# Intentional "wrong" afma for creative backfocus?



## Marsu42 (Aug 21, 2014)

I was always wondering if this is possible and would like to ask around for experiences: Afaik the servo af simply focuses to the front of the object, at least my 60d/6d do. Now there would be the possibility of intentional backfocus for ...

a) using the optimal dof because focusing on the very front results in a 1/3-1/2 dof thick layer layer of sharp air 
b) getting an animal's eyes (or even human's?) in focus because otherwise the nose (or whatever front part) is in focus

Obviously the problem is figuring out the correct afma value, did anyone try this and succeeed?

Imho it's pity today's dslrs are still so dumb you cannot tell them "please focus 1cm behind" because the lens does return an approximate distance information. With Magic Lantern, you can use extended afma values of -100...+100 (Canon fw only allows for 20), but they don't have access to the af module yet.


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## AcutancePhotography (Aug 21, 2014)

I am confused. Why not just manually defocus the shot?


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## bseitz234 (Aug 21, 2014)

AcutancePhotography said:


> I am confused. Why not just manually defocus the shot?


That was my thought... just bump the focus ring a bit towards infinity. Also, as far as b) goes, if you put the focus point on the eye, it should focus there and not the nose...


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## jebrady03 (Aug 21, 2014)

I _think_ what the OP is saying is that if the DOF is thick enough to get the eyes and ears in focus with the tip of the nose out of focus, why not AFMA your camera and/or lens so that it front focuses a little and gets the nose and eyes in focus and the ears slightly out of focus instead.

Could be wrong in my interpretation though.


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## tculotta (Aug 21, 2014)

Why not use spot focusing instead of some type of multi-point grid that "grabs" something. By using the point, you can determine what is being focused rather than letting the camera's sensor and CPU determine it for you. This also helps when there is lots of clutter, like birds in trees.


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## Marsu42 (Aug 22, 2014)

AcutancePhotography said:


> I am confused. Why not just manually defocus the shot?



Might work for static portrait, but when *tracking*a horse running towards you with thin dof, trying to get the eyes in focus that are 5cm behind the point where the *servo af* ends up? Hmmm, tricky 

But I admit I'm really bad at mf override, however I excuse myself with saying that the focus is very hard to see in the tiny crop vf, and the 6d unfortunately also isn't near the vf size of my old analog film cameras. I'll probably end up creating another thread about mf, but this is about intentional afma override.



jebrady03 said:


> I _think_ what the OP is saying is that if the DOF is thick enough to get the eyes and ears in focus with the tip of the nose out of focus, why not AFMA your camera and/or lens so that it front focuses a little and gets the nose and eyes in focus and the ears slightly out of focus instead.



Yes, that's it, the concept doesn't seem to be self-explanatory.



tculotta said:


> Why not use spot focusing instead of some type of multi-point grid that "grabs" something.



Because I don't have a real af system but only cheaper 60d & 6d, the latter only allows for "one or all 11" af point selection plus the outer points are so bad you cannot reliably track with them. 

Still, even with a 1dx I imagine it's very hard to keep one af point on a horses's eyes (running towards you) at all the times, so simply telling the camera to backfocus via afma might do the trick.


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## mackguyver (Aug 22, 2014)

Marsu, I think the core problem with this would be the moment you switch to another shot and want the AF to be set to perfect focus. If it were a simple switch, that would be fine, but otherwise, it's too slow, and if you forgot to switch it back, all other shots would be out of focus.

Also, in the case of a horse, I agree that it would be tough to lock onto the eyes alone, but it would be possible to lock onto the head (or riders head [even at f/2.8, 300mm] as shown below) with relative ease using a 5DIII or 1D X and have AI Servo track it. You can pre-focus as well to get perfect focus for action shots and use an off-center point, or focus/recompose on the eye for portraits.


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## Marsu42 (Aug 22, 2014)

mackguyver said:


> If it were a simple switch, that would be fine, but otherwise, it's too slow, and if you forgot to switch it back, all other shots would be out of focus.



No problem there, I can program/script Magic Lantern to tie different afma settings to a button.



mackguyver said:


> but it would be possible to lock onto the head (or riders head [even at f/2.8, 300mm] as shown below) with relative ease using a 5DIII or 1D X and have AI Servo track it.



It depends on the distance, but with my 70-300L @300mm/5.6 or @180mm/f4 the dof on horses _near_ you is way to thin for this to work. They eyes are out of focus, and even if only slightly so this kills the "alive" look of the animal. Using a deeper dof is also no option as the background quickly gets too distracting or the shutter speeds is too low.



mackguyver said:


> You can pre-focus as well to get perfect focus for action shots and use an off-center point, or focus/recompose on the eye for portraits.



Hmmmyes, but the wild horses have the uncanny tendency to do something different than you expect them to  ... I've gotten better at predicting them though, that's why I manage to get any servo af shots in focus at all.


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## mackguyver (Aug 22, 2014)

With you subjects - those beautiful horses - and shooting wide open, it's going to be difficult no matter what you do. I think this is a valid way to try this, but the nose-to-eye distance will change as the horse changes direction or turns its head towards or against you. I think I would try using Spot AF (not sure if the 6D has this) and AI Servo, but ultimately it's not going to be easy.

The other option is to go with the environmental shots you've been taking (like that great rainbow shot), but I'm guessing you're looking for some variety and wanting to take some closer portraits.

I think the AFMA offset is worth a shot. I'd try to come up with an average nose-to-eye distance and an average shooting distance and manually determine what the AFMA offset is using a ruler. I bet it would be somewhere around 10 from 10-15M and then program that to be a button in ML. I'd be curious to see how this works out.


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## Mt Spokane Photography (Aug 22, 2014)

Focus and recompose. This will result in backfocus and is quick. Probably not as easy to calibrate as AFMA, but no fooling around to adjust it back to normal.


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## mackguyver (Aug 22, 2014)

Mt Spokane Photography said:


> Focus and recompose. This will result in backfocus and is quick. Probably not as easy to calibrate as AFMA, but no fooling around to adjust it back to normal.


I think he's trying to take photos of wild horses that are moving and even running so that won't work with AI Servo shooting.


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## Jack Douglas (Aug 22, 2014)

I have added some back focus on my lowly 6D on occasion when shooting flitting birds and typically catching their shoulder as the focus point when really wanting the eye. It works in those cases where the eye simply is too small to dominate the spot focus and the action makes one shot and manual pretty tricky. Once you've used AFMA a few times it is really very easy to change in a moment provided you know the numbers that give you the desired results. Still can be a fairly high failure rate though. 

I've personally been baffled by all the scientific talk about such a simple operation as AFMA - you don't need a PhD to tune it in, just a basic understanding and a critical eye when viewing your results. Play with it in the field, it doesn't break anything. 

Jack


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## mackguyver (Aug 22, 2014)

Jack Douglas said:


> Play with it in the field, it doesn't break anything.


Unless your forget to change it back...that's gotten me in trouble when I've tried to tune by eye on the LCD out in the field. And yes, no PhD needed, but FoCal does make it more precise.


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## Jack Douglas (Aug 22, 2014)

As an electronics engineer I have no objection to people getting as technical as they like. I'm not immune. However, sometimes simple things are made to look so technical that it scares folk away. AFMA can only be as precise as the settings 0 +- 1, 2, 3 ......

Here is my tale regarding AFMA. Spent big bucks on a 6D and 300 2.8 etc. and was all worked up about whether things were as good as they should be, pixel peeping and all. So I parted with the gear for nearly 2 months and Canon set it all perfectly for me. 300 mounted AFMA +3 Then there was the time of charts and shots and more shots and ... oh dear oh dear. Then I progressed to, "hey set it to whatever and go out and shoot". Well now it's at +12 and my results are pretty consistent, thanks Canon. When I view a shot such as this I think, well maybe a little back focused but how in the world could the focus ever be 100% - an eyball is not likely going to catch the algorithim like an eyelid so it may be focused on the front or rear eyelid or .....??
So I can just change it by a digit and maybe I'll prefer what I get. Right now I'm getting great results overall so it stays put. The point is there is a lot of hit and miss in all of this and it's not like a mathematical calculation to 10 decimal places. Each person chooses what they prefer but if you're uneasy about it, don't be, relax and just experiment.

And as stated don't forget to set it back to what worked best or what is correct. 

Jack


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## mackguyver (Aug 22, 2014)

Marsu42 said:


> The reason I'm posting this shot is to agree that afma doesn't matter at all in these cases, there are so many other variables that determine where the focus ends up.


Exactly and I think that's one of many reasons why wildlife photography is so challenging - and rewarding when you actually get the shot. Cool eyeball photo, too!


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## Marsu42 (Aug 22, 2014)

Jack Douglas said:


> Still can be a fairly high failure rate though.



Great to find someone who had the same idea and actually tried it!

What's the cause of the high failure rate - problems figuring out the correct afma setting for the distance offset or the fact that you need different afma settings for different subject distances?



Jack Douglas said:


> When I view a shot such as this I think, well maybe a little back focused but how in the world could the focus ever be 100% - an eyball is not likely going to catch the algorithim like an eyelid so it may be focused on the front or rear eyelid or .....??



I deeply sympathize because I recently tried to shoot macros of horse eyes to see other horses reflections. You don't really want to know how many frames I needed to get one in focus shot with f5.6 on ff. If you look closely, you can see my shadow with the macro lens directly in front of the horse 

The reason I'm posting this shot is to agree that afma doesn't matter at all in these cases, there are so many other variables that determine where the focus ends up. The afma idea of this thread is for tracking something like horses 5-30m away.

Edit: Reposted, mackguyver's comment above now applies to this post below. Please note that I managed to annotate the picture with the camera settings used, including the object distance


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## Jack Douglas (Aug 23, 2014)

I like that! 

The success with altered AFMA would depend to a large extent on the predictability of say the *distance* of the birds shoulder from its eye, which in itself implies a kind of side shot, which is not that uncommon. Since DOF helps I do believe there is a net benefit to being slightly back focused in such cases. What you gain in one shot you may well lose in the next assuming no time to switch AFMA back. I place the odds on slight back focus for small bird shots. For front facing horses jumping a predictable barrier I'd bet it could benefit similarly. But will the focus reliably lock on the horses nose? Some trial shots would determine the odds there, then dial in some back focus and see what happens - I'm all ears.

Jack


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## mackguyver (Aug 25, 2014)

I had to post this one from my last shoot - LOL - the nose is perfectly in focus, but the eyes and eyelashes, well let's just say I missed...


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## Jack Douglas (Aug 25, 2014)

mackguyver, good illustration. I'm interested in your thoughts on what is happening when spot focus is apparently too broad to allow one to nail the eyes. Would you say it's more the closer or the sharper edged object or does the shape ever enter into the equation. Camera dependent of course, but Canon probably has algorithm similarities on say their center points. How much of a difference does cross, double cross points make? Is there any sense of round glossy objets (eyes) being given priority. Tough questions? 

And one never knows if the focus has wandered off target. 

Jack


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## mackguyver (Aug 25, 2014)

Jack Douglas said:


> mackguyver, good illustration. I'm interested in your thoughts on what is happening when spot focus is apparently too broad to allow one to nail the eyes. Would you say it's more the closer or the sharper edged object or does the shape ever enter into the equation. Camera dependent of course, but Canon probably has algorithm similarities on say their center points. How much of a difference does cross, double cross points make? Is there any sense of round glossy objets (eyes) being given priority. Tough questions?
> 
> And one never knows if the focus has wandered off target.
> 
> Jack


Jack, this was user error, pure and simple. I'd have to look at my settings to confirm, but I the deer were moving fast through heavy brush and I'm pretty sure I was using AI Servo (61-points) with preselected (cross-only) point in my 1D X. I obviously misplaced it on the nose. If I had more time, I would have hit it with the AE lock button, which I have set to One Shot, center point, spot AF and done a focus-recompose. The standard AF sensor in the 1D X / 5DIII is too big to get an accurate lock on those beady eyes, at least in my experience. Unfortunately the deer only paused for a moment before darting back into the cover of the undergrowth.


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## Jack Douglas (Aug 25, 2014)

Mackguyver, I assume this is uncropped in which case eye focus could be no problem but I'm frustrated by the small moving birds and catching their shoulders or other features more often than I'd like. Usually this would be when somewhat reach limited but still a decent shot when cropped. One shot with a ready finger on the focus ring seems to work some of the time but I guess it all comes down to reflexes and mine aren't the best and of course you have to see the focus is sharp in that instant before commiting.

How do you rate your 1DX vs 5D3 relative to subtle AF differences, how/where does the 1DX shine? 

Jack


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## Marsu42 (Aug 25, 2014)

Jack Douglas said:


> mackguyver, good illustration. I'm interested in your thoughts on what is happening when spot focus is apparently too broad to allow one to nail the eyes.



I can help here for the rest of us with cheaper af system: If the af point is too large for the area you want to af, it's purely random where the focus ends up. Solution: Shoot more frames, then delete. This is what I usually do when focusing on an animal (snake, horse, ...) directly looking towards me with the eyes just vertical half moon shape.



mackguyver said:


> I had to post this one from my last shoot - LOL - the nose is perfectly in focus, but the eyes and eyelashes, well let's just say I missed...



The problem with missing the eyes is that the shot loses the brilliance, though this is often only realizable when comparing one in-focus and one slightly out of focus shot side by side. And selecting such a deep dof that nose and eyes are in focus - even if iso noise is no problem - kills the "3d" look.



mackguyver said:


> The standard AF sensor in the 1D X / 5DIII is too big to get an accurate lock on those beady eyes, at least in my experience.



By the way: Did you people ever look at the latest 70d's af points size? Since Canon removed spot af from 7d->70d I would guess that using the 70d with the scenes in discussion is very frustrating indeed.



mackguyver said:


> If I had more time



Right, and since this usually isn't the case I came up with the "wrong afma" idea. Problem here is that you really have to do a lot of trial & error, pref. on a known distance, and I don't have the enthusiasm to do this right now ... that's why I was hoping someone else already did it


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## mackguyver (Aug 25, 2014)

Marsu42 said:


> The problem with missing the eyes is that the shot loses the brilliance, though this is often only realizable when comparing one in-focus and one slightly out of focus shot side by side. And selecting such a deep dof that nose and eyes are in focus - even if iso noise is no problem - kills the "3d" look.


Yep and it's not as visible at web resolution, but is painfully obvious on screen and it prints 



Marsu42 said:


> Right, and since this usually isn't the case I came up with the "wrong afma" idea. Problem here is that you really have to do a lot of trial & error, pref. on a known distance, and I don't have the enthusiasm to do this right now ... that's why I was hoping someone else already did it


As I said before, it would be nice, but wildlife shoot, at least to me, is about trying to be prepared for the right situation at the right time. Sometimes you get lucky, sometimes you don't. I have hundreds and hundreds of photos where my exposure compensation was too high or too low, my shutter speed or aperture wrong, ISO too high, wrong lens, etc., etc., etc. because I was shooting something else and then the shot suddenly appeared for a brief moment. These could have been good, great, or even amazing photos, if only I had the right camera/lens combination or settings. Instead they are out of focus, over or underexposed, motion blurred, too tight or far away, etc. Like fishermen, I have too many tales of "the one that got away" as we say here in the U.S.

You do the best you can and try to use settings that you can change quickly, zoom lenses or two bodies, etc., but in many cases, you have just a second or even less to get the shot. Sometimes you get lucky and you're in the right place, right time, with the right gear set to the right settings, with good light. Those are the shots I live for as few as they are. Fortunately for me, my income doesn't depend on getting these shots!


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## Marsu42 (Aug 25, 2014)

mackguyver said:


> Yep and it's not as visible at web resolution, but is painfully obvious on screen and it prints



I'd even double-check that, I recently viewed some of my old shots on a small lcd (played back to the camera) and immediately saw which shots had a front- or backfocus from the eyes. Probably people who aren't really looking for it won't actively notice, but even at web size if can make a difference as to said "brilliance" factor. In your example shot my view is drawn away from the eyes to the nose because there's so much detail there while the ears are clearly out of focus.


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## mackguyver (Aug 25, 2014)

Marsu42 said:


> mackguyver said:
> 
> 
> > Yep and it's not as visible at web resolution, but is painfully obvious on screen and it prints
> ...


I agree and fortunately it wasn't a great shot anyways, but it's still painful to miss the focus like that. I've noticed that the phase detect face detection in the 1D X seems to work on animals as well, but apparently not on the ellipses for side-facing eyes like these. Predators with front-facing eyes seem to be detected if large enough in the frame...so I guess an enhanced version of that may be the ultimate solution...


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## Marsu42 (Aug 26, 2014)

mackguyver said:


> I agree and fortunately it wasn't a great shot anyways



Imho it always pays to be on eye level with the animal, at least I find these most attractive or it has got this "zoo look".



mackguyver said:


> Predators with front-facing eyes seem to be detected if large enough in the frame...so I guess an enhanced version of that may be the ultimate solution...



First, of course I'm happy 1dx users face similar problems as 60d/6d people :-> and I agree that the current software is an absolute disgrace to the computing power available in today's dslrs.

I'm very confident with mirrorless (= the image processing sensor can see the sensor image all the time) we'll see much more powerful autotetection algorithms for various popular shot types, but alas, good ol' conservative Canon most likely won't be the first to implement it.


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## Jack Douglas (Sep 4, 2014)

Here's a sample of what I run into fairly commonly with birds. The 6D algorithm will pick up on the sharpest features in the region of the eye and for many birds when the DOF is shallow that leaves the eye slightly out of focus. This is where I may choose a slight backfocus.

This was a vertical shot using the spot upper focus point on the eye.

Jack


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