Sony 20 f2.8 on A99 - focus issue on short distance

Started 8 months ago | Discussions
Faith Yeung Contributing Member • Posts: 595
Sony 20 f2.8 on A99 - focus issue on short distance

Hi,

I just got a Sony 20mm f2.8. On A99, when I use central focus point, the distance scale on lens body reads 1 m. The image is very soft at the outer edge.

When I use the side focus point to focus the same wall facing me, it reads 0.6 m. The image edge is much sharper but the image centre becomes blur.

Do you experienced the same? How do you handle it?

I think the issue will be less prominent for long distance shot because of the longer depth of view.

 Faith Yeung's gear list:Faith Yeung's gear list
Sony SLT-A77 Sony SLT-A37 Sony Alpha a99 Nikon 1 V2
Sony Alpha a99
If you believe there are incorrect tags, please send us this post using our feedback form.
QuietOC
QuietOC Veteran Member • Posts: 4,142
Re: Sony 20 f2.8 on A99 - focus issue on short distance

Faith Yeung wrote:

Hi,

I just got a Sony 20mm f2.8. On A99, when I use central focus point, the distance scale on lens body reads 1 m. The image is very soft at the outer edge.

When I use the side focus point to focus the same wall facing me, it reads 0.6 m. The image edge is much sharper but the image centre becomes blur.

Do you experienced the same? How do you handle it?

I think the issue will be less prominent for long distance shot because of the longer depth of view.

The copies I have had of the Minolta 20 F2.8 have had field curvature of that general shape at close focus but not as severe.

 QuietOC's gear list:QuietOC's gear list
Pentax Q7 Sony a7 III Canon EF 100mm f/2.0 USM Canon EF 28-105mm f/3.5-4.5 II USM Canon EF 70-200mm F4L USM +116 more
stan_pustylnik Veteran Member • Posts: 4,017
Re: Sony 20 f2.8 on A99 - focus issue on short distance

You got lemon lens or need to learn depth of field with this lens.

My Minolta Maxxum 20mm f/2.8 AF is very reliable, works good with close focus while taking landscapes.

https://stan-pustylnik.smugmug.com/Nature/Summer-Nature-Photos/i-KxzxSQP/A

https://stan-pustylnik.smugmug.com/Nature/Summer-Nature-Photos/i-fPLj2Jp/A

-- hide signature --

Person is taking photos, not camera. When photograph is bad, it's because photographer doesn't know how to choose settings optimal to "own preferences". Then blames camera for bad IQ.
This is same as blaming car about arriving to wrong destination.
http://stan-pustylnik.smugmug.com

 stan_pustylnik's gear list:stan_pustylnik's gear list
Panasonic Lumix DMC-TS2 Sony Alpha DSLR-A850 Sony SLT-A55 Sony Alpha DSLR-A580 Sony DT 18-55mm F3.5-5.6 SAM +14 more
sybersitizen Forum Pro • Posts: 17,464
Re: Sony 20 f2.8 on A99 - focus issue on short distance

stan_pustylnik wrote:

Faith Yeung wrote:

I just got a Sony 20mm f2.8. On A99, when I use central focus point, the distance scale on lens body reads 1 m.

There is a possibility that the distance scale is off. What point on the distance scale actually produces the sharpest distant image in the center of the frame when shooting wide open ... say something at least a couple hundred feet away?

The image is very soft at the outer edge.

You got lemon lens or need to learn depth of field with this lens.

You've jumped to a conclusion.

My Minolta Maxxum 20mm f/2.8 AF is very reliable, works good with close focus while taking landscapes.

https://stan-pustylnik.smugmug.com/Nature/Summer-Nature-Photos/i-KxzxSQP/A

https://stan-pustylnik.smugmug.com/Nature/Summer-Nature-Photos/i-fPLj2Jp/A

Those were shot at f/16 and f/20. Field curvature in a lens is very evident wide open, but can be harder to detect at those tiny apertures. Incidentally, both of your examples still show soft upper corners.

stan_pustylnik Veteran Member • Posts: 4,017
Re: Sony 20 f2.8 on A99 - focus issue on short distance

Very corners are distorted, not soft. Distortion is from CPL filter.

-- hide signature --

Person is taking photos, not camera. When photograph is bad, it's because photographer doesn't know how to choose settings optimal to "own preferences". Then blames camera for bad IQ.
This is same as blaming car about arriving to wrong destination.
http://stan-pustylnik.smugmug.com

 stan_pustylnik's gear list:stan_pustylnik's gear list
Panasonic Lumix DMC-TS2 Sony Alpha DSLR-A850 Sony SLT-A55 Sony Alpha DSLR-A580 Sony DT 18-55mm F3.5-5.6 SAM +14 more
sybersitizen Forum Pro • Posts: 17,464
Re: Sony 20 f2.8 on A99 - focus issue on short distance

stan_pustylnik wrote:

sybersitizen wrote:

Incidentally, both of your examples still show soft upper corners.

Very corners are distorted, not soft. Distortion is from CPL filter.

Perhaps, but I have no reason to believe that's the cause. My own polarizer on my Sony 11-18mm at 11mm f/16 doesn't introduce any extra distortion at the corners. These are both uncorrected in-camera JPEGs, and (manual) focus distance was the same in both:

Without polarizer

With polarizer

These are the same shots, with lens correction and sharpening:

Without polarizer

With polarizer

We can see hard vignetting in a couple of the extreme corners caused by the filter ring, but that's not softness.

If you want to convince me that your polarizer is at fault for the softness, shoot another scene with and without the filter and show the results. I'm open to looking at actual evidence.

I should emphasize that your shots look very sharp overall to me, and only slightly less so in the corners ... certainly much better than my quick test shots.

Ron Poelman
Ron Poelman Veteran Member • Posts: 7,954
Probably about right, you'll have to make choices at close range

https://www.dyxum.com/dforum/topic11337.html

Scroll down to the tulip shots, they pretty much tell the story.
I just use Focus Magnify on my 24 and shut down aperture as much as I can after that.
The 20 won't be much different.

-- hide signature --

Ron.
Volunteer, what could possibly go wrong ?

 Ron Poelman's gear list:Ron Poelman's gear list
Sony Cyber-shot DSC-H2 Sony Cyber-shot DSC-R1 Sony SLT-A57 NEX5R A3000 +26 more
stan_pustylnik Veteran Member • Posts: 4,017
good reminder to get over-sized CPL

Going to get 72mm Minolta's CPL to minimize vignette. Minolta Maxxum 20mm is my super favorite wide landscape lens on A850.

-- hide signature --

Person is taking photos, not camera. When photograph is bad, it's because photographer doesn't know how to choose settings optimal to "own preferences". Then blames camera for bad IQ.
This is same as blaming car about arriving to wrong destination.
http://stan-pustylnik.smugmug.com

 stan_pustylnik's gear list:stan_pustylnik's gear list
Panasonic Lumix DMC-TS2 Sony Alpha DSLR-A850 Sony SLT-A55 Sony Alpha DSLR-A580 Sony DT 18-55mm F3.5-5.6 SAM +14 more
Keyboard shortcuts:
FForum MMy threads