# When do you use all of your autofocus points?



## gl600 (Dec 24, 2009)

Why is 51 points of AF better than, lets say, 9?
For 99% of my shots I use one AF point, get the focus locked, recompose then shoot. Is it any better to change AF points to where you want to focus in the frame?


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## Derrel (Dec 24, 2009)

Multiple autofocusing points allow the camera to accept and input data from *multiple points* across the frame. If you have a Nikon body with the Scene Recognition System, that system uses color information (RGB color analysis) and distance information to "identify" the original subject and to follow that subject as it moves across the frame, it would be a good idea to learn how to use a grouped AF point focusing strategy for some situations. The multi-point AF focusing concept is one of the advantages of using one of the newer Nikon bodies that have color-aware and distance-aware light metering. If you had a car with five gears, would you ALWAYS use it in 3rd gear? Probably not.

Your question: is it better to change your AF points where you want the focus in the frame? is a good one; that is one way the Nikon SRS knows what target to follow across the frame; the initial lock-on,as determined by the photographer, is the way the camera knows what the original subject is; you use the multi-controller to rapidly SELECT an AF area, and then the SRS system reads the RGB values, reflectance values, and distance information,and then it can track that subject as it moves across the frame. So, yes, there is  a well-known method and a known reason for the shooter selecting his/her preferred intial focusing point(s) underlying the 51-point AF system Nikon has developed.

Using just a single,center AF point in effect, is throwing away much of the capability of the autofocusing system. An AF system that can collect data from multiple locations around the frame will, if it's a newer Nikon body, be able to do better focus tracking than using *just ONE* AF location.

On the professional-level Nikon AF systems, people who encounter a lot of difficult autofocusing situations will tell you that they rely upon a multi-point AF configuration for a number of specific scenarios where using only one AF point  does not produce the results they want. I would suggest some of the very comprehensive guide books, like the Thom Hogan Complete Guide to the Nikon _______ series as a way to learn more about how to use a modern, complex AF system. AF systems have become very sophisticated,and they require both understanding of the concepts AND practice to master.


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## gl600 (Dec 24, 2009)

Thanks!


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## Garbz (Dec 24, 2009)

Do you really just use the centre AF point? I know even older cameras like the D200 with it's 11 point AF have options where you select 1 AF point, however the surrounding points are used to assess the image and assist in accurate autofocus and tracking. On this camera there's 4 different options on a selector switch on the camera, and other 4 or 5 options to customise these points, and all in all only 1 set of options will truly give you simple single point AF.

Even if you don't intend to use the 51 points they improve the AF performance of the camera. But evenutally you'll get into a situation like:

- Macro photography where the camera is on a tripod, the chance of error is large, and the subject doesn't quite line up with one of the 9AF points of a cheaper camera.
- Sports where using 51 AF points to dynamically track the ball as it's moving across the field is a godsend. 
- Portraits, because some people just outright don't like focusing then recomposing. The people with 85mm f/1.2s would be the culprits here.


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## KmH (Dec 24, 2009)

I believe the OP is contemplating getting either a D90 (9 focus points, 1 cross-type point, Multi-CAM 1000 autofocus module) or a D300 (15 cross-type focus points, Multi-CAM 3500DX autofocus module) so they can shoot weddings.


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## Aritay (Dec 24, 2009)

Good question.

What if nothing in the pic is moving.  Then isn't just using the one point, pushing the shutter half-way down, then re-composing just as good??

(I do understand if things are moving.  But otherwise, isn't it just as easy (easier) to use a centerpoint??)


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## IgsEMT (Dec 24, 2009)

I use one center point, lock the focus and recompose.


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## gl600 (Dec 25, 2009)

Garbz said:


> Do you really just use the centre AF point? I know even older cameras like the D200 with it's 11 point AF have options where you select 1 AF point, however the surrounding points are used to assess the image and assist in accurate autofocus and tracking. On this camera there's 4 different options on a selector switch on the camera, and other 4 or 5 options to customise these points, and all in all only 1 set of options will truly give you simple single point AF.



What I mean t was not to completely disable the other AF points, rather to just select one AF point as the area that the camera will always focus to and then simply recompose. Again, if I am shooting in a studio, a wedding, a landscape (anything besides sports or fast paced wildlife) why would I select all of my AF points to be active?


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## feRRari4756 (Dec 25, 2009)

hey guy i was just reading this thread and was curious about this also. I have a Canon 30d and will be using my 70-200 f4 USM L or 17-55 2.8 IS USM to shoot surfing from the water (with a waterproof housing). What points and AF mode (one shot, servo, etc) do you guys reccomend i should use because the will be coming at me at about a 45 degree angle. You guys might have answered it already but i dont quite understand. 

thanks!


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## Josh66 (Dec 25, 2009)

Why Focus-Recompose Sucks


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## keith foster (Dec 25, 2009)

Thanks O!  That was a good read and good to know stuff.


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## Garbz (Dec 25, 2009)

gl600 said:


> What I mean t was not to completely disable the other AF points, rather to just select one AF point as the area that the camera will always focus to and then simply recompose. Again, if I am shooting in a studio, a wedding, a landscape (anything besides sports or fast paced wildlife) why would I select all of my AF points to be active?



Jeep hit the nail on the head in the above post. The parallax error when shifting the lens will shift the focus point. Now let me just say if you're in a studio and nuking your subject with light so you can use your wide lens at f/16 then realistically this will make no difference to you at all. 

But focus and recompose simply does not work when you're shooting at f/1.4. You will have a high failure rate simple because of the hair thin depth of field. Same for macro photography.

Even in the studio the focus points are simply there to give you options. You'll ultimately find the points in the centre are the most accurate and reliable, but sometimes they are just not suited for the job.


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## Shockey (Dec 25, 2009)

When shooting people I always use one focus point. Normally focus recompose will work ok if you are more than 5-6 feet away because the depth of field will cover the change in focus point when you move, and if you have time to do it. For close ups you need to switch to a focus point closer to the eye, (always focus on the eyes), with focus recompose on closeups you will have a hard time maintaining the focus on the eyes as you move the camera to recompose due to the small depth of field.
Also for fast moving situations like weddings you need to move the focus points, with practice you can get really fast at it...it is way faster than shooting them all with the middle point and then having to crop a few hundred pictures!!!

If you are using anything other than one focus point on people you will have a hard time getting critical focus on the eyes, which is a must. You must control where the focus point is don't let the camera do it.

For moving subjects or anything other than people then other focus point options are much better.


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## cliffy13 (Dec 26, 2009)

KmH said:


> I believe the OP is contemplating getting either a D90 (9 focus points, 1 cross-type point, Multi-CAM 1000 autofocus module) or a D300 (15 cross-type focus points, Multi-CAM 3500DX autofocus module) so they can shoot weddings.



Considering that even in modern reportage style weddings the subject is pretty well centre frame in all the shots why does anyone need more than the centre focus point


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## feRRari4756 (Dec 26, 2009)

hey guy i was just reading this thread and was curious about this also. I have a Canon 30d and will be using my 70-200 f4 USM L or 17-55 2.8 IS USM to shoot surfing from the water (with a waterproof housing). What points and AF mode (one shot, servo, etc) do you guys reccomend i should use because the will be coming at me at about a 45 degree angle. You guys might have answered it already but i dont quite understand. 

thanks!


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## Josh66 (Dec 26, 2009)

feRRari4756 said:


> What points and AF mode (one shot, servo, etc) do you guys reccomend i should use because the will be coming at me at about a 45 degree angle.



AF point - use the one that is closest to what you want to focus on.

Mode - for what you're doing, one of the servo modes would be best.  Definitely NOT one-shot, you want something that is going to track the subject.


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## Garbz (Dec 26, 2009)

cliffy13 said:


> Considering that even in modern reportage style weddings the subject is pretty well centre frame in all the shots why does anyone need more than the centre focus point



That's a large generalisation. Any wedding photography who centres the subject in all of their shots isn't one worth hiring in my option. I mean weddings are the one thing where there are no rules and on this very forum I have seen every possible style and expression of the photographic art in wedding photos, and of these they definitely did not all have the subject in the centre.


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## kkamin (Dec 28, 2009)

O|||||||O said:


> Why Focus-Recompose Sucks



Thanks for the link.  Very illuminating.

In the example he gives with the model, where the camera is tilted up to focus on the eye then swung back down to compose the shot, what if the photographer stood up to her eye height instead of tilting up?  I think that would be helpful if you are in a single point focus situation.


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## Josh66 (Dec 28, 2009)

kkamin said:


> O|||||||O said:
> 
> 
> > Why Focus-Recompose Sucks
> ...



You would still get the same problem...basically.  I think it would make you front focus instead of backfocus though, since the second "recomposed" orientation would be farther away (instead of closer, like the example).
(Above assums the camera is on a tripod, raised to the models eye level and only tilting)
*-EDIT-* But, it wouldn't be as bad as the example, since 2/3 of the DOF is behind the focus point.  Front focusing would 'miss less' than back focusing. *-EDIT-*

If you raised the center column, focused, then lowered it (never actually tilting the camera), I think that would work.  In the time it would take to do all of that, the model may have moved though...  Trying to do that hand-held, it would be pretty hard to ensure that the camera-to-subject distance stayed consistent.
In theory, it would work.  In practice, it would be hard to pull off.


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## Garbz (Dec 28, 2009)

In practice I will still come back to the kind of photography matters.

An 85mm f/1.2 will take a photo such that the eyes are in focus, but the nose and ears are a blur. Focus and recompose if you must, but there are electrical aids for this in many cameras


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