# Idea--Looking at autofocus from a new perspective



## helpful (Sep 19, 2015)

*Problem statement:*

Autofocus systems currently provide the ability to focus on the nearest subject among all active autofocus points.

And although this limitation doesn't apply _after_ autofocus tracking is initiated, this limitation does apply _during_ the initial focus acquisition. Among whatever subjects are detectable by the active focus points or focus region, the focus is placed on the closest subject detected.

From a mathematical viewpoint, this is a "distance priority" focusing algorithm to acquire focus on any object at a distance X, with priority set to find an X that is as close as possible to a distance of 0.

The mathematical, and creative, question that begs to be asked is: why always choose 0?

*Current solutions:*

We can deal with this now using focus limiters during continuous autofocus, or by using focus and recompose during one-shot autofocus. Focus limiters introduce limitations of their own as well as offering only a few settings. Focus and recompose places the plane of sharpest focus behind the subject unless a photographer is very good at mentally solving geometry and trigonometry problems while shooting.

*Proposed solution:*

A better solution would be to simply recognize the mathematical nature of focusing as a "distance priority" algorithm, and to allow the photographer to set their own distance priority instead of 0.

An effective implementation would be a simple switch: flip left to set distance priority to 0; flip right to set distance priority at the current focus distance. The camera would then find, focus on, and/or track subjects that are closest to this distance within active autofocus points.

*What could this do for a photographer?*

Here are just a few examples and scenarios of so many countless problems this could solve for photographers, in a much more simple way than focus limiters. It is likely to also greatly reduce the complexity of focus tracking methods while at the same time increasing reliability.

1. Focus and recompose scenarios, like environmental portraits. Focus on subject. Flip distance priority switch to the right. Recompose and do whatever you like, using wide area AF. Focus always will lock exactly on the subject, without shifting the plane of focus behind the subject like normal focus and recompose methods. And just as with normal focus and recompose, focus will never shift to the foreground or background. Best of all, you don't have to keep on focusing and recomposing again and again.

2. Volleyball from the far side of the net. Focus on a player behind the net. Flip distance priority switch to the right. Use autofocus tracking and forget all about the problem of having your camera focus on the net instead of the players behind it (a problem that not even the 1D X focus tracking has solved).

3. The list could go on and on practically forever.


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## Valvebounce (Sep 19, 2015)

Hi Helpful. 
This seems like a well thought through piece of reasoning, my only comment is you need to get this in front of Canon, none of us can get this implemented. 

Cheers, Graham. 



helpful said:


> *Problem statement:*
> 
> Autofocus systems currently provide the ability to focus on the nearest subject among all active autofocus points.
> 
> ...


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## Busted Knuckles (Sep 20, 2015)

Or Magic Lantern.


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## Bundu (Sep 20, 2015)

Elegant, simple and brilliant idea. Get it to Canon!!!


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## Mt Spokane Photography (Sep 20, 2015)

What am I missing? Maybe I do not understand why you can't track a desired subject now. Place the focus point on the subject, it will focus on that subject and will track it, even if something comes to interrupt it briefly, focus will not shift. You can set the delay time.

If you are selecting all AF points, try selecting a single point or a small group based on the subject size. The camera will focus where you tell it to if you setup the AF points accordingly. It also uses color to help keep tracking the subject. 


http://www.learn.usa.canon.com/resources/articles/2012/1dx_guidebook.shtml


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## Bundu (Sep 20, 2015)

I was taking some BIF fotos a few weeks ago. Small river, about 15m wide. I was about 30m from the river. There was lots of trees on both banks of the river but there was a clearing my side of the river 10 to 15 meters where the birds was clear from obstructions. Before and after the clearing there were also gaps but much smaller. I tried to start tracking the birds flying down the river so that i can shoot away the moment they pass through the clearing. I tried single point and the centre wide group. Sometimes it worked sometimes not. A 50 percent hit rate more or less. I manually focused before to about the middle of the river but it was not always working. If I could have selected the middle of the river as the zero point as the OP suggest in his idea i think the hit rate could have been much higher. I used a 7dii and 100-400ii. When the 7d locked on it worked perfect but to get the initial lock with all the trees on both sides of the river it was not that easy. Or maybe i just need to practise a lot more and/or play with the autofocus settings more. What would the best approach be in the situation as described above with what i have available? Cant afford a 1dx or such fancy equipment!


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## helpful (Sep 21, 2015)

dilbert said:


> helpful said:
> 
> 
> > *Problem statement:*
> ...



Choosing the center point only versus a group of autofocus points is not the issue at hand. If you choose the center point only, does your camera then provide the option to prioritize initial focus acquisition on a potential subject at 10 feet versus a potential subject at 5 feet, if both subjects are detectable by the sensor? I may be wrong, but I don't think so.



dilbert said:


> > ...
> > A better solution would be to simply recognize the mathematical nature of focusing as a "distance priority" algorithm, and to allow the photographer to set their own distance priority instead of 0.
> > ...
> 
> ...



It's not a distance range at all. When tracking with this method, there would be no "range" such as there is with focus limiters.


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## helpful (Sep 21, 2015)

Mt Spokane Photography said:


> What am I missing? Maybe I do not understand why you can't track a desired subject now. Place the focus point on the subject, it will focus on that subject and will track it, even if something comes to interrupt it briefly, focus will not shift. You can set the delay time.
> 
> If you are selecting all AF points, try selecting a single point or a small group based on the subject size. The camera will focus where you tell it to if you setup the AF points accordingly. It also uses color to help keep tracking the subject.
> 
> ...



As I mentioned to another member, selection of the autofocus point(s), such as the center point only (or center + 4-point expansion) versus a group of autofocus points, is not the issue at hand.

I mentioned in my OP that tracking does handle some scenarios, provided that initial focus acquisition can acquired. Often it cannot, however, and never when two conflicting objects both detectable by the active AF sensor(s) are present at different distances.

Also, focus tracking only works momentarily in many cases, and when the conflicting objects are unmoving (like a volleyball net, which is just one tiny example), then it is useless altogether. Manual focus works fine (or moving to a different perspective and producing stale, repetitive, non-creative results), but then why spend $6,800 for an autofocus system and then not use it?


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## Mt Spokane Photography (Sep 21, 2015)

helpful said:


> dilbert said:
> 
> 
> > helpful said:
> ...




Perhaps, a photo of one of your difficult to acquire subjects would help me understand more of what you are seeing. Its entirely possible that your 1DX has a issue acquiring focus. Bad AF points or a bit of dust on the AF sensor can make life difficult.

I have never had a issue focusing on a object that I wanted once I set up the focus points correctly..

In this example, I focused thru openings in branches on flowers with no issues at all. I used single point spot AF 







Here is another






Focusing on the rider on the ground thru the railings. The High ISO required was beyond the capability of the 7D, but it still acquired focus.







I don't know where the focus point this one was on, but it had no trouble with the fence. Both the bull and the High School kid might use chiropractic treatment. The boy was a accomplished dancer and loved Rodeo too. Its pretty dangerous around a animal like that.


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## privatebydesign (Sep 21, 2015)

helpful said:


> Here are just a few examples and scenarios of so many countless problems this could solve for photographers, in a much more simple way than focus limiters. It is likely to also greatly reduce the complexity of focus tracking methods while at the same time increasing reliability.
> 
> 1. Focus and recompose scenarios, like environmental portraits. Focus on subject. Flip distance priority switch to the right. Recompose and do whatever you like, using wide area AF. Focus always will lock exactly on the subject, without shifting the plane of focus behind the subject like normal focus and recompose methods. And just as with normal focus and recompose, focus will never shift to the foreground or background. Best of all, you don't have to keep on focusing and recomposing again and again.
> 
> ...



1. Use a focus point such that you don't need to focus and recompose, it isn't difficult. Select a focus point suitable for your framing, focus, shoot. It doesn't matter what your subject does they are in focus. Not difficult and easily covered with current tech.

2. Use a lens with focus registration on it, 200 f2 and up. This allows you to set a focus at any distance and instantly refocus at that distance, it will then prioritize and track anything covered by the AF system as selected at that distance. You can easily focus through a volleyball net using this technique, so again, not difficult and easily covered with current tech.

3. So could the list of people who use the current tech to cover every imaginable 'issue' you have not taken the time or trouble to work at.


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## coldsweat (Sep 21, 2015)

I'm strictly a focus - recompose guy, & haven't delved into the canon AF menus other than on initial setup on my 5D, however do no Canon bodies have focus distance settings in their AF systems?

Before making a switch to Canon I was a Sony SLT guy (please don't judge me) & the A99 had an easy to use focus distance limiter setting where you could set the minimum focus distance & max focus distance by moving the front & rear dials, then the camera would only lock on to subjects in between those two limits say 25m & 35m, that would surely solve all your 'BIF' & 'player behind a net' AF issues? - Took just seconds to set up as well!

Thier description of the feature is... 'You can restrict the autofocus range. This function allows the camera to focus on subject without interference from objects in the back-ground and fore-ground objects.'

https://docs.sony.com/release/slt-a99_a99v_handbook.pdf pages 98 & 99


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## helpful (Sep 22, 2015)

Thanks everyone for the replies. The current autofocus mechanisms, either in body or in lens, definitely don't cover what I'm asking for. There are workarounds, and of course I'm familiar with using them. But what I'm looking for is the solution itself.

The Sony options for focus limiting are similar in principle, but focus limiting does just that--it limits the range of focus. What I'm suggesting wouldn't limit the range of focus at all.

I think I may contact Canon about this. It may sound crazy now, but I'm sure you will love it if you had this feature available.


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## Aglet (Sep 22, 2015)

*That's a really good idea*, and much better than the usual workarounds for some of those situations.
Considering there's a pretty good processor in charge of AF functions, it should be a pretty simple solution to provide a quick setting button + control-wheel and you could select not only, "not zero," but other target depth options (shooting thru a fence AND a volleyball net, select "2" to ignore the 2 closest targets) like multiple branches.
Older Olympus 4/3 SLRs had a neat feature that's available in similar form on other bodies that allowed a much reduced size AF point, like targeting a bird partially obscured by branches. But this was still just a finer AF point function, not a true selection of which possible focus plane to choose.

YUP! That would be a great feature for some situations.


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## privatebydesign (Sep 22, 2015)

helpful said:


> Thanks everyone for the replies. The current autofocus mechanisms, either in body or in lens, definitely don't cover what I'm asking for. There are workarounds, and of course I'm familiar with using them. But what I'm looking for is the solution itself.
> 
> The Sony options for focus limiting are similar in principle, but focus limiting does just that--it limits the range of focus. What I'm suggesting wouldn't limit the range of focus at all.
> 
> I think I may contact Canon about this. It may sound crazy now, but I'm sure you will love it if you had this feature available.



I fail to see how the lens focus distance switch which is currently available, and has been for many years, is a workaround, it is exactly what you are asking for. Start focus at a predetermined distance and allow focus to follow whatever is at that distance however it subsequently moves. Of course most people don't have an issue doing exactly that with current AF systems even without the focus distance switch on many tele lenses.


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## Bundu (Sep 22, 2015)

Bundu said:


> I was taking some BIF fotos a few weeks ago. Small river, about 15m wide. I was about 30m from the river. There was lots of trees on both banks of the river but there was a clearing my side of the river 10 to 15 meters where the birds was clear from obstructions. Before and after the clearing there were also gaps but much smaller. I tried to start tracking the birds flying down the river so that i can shoot away the moment they pass through the clearing. I tried single point and the centre wide group. Sometimes it worked sometimes not. A 50 percent hit rate more or less. I manually focused before to about the middle of the river but it was not always working. If I could have selected the middle of the river as the zero point as the OP suggest in his idea i think the hit rate could have been much higher. I used a 7dii and 100-400ii. When the 7d locked on it worked perfect but to get the initial lock with all the trees on both sides of the river it was not that easy. Or maybe i just need to practise a lot more and/or play with the autofocus settings more. What would the best approach be in the situation as described above with what i have available? Cant afford a 1dx or such fancy equipment!


The idea will work great in this scenario to get the initial lock on the bird as it is flying behind the trees an bushes towards the clearing. It might even work with one single af point selected.


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## neuroanatomist (Sep 22, 2015)

helpful said:


> Choosing the center point only versus a group of autofocus points is not the issue at hand. If you choose the center point only, does your camera then provide the option to prioritize initial focus acquisition on a potential subject at 10 feet versus a potential subject at 5 feet, if both subjects are detectable by the sensor? I may be wrong, but I don't think so.



Choosing focus points is _exactly_ the issue at hand. I don't believe there is any distance priority for a single AF point. In any of the automatic AF point selection modes, yes – the AF system will choose the AF point(s) that achieve focus on the closest subject within a zone or the whole array. With a single point selected, if there are multiple 'subjects' at different distances the AF system will lock onto the feature with the highest contrast, regardless of distance. You can see this especially with a complex 3D subject like a tree with bare branches, in single point AF the closest branch is not consistently where the AF system locks focus. In fact, in that scenario in diffuse lighting, where contrast between branches is pretty uniform, the process appears stochastic. 

Note that the above doesn't change the applicability of your suggestion to the _automatic_ AF point selection process – a distance priority could be applied among AF points, but not for a single AF point. It's an interesting idea, but I highly doubt we'd ever see it implemented, due to the complexity. 

This concept reminds me a bit of the old A-DEP setting, where the camera used the distance between the closest and furthest in-focus AF points to determine the aperture value needed to have both in the DoF. In the context of the above discussion it's worth noting that on cameras with the A-DEP setting, that mode forced the camera into automatic AF point selection among all points, it can't function with just one AF point.


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