How accurate should one expect autofocus to be?

Started Mar 30, 2013 | Questions
SixtenB
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How accurate should one expect autofocus to be?
Mar 30, 2013

This is my first post here. I have just recently bought a used D800 (with a AF-S Nikkor 24-70mm 1:2.8G). I intend to use it mainly for taking photos of my family and maybe some nature photos if I ever get the time off. I am a beginner photographer, and this is my first real experience with an autofocus SLR (having previously mainly used a manual focus Minolta film SLR).

Now to my question: I'm having problems getting sharp photos. One typical example would be taking photos of my 2 year old. I set the camera at 70mm, 1/250 (she's never still), ƒ/2.8, AF-C, d9 area mode and keep the AF-point centered on her eye while keeping AF-ON depressed (I have disabled shutter half-press AF). I then wait a few seconds for the right moment and release the shutter. The result is a perfectly sharp eye (when viewed at 100 %) only in about 10 % of the cases. The rest are either significantly back- or front focused (seemingly at random).

Having never operated such a camera before, I don't know if there is anything wrong with my settings, my technique, my equipment or if the results are just what one should expect. All advice is highly appreciated.

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Nikon D800
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Robin Casady
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Re: How accurate should one expect autofocus to be?
In reply to SixtenB, Mar 30, 2013

In what kind of lighting conditions are you shooting your kids? If it is tungsten, that could be the problem. Change to LED or CFL and see if that helps.

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PHXAZCRAIG
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Re: How accurate should one expect autofocus to be?
In reply to SixtenB, Mar 30, 2013

You might be experiencing a D800 focus issue.   Still being 'sorted out' by the internet community to determine fact from opinion.

One suggestion I have is to use F4 - you need some depth of field anyway, and the D800 has plenty of high ISO performance.

Another suggestion - try a multitude of different AF settings.   What worked on previous cameras may not be the best choice on a D800.    Might as well try 51-pt 3d and see if the face recognition tech in the camera works better than single point...

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mironv
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Re: How accurate should one expect autofocus to be?
In reply to PHXAZCRAIG, Mar 30, 2013

Stop using AF-C and set to AF-S if a kid moves a bit just re touch shutter button and AF will re focus.

When I focus off a face I never focus of eyes I aim at lips and DOF dose a rest. 1/3 in front of focus point 2/3 after is so I just move a focus point forrward a bit. Is like od times in amnual focusing that you often shift focus based on DOF. Anyway with AF-S use single point in good light and 9 in bit dimm light.Since it is your first AF camera ( I can't belive that dinosaurs like that sill exist in 2013 after all first integrated AF 35mm camera was Minolta in 1985 that's 28 years) practice practice practice and don't limit your self for kid target practice get out and shoot as much as you can and you will see that AF is 8 wonders of a world.

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SixtenB
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Re: How accurate should one expect autofocus to be?
In reply to Robin Casady, Mar 30, 2013

Robin Casady wrote:

In what kind of lighting conditions are you shooting your kids? If it is tungsten, that could be the problem. Change to LED or CFL and see if that helps.

Thank you Robin. My light is mainly 2700 K compact fluorescent. Would that have the same effect as real tungsten?

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SixtenB
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Re: How accurate should one expect autofocus to be?
In reply to mironv, Mar 30, 2013

mironv wrote:

Stop using AF-C and set to AF-S if a kid moves a bit just re touch shutter button and AF will re focus.

Thank you Mirnov. I had similar issues with AF-S, and switched to AF-C since I thought motion (either mine or the subject's) was causing the off focus.

When I focus off a face I never focus of eyes I aim at lips and DOF dose a rest. 1/3 in front of focus point 2/3 after is so I just move a focus point forrward a bit. Is like od times in amnual focusing that you often shift focus based on DOF. Anyway with AF-S use single point in good light and 9 in bit dimm light.Since it is your first AF camera ( I can't belive that dinosaurs like that sill exist in 2013 after all first integrated AF 35mm camera was Minolta in 1985 that's 28 years) practice practice practice and don't limit your self for kid target practice get out and shoot as much as you can and you will see that AF is 8 wonders of a world.

Thank you, good advice. I guess I'm just a bit frustrated. Without a split focusing screen, I'm having a hard time manual focusing, and I feel I can't trust the AF to get it right either.

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SixtenB
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Re: How accurate should one expect autofocus to be?
In reply to PHXAZCRAIG, Mar 30, 2013

Craig,

PHXAZCRAIG wrote:

You might be experiencing a D800 focus issue.   Still being 'sorted out' by the internet community to determine fact from opinion.

I've read a bit about that, but it seems more likely that the problem lies with my technique or my expectations.

One suggestion I have is to use F4 - you need some depth of field anyway, and the D800 has plenty of high ISO performance.

Thank you. This was in fact the answer I was afraid of; that the AF can't be trusted to be accurate at ƒ/2.8.

Another suggestion - try a multitude of different AF settings.   What worked on previous cameras may not be the best choice on a D800.    Might as well try 51-pt 3d and see if the face recognition tech in the camera works better than single point...

I will do that.

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primeshooter
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Re: How accurate should one expect autofocus to be?
In reply to SixtenB, Mar 30, 2013

SixtenB wrote:

This is my first post here. I have just recently bought a used D800 (with a AF-S Nikkor 24-70mm 1:2.8G). I intend to use it mainly for taking photos of my family and maybe some nature photos if I ever get the time off. I am a beginner photographer, and this is my first real experience with an autofocus SLR (having previously mainly used a manual focus Minolta film SLR).

Now to my question: I'm having problems getting sharp photos. One typical example would be taking photos of my 2 year old. I set the camera at 70mm, 1/250 (she's never still), ƒ/2.8, AF-C, d9 area mode and keep the AF-point centered on her eye while keeping AF-ON depressed (I have disabled shutter half-press AF). I then wait a few seconds for the right moment and release the shutter. The result is a perfectly sharp eye (when viewed at 100 %) only in about 10 % of the cases. The rest are either significantly back- or front focused (seemingly at random).

Having never operated such a camera before, I don't know if there is anything wrong with my settings, my technique, my equipment or if the results are just what one should expect. All advice is highly appreciated.

As Robin has said, that is a true issue with the camera. Plus, i'd forget "tracking" area modes generally. I never use them for sports. Most people use the single AF-C mode. Ie YOU put the point over the subject and hold down AF-ON, you sometimes will have to move the point with the D pad or the viewfinder (obviously) as the subject moves. Hit rate is much higher. You can also set the tracking delay to OFF which can further help. Tracking is a mode that feels like something in it's first generation, twitchy at best.

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tiko
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Re: How accurate should one expect autofocus to be?
In reply to SixtenB, Mar 30, 2013

SixtenB wrote:

mironv wrote:

Stop using AF-C and set to AF-S if a kid moves a bit just re touch shutter button and AF will re focus.

Thank you Mirnov. I had similar issues with AF-S, and switched to AF-C since I thought motion (either mine or the subject's) was causing the off focus.

Try using AFC single point instead of 9 point dynamic while still keeping the focus point on the eye. In the dynamic mode the camera will initially use the point you selected but MAY change it to another point if  it finds something with better contrast under ANY of the other (9, 21 or 51) dynamic points. While this is not how Nikon states it in the manual, I found it to be very true

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@AT

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rgolub
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Re: How accurate should one expect autofocus to be?
In reply to SixtenB, Mar 30, 2013

SixtenB wrote:

Thank you. This was in fact the answer I was afraid of; that the AF can't be trusted to be accurate at ƒ/2.8

Oh, the AF will be accurate, but not much else will be.  Play with the depth of focus calculator at DOFmaster.   At 70 mm focal length, 5 feet from subject and f 2.8 your DOF is 3 inches.  Hard to expect a child to stay still enough to get everything framed and composed with that narrow of a DOF.

As has been mentioned, you can easily go to ISO 3200 on a D800.  It expands your world tremendously.

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RockyBalboa
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Re: How accurate should one expect autofocus to be?
In reply to SixtenB, Mar 30, 2013

10% success rate is too low under any circumstances. I have d7000 and d600 and I would throw them out of window with that rate. You have definitely problem either in camera or your technique or both. Try to find someone in your area who can help you.

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Prairie Pal
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How is the focus on non moving subjects?
In reply to SixtenB, Mar 30, 2013

ie. a newsprint or object on your wall?

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Robin Casady
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Re: How accurate should one expect autofocus to be?
In reply to SixtenB, Mar 30, 2013

SixtenB wrote:

Robin Casady wrote:

In what kind of lighting conditions are you shooting your kids? If it is tungsten, that could be the problem. Change to LED or CFL and see if that helps.

Thank you Robin. My light is mainly 2700 K compact fluorescent. Would that have the same effect as real tungsten?

I'm not sure. I've only experimented with tungsten and daylight CLF. Haven't tried warm white bulbs.

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Robin Casady
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Re: How accurate should one expect autofocus to be?
In reply to SixtenB, Mar 30, 2013

SixtenB wrote:

Without a split focusing screen, I'm having a hard time manual focusing, and I feel I can't trust the AF to get it right either.

If you don't wear glasses, try using a Nikon DK-17M magnifying eyepiece.

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Robin Casady
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mironv
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Re: How accurate should one expect autofocus to be?
In reply to tiko, Mar 30, 2013

tiko wrote:

SixtenB wrote:

mironv wrote:

Stop using AF-C and set to AF-S if a kid moves a bit just re touch shutter button and AF will re focus.

Thank you Mirnov. I had similar issues with AF-S, and switched to AF-C since I thought motion (either mine or the subject's) was causing the off focus.

Try using AFC single point instead of 9 point dynamic while still keeping the focus point on the eye. In the dynamic mode the camera will initially use the point you selected but MAY change it to another point if  it finds something with better contrast under ANY of the other (9, 21 or 51) dynamic points. While this is not how Nikon states it in the manual, I found it to be very true

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@AT

AF-C for slow moving people is pointless since camera AF is making all decisions and moment one trips a shooter may not be when critical focus is achived,specialy at small DOF tham my be a problems. At longer distance for sports this is preffered method of focusing and tracking object taking camera AF capabititys of AF-C. AF-S like it or not will do own small ajustmants when will detects that object moves but in less rapid sucsesions than AF-C. More than that one can luck and hold AF and just wait to have a perfect moment to take a shot. AF-C fore interior shots of people will always have some problems since this mode picks most contrasty point that it sees not nessesary where you need it to e and that waht makes all this storys about bad focus. It is just bad choice of camera AF that people choose for a given object. Even when wedding party walks from or to altar I never ever used AF-C anlways AF-s and just tap on shutter button and I never have any missed focus shots. I often luck focus point from other objects that are in same distance and just wait for whatever I shoot to get there so I'm in control when and where if you set to AF-C all this decisions where and when is up to a camera AF system.

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PHXAZCRAIG
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Re: How accurate should one expect autofocus to be?
In reply to tiko, Mar 30, 2013

This could explain a lot of AF misses..

Easy enough to see if the change works too.

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tiko
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Re: How accurate should one expect autofocus to be?
In reply to mironv, Mar 30, 2013

mironv wrote:

AF-S like it or not will do own small ajustmants when will detects that object moves but in less rapid sucsesions than AF-C. .

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Mironv

Are you sure about this? I mean wouldn't that make the single servo concept pointless?

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mironv
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Re: How accurate should one expect autofocus to be?
In reply to tiko, Mar 30, 2013

tiko wrote:

mironv wrote:

AF-S like it or not will do own small ajustmants when will detects that object moves but in less rapid sucsesions than AF-C. .

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Mironv

Are you sure about this? I mean wouldn't that make the single servo concept pointless?

@AT

No it dose not as time between holding lucking shutter and keeping AF point and time you trip a shutter your object can move and where there is detectable movemant AF-S dose track this and ajust it self you can read it in every Nikon description of AF function of camera. They in past few generations of AF make sych an issue of tracking thak we don't have a trap focus anymore. You know what trap fosus is??? My N90s when set to af but I switch lens to manual and preset at distance I need will not fire untill AF detects object in focuas so this was preffere method for macro AF shooting. You just moved camera a bit holding shutter button fully pressesd and camera trip it when AF modul sees object in focus. You can pre focus at empty space like above obstycels for Jumper Horses and just wait till gets there and have perfect shot. Fuji S5 is last camera that did this but only with manual lenses.

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Truman Prevatt
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Re: How accurate should one expect autofocus to be?
In reply to Robin Casady, Mar 30, 2013

Robin Casady wrote:

SixtenB wrote:

Without a split focusing screen, I'm having a hard time manual focusing, and I feel I can't trust the AF to get it right either.

If you don't wear glasses, try using a Nikon DK-17M magnifying eyepiece.

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Robin Casady
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"The whole problem with the world is that fools and fanatics are always so certain of themselves, and wiser people so full of doubts."
— Bertrand Russell

For those wanting to manual focus the DK-17M I highly recommend.  I recently added on to my D800 and it really helps.  It makes manual focusing a reasonable alternative.

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Truman
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Truman Prevatt
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Re: How accurate should one expect autofocus to be?
In reply to SixtenB, Mar 30, 2013

SixtenB wrote:

Now to my question: I'm having problems getting sharp photos. One typical example would be taking photos of my 2 year old. I set the camera at 70mm, 1/250 (she's never still), ƒ/2.8, AF-C, d9 area mode and keep the AF-point centered on her eye while keeping AF-ON depressed (I have disabled shutter half-press AF). I then wait a few seconds for the right moment and release the shutter. The result is a perfectly sharp eye (when viewed at 100 %) only in about 10 % of the cases. The rest are either significantly back- or front focused (seemingly at random).

I suspect your real problem is narrow DOF at 70 mm f2.8 and a moving subject in indoor lighting.

Take the kid outside and try it in natural light at 5.6 and see what happens.

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Truman
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