AF not reliable with wide angle lenses

Wheatfield · 12-29-2020, 09:47 AM - **1 Like**

Originally posted by Paulo

As mentioned in my the 1st post I use spot AF.S only. It works perfectly with da*300 for nature even with TC 1.4x. The only problem I have relates to WA lenses.

The focus spot is probably bigger than what you are trying to focus on, causing the camera to miss focus.
This presumes you have your lens AF offset dialed in correctly.

**Serkevan** · 12-29-2020, 10:13 AM - **1 Like**

Originally posted by Wheatfield

The focus spot is probably bigger than what you are trying to focus on, causing the camera to miss focus.
This presumes you have your lens AF offset dialed in correctly.

My bet's on this as well. I'd like to see some images that demonstrate OP's problem to make sure we're all looking at the same thing.

stevebrot · 12-29-2020, 11:05 AM

Originally posted by Wheatfield

The focus spot is probably bigger than what you are trying to focus on, causing the camera to miss focus.
This presumes you have your lens AF offset dialed in correctly.

Originally posted by Serkevan

My bet's on this as well. I'd like to see some images that demonstrate OP's problem to make sure we're all looking at the same thing.

I think I am on the same track with y'all.

Steve

MikeMcE · 12-29-2020, 02:38 PM

Logical.....OP??

Hang up and DRIVE!

**mikesbike** · 12-29-2020, 03:53 PM - **1 Like**

Originally posted by Wheatfield

The focus spot is probably bigger than what you are trying to focus on, causing the camera to miss focus.
This presumes you have your lens AF offset dialed in correctly.

Plus another same from me. I have found this to be specific to ultra-wide lenses. I've found I must take extra care with my Sigma 10-20mm f/3.5 lens when using at or near the 10mm setting. I would recommend first, use spot AF and if needed then hold focus with the half press while re-positioning the camera to get the framing you want. If still problematic due to the objects still bing so small compared to the size of the focusing sensor, this lens is probably of par focal type, so you can focus at the long zoom end, switch to manual focus to preserve the focus setting, then zoom back to the wider FL.

Aperture does make some difference because of DOF, but with such a wide FL success should be easy to achieve, even if wide open.

pschlute · 12-29-2020, 04:18 PM

With ultra-wide lenses I either focus using hyperfocal distance method or Live View zoomed for the reasons mentioned.

**hjoseph7** · 12-30-2020, 06:12 PM

Originally posted by UncleVanya

You mentioned centered subjects, I otherwise I might have suggested field curvature.

What happens if you try live view does the focus work more accurately?

Metering and Focus Point selection are two different things. If your camera is set for Automatic AF selection then the camera chooses whatever focusing points it wants to use. Maybe because you are using a wide angle lens there is a larger area for the camera to choose from ? Sincerely, I never had that problem with wide angle lenses whether manual or AF or with any DSLR. Actually it is easier to find focus with a wide angle lens, because the focusing-throw is much shorter than on tele lenses, or macro lens. A couple of twists and you are at infinity where everything is in focus.

Last edited by hjoseph7; 12-30-2020 at 06:52 PM.

**UncleVanya** · 12-30-2020, 07:00 PM

Originally posted by hjoseph7

Metering and Focus Point selection are two different things. If your camera is set for Automatic AF selection then the camera chooses whatever focusing points it wants to use.

I'm well aware of this and didn't reference it in the post you quoted. I'm not sure what you are getting at.

Originally posted by hjoseph7

Maybe because you are using a wide angle lens there is a larger area for the camera to choose from ? Sincerely, I never had that problem with wide angle lenses whether manual or AF or with any DSLR. Actually it is easier to find focus with a wide angle lens, because the focusing-throw is much shorter than on tele lenses, or macro lens. A couple of twists and you are at infinity where everything is in focus.

Maybe you mean you to refer to the original poster? I am not having this issue either. I'm not the person asking - I'm the person trying to help. I may be misunderstanding your intent of quoting me and saying this however so I apologize if this was meant to be something I'm not following. But if you mean for those comments to go to the OP you quoted the wrong person.

**hjoseph7** · 12-30-2020, 08:32 PM

Originally posted by UncleVanya

I'm well aware of this and didn't reference it in the post you quoted. I'm not sure what you are getting at.

Maybe you mean you to refer to the original poster? I am not having this issue either. I'm not the person asking - I'm the person trying to help. I may be misunderstanding your intent of quoting me and saying this however so I apologize if this was meant to be something I'm not following. But if you mean for those comments to go to the OP you quoted the wrong person.

Oops sorry i must have hit the wrong button, I meant this for the original poster ?

**UncleVanya** · 12-30-2020, 09:23 PM

Originally posted by hjoseph7

Oops sorry i must have hit the wrong button, I meant this for the original poster ?

Phew! Ok. That’s much less confusing. I apologize for not simply PM’img you. Hindsight is 20/20.

**TwoUptons** · 12-31-2020, 08:46 AM

Roger Cicala did a thing at the other website showing how to check the field curvature of a lens, and his hints are also useful for checking focus in general.

The short version is to photograph a field of grass and do a “find edges” in your favorite editor to reveal where it is sharpest. But you can often look at the photo and see what’s in focus... but an important part of that is that the scene needs to have some depth to it (not just a brick wall).

His broader point is that what we call “soft edges” is often field curvature, and if you know how to accommodate it, it can be used to your advantage, but it’s a good test for finding where a lens is sharp...

---------- Post added 12-31-20 at 08:48 AM ----------

Originally posted by UncleVanya

Phew! Ok. That’s much less confusing. I apologize for not simply PM’img you. Hindsight is 20/20.

Not until tomorrow

-Eric

stevebrot · 12-31-2020, 01:59 PM

Originally posted by hjoseph7

Metering and Focus Point selection are two different things.

Unless one has them set to be the same. (Not a good setting choice, IMHO.)

Steve

**mikesbike** · 12-31-2020, 03:54 PM

Yes, there could be a field-curvature issue, but when testing for this some latitude should be given, as even very fine lenses, more often than not, will be somewhat less sharp at frame edges than in the central area. Especially at or near wide open aperture.

pentasonic49 · 01-02-2021, 01:45 PM

Since you use spot afs with telephotos, maybe you could experiment with the other options available when using wide angle.

leekil · 01-02-2021, 04:03 PM

Originally posted by stevebrot

Unless one has them set to be the same. (Not a good setting choice, IMHO.)

It seems like it should be the best setting, but it never is.

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12-29-2020, 09:47 AM - 1 Like	#16
Wheatfield Moderator Join Date: Apr 2008 Location: The wheatfields of Canada Posts: 15,981	Originally posted by Paulo As mentioned in my the 1st post I use spot AF.S only. It works perfectly with da*300 for nature even with TC 1.4x. The only problem I have relates to WA lenses. The focus spot is probably bigger than what you are trying to focus on, causing the camera to miss focus. This presumes you have your lens AF offset dialed in correctly.

12-29-2020, 10:13 AM - 1 Like	#17
Serkevan Site Supporter Join Date: May 2019 Photos: Albums Posts: 5,976	Originally posted by Wheatfield The focus spot is probably bigger than what you are trying to focus on, causing the camera to miss focus. This presumes you have your lens AF offset dialed in correctly. My bet's on this as well. I'd like to see some images that demonstrate OP's problem to make sure we're all looking at the same thing.

12-29-2020, 11:05 AM	#18
stevebrot Otis Memorial Pentaxian Join Date: Mar 2007 Location: Vancouver (USA) Photos: Gallery \| Albums Posts: 42,007	Originally posted by Wheatfield The focus spot is probably bigger than what you are trying to focus on, causing the camera to miss focus. This presumes you have your lens AF offset dialed in correctly. Originally posted by Serkevan My bet's on this as well. I'd like to see some images that demonstrate OP's problem to make sure we're all looking at the same thing. I think I am on the same track with y'all. Steve

12-29-2020, 02:38 PM	#19
MikeMcE Pentaxian Join Date: Jun 2020 Photos: Albums Posts: 1,093	Logical.....OP?? Hang up and DRIVE!

12-29-2020, 03:53 PM - 1 Like	#20
mikesbike Site Supporter Join Date: Dec 2016 Location: Southeastern Michigan Posts: 4,549	Originally posted by Wheatfield The focus spot is probably bigger than what you are trying to focus on, causing the camera to miss focus. This presumes you have your lens AF offset dialed in correctly. Plus another same from me. I have found this to be specific to ultra-wide lenses. I've found I must take extra care with my Sigma 10-20mm f/3.5 lens when using at or near the 10mm setting. I would recommend first, use spot AF and if needed then hold focus with the half press while re-positioning the camera to get the framing you want. If still problematic due to the objects still bing so small compared to the size of the focusing sensor, this lens is probably of par focal type, so you can focus at the long zoom end, switch to manual focus to preserve the focus setting, then zoom back to the wider FL. Aperture does make some difference because of DOF, but with such a wide FL success should be easy to achieve, even if wide open.

12-29-2020, 04:18 PM	#21
pschlute Moderator Loyal Site Supporter Join Date: Mar 2007 Location: Surrey, UK Photos: Gallery Posts: 8,202	With ultra-wide lenses I either focus using hyperfocal distance method or Live View zoomed for the reasons mentioned.

12-30-2020, 06:12 PM	#22
hjoseph7 Site Supporter Join Date: May 2014 Location: Minnesota Photos: Gallery \| Albums Posts: 2,047	Originally posted by UncleVanya You mentioned centered subjects, I otherwise I might have suggested field curvature. What happens if you try live view does the focus work more accurately? Metering and Focus Point selection are two different things. If your camera is set for Automatic AF selection then the camera chooses whatever focusing points it wants to use. Maybe because you are using a wide angle lens there is a larger area for the camera to choose from ? Sincerely, I never had that problem with wide angle lenses whether manual or AF or with any DSLR. Actually it is easier to find focus with a wide angle lens, because the focusing-throw is much shorter than on tele lenses, or macro lens. A couple of twists and you are at infinity where everything is in focus. Last edited by hjoseph7; 12-30-2020 at 06:52 PM.

12-30-2020, 07:00 PM	#23
UncleVanya Loyal Site Supporter Join Date: Jul 2014 Photos: Gallery \| Albums Posts: 28,404	Originally posted by hjoseph7 Metering and Focus Point selection are two different things. If your camera is set for Automatic AF selection then the camera chooses whatever focusing points it wants to use. I'm well aware of this and didn't reference it in the post you quoted. I'm not sure what you are getting at. Originally posted by hjoseph7 Maybe because you are using a wide angle lens there is a larger area for the camera to choose from ? Sincerely, I never had that problem with wide angle lenses whether manual or AF or with any DSLR. Actually it is easier to find focus with a wide angle lens, because the focusing-throw is much shorter than on tele lenses, or macro lens. A couple of twists and you are at infinity where everything is in focus. Maybe you mean you to refer to the original poster? I am not having this issue either. I'm not the person asking - I'm the person trying to help. I may be misunderstanding your intent of quoting me and saying this however so I apologize if this was meant to be something I'm not following. But if you mean for those comments to go to the OP you quoted the wrong person.

12-30-2020, 08:32 PM	#24
hjoseph7 Site Supporter Join Date: May 2014 Location: Minnesota Photos: Gallery \| Albums Posts: 2,047	Originally posted by UncleVanya I'm well aware of this and didn't reference it in the post you quoted. I'm not sure what you are getting at. Maybe you mean you to refer to the original poster? I am not having this issue either. I'm not the person asking - I'm the person trying to help. I may be misunderstanding your intent of quoting me and saying this however so I apologize if this was meant to be something I'm not following. But if you mean for those comments to go to the OP you quoted the wrong person. Oops sorry i must have hit the wrong button, I meant this for the original poster ?

12-30-2020, 09:23 PM	#25
UncleVanya Loyal Site Supporter Join Date: Jul 2014 Photos: Gallery \| Albums Posts: 28,404	Originally posted by hjoseph7 Oops sorry i must have hit the wrong button, I meant this for the original poster ? Phew! Ok. That’s much less confusing. I apologize for not simply PM’img you. Hindsight is 20/20.

12-31-2020, 08:46 AM	#26
TwoUptons Loyal Site Supporter Join Date: Nov 2015 Photos: Albums Posts: 4,214	Roger Cicala did a thing at the other website showing how to check the field curvature of a lens, and his hints are also useful for checking focus in general. The short version is to photograph a field of grass and do a “find edges” in your favorite editor to reveal where it is sharpest. But you can often look at the photo and see what’s in focus... but an important part of that is that the scene needs to have some depth to it (not just a brick wall). His broader point is that what we call “soft edges” is often field curvature, and if you know how to accommodate it, it can be used to your advantage, but it’s a good test for finding where a lens is sharp... ---------- Post added 12-31-20 at 08:48 AM ---------- Originally posted by UncleVanya Phew! Ok. That’s much less confusing. I apologize for not simply PM’img you. Hindsight is 20/20. Not until tomorrow -Eric

12-31-2020, 01:59 PM	#27
stevebrot Otis Memorial Pentaxian Join Date: Mar 2007 Location: Vancouver (USA) Photos: Gallery \| Albums Posts: 42,007	Originally posted by hjoseph7 Metering and Focus Point selection are two different things. Unless one has them set to be the same. (Not a good setting choice, IMHO.) Steve

12-31-2020, 03:54 PM	#28
mikesbike Site Supporter Join Date: Dec 2016 Location: Southeastern Michigan Posts: 4,549	Yes, there could be a field-curvature issue, but when testing for this some latitude should be given, as even very fine lenses, more often than not, will be somewhat less sharp at frame edges than in the central area. Especially at or near wide open aperture.

01-02-2021, 01:45 PM	#29
pentasonic49 Veteran Member Join Date: Oct 2012 Location: weston-super-mare Posts: 395	Since you use spot afs with telephotos, maybe you could experiment with the other options available when using wide angle.

01-02-2021, 04:03 PM	#30
leekil Pentaxian Join Date: May 2016 Photos: Albums Posts: 2,003	Originally posted by stevebrot Unless one has them set to be the same. (Not a good setting choice, IMHO.) It seems like it should be the best setting, but it never is.