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10-29-2020, 12:08 AM   #1
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Is it the camera settings, the lens or the idiot holding the camera?

Hi All,

Just looking for some guidance.

Took these shots today, using my K3-ii with the Sigma 24 - 70mm 2.8. The pic settings are @ 70mm on AV mode. ISO 100 @ 1/800.

They're not coming out razor sharp. This is a sample of the shots. The focus point was on the kookaburra. I was about 5 metres away and the camera settings is on 27 point. What am I doing wrong here with the focus? (I am fairly experienced with the camera with over 50,000 shots of mostly fast moving objects, just finding it strange that I have lost the ability to focus ...)

I posted this to the Pentaxians FB Group (apologies to anyone who has already seen this) and there has been a suggestion that there's a known issue with the lens. I am going to try a different lens and with single point focus, as suggested there.

Keen to hear your thoughts.

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10-29-2020, 12:40 AM   #2
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I would use spot AF and maybe the lens is simply not sharp at 2.8? Did you try 5.6 or 8? Did you get focus confirmation?
10-29-2020, 12:46 AM   #3
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QuoteOriginally posted by SalT Quote
Took these shots today, using my K3-ii with the Sigma 24 - 70mm 2.8. The pic settings are @ 70mm on AV mode. ISO 100 @ 1/800.

They're not coming out razor sharp. This is a sample of the shots. The focus point was on the kookaburra. I was about 5 metres away and the camera settings is on 27 point. What am I doing wrong here with the focus?
First, were you shooting thru a window screen or window? If not then:

Process of elimination, because as you admit, it could be the lens, the AF, or the photographer.

Lens? I would start with a flat surface with the lens wide open at 70mm at about the same distance as the bird. Try manual focus with the OVF and then the EVF live view.

AF? I'd also try the same as above but with AF using OVF and EVF. It may need an AF Fine Adjustment.

User? If you can't replicate the problem with a flat subject, then your focus point was not on the bird. Keep in mind that with the aperture wide open and the long end of a zoom lens is a combination for soft images and requires perfect technique with a very shallow depth of field.
10-29-2020, 01:14 AM - 2 Likes   #4
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It's the idiot holding the camera I'm afraid. For a backlit subject like that I'd just use the central AF point - I use that one far more than the others because it is simpler. Though your choice of using AV mode was good, DOF control is a very important factor in a good photo.

As a rule Most lenses perform best stopped down a bit - this holds true particularly with Zoom lenses. Lighting is a critical factor - If the subject is in bad light it frequently leads to a bad photograph, of course there are exceptions where bad lighting can be exploited for dramatic effect.

I suppose taking the time to think about what you are photographing, and why you are photographing it will help. No-one gets anywhere by being completely aimless.



Pentax K10D - Sigma 100-300mm f/4 APO EX DG ISO 100 f/5.6 1/180th - wireless AF540FGZ with 1/2 CTO Gel used.


Last edited by Digitalis; 10-29-2020 at 01:33 AM.
10-29-2020, 02:00 AM - 1 Like   #5
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I took a look at the photo's and one thing struck me: at the bottom on the right side you see some wash pegs and just left of that you see a kind of screw, it is about the only thing that is sharp. If I go to the left then on the same line there are some sharp looking pegs as well. It are the only things that are sharp (or reasonably). It still can be any of the three things you mentioned. But also the combination of the three. If you had the idea that the Kookab(l)urra was sharp looking through the viewfinder, I think the AF can be the culprit. As for the idiot, I sometimes have this effect when pushing the button I move a bit, but then nothing would be sharp. So I do not think it is the idiot holding the camera.
10-29-2020, 02:22 AM - 1 Like   #6
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27 pt AF is a very dodgy strategy for such a busy scene. It will not necessarily select the focus point you expect. I would use it is for birds in flight against a featureless sky, but not for this shot. Single point is the go.

Last edited by Paul the Sunman; 10-29-2020 at 01:03 PM.
10-29-2020, 03:03 AM   #7
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Others can give more technical advice than I can. I use centre spot focusing for wildlife. I think it increases my success rate but sometimes (particularly with very small birds) the system gets the focus wrong. A small bird is not your problem here but f2.8 gives you a very narrow DOF. When I look at the first pic you posted I can see a couple of red pegs (first on the right and first on the left - red not pink) that appear to be sharper that your Kookaburra. As you have a very shallow DOF it looks like the focus might be in the plane of those pegs rather than the bird. Did the camera focus on the wrong thing, or have you got front or back focus? It is something else you might need to look at. I have a Sigma 24-60/f2.8 and they have a reputation for front or back focus. I depends on the individual lens. Another thing I noticed is that rainbow effect at the bottom left in some of your images. Were the images taken through a window or did something else cause this? It is hard to say what other effect that might be having.

Last edited by PJ1; 10-29-2020 at 03:04 AM. Reason: Correction
10-29-2020, 03:22 AM   #8
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Focusing concerns aside, it looks to me like that Sigma 24-70 f/2.8 might suffer from pronounced spherical aberration wide open, creating a "glow" around in-focus elements. I'd try stopping it down to f/5.6 and (along with suggestions for centre point AF) see how you get on. Also note that this particular lens isn't known for its attractive bokeh behind the subject, which is contributing to the overall unpleasantness of the image.

10-29-2020, 04:32 AM - 1 Like   #9
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27 point focusing is very random in my opinion, you have to chose the focusing. I read something where somebody said getting birds in flight was easy with multi point focusing and AF-S, so I experimented and got nothing in focus but wingtips. Center spot is the only thing I will use for any wildlife, and pretty much anything else. And as other have said, do you know that the lens is sharp at 2.8, many zooms are not. And Sigma lenses are not know for their great autofocus in general.
10-29-2020, 04:56 AM   #10
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Another vote for center point AF. The camera couldn't pick the correct focus point, it seems.
10-29-2020, 11:12 AM   #11
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Another suggestion, which builds on the use of center point (sensor) for AF. It may be faster/more positive to set focus by the rear AF button, and only use the shutter release for exposure and image acquisition (this is my practice, and I find it far superior).
10-29-2020, 11:51 AM   #12
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Were you using a tripod? If you were, then turn the shake reduction off.
10-29-2020, 12:18 PM   #13
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According to one depth-of -field calculator I checked, with the lens set at 70mm and f/2.8, the total depth of field would be 0.6m at a focus distance of 5m. That should be plenty if the focus is centered on the bird.

Have you looked at the user reviews of this lens?
Sigma 24-70mm F2.8 IF EX DG HSM Lens Reviews - Sigma Lenses - Pentax Lens Review Database

Some say the lens isn't sharp at f/2.8, some say it is. How do you define 'sharp'? Different for different people. Most lenses aren't their sharpest wide open, so I would vote for using f/4 or f/5.6 like others have said.
10-29-2020, 01:48 PM - 2 Likes   #14
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I would agree that using single point (center) AF would give you more of a specific point to focus on, and also I would recommend focusing on a part of the subject that has contrast, not just completely white. Also, if you want any sort of depth to the shot you may want to use a higher number F stop, such as 4 or 5. When i shoot wildlife I use at least F9 or higher F stop to maintain some type of detail. I would also recommend using either Center weighted or Spot metering to include the subject itself in a more localized area than Multi Pattern metering. I use TAV mode in most instances when I am shooting wildlife, with exceptions where I may use Manual if the available light stays consistent for a reasonable period of time.

Last edited by C_Jones; 10-29-2020 at 01:57 PM.
10-29-2020, 03:44 PM   #15
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QuoteOriginally posted by yucafrita Quote
I would use spot AF and maybe the lens is simply not sharp at 2.8? Did you try 5.6 or 8? Did you get focus confirmation?
Thanks Yucafrita, I will take some shots today at F4 or f5.6 as suggested.

---------- Post added 10-29-20 at 03:45 PM ----------

QuoteOriginally posted by Alex645 Quote
First, were you shooting thru a window screen or window? If not then:

Process of elimination, because as you admit, it could be the lens, the AF, or the photographer.

Lens? I would start with a flat surface with the lens wide open at 70mm at about the same distance as the bird. Try manual focus with the OVF and then the EVF live view.

AF? I'd also try the same as above but with AF using OVF and EVF. It may need an AF Fine Adjustment.

User? If you can't replicate the problem with a flat subject, then your focus point was not on the bird. Keep in mind that with the aperture wide open and the long end of a zoom lens is a combination for soft images and requires perfect technique with a very shallow depth of field.
No, I was outside taking the shot with clear view of the bird. Thanks

---------- Post added 10-29-20 at 03:48 PM ----------

QuoteOriginally posted by Digitalis Quote
It's the idiot holding the camera I'm afraid. For a backlit subject like that I'd just use the central AF point - I use that one far more than the others because it is simpler. Though your choice of using AV mode was good, DOF control is a very important factor in a good photo.

As a rule Most lenses perform best stopped down a bit - this holds true particularly with Zoom lenses. Lighting is a critical factor - If the subject is in bad light it frequently leads to a bad photograph, of course there are exceptions where bad lighting can be exploited for dramatic effect.

I suppose taking the time to think about what you are photographing, and why you are photographing it will help. No-one gets anywhere by being completely aimless.



Pentax K10D - Sigma 100-300mm f/4 APO EX DG ISO 100 f/5.6 1/180th - wireless AF540FGZ with 1/2 CTO Gel used.
That's what I was hoping and not a failing of the equipment. The idiot, I can fix ... Thanks for responding, I am going to play around with a few things in the camera first and update the photos.

---------- Post added 10-29-20 at 03:49 PM ----------

QuoteOriginally posted by PJ1 Quote
Others can give more technical advice than I can. I use centre spot focusing for wildlife. I think it increases my success rate but sometimes (particularly with very small birds) the system gets the focus wrong. A small bird is not your problem here but f2.8 gives you a very narrow DOF. When I look at the first pic you posted I can see a couple of red pegs (first on the right and first on the left - red not pink) that appear to be sharper that your Kookaburra. As you have a very shallow DOF it looks like the focus might be in the plane of those pegs rather than the bird. Did the camera focus on the wrong thing, or have you got front or back focus? It is something else you might need to look at. I have a Sigma 24-60/f2.8 and they have a reputation for front or back focus. I depends on the individual lens. Another thing I noticed is that rainbow effect at the bottom left in some of your images. Were the images taken through a window or did something else cause this? It is hard to say what other effect that might be having.
Thanks PJ1, that's helpful. I didn't notice the pegs in the lower areas of the shot. I am going to play around with centre point focus, as a few have suggested, then I will look into the calibration issue.

---------- Post added 10-29-20 at 03:51 PM ----------

QuoteOriginally posted by dms Quote
Another suggestion, which builds on the use of center point (sensor) for AF. It may be faster/more positive to set focus by the rear AF button, and only use the shutter release for exposure and image acquisition (this is my practice, and I find it far superior).
Ok, I'll try that.

---------- Post added 10-29-20 at 03:52 PM ----------

QuoteOriginally posted by Apet-Sure Quote
According to one depth-of -field calculator I checked, with the lens set at 70mm and f/2.8, the total depth of field would be 0.6m at a focus distance of 5m. That should be plenty if the focus is centered on the bird.

Have you looked at the user reviews of this lens?
Sigma 24-70mm F2.8 IF EX DG HSM Lens Reviews - Sigma Lenses - Pentax Lens Review Database

Some say the lens isn't sharp at f/2.8, some say it is. How do you define 'sharp'? Different for different people. Most lenses aren't their sharpest wide open, so I would vote for using f/4 or f/5.6 like others have said.
I have now Apet ... thanks.
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