2.8 and TCs. It popped up here on FaceBook.

I've been able to replicate it. As far as I can tell it's a failure of CDAF to work accurately.

Here's one example ...

A9, 400/2.8 & 1.4x TC, f4, 1/1000s, small spot AF, OSS off, AF-S on timer, on tripod.

10m away, heavy crop, no sharpening or NR in post or export.

DMF & VF magnification showed the centre panel on which AF was achieved was obviously soft.

• ILCE-9
• FE 400mm F2.8 GM OSS + 1.4X Teleconverter
• 560.0 mm
• ƒ/4
• 1/1000 sec
• ISO 100

 

[Ziggy]

My 400 2.8 has now been been tested by an independent tech contracted by Sony to do warranty work.
He found back-focusing that was exaggerated by the teleconverters. (Doh).
It has to be sent back to Japan to be fixed.

 

[Uncle Kevriano]

My 400 2.8 has now been been tested by an independent tech contracted by Sony to do warranty work.
He found back-focusing that was exaggerated by the teleconverters. (Doh).
It has to be sent back to Japan to be fixed.

Damn! At least it's getting sorted, or hopefully so.

 

[Ziggy]

Yeah.
There's a UK guy with the same problem - clear as could be in his tests. Sony tested it and said it was sharp.
But they offered to trade it in plus a grand on a 600/4.

 

[Uncle Kevriano]

Yeah.
There's a UK guy with the same problem - clear as could be in his tests. Sony tested it and said it was sharp.
But they offered to trade it in plus a grand on a 600/4.

Did they. That kind of shows an admission of fault in my opinion.

 

[Ziggy]

Agree.
His was at fault from the off. He knows of another case in the UK.
Mine developed the fault about 9 months in.

 

[Deleted Member 0001]

Hmmm this is very interesting as I will be buying a A9ii and a FE 100-400 G OSS lens in two or three weeks. What exactly happened with this set up?

 

[Ziggy]

Sony AF weaknesses - A9, A7R III

www.fredmiranda.com

 

[Deleted Member 0001]

I will have a read.

 

[Jeff A]

He found back-focusing that was exaggerated by the teleconverters.

I'm a Newbie. Could some explain this to me. Be gentle, OK?

 

[garuda]

....He found back-focusing that was exaggerated by the teleconverters.....

I have read in several places that the Sony teleconverters compromise focusing performance even w native lenses - tend to slow foc speeds & sometimes soften.

That's why I passed on a 2x purchase when buying my 200-600.

 

[garuda]

I'm a Newbie. Could some explain this to me. Be gentle, O(K?

See attachment below.

 

[Ziggy]

I have read in several places that the Sony teleconverters compromise focusing performance even w native lenses - tend to slow foc speeds & sometimes soften.

That's why I passed on a 2x purchase when buying my 200-600.

The effect depends on the lens.

 

[garuda]

The effect depends on the lens.

So it's entirely due to the lens and not the TC? Does it require lens calibration or will firmware update fix?

 

[Ziggy]

I talked to the Sony agent's camera tech here in Melbourne about the small bird focus fails.

He said it's due to the small split PD sensors on the chip not performing as well as separate PD modules that DSLRs have. They don't get as much data and get confused.

 

[G-FOTO.de]

All this news from different owners makes me kind of nervous for my 400.

I did not encounter these kind of issues yet, although I own it since 05/2020. But it was not used that much because its still a bulky lens to carry around.
But this makes it even worse, because if this will happen when the 2y warranty is finished, it will be very expensive to repair.

 

[Ziggy]

It's not hard to test for this. I used an eBay knockoff of the Lens Align.
In Australia there is consumer law that provides guarantees that are greater than warranty provisions usually.