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Improving the effectiveness of a6000 AF
#1
I feel much more comfortable with mirrorless than DSLR for a number of aspects, including focus accuracy... with an exception. Sometimes the camera just does it wrong - I mean, it really misfocuses. I'm talking of stationary objects (landscapes), so it's not a matter of tracking. I know that no system is perfect and I expect a small percentage of failures - in the end, DSLR weren't perfect either.

 

Still I'm trying to understand whether there's something I can do to improve things. Statistics are that - say - one image out of 20 is misfocused. In most cases, even though I can't say I'm clearly seeing it in the EVF (especially in the lo-res of the a6000) I have a sort of feeling about that, so I re-shoot re-focusing a number of times. During the post-processing I can confirm that when I find a subject that has been shot more than the average, it happens that the first images are misfocused. Multiple attempts improve chances of having it right, so, in the end, most of the problems are compensated and the final percentage of lost images - I mean, after the post-processing and final selection - is about 1%. Of these, a handful in a year are those that I really miss because they could have been great photos.

 

During the latest experience with the Sigma 150-600mm the percentage has been higher. There are at least three shots in a day that I'm sad about, for instance the one that you can see below.

 

Now, perhaps is the new lens, perhaps is the MC-11 adapter, perhaps is the fact that zooming in a landscape, especially in the warm hazy season, increases chances of pointing the AF sensor to an area where there is no enough contrast. But in the case below, I autofocused on the rightmost tree leaves, which seems to be dark enough to stand out of the bright background.

 

Fortunately I spotted the problem during the review of the first day, and the next days I switched to manual focusing when I perceived the problem again, and didn't experience any further loss. Still, autofocusing with the big beast is not the better experience in the world if one doesn't want to set up the tripod every time. Also, as said, the low resolution EVF of the a6000 doesn't help a lot. I won't buy the a6300 until the end of the year (perhaps) because of budget restrictions.

 

Any hint? I'm using the central sensor, in "small" mode to precisely select the area where to focus. Indeed I did a few attempts with "large", but things didn't seem to improve.

 

** NOTE: I'm still struggling with image upload - please come back later :-)

 

** Note: the whole image picture will probably look with several compression artefacts, because even misfocused it has quite a number of details and I had to lower the quality.

 

 

 

stoppingdown.net

 

Sony a6300, Sony a6000, Sony NEX-6, Sony E 10-18mm F4 OSS, Sony Zeiss Vario-Tessar T* E 16-70mm F4 ZA OSS, Sony FE 70-200mm F4 G OSS, Sigma 150-600mm Æ’/5-6.3 DG OS HSM Contemporary, Samyang 12mm Æ’/2, Sigma 30mm F2.8 DN | A, Meyer Gorlitz Trioplan 100mm Æ’/2.8, Samyang 8mm Æ’/3.5 fish-eye II | Zenit Helios 44-2 58mm Æ’/2 
Plus some legacy Nikkor lenses.
#2
No idea why, stopping down. I do remember a reviewer contemplating switching from Canon FF to one of the Sony A7 cameras and not doing so for exactly that reason: total missfocus in some images without a hint as to why.

#3
Did you notice a recurrent pattern where the images were OOF?

Is it totally off or just a bit?

Could it be shutter shock?

Does it also happen with native lenses? (ie. without using the MC-11 adapter).

--Florent

Flickr gallery
#4
stoppingdown, are you sure your Sigma has the latest firmware-update? There were at least two I'm aware of.

 

To me it appears you were shooting handheld. My in-focus rate with the 150-600 increased when using a tripod and I think, it's quite easy to send the focus unit to the wrong place when you consider all the delays in between. You move just a little bit and the contrast detection gets the wrong impression.

 

Also, are you using OS? Although I believe you already set it off - in case no, set it off as it's causing also a kind of moving error.

#5
I'm shooting a lot of 500mm+ images and if you are talking about 1% missed shots you could be  tutoring students, not asking for advice, bravo! 

 

A couple of things I have noticed,

 

 Any sort of mist/haze significantly reduces focus accuracy.

 

Shooting in the heat of the day reduces focus accuracy.

 

 The wider the aperture the more likely these conditions will affect sharpness in the conditions above. (kind of a new theory of mine)

 

 After buying the Nikor 500mm F4 the weather had a certain amount of haze/ humidity...I struggled to get any sort of sharpness applicable to the quality I expected from the lens. So I went out and shot early in the morning.... the lens was sharp all along.

 When shooting in "hazyish" conditions nothing was sharp wide open, but when stopped down to F11 there was decent sharpness.

 I came to the (ongoing) conclusion that when shooting in humid conditions (if you have to) , stop down. If you want the sharpest results shoot early in the morning or late in the evening, unless you are shooting fairly close up.

 

The seller of the lens said "never shoot telephoto between 10 am and 6 pm in late spring- autumn"

 

He gave me a copy of his published book "Wildlife in the Pyrenees" as a gift when I bought the lens, most of the pictures in the book were taken with the Nikor!

Dave's clichés
#6
Quote:I'm shooting a lot of 500mm+ images and if you are talking about 1% missed shots you could be  tutoring students, not asking for advice, bravo! 

 

 
 

Well, it's not what I wrote.  Smile That's the ratio of missed shots in general with mirrorless... And "missed" because of misfocusing, so the photo is completely (or almost) ruined. My rate of final keepers is much, much lower (that is, the rate of deleted photos is much, much higher).

 

I agree that haze plays a role, and atmospheric blur might also be a cause.

stoppingdown.net

 

Sony a6300, Sony a6000, Sony NEX-6, Sony E 10-18mm F4 OSS, Sony Zeiss Vario-Tessar T* E 16-70mm F4 ZA OSS, Sony FE 70-200mm F4 G OSS, Sigma 150-600mm Æ’/5-6.3 DG OS HSM Contemporary, Samyang 12mm Æ’/2, Sigma 30mm F2.8 DN | A, Meyer Gorlitz Trioplan 100mm Æ’/2.8, Samyang 8mm Æ’/3.5 fish-eye II | Zenit Helios 44-2 58mm Æ’/2 
Plus some legacy Nikkor lenses.
#7
BTW, I don't know why but I see "you can upload up yo 1.95MB" and so I can't upload the full image. Anyway you can see it here:

 

http://stoppingdown.net/media/stillimage.../image.jpg

 

The pattern occurs also with native lenses, e.g. the SEL70200G, but with a less frequent chance. 

 

It's not just a bit off focus, but not too much. If it was totally off focus, I could easily spot in the EVF.

 

 

I was shooting with the beanbag and remote trigger, so no hand-holding. I don't think it was a problem of the stabiliser, since it introduces a different kind of blurring. It's also not "normal" blurring. As I said I "fixed" the problem the following days recurring to manual focusing, but still with the beanbag and remote trigger, and stabiliser enabled.

 

I wouldn't call it a big trouble, in the end focusing, stabilisation, etc... are features which work "statistically"... 

stoppingdown.net

 

Sony a6300, Sony a6000, Sony NEX-6, Sony E 10-18mm F4 OSS, Sony Zeiss Vario-Tessar T* E 16-70mm F4 ZA OSS, Sony FE 70-200mm F4 G OSS, Sigma 150-600mm Æ’/5-6.3 DG OS HSM Contemporary, Samyang 12mm Æ’/2, Sigma 30mm F2.8 DN | A, Meyer Gorlitz Trioplan 100mm Æ’/2.8, Samyang 8mm Æ’/3.5 fish-eye II | Zenit Helios 44-2 58mm Æ’/2 
Plus some legacy Nikkor lenses.
#8
I was refering to your comments about the Sigma 150-600mm!

Dave's clichés
  


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