Back focusing?

htid

htid

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Chris
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Hi,

I gave my girlfriend my old Nikon D5000 and she recently got a Tamrom 70-300 f4-5.6 VC USD. She showed me some photos and was disappointed that they were blurry, but I can't work out if the lens is back focusing or not! The photos she showed me are as follows, all at 300mm (these are SOOC screenshots showing the focus point...not necessarily showing the centre of the picture, just cropped to show the OOF/In focus areas):

4000th/s. OK the focus point isn't over the bird exactly but it's certainly not on the grass to the left of the bird that is sharp
4000th/s by Chris Cotton, on Flickr

2500th/s. Surely the bird should be in focus here? Instead it's the background
2500th/s by Chris Cotton, on Flickr

400th/s. The rocks at the top of the image are in focus here
400th/s by Chris Cotton, on Flickr

Unfortunately she doesn't have a tripod so the best test I could do was to put the camera on a flat wall, with some spice pots about 10m away, spaced about 5cm away from each other at a 45 degree angle. The results seemed to show no back focusing...

Back Focusing G by Chris Cotton, on Flickr

I tried moving the spice pots 15m or so away and spacing them 10cm apart (what I don't know is how far apart they should be with an f5.6 lens as that's not such a narrow DoF).
Back Focusing O by Chris Cotton, on Flickr

(continued in next post)
 
I told her that I can't find anything wrong, although the cinnemon above does look slightly more in focus than the nutmeg.

She then took some more and maybe I'm missing something but how can the same photo be sharp and not sharp on multiple shots one after the other? The shutter speed is very fast...

The bird here is OOF...
1250th/s by Chris Cotton, on Flickr

Then next shot the feather detail is much better! (well, full size on flickr/the original file is much sharper even if it doesn't show here)
1250th/s by Chris Cotton, on Flickr

Anyway any ideas as to what's going on? I'm lost if when I do the tests, I can't replicate what happens in the real world :confused: Any help much appreciated!
 
She said that she always waits until it is in focus through the viewfinder before depressing the button all the way down so I don't think that can be the issue unfortunately
 
I don't have a D5000 but on the other Nikons I have you can set the shutter to release on the press of the button or the press of the button and focus lock. So if you have it set to button only it may not have had enough time to fully focus by the time the second shot is fired. The benefit of the first option is that you will get a shot but it may not be in focus and the benefit of the second option is that while the shot is more likely to be in focus it may not get any shot at all if it's not fully focused. The best option is probably to go for option one but keep firing continuously until you are sure it has focused.

It is also a big ask for the camera to focus on something that only partially covers one focus point. I think you would be better off focusing on the ground at the birds feet and filing the focus point.

It may also be that the lens is not working correctly. I did buy a Tamron 70 - 200 but sent it back because the focusing was all over the place.
 
:agree: What software are using for the focus point confirmation?

I have owned a few (3) of these Tamrons and they have been okay for my needs and never needed major AF fine tune on my D7000, D7100 and the one I got now on my D750. I know there variances with the 24-70 & 70-200 f2.8 lenses mentioned above.

What I have noticed is that the lens does get softer after 280mm which is usually the case with most zooms, but another thing I find, is that very high shutter speeds can give some variances and and I usually stick below 1/1600 but more usually 1/800 - 1/1250. This maybe due to my arm and shoulder problems or there is shutter shock??? best thing to do is get it on a tripod and do more controlled tests. But the SS she has been using seem high for static / perched birds and there maybe some user error?

For your testing, you would need to run at a 45 degree angle to check focusing, they look as if there in a straight line.


Have a look here >https://photographylife.com/how-to-calibrate-lenses

http://cameralightlens.com/newsblog/?p=264
 
Swanseajack said:
:agree: What software are using for the focus point confirmation?

I have owned a few (3) of these Tamrons and they have been okay for my needs and never needed major AF fine tune on my D7000, D7100 and the one I got now on my D750. I know there variances with the 24-70 & 70-200 f2.8 lenses mentioned above.

What I have noticed is that the lens does get softer after 280mm which is usually the case with most zooms, but another thing I find, is that very high shutter speeds can give some variances and and I usually stick below 1/1600 but more usually 1/800 - 1/1250. This maybe due to my arm and shoulder problems or there is shutter shock??? best thing to do is get it on a tripod and do more controlled tests. But the SS she has been using seem high for static / perched birds and there maybe some user error?

For your testing, you would need to run at a 45 degree angle to check focusing, they look as if there in a straight line.


Have a look here >https://photographylife.com/how-to-calibrate-lenses

http://cameralightlens.com/newsblog/?p=264
Click to expand...

As I said unfortunately she doesn't own a tripod and neither do I :/ So there's no possible way of doing a test with one. The best I could manage is putting the camera on the wall as I did. The spice pots weren't in a straight line, they were going away at a 45 degree angle, in the first image at about 5cm back from each other and the second about 10cm back from each other (the same as the batteries in the 2nd link).

I've seen the second link before but trouble is that the lens is f5.6 so as I said, at 300mm, I don't know if batteries are big enough. At quite a small aperture like this, I imagine all the batteries would be in focus anyway which wouldn't show any issues? Or am I completely wrong in thinking this?
 
The best way to check a camera and lens combo for focus accuracy, is the battery test, as in my image below. Set 5 batteries in a dead straight line, about 250mm apart, camera on a tripod or something solid and focus so that you can see all 5 batteries, but only focus on the centre one and do it with all of your lenses. This will tell you if they are front or back focusing.


IMG_1349 by Alan Perry, on Flickr
 
OK I just did the battery test, using timer release and the camera on the table. Everything looks OK and focus was spot on where I aimed so clearly not a back focusing issue....unless at 300mm back focusing can not happen when the subject is 1.5m away but can happen when it's 10m away? Is that possible?
 
htid said:
OK I just did the battery test, using timer release and the camera on the table. Everything looks OK and focus was spot on where I aimed so clearly not a back focusing issue....unless at 300mm back focusing can not happen when the subject is 1.5m away but can happen when it's 10m away? Is that possible?
Click to expand...

Hopefully it's all fine Chris.

If you have the space try increasing the focal length and the distance. As you know the bird can look OOF against the expanse of the surrounding area if its to far away.. With the battery test you will get a better idea as the batteries are the same size and shape, with the spice pots there was four different shapes which will could give inconsistent results.

Looking at the pics again, what type of distance was she shooting? and the one with the grass in focus (1) looks as if it's side focusing, not sure that's possible unless the lens is de-centered? Looks like some user error or the distance is too far to get a sharp image of the bird.

I believe Cannon allow AF fine tune with some of there bodies at different lens focal lengths and Sigma with there new dock thingy, so I suppose it can happen that focus can change over the focal length.
 
Swanseajack said:
Hopefully it's all fine Chris.

If you have the space try increasing the focal length and the distance. As you know the bird can look OOF against the expanse of the surrounding area if its to far away.. With the battery test you will get a better idea as the batteries are the same size and shape, with the spice pots there was four different shapes which will could give inconsistent results.

Looking at the pics again, what type of distance was she shooting? and the one with the grass in focus (1) looks as if it's side focusing, not sure that's possible unless the lens is de-centered? Looks like some user error or the distance is too far to get a sharp image of the bird.

I believe Cannon allow AF fine tune with some of there bodies at different lens focal lengths and Sigma with there new dock thingy, so I suppose it can happen that focus can change over the focal length.
Click to expand...

I think it's more likely user error then but I can't see why if the SS is high enough and the focus point is over the bird. I've had a read and by default in AF-S the camera won't take the photo until focus is locked. I imagine it must just be that the lens is slightly too slow to focus (after all it's not a 300f2.8!) and the bird has moved slightly by the time it thinks it has locked :S It still doesn't seem to explain the first and second shots...I have no idea what's happened there. The body is too low spec so doesn't have AF fine tune unfortunately. It would mean either sending it off to Nikon or somewhere else to be calibrated but it seems to not BF so I can't see much point.

She's at uni atm but I'm sure she'll maintain there's something wrong because I can't explain to her why some of the images are not sharp when as far as I've told her, with a high SS and the focus point on the subject, you should get in focus shots! :/
 
htid said:
I think it's more likely user error then but I can't see why if the SS is high enough and the focus point is over the bird. I've had a read and by default in AF-S the camera won't take the photo until focus is locked. I imagine it must just be that the lens is slightly too slow to focus (after all it's not a 300f2.8!) and the bird has moved slightly by the time it thinks it has locked :confused: It still doesn't seem to explain the first and second shots...I have no idea what's happened there. The body is too low spec so doesn't have AF fine tune unfortunately. It would mean either sending it off to Nikon or somewhere else to be calibrated but it seems to not BF so I can't see much point.

She's at uni atm but I'm sure she'll maintain there's something wrong because I can't explain to her why some of the images are not sharp when as far as I've told her, with a high SS and the focus point on the subject, you should get in focus shots! :/
Click to expand...

I just find that I have a better keeper rate when I keep the SS below 1/1600 with the lens as it also has VC. It maybe me and my shoulder and elbow problems and I have put it down to shutter shock??. I think the bird is too far away for the lens and is loosing the definition as it's so small in the frame for pic 2 and she has missed focus in pic 1 as the bird may have moved a little. I get similar pics to 2 & 3 when I take pics of birds in the trees at the bottom of the garden, they are just too far away for my lens and camera.
 
I'm not a Nikon user, so had to Google the D5000 focus system. It would appear that the D5000 does have spot metering, which would be much better for the images you have in this thread. The link below is a thread which will give you some idea.

When I shoot wildlife/birds, I always use spot metering and focus on the eye, immaterial to what lens I am using, whether it be 55-250, or 150-500.

http://photo.stackexchange.com/questions/16408/how-do-i-select-a-focus-point-on-the-nikon-d5000
 
@killwill: are you writing metering when you mean focussing?

@htid: I'm not sure what's causing this to happen but as the apparent shift in focus isn't consistent it does rather point to user error. Might I suggest that your GF turns the VC off when shooting with shutter speeds faster than 1/2000s - this is recommended by Nikon in some of their lens handbooks because the electronics in the camera apparently can't keep up with the lens shift in the lens and it can cause blurred images. This may, or may not, help :)
 
What focus mode? In a multi point dynamic AF mode the camera is *not* using only the highlighted focus point. If one of the 8 surrounding points catches focus before the chosen point does it will focus there.
Most of your examples are of a bird with low contrast/detail near something with better detail/contrast. It is quite possible the camera chose the nearby detail instead. Additionally, on the D5000 only the central AF point is cross sensing... all of the other points are horizontal line sensing (less reliable).
 
Bristolian said:
@killwill: are you writing metering when you mean focussing?

@htid: I'm not sure what's causing this to happen but as the apparent shift in focus isn't consistent it does rather point to user error. Might I suggest that your GF turns the VC off when shooting with shutter speeds faster than 1/2000s - this is recommended by Nikon in some of their lens handbooks because the electronics in the camera apparently can't keep up with the lens shift in the lens and it can cause blurred images. This may, or may not, help :)
Click to expand...

Yes, Steve, I meant spot focusing, thanks for the correction.:(
 
@killwilly She's using single point mode, with AF-C and always using the centre point (I knew about the centre point being the only one on this body of the crosshair type so have made sure she's used that since day 1).

@Bristolian That's something worth considering, thanks. I'd never heard of that so I'll make sure she's aware of it. It's been raining every day the week I've been down here so there's been no chance to actually go out and test and of these different things.

As has been said, I'm sure since there's no BF, it must be down to her error and inexperience (and also down to the birds being too far away and small in the frame). Hopefully some better weather will come along soon and she can try again taking into account the things that have been mentioned here. Thanks for the help everybody.
 
htid said:
I've had a read and by default in AF-S the camera won't take the photo until focus is locked
Click to expand...

htid said:
She's using single point mode, with AF-C and always using the centre point
Click to expand...

I'm kind of confused here now. The inference is that she is using AF-C which can cause all manner of problems if she is 'waving' the combination around the subject. On top of which, almost anything can be in focus thereby allowing the shot to be taken/shutter released simply because it has got a focus-lock. In either AF-S or AF-C focus lock is linked to the shutter but you almost, always get a lock on something in AF-C - invariably not always what you want it to be!

Another (vague) possibility is she is reframing after getting a focus lock onto something else - possibly in the background
 
chuckles said:
I'm kind of confused here now. The inference is that she is using AF-C which can cause all manner of problems if she is 'waving' the combination around the subject. On top of which, almost anything can be in focus thereby allowing the shot to be taken/shutter released simply because it has got a focus-lock. In either AF-S or AF-C focus lock is linked to the shutter but you almost, always get a lock on something in AF-C - invariably not always what you want it to be!

Another (vague) possibility is she is reframing after getting a focus lock onto something else - possibly in the background
Click to expand...

Sorry! Totally cocked that up didn't I, I meant she's in AF-C mode (as in continuous auto focus) which apparently won't take the photo until focus is locked. I can understand that can lead to slight inaccuracies if she's not steady and the centre focal point isn't over the bird (which she's done before) but on the ones where it is, that wouldn't make a difference because there's no way on image #1 she has accidentally put the focus point over the in focus grass. I'm just using the Nikon software (View NX-I I think) to view where the focus point was when the photo was taken.
 
I would suggest she tries it again NOT using AF-C but AF-S - it'll be slower and she'll have to be more deliberate in her 'aim'. It will prove a point though.

I'm of the opinion she has focussed on the background, moved to locate the bird, focus is happy because it's still locked onto something (background in this instance) but then the camera/lens combination is not quick enough to refocus on the bird which is now in 'the zone'.

Only a guess, but sometimes AF-C is not the be-all and end-all of Auto-focus.... now if you were to buy her a body which has AF-C, 3D tracking you're into a whole new ballgame! :)
 
I have this lens on a fairly low end Canon. I've noticed the following. I never use VC as I seem to get fewer blurred shots without it even hand held. The VC seems to be very slow compared to the IS (same thing) on my Canon 18-35mm, which works brilliantly and I use all the time. The lens definitely sharper backed off a bit from 300mm. It will struggle to focus accurately on a bird that's very small in the frame and of low contrast and can't change focus quickly using continuous auto focus if the bird moves slightly. As soon as the light level starts to drop it struggles even more to focus. As everyone else has pointed out, with so much else close to the bird the lens will lock focus somewhere, but not always where you want it. Is your girlfriend handholding or using a beanbag or similar support? I'm pretty small and I find handholding the camera/lens combination steady on a subject at any distance almost impossible. When it all comes together it is a good lens for what it costs.
 
chuckles said:
I would suggest she tries it again NOT using AF-C but AF-S - it'll be slower and she'll have to be more deliberate in her 'aim'. It will prove a point though.

I'm of the opinion she has focussed on the background, moved to locate the bird, focus is happy because it's still locked onto something (background in this instance) but then the camera/lens combination is not quick enough to refocus on the bird which is now in 'the zone'.

Only a guess, but sometimes AF-C is not the be-all and end-all of Auto-focus.... now if you were to buy her a body which has AF-C, 3D tracking you're into a whole new ballgame! :)
Click to expand...

Trouble is, she was using AF-S at first (she's at uni living away from me in case I haven't said that) and when she first showed me some photos saying there must be something wrong with the lens, I said it's probably because she was on AF-S. The focus point was over the bird in a lot of photos but the bird was OOF. I put that down to her having pressed the shutter halfway to lock focus then the bird moved and she just followed without knowing (she assumed it would re-focus by default). So I told her not to use AF-S. Although she could use it and then keep letting go and re-pressing the shutter until the bird is a bit more static I guess.
 
Jannyfox said:
I have this lens on a fairly low end Canon. I've noticed the following. I never use VC as I seem to get fewer blurred shots without it even hand held. The VC seems to be very slow compared to the IS (same thing) on my Canon 18-35mm, which works brilliantly and I use all the time. The lens definitely sharper backed off a bit from 300mm. It will struggle to focus accurately on a bird that's very small in the frame and of low contrast and can't change focus quickly using continuous auto focus if the bird moves slightly. As soon as the light level starts to drop it struggles even more to focus. As everyone else has pointed out, with so much else close to the bird the lens will lock focus somewhere, but not always where you want it. Is your girlfriend handholding or using a beanbag or similar support? I'm pretty small and I find handholding the camera/lens combination steady on a subject at any distance almost impossible. When it all comes together it is a good lens for what it costs.
Click to expand...

If the weather ever gets any better I'll give it a go myself with VC off. I'm used to hand holding my 300f4 (which doesn't have VR) which is heavier than her lens and can get very sharp shots.
 
htid said:
If the weather ever gets any better I'll give it a go myself with VC off. I'm used to hand holding my 300f4 (which doesn't have VR) which is heavier than her lens and can get very sharp shots.
Click to expand...

It's not a VC problem - if it was the whole image will be blurred, with no sharp or in focus parts. The first shot shows the rock as sharp as a sharp thing.
 
I'm keeping an eye on this thread as I have similar issues, with a D7000 and Tamron 70-300 lens mentioned.
During a burst of shots, I find that the focus can shift but have put it down to the subject being too small in the frame. I keep meaning to try it on the tripod .... crap weather tomorrow might inspire me to test/calibrate it properly.
 
AF-C expects significant motion. If there is no motion it will "recheck" focus after a time which can actually mess it up. On some cameras this time delay is settable, but not on the 5300.
Also, by default the shutter priority for AF-C is "release" which means it will fire w/o focus. That setting is available and can be changed to "focus."
 
nickEnackEnoo said:
I'm keeping an eye on this thread as I have similar issues, with a D7000 and Tamron 70-300 lens mentioned.
During a burst of shots, I find that the focus can shift but have put it down to the subject being too small in the frame. I keep meaning to try it on the tripod .... crap weather tomorrow might inspire me to test/calibrate it properly.
Click to expand...
I have the same combination, and have had the same issues.
I've tried focus tuning, tripod etc and have come to the conclusion that's it's me that's the problem, whether it's my technique or the settings I've chosen.
 
sk66 said:
AF-C expects significant motion. If there is no motion it will "recheck" focus after a time which can actually mess it up. On some cameras this time delay is settable, but not on the 5300.
Also, by default the shutter priority for AF-C is "release" which means it will fire w/o focus. That setting is available and can be changed to "focus."
Click to expand...

If you'd have paid attention you'd notice she has a d5000 not a 5300 ;) Unfortunately the 5000 doesn't have this option, I've checked.

@nickEnackEnoo @Bobsyeruncle isn't it a bit suspicious that there are now 3 of us saying the same thing :S I wonder if there really could be an issue?
 
htid said:
If you'd have paid attention you'd notice she has a d5000 not a 5300 ;) Unfortunately the 5000 doesn't have this option, I've checked.

@nickEnackEnoo @Bobsyeruncle isn't it a bit suspicious that there are now 3 of us saying the same thing :confused: I wonder if there really could be an issue?
Click to expand...
Any tests I've done using a tripod, or higher shutter speeds are pin sharp, hence in my case it's my technique or settings that are causing the issue
 
IIRC there was also a AF problem with early batches of the D7000. The two I had were fine from later batch.
 
Oh well just have to wait for better weather to see how it performs out in the field! I've told her she just has to get closer to the birds so they aren't less than the size of the centre focal point! Trouble is she's at uni here 7 hours away from me so when it's sunny I won't be here to have a look myself (at least not until next time I visit next month) so I wanted to get this sorted before I leave tomorrow (but its rained pretty much every day I've been here!). Thanks for the help anyway!
 
Swanseajack said:
IIRC there was also a AF problem with early batches of the D7000. The two I had were fine from later batch.
Click to expand...

Don't remember any issues with AF on early D7000's (could be wrong) it was `oil` spatter on sensors.
 
OldCarlos said:
Don't remember any issues with AF on early D7000's (could be wrong) it was `oil` spatter on sensors.
Click to expand...
I had a D7000 that had the AF problems, it back focused badly to the point I nearly sold a 70-200 f2.8 vr1 as I thought it was rubbish and micro adjusting didn't fix it. Some lenses were worse than others, the shallow DoF at f2.8/f4 showed the problem.
 
For a week or two now I've been trying out 'back button focusing' on my D810 as it's meant to be better/more handy (??). Hmmm really not sure if there's any benefits over using the usual shutter button to be honest. When I back button focus numerous times I actually miss the shot as I take my eye of the subject to find the button on the rear. What's the point in this...?

Question is....?......is it meant to be that much better than the normal method...? I'm really not getting it's idea at the moment.
 
macvisual said:
For a week or two now I've been trying out 'back button focusing' on my D810 as it's meant to be better/more handy (??). Hmmm really not sure if there's any benefits over using the usual shutter button to be honest. When I back button focus numerous times I actually miss the shot as I take my eye of the subject to find the button on the rear. What's the point in this...?

Question is....?......is it meant to be that much better than the normal method...? I'm really not getting it's idea at the moment.
Click to expand...
I've been using back button focusing for a month now, and my hit rate has improved.
I was taking my eye off the subject to find the button too, but now I don't need to.
I wouldn't go back to be honest.
 
Forgive me, but I have only skipped through this thread as it's late. I did some shots like these recently, because I had been shooting aircraft, and was on tracking/servo. I then went on to do some cars and completely forgot to switch back to the correct mode to focus lock, and of course, as I focused and recomposed the frame, the focus moved too.
As for using back button focusing, I thought the idea was so that you could have the camera in servo mode on the shutter button, but could use the back button for one shot, and therefore always be able to use the right mode for what you need at speed? Not sure, as I have only fiddled with it briefly.
I could be talking complete rubbish as usual :D
 
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