Focusing problems

HairyB · Jul 11, 2016

Hi all

I've been doing photography for years, as a hobby and intermittently, and generally know what I'm doing with a camera (well to an amateur level). I use a Nikon D5100. I'm having a problem lately with focus. It's particularly photographs of people that aren't coming out focused - mainly when it's from a distance and there's surrounding objects/scenery, but also closer ones, from a few feet away. This is with my 18-200 lens. With my prime 35 lens they're a lot better. So I tested the zoom one for front/back focusing and it comes out fine. So it's probably user error but I can't see what I'm doing wrong. Like I say, I know mostly what settings to use (although willing to be educated on that!) and it's only recently become a problem. I even tried a shot in auto and it wasn't any better. (on all of them I use single point focus and focus on the nearest eye).

Here are two photos with all details. At 100% zoom, the face isn't in focus.

f/4 1/2000
iso 800 18-200@18mm

f/3.8 1/2000
iso 125 18-200@25

David Wrench · Jul 11, 2016

It looks to me as if you are using unnecessarily large apertures. Also, one of the pictures is taken at ISO 800, which degrades the quality. The bigger the aperture, the smaller your depth of focus. and at very wide apertures the lens will not perform at its best. Prime lenses are usually better at wide apertures; that's consistent with your experience.

If you're not doing so already, I'd use 'P' mode, and it's easy then to trade a lower shutter speed for a narrower aperture. Try to keep it to about f.8 to see what happens. If you start off (in normal conditions) with an ISO of 100 or 200, you can then increase it only if the shutter speed indicated is too long.

David

Gerry Winterbourne · Jul 11, 2016

HairyB said:
I've been doing photography for years, as a hobby and intermittently, and generally know what I'm doing with a camera (well to an amateur level). I use a Nikon D5100. I'm having a problem lately with focus. It's particularly photographs of people that aren't coming out focused - mainly when it's from a distance and there's surrounding objects/scenery, but also closer ones, from a few feet away. This is with my 18-200 lens. With my prime 35 lens they're a lot better.

You'd expect a prime to be sharper all over than a long-throw zoom, but in fact the backgrounds are reasonably sharp here. I'd deal with the chromatic aberrations, though.

HairyB said:
So I tested the zoom one for front/back focusing and it comes out fine. So it's probably user error but I can't see what I'm doing wrong.

I even tried a shot in auto and it wasn't any better. (on all of them I use single point focus and focus on the nearest eye). Here are two photos with all details. At 100% zoom, the face isn't in focus.

The first shot is much sharper on the vegetation to left of your subject (his right). So either you do, in fact, have a serious back-focus problem or you aren't really focusing where you think.

If the single focus point you used is the centre one, the centre position in the shot is on his right-hand breast pocket. This suggests that you focused and recomposed: if so, perhaps you didn't keep the shutter half depressed.

HairyB said:
Like I say, I know mostly what settings to use (although willing to be educated on that!) and it's only recently become a problem.

Why 1/2000s? Why the variable ISO?

HairyB said:
f/4 1/2000
iso 800 18-200@18mm

f/3.8 1/2000
iso 125 18-200@25

--
---
Gerry
___________________________________________
First camera 1953, first Pentax 1985, first DSLR 2006

Galleries by Gerry Winterbourne

www.pbase.com

[email protected]

Gerry Winterbourne · Jul 11, 2016

David Wrench said:
It looks to me as if you are using unnecessarily large apertures. Also, one of the pictures is taken at ISO 800, which degrades the quality. The bigger the aperture, the smaller your depth of focus. and at very wide apertures the lens will not perform at its best. Prime lenses are usually better at wide apertures; that's consistent with your experience.
If you're not doing so already, I'd use 'P' mode, and it's easy then to trade a lower shutter speed for a narrower aperture. Try to keep it to about f.8 to see what happens.

The centre sharpness on the Nikkor 18-200 is actually the same (possibly slightly better) wide open than at f/8 at the shorter focal lengths used here, http://www.photozone.de/nikon--nikkor-aps-c-lens-tests/633-nikkor182003556vrii?start=1 and DOF wide open is certainly adequate for the portrait subjects.

David Wrench said:
If you start off (in normal conditions) with an ISO of 100 or 200, you can then increase it only if the shutter speed indicated is too long.

John Michael Winterbourne · Jul 11, 2016

I don't have a 5100, but one of the very few things that I don't like about the handling of my 3300 is that I often inadvertently move the single focus point - I usually notice, but not always.

If there's a way of locking a single focus point, I've never found it.... but that might just be me.

Tom Axford · Jul 11, 2016

I think your problem is simply that the autofocus system on the camera is not as precise as you assume. Single point focus does not mean that it is focussing exactly on the point you select. The autofocus will always have a small region around that point within which it tries to find something to focus on. It will look for something high-contrast and fairly bright, which often happens to be in the background rather than the foreground object you want to focus on.

Cameras vary in how good they are in finding focus, but in my experience, all have their shortcoming in this type of situation.

I suggest that you would have been better off focussing on the subject's hands rather than his eyes. At that distance, his eyes are quite small and can be missed by the autofocus and instead the focus point selected can easily move a little and be on the background scenery.

If you focussed on his hands, no such error is so easily possible. He hands are very bright against the surrounding clothing and there is really no background scenery close to his hands to allow the autofocus to stray onto it.

I don't think you are alone in finding this sort of situation to be problematic.

You really need to check in the viewfinder that the things you want to be in focus are indeed in focus before you take the shot (which is not always easy to do).

Halina123 · Jul 11, 2016

Interesting problem.

I cannot decide between user or camera error or a very poor lens resolution at this aperture. Or where the focus is. View NX 2 does not display a focus point.

On the first image, the background is in better focus than the face. Although the background is not sharp itself.

Second image is just poor.

Almost ruled out camera shake. Ss speed is ok.

Halina123 · Jul 11, 2016

Definitely problem with IQ or focusing, but I cannot solve it. For comparison purposes I have dug out a similar image to your second one of an artificially piece in a military museum, at a similar distance and light level. Both downsized to 6MP. Mine with cheap tiny sensor compact is sharper.

barrym1966 · Jul 11, 2016

HairyB said:
Hi all

I've been doing photography for years, as a hobby and intermittently, and generally know what I'm doing with a camera (well to an amateur level). I use a Nikon D5100. I'm having a problem lately with focus. It's particularly photographs of people that aren't coming out focused - mainly when it's from a distance and there's surrounding objects/scenery, but also closer ones, from a few feet away. This is with my 18-200 lens. With my prime 35 lens they're a lot better. So I tested the zoom one for front/back focusing and it comes out fine. So it's probably user error but I can't see what I'm doing wrong. Like I say, I know mostly what settings to use (although willing to be educated on that!) and it's only recently become a problem. I even tried a shot in auto and it wasn't any better. (on all of them I use single point focus and focus on the nearest eye).

Here are two photos with all details. At 100% zoom, the face isn't in focus.

f/4 1/2000
iso 800 18-200@18mm

f/3.8 1/2000
iso 125 18-200@25

what focus mode did you use? You should use AFS-S for this.

It looks like the camera decided the scenery behind had a better contrast for the autofocus to lock on to

HairyB · Jul 11, 2016

Gerry Winterbourne said:
The first shot is much sharper on the vegetation to left of your subject (his right). So either you do, in fact, have a serious back-focus problem or you aren't really focusing where you think.

If the single focus point you used is the centre one, the centre position in the shot is on his right-hand breast pocket. This suggests that you focused and recomposed: if so, perhaps you didn't keep the shutter half depressed.

Yes I use the centre focus point and re-compose. I could try doing this by locking the focus with the AF-L instead, so no risk of slipping on the shutter.

Gerry Winterbourne said:
Gerry Winterbourne said:

Like I say, I know mostly what settings to use (although willing to be educated on that!) and it's only recently become a problem.

Click to expand...

Why 1/2000s? Why the variable ISO?

Haha, I'm beginning to think I don't know much at all! Especially photographing people as I don't have much experience with that. I can't answer those questions, I can't remember specifically why I did what I did then. I think I was upping the shutter speed to reduce camera shake, in case that was the problem, in which case I needed to get more light in. But I don't know why I had such a different range in ISO between the two pics. I could have forgotten to change it. I'm thinking of using auto ISO for now.

Gerry Winterbourne said:
Gerry Winterbourne said:

f/4 1/2000
iso 800 18-200@18mm

f/3.8 1/2000
iso 125 18-200@25

Click to expand...

--
---
Gerry
___________________________________________
First camera 1953, first Pentax 1985, first DSLR 2006
http://www.pbase.com/gerrywinterbourne
[email protected]

HairyB · Jul 11, 2016

John Michael Winterbourne said:
I don't have a 5100, but one of the very few things that I don't like about the handling of my 3300 is that I often inadvertently move the single focus point - I usually notice, but not always.

If there's a way of locking a single focus point, I've never found it.... but that might just be me.

I've just found that if I half press the shutter and focus, then hold down AF-L, I can release the shutter and recompose, then press the shutter fully to take the shot.

HairyB · Jul 11, 2016

Tom Axford said:
I think your problem is simply that the autofocus system on the camera is not as precise as you assume. Single point focus does not mean that it is focussing exactly on the point you select. The autofocus will always have a small region around that point within which it tries to find something to focus on. It will look for something high-contrast and fairly bright, which often happens to be in the background rather than the foreground object you want to focus on.

Cameras vary in how good they are in finding focus, but in my experience, all have their shortcoming in this type of situation.

I suggest that you would have been better off focussing on the subject's hands rather than his eyes. At that distance, his eyes are quite small and can be missed by the autofocus and instead the focus point selected can easily move a little and be on the background scenery.

If you focussed on his hands, no such error is so easily possible. He hands are very bright against the surrounding clothing and there is really no background scenery close to his hands to allow the autofocus to stray onto it.

I don't think you are alone in finding this sort of situation to be problematic.

You really need to check in the viewfinder that the things you want to be in focus are indeed in focus before you take the shot (which is not always easy to do).

That's interesting, thanks. So if it's not a close up shot, don't necessarily try and focus on the eyes. I need to consider the surroundings, and the contrast, as well. I find it difficult to tell if something is in focus through the viewfinder and tend to rely on the camera. My eyes aren't great, I wear contact lenses, and I trust the camera more than my eyes!

HairyB · Jul 11, 2016

Halina123 said:
Definitely problem with IQ or focusing, but I cannot solve it. For comparison purposes I have dug out a similar image to your second one of an artificially piece in a military museum, at a similar distance and light level. Both downsized to 6MP. Mine with cheap tiny sensor compact is sharper.

Thanks, yes it doesn't seem like the compact should produce a better image than my DSLR? I'm going to get the camera and the lens professionally cleaned. Could that have any bearing on it?

HairyB · Jul 11, 2016

barrym1966 said:
HairyB said:

Hi all

I've been doing photography for years, as a hobby and intermittently, and generally know what I'm doing with a camera (well to an amateur level). I use a Nikon D5100. I'm having a problem lately with focus. It's particularly photographs of people that aren't coming out focused - mainly when it's from a distance and there's surrounding objects/scenery, but also closer ones, from a few feet away. This is with my 18-200 lens. With my prime 35 lens they're a lot better. So I tested the zoom one for front/back focusing and it comes out fine. So it's probably user error but I can't see what I'm doing wrong. Like I say, I know mostly what settings to use (although willing to be educated on that!) and it's only recently become a problem. I even tried a shot in auto and it wasn't any better. (on all of them I use single point focus and focus on the nearest eye).

Here are two photos with all details. At 100% zoom, the face isn't in focus.

f/4 1/2000
iso 800 18-200@18mm

f/3.8 1/2000
iso 125 18-200@25

Click to expand...

what focus mode did you use? You should use AFS-S for this.

It looks like the camera decided the scenery behind had a better contrast for the autofocus to lock on to

I had it on AF-A. I read that the camera is usually clever enough to recognise which you want if you have it on that auto setting, and nearly always is right? Maybe it's better to manually choose instead though?

lehill · Jul 11, 2016

I'm just as stumped as all the others which probably doesn't mean very much.

I took the liberty of superimposing the D5100 focus points over your photo. Maybe this can be of some help to everyone:

Nikon Multi-CAM 1000 focus sensor

According to the sources I've read only the center focus point is cross-type. I've seen some conflicting information but it seems the top-most and bottom-most focus points are horizontal-type (sensitive to horizontal lines), the rest are vertical-type. Plus it seems Nikon has a gazillion settings on how they can be used and combined.

I had a camera with a similar focus array and wound up using the center point for most situations and recomposing.

Do you recall which focus point you used for this shot? Did you focus and recompose?

--
Lance H

Gerry Winterbourne · Jul 11, 2016

HairyB said:
barrym1966 said:

HairyB said:

Hi all

I've been doing photography for years, as a hobby and intermittently, and generally know what I'm doing with a camera (well to an amateur level). I use a Nikon D5100. I'm having a problem lately with focus. It's particularly photographs of people that aren't coming out focused - mainly when it's from a distance and there's surrounding objects/scenery, but also closer ones, from a few feet away. This is with my 18-200 lens. With my prime 35 lens they're a lot better. So I tested the zoom one for front/back focusing and it comes out fine. So it's probably user error but I can't see what I'm doing wrong. Like I say, I know mostly what settings to use (although willing to be educated on that!) and it's only recently become a problem. I even tried a shot in auto and it wasn't any better. (on all of them I use single point focus and focus on the nearest eye).

Here are two photos with all details. At 100% zoom, the face isn't in focus.

f/4 1/2000
iso 800 18-200@18mm

f/3.8 1/2000
iso 125 18-200@25

Click to expand...

what focus mode did you use? You should use AFS-S for this.

It looks like the camera decided the scenery behind had a better contrast for the autofocus to lock on to

Click to expand...

I had it on AF-A. I read that the camera is usually clever enough to recognise which you want if you have it on that auto setting, and nearly always is right? Maybe it's better to manually choose instead though?

Here's a paradox - we're giving you advice and you're reading it - but my advice here is don't believe all you read.

You don't trust the camera to compose the picture for you, so why trust it to know what part of the composition is most important? All it's doing is applying a set of algorithms devised by an engineer on the other side of the world.

I don't know your camera so I don't know what AF-A means, but what you say about it being clever enough to choose the focus point clashes with your saying that you selected the focus point on the eyes (or anywhere else).

--
---
Gerry
___________________________________________
First camera 1953, first Pentax 1985, first DSLR 2006

Galleries by Gerry Winterbourne

www.pbase.com

[email protected]

lehill · Jul 11, 2016

HairyB said:
I had it on AF-A. I read that the camera is usually clever enough to recognise which you want if you have it on that auto setting, and nearly always is right? Maybe it's better to manually choose instead though?

I looked up Nikon's AF-A and it's just like Sony's AF-A. In AF-A the camera decides whether to use continuous AF (re-focus all the time) or single AF (focus once and stay there). Even worse, from what I've read, it switches back and forth anytime it wants to.

I'm familiar with Sony's AF-A and it's not a good way to control your focus. We in the Sony forum just advise new users to choose continuous or single as the situation dictates and avoid AF-A.

--
Lance H

Halina123 · Jul 11, 2016

lehill said:
HairyB said:

I had it on AF-A. I read that the camera is usually clever enough to recognise which you want if you have it on that auto setting, and nearly always is right? Maybe it's better to manually choose instead though?

Click to expand...

I looked up Nikon's AF-A and it's just like Sony's AF-A. In AF-A the camera decides whether to use continuous AF (re-focus all the time) or single AF (focus once and stay there). Even worse, from what I've read, it switches back and forth anytime it wants to.

I'm familiar with Sony's AF-A and it's not a good way to control your focus. We in the Sony forum just advise new users to use continuous or single and avoid AF-A.

--
Lance H

The camera is usually clever enough to decide what to focus on. But it is not full proof. Here is a classic where the camera on automatic focus with multiple focus points decided to focus on the background. Straight forward single focus on the centre would have been best.

HairyB · Jul 11, 2016

lehill said:
I'm just as stumped as all the others which probably doesn't mean very much.

I took the liberty of superimposing the D5100 focus points over your photo. Maybe this can be of some help to everyone:

Nikon Multi-CAM 1000 focus sensor

According to the sources I've read only the center focus point is cross-type. I've seen some conflicting information but it seems the top-most and bottom-most focus points are horizontal-type (sensitive to horizontal lines), the rest are vertical-type. Plus it seems Nikon has a gazillion settings on how they can be used and combined.

I had a camera with a similar focus array and wound up using the center point for most situations and recomposing.

Do you recall which focus point you used for this shot? Did you focus and recompose?

--
Lance H

I don't remember specifically. I pretty much always use centre point and re-compose, so I imagine that was the case here.

Doug Haag · Jul 11, 2016

HairyB said:
I had it on AF-A. I read that the camera is usually clever enough to recognise which you want if you have it on that auto setting, and nearly always is right? Maybe it's better to manually choose instead though?

Before this post by me, there have been several responses from others regarding AF-A that suggest it is not a desirable focus mode. It might be interesting to note that the latest and most expensive Nikon Dx camera (the D500 which is classified by DPR as a PRO camera) does not have an AF-A mode. People who use that camera tell the camera where they want to focus -- not the other way around.

Your comment that you think the camera is "clever" might be one of the problems, Your original post says "I know mostly what settings to use ..." But if you are shooting with settings (not just focus but also those that establish exposure, ISO, etc.) that assume the camera is "clever", that means you have a long way to go, The "clever" aspect of cameras often gets it right, but sometimes it doesn't. Until you know how to control all aspects of the settings without relying on the "cleverness" of the camera, you are operating as a point and shoot snapshooter and not a photographer. Sometimes the "clever" camera won't give you the best result.

Focusing problems

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