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16-35mm Inconsistent edge performance from shot to shot

Quentin_Bargate

Well-known member
A recent test has confirmed what i had suspected based on other images - that I am seeing wildly different edge performance with my 16-35mm F/4 Zeiss from one shot to another, even though the centres look equally sharp.

Here is what I mean (not exact crops but you will see the point)

Here are 100% crops from the centre and right edge for Shot "A". Both look pretty good, both taaken at F/5.6, Steady shot on, about 1/200 sec.

A, centre



A, Edge



Then here is the centre and right egde shot for shot "B" taken immediately before shot "A". Centre is fine, but edge is awful.

B, centre:



B, Edge



In both cases the centres are sharp, but the edges are very different.

And for reference, here is the whole of shot "A"

 

Guy Mancuso

Administrator, Instructor
Is this issue pretty consistent through the focal range or at a certain point. This lens goes pretty south after about 26mm. It was the reason I decided to sell it and get the Batis 25 and the VC 15mm.
 

dmward

Member
Is this issue pretty consistent through the focal range or at a certain point. This lens goes pretty south after about 26mm. It was the reason I decided to sell it and get the Batis 25 and the VC 15mm.
They look to have been shot at the same focal length.

If its on a tripod then it suggests that OSS should be turned off.

If its handheld, then there may be an issue with OSS settings or operation.

In my experience the only thing that would cause a lens to change as illustrated is a good bang to dislocate an element.

With OSS, there is also the gyro to dislocate an element.
 

Quentin_Bargate

Well-known member
Handheld, with OSS on.

Most of the time its great. Then this happens once every few shots. I suppose it just might be luck - the shot might have been taken just as adjustments are made to the stabilization.
 

waardij

New member
I see the same thing with my 16-35 f4. mostly at 16mm. when not using OSS I does not happens or it is so much less I do not notice it anymore. using f11 seems to mostly solve this, but is not always convenient and needs more sharpening. My theory is that it is caused by OSS, decentering the lens somewhat. It is a shame you can not disable OSS and let IBIS do all the stabilization (on the assumption this would help).
 

tashley

Subscriber Member
Firmware update request to Sony: allow users to turn off OSS but keep IBIS on.
Just a thought, but it could be an issue with field curvature? If you focussed near into the scene in one shot and further in the other, that could affect the edges with no discernible impact on the centre.

Probably not but it's worth throwing it into the mix. It should be easy to test for all this using MF and several handheld shots in a row without changing focus, with OSS on, and then tripod with OSS off?

I got my repaired unit back today, they replaced the entire optical assembly. It's a lot better at 35mm but in many ways it feels like a totally different lens. Sony's manufacturing is the only one to be inconsistent though!

Good luck!
 

Quentin_Bargate

Well-known member
Just a thought, but it could be an issue with field curvature? If you focussed near into the scene in one shot and further in the other, that could affect the edges with no discernible impact on the centre.

Probably not but it's worth throwing it into the mix. It should be easy to test for all this using MF and several handheld shots in a row without changing focus, with OSS on, and then tripod with OSS off?

I got my repaired unit back today, they replaced the entire optical assembly. It's a lot better at 35mm but in many ways it feels like a totally different lens. Sony's manufacturing is the only one to be inconsistent though!

Good luck!
No, its not field curvature. Sometime its absolutely fine, the next shot its not. It does seem to be connected with OSS.

These issues with expensive lenses are completely unacceptable. Like you, Tim, I have had a number of faulty lenses in my time. We pay the same money, good lens or bad, but each should be individually checked and faults corrected. When it works, mine is superb.

Do we really need OSS and IBIS in a wide angle lens? I think not.
 

uhoh7

New member
No, its not field curvature. Sometime its absolutely fine, the next shot its not. It does seem to be connected with OSS.
Actually it could be FC with a varied focal point. You see this all the time with WA on the Sony, if the focus is dead center the edge will show soft or "smeared", but if you focus just a tad before infinity the DOF at f/8 will bring in the edges.

It's why I hate AF on the Sony cameras with a passion, and the lack of a hard infinity stop is.....grrrrrr. :banghead:

I had this happen on the nex-5n and that nice little 10-18 all the time.
 

Viramati

Member
Actually it could be FC with a varied focal point. You see this all the time with WA on the Sony, if the focus is dead center the edge will show soft or "smeared", but if you focus just a tad before infinity the DOF at f/8 will bring in the edges.

It's why I hate AF on the Sony cameras with a passion, and the lack of a hard infinity stop is.....grrrrrr. :banghead:

I had this happen on the nex-5n and that nice little 10-18 all the time.
Couldn't agree with you more. The lack of an infinity hard stop (and no DOF scale) is the most frustrating thing about the Sony FE lenses and can make landscape focussing quite a hit and miss affair
 

Quentin_Bargate

Well-known member
Actually it could be FC with a varied focal point. You see this all the time with WA on the Sony, if the focus is dead center the edge will show soft or "smeared", but if you focus just a tad before infinity the DOF at f/8 will bring in the edges.

It's why I hate AF on the Sony cameras with a passion, and the lack of a hard infinity stop is.....grrrrrr. :banghead:

I had this happen on the nex-5n and that nice little 10-18 all the time.
Its a very good point. Added to that, the speed of operation of the focus ring seems to vary depending on how fast you turn it, making accurate, precise and repeatable manual focussing a nightmare.
 

slickster

Member
Hi Quentin

How do you normally focus, manual, halfpress shutter, af-on, etc. Could it be that (if auto) it did not complete focusing before shot fired. (I do understand the center seems to be in focus)

Regards, Monty:)
 

Quentin_Bargate

Well-known member
Hi Quentin

How do you normally focus, manual, halfpress shutter, af-on, etc. Could it be that (if auto) it did not complete focusing before shot fired. (I do understand the center seems to be in focus)

Regards, Monty:)
Monty,

It depends. These were autofocus, but for a lot of the time, and particularly when using a tripod, its manual focus all the way (manual everything in fact).
 

dmward

Member
Looking again at the out of focus building, it appears that motion blurr may also be a factor. Since the center is sharp, that suggests that the OSS element was moving or jittering. Not sure what that implies or how that could happen.

As for focus by wire, I've read that faster twisting of the focus ring results in larger focus movement while slower means less. Suggesting that the design is intended to speed gross focus change while making fine tuning easier.

Haven't had time to experiment with Batis readout for AF but it seems to be a good alternative to no focus scale. Infinity focus has always been an approximation with lenses. My recollection is that every lens I've owned with a focus scale has an L at infinity to suggest that its a relative focus position.

Ground glass was always a better option for me. The magnification AF assist with EVF seems a good alternative.
 

tashley

Subscriber Member
Quentin, Lloyd has a piece on his free to view page that seems to be about the same issue...
 

Quentin_Bargate

Well-known member
Quentin, Lloyd has a piece on his free to view page that seems to be about the same issue...
Interesting, Tim, but for full info I'd have to subscribe, a big no no for me.


With IBIS tuned off, and camera located on a sturdy tripod, manual focus- i.e. treating A7RII and 16-35mm combo in a similar way as I would use MF digital - then the issue seems to go away. Then its just a very good camera lens combo that renders MF redundant :thumbup:

I guess as Lloyd suggests, there must be a downside to the sensor moving to correct pitch and yaw, meaning the sensor may not be parallel to the plane of focus. That would not be a fault, simply an downside to IBIS.
 
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