Canon 50D back button AF

RJL2005

RJL2005

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Rhod
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Well I've read the manual and googled it but it confuses the hell out of me.

I would like to remove AF from the shutter button and just use the rear AF button for focus while keeping metering with the shutter button. Is CF IV -2 the way to go:thinking:

Thanks:)
 
iancandler said:
Oh god why would you want to? its sooooo sloooooow
Click to expand...

What on earth makes you say that?

It's no different in speed to using the shutter button but allows for more creative control :shrug:
 
RJL2005 said:
Well I've read the manual and googled it but it confuses the hell out of me.

I would like to remove AF from the shutter button and just use the rear AF button for focus while keeping metering with the shutter button. Is CF IV -2 the way to go:thinking:

Thanks:)
Click to expand...

It's been a while since I looked at this on the 50D. IV-2 is I believe necessary for enabling the button

Then Look a CF IV - 1.
This allows you to remove AF operation from the shutter button - you can then use the shutter for metering/AE lock (whichever you choose in the custom function) and focus purely with the back button.
 
CFIV-1 set to 2.

Rear-button AF is by far superior to any other way of using the camera, particularly in speed and action scenarios. I haven't had my camera set up any other way in about 10 years.
 
I-S said:
CFIV-1 set to 2.

Rear-button AF is by far superior to any other way of using the camera.
Click to expand...

Is that fact? Or just your opinion I-S? ;)
 
It's my opinion, but fact to me. YMMV and all that, but it's certainly not slow.
 
I think Ian is referring to live view AF.. back button AF is certainly no slower than normal shutter button focus :)
 
Thanks guys. I'll give CFIV 1 -2 a go next time I'm out.
 
This is interesting, as the 50D is the first body I've owned that has this feature and I was wondering what the advantages are with this, particually with sports... Silly question, but why is this better than, for example, shooting sports and using the shutter button with servo AI?
 
odd jim said:
This is interesting, as the 50D is the first body I've owned that has this feature and I was wondering what the advantages are with this, particually with sports... Silly question, but why is this better than, for example, shooting sports and using the shutter button with servo AI?
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Try this - http://www.usa.canon.com/dlc/controller?act=GetArticleAct&articleID=2286

FWIW I use back button focusing almost exclusively on all my cameras. I very occasionally swap back to shutter button focusing, but those times are rare and only to meet a very specific purpose. By default it's back button focusing for me. It is not slower than using shutter button focus, unless you lack dexterity and coordination skills, and it is more flexible over a range of shooting scenarios.

I should add that I started out focusing with the shutter button for a while and when I first switched to back button AF I did not like it and switched back within a day. A few weeks later I tried it again and it stuck. It is far more convenient, most of the time.

Quick summary of advantages....

- You can simulate One Shot AF when in AI Servo mode, without fiddling about changing AF modes.

- If an obstruction blocks your view you can cease AF function momentarily but continue shooting if it is useful to do so. When the obstruction clears your focus will pick up where it left off, and not be thrown wildly out of whack, wasting time trying to relocate and focus on the subject.

- If you lose track of your subject with the AF point you can cease AF function momentarily, until you are back on track again, but still continue shooting. When shooting BIF, for example, this means your camera will not go on an AF hunting expedition and lose sight of the bird altogether. You just reacquire the subject and continue shooting. If the background gets busy and distracting you can cease AF but still shoot, which is fine if the subject distance is not altering (much).

- If you have a stationary subject you can AF once and then have freedom to recompose and shoot as you wish without having the camera keep trying to re-focus every time you press the shutter button, and without needing to keep flicking back and forth between AF and MF on your lens.
 
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Excellent summary there.

I would just emphasise that not only can you simulate one-shot behaviour when in AI servo, but Tim did not really mention the ability to MF as desired - again without messing around with switches or modes.
 
I-S said:
but Tim did not really mention the ability to MF as desired - again without messing around with switches or modes.
Click to expand...

Probably not considered healthy for some lenses that don't have full time MF, officially anyway :) (unless I misunderstood)

Often been tempted to try back button AF, the only thing that puts me off is that it will confuse anyone I happen to hand my camera over to... not a great reason really :p
 
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tdodd said:
Try this - http://www.usa.canon.com/dlc/controller?act=GetArticleAct&articleID=2286

FWIW I use back button focusing almost exclusively on all my cameras. I very occasionally swap back to shutter button focusing, but those times are rare and only to meet a very specific purpose. By default it's back button focusing for me. It is not slower than using shutter button focus, unless you lack dexterity and coordination skills, and it is more flexible over a range of shooting scenarios.

I should add that I started out focusing with the shutter button for a while and when I first switched to back button AF I did not like it and switched back within a day. A few weeks later I tried it again and it stuck. It is far more convenient, most of the time.

Quick summary of advantages....

- You can simulate One Shot AF when in AI Servo mode, without fiddling about changing AF modes.

- If an obstruction blocks your view you can cease AF function momentarily but continue shooting if it is useful to do so. When the obstruction clears your focus will pick up where it left off, and not be thrown wildly out of whack, wasting time trying to relocate and focus on the subject.

- If you lose track of your subject with the AF point you can cease AF function momentarily, until you are back on track again, but still continue shooting. When shooting BIF, for example, this means your camera will not go on an AF hunting expedition and lose sight of the bird altogether. You just reacquire the subject and continue shooting. If the background gets busy and distracting you can cease AF but still shoot, which is fine if the subject distance is not altering (much).

- If you have a stationary subject you can AF once and then have freedom to recompose and shoot as you wish without having the camera keep trying to re-focus every time you press the shutter button, and without needing to keep flicking back and forth between AF and MF on your lens.
Click to expand...

Excellent link, thanks, explains all!
 
Zogger said:
Often been tempted to try back button AF, the only thing that puts me off is that it will confuse anyone I happen to hand my camera over to... not a great reason really :p
Click to expand...

Someone else use your camera! :eek: :D

:thumbs: for back button AF, but I agree anyone else using your camera can get a little confused, or in some cases a lot confused! :lol:
 
Hmmm, ok I cant seem to aet this up on my 50D despite alerting the custom function described on the link... (cant seem to disable focus on the shutter button).

Time to get the manual out!

EDIT - the manual is useless, only explains how to activate the button not how to disable AF on the shutter button. Hmmm, need to play with the menu a bit more...

Ok all sorted, though I had to 'disable' the rear AF button to activate it???! Strange.
 
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I'm liking the sound of this. Will give it a shot and see how it feels. Thanks for the info and the link.
 
Thanks to this thread I have been trying rear button focus lately. Generally I'm liking it, especially for those shots where I pre-focus and then don't have to switch the lens to manual so as not to lose the focus point. This way also makes me more inclined to recompose my shots, rather than exposure/focus/shutter all on one button.

There have been a couple times where I've forgot that I have it set up this way, then wondered why it didn't focus when I pressed the shutter release :bonk:, but at the momment I think I'm going to keep it this way for at least a while longer as the advantages look as though they might outway the disadvantages. The real acid test will be the next sporting event I go to.
 
tdodd said:
Try this - http://www.usa.canon.com/dlc/controller?act=GetArticleAct&articleID=2286

FWIW I use back button focusing almost exclusively on all my cameras. I very occasionally swap back to shutter button focusing, but those times are rare and only to meet a very specific purpose. By default it's back button focusing for me. It is not slower than using shutter button focus, unless you lack dexterity and coordination skills, and it is more flexible over a range of shooting scenarios.

I should add that I started out focusing with the shutter button for a while and when I first switched to back button AF I did not like it and switched back within a day. A few weeks later I tried it again and it stuck. It is far more convenient, most of the time.

Quick summary of advantages....

- You can simulate One Shot AF when in AI Servo mode, without fiddling about changing AF modes.

- If an obstruction blocks your view you can cease AF function momentarily but continue shooting if it is useful to do so. When the obstruction clears your focus will pick up where it left off, and not be thrown wildly out of whack, wasting time trying to relocate and focus on the subject.

- If you lose track of your subject with the AF point you can cease AF function momentarily, until you are back on track again, but still continue shooting. When shooting BIF, for example, this means your camera will not go on an AF hunting expedition and lose sight of the bird altogether. You just reacquire the subject and continue shooting. If the background gets busy and distracting you can cease AF but still shoot, which is fine if the subject distance is not altering (much).

- If you have a stationary subject you can AF once and then have freedom to recompose and shoot as you wish without having the camera keep trying to re-focus every time you press the shutter button, and without needing to keep flicking back and forth between AF and MF on your lens.
Click to expand...
I agree 100% with Tim here - I have been using the AF-ON button for focus for a couple of years now (40D and 7D) and could never seem myself going back to the shutter button method again. Being a bird photographer the ability to be able to shoot in AI Servo, One shot or manual without having to change a thing is invaluable to me. Also, as Tim says, recomposing is a snap.
 
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I use a 400d and find AI servo useless, it doesn't quite hold focus, it seems to duck in and out as if it cant quite keep up (1 out of 5 in focus). This is the only thing holding me back at the moment, maybe when i get better lenses i'll give it a try. Currently using 18-55 IS & Tamron 55-200).
 
Adey said:
I use a 400d and find AI servo useless, it doesn't quite hold focus, it seems to duck in and out as if it cant quite keep up (1 out of 5 in focus). This is the only thing holding me back at the moment, maybe when i get better lenses i'll give it a try. Currently using 18-55 IS & Tamron 55-200).
Click to expand...

The 50D AF is much better than the 400D autofocus but lens choice makes a difference here too. if you can get a lens faster than F5.6 with better AF (USM or Sigma HSM) you will see a big difference
 
Adey said:
I use a 400d and find AI servo useless, it doesn't quite hold focus, it seems to duck in and out as if it cant quite keep up (1 out of 5 in focus). This is the only thing holding me back at the moment, maybe when i get better lenses i'll give it a try. Currently using 18-55 IS & Tamron 55-200).
Click to expand...

I found AI servo very, very good on my old 400D, all my equestrian stuff was done using AI servo and coupled with the Canon 55-250 IS it hardly ever missed a beat (and on the rare occasions it did it was my fault)!
 
odd jim said:
I found AI servo very, very good on my old 400D, all my equestrian stuff was done using AI servo and coupled with the Canon 55-250 IS it hardly ever missed a beat (and on the rare occasions it did it was my fault)!
Click to expand...

Well i appreciate you saying that Jim, it says to me that when i buy a new lens i should see a good improvement :D

Anywhere i can see these horsey pics? i wouldnt mind seeing some real-world results from the 55-250. It was right at the top of my wish list untill the review i read about it made it sound like just a longer version of the 18-55 IS kit lens.

Cheers!:thumbs:
 
Heres a few taken with my old 400D, 55-250 IS and using AI servo;

Georgelastjump.jpg


IMG_8026.jpg


Georgejumpingatthefinish.jpg


Alanalastjump2.jpg


The IQ of the 55-250 IS is leagues above the 18-55 kit lens!
 
Jim, some really nice photos there, but why not use sRGB for the web? Although the pictures look good in my browser they burst into life when viewed in Lightroom, with more vibrant (and different) colouring.

EDIT : in fact there seems to be something very odd going on, which I don't fully understand. One image was processed in DPP and says it is in the sRGB colour space, yet it looks different in my browser vs Lightroom. The others were processed in CS3 and say the colour space is unassigned, but appear (I think) to be using the Adobe RGB colour space. They also look different in Lightroom vs IE8.

Either way, they look good, but how did you want them to look? People in webland may not be seeing the images the way you do on your system.
 
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Hmmm interesting.... Not sure why the srgb image should look different? I use both DPP and cs3, i think it defaults to srgb on dpp and acr with cs3? I must admit that I havnt given much though to web display but I have noticed they don't look anywhere near as good as through zoombrowser, cs3 etc...
 
Thanks for the pics Jim, look good (at least concerning focus:lol:)

I had a chance today to try out a 70-300 IS USM, but decided against trying back button focusing because i couldn't afford to experiment today, it was too important. I did try AI servo though, again seemed really useless, even with the 'better' lens half the shots were out of focus.

Oh, and i'd just like to say, either my father-inlaw has bought a duffer or the 70-300 IS USM is just an awefull lens. Seriousley, zoom ring waaaay to stiff, IS seems to jump around all over the place making focusing hard, and woefully....YES woefully soft past 200mm, and only 'decent-sharp' under 100mm. Honestly i went back to using my tamron 55-200 and it was just an instant improvement. In all departments. Damn i was gonna by that thing, lets hope he has a duffer. Do i tell him what i think of it?

:eek:
 
For one thing, the USM in the 70-300 IS is not real USM.

As on your other thread, post samples of the 70-300 problem.
 
Adey said:
Thanks for the pics Jim, look good (at least concerning focus:lol:)

I had a chance today to try out a 70-300 IS USM, but decided against trying back button focusing because i couldn't afford to experiment today, it was too important. I did try AI servo though, again seemed really useless, even with the 'better' lens half the shots were out of focus.

Oh, and i'd just like to say, either my father-inlaw has bought a duffer or the 70-300 IS USM is just an awefull lens. Seriousley, zoom ring waaaay to stiff, IS seems to jump around all over the place making focusing hard, and woefully....YES woefully soft past 200mm, and only 'decent-sharp' under 100mm. Honestly i went back to using my tamron 55-200 and it was just an instant improvement. In all departments. Damn i was gonna by that thing, lets hope he has a duffer. Do i tell him what i think of it?

:eek:
Click to expand...

What were you shooting?
 
In my opinion, when shooting action at high(ish) shutter speeds IS offers no advantage and may on fact affect IQ negatively. If you are attempting to track motion in any direction that conflicts with IS operation then IS is better turned off. My experience comes mostly from shooting BIF, but jumping horses and sportsmen/women will provide a similar challenge. If you are shooting sports at high shutter speeds, and aided by a monopod for stability then disable IS. If you insist on using it then at least give it enough time to become effective before taking the shot. You cannot mash the shutter down when shooting with IS. It needs at least 1/2 second to become effective.

On the subject of mashing shutter buttons, apart for the jerk/shake that might result, in AI Servo mode Canon recommends tracking the subject for up to one second before taking a shot. This is to allow time for the camera to work out the predicted path for the subject and to position the focus where it expects the subject to be by the time the shutter releases. This may take longer with a consumer can like a Rebel, but even with the 1 series bodies the advice is the same.

There is also some skill required in keeping the focus point positioned accurately over the subject, and over an area with sufficient contrast for the AF to work. Using all focus points is often not the best approach. A single focus point, perhaps with some form of focus point expansion if the camera offers it, is the way to go. My own experience tells me to use as few focus points as possible to get the job done. The more focus points you have active the more data the camera has to process, the more decisions it has to make, and the more possibility it has to decide unwisely.

Sample picture with full EXIF intact may help diagnosis, but it does sound a bit like a duff lens. Of course, if the AF is poorly calibrated either in absolute terms, or when used with that particular body, then disappointing results are the likely outcome. There are many possible reasons for poor results, but insufficient information in this thread upon which to form any solid conclusions.
 
tdodd i completely agree with everything you've just said, although i didnt know about the AI servo thing, but what living thing keeps a steady pace and direction for more than a second anyway? Footballers and animals certainly dont.
 
Adey said:
tdodd i completely agree with everything you've just said, although i didnt know about the AI servo thing, but what living thing keeps a steady pace and direction for more than a second anyway? Footballers and animals certainly dont.
Click to expand...

A horse approaching a jump is not stopping and starting and ducking and weaving. It has a lot of momentum and will maintain a pretty even pace for the most part. A large bird cruising in a straight line will maintain very even pace and direction. A dog running towards or retrieving a ball will usually not vary pace or direction wildly. I've shot running dogs quite a bit. Skill is needed to keep the focus point positioned accurately, but the path is usually pretty predictable. A footballer running in for a tackle, or chasing down a ball. A sprinter/runner on the home straight. At least they don't usually reverse direction repeatedly and mostly they don't stop and start all the time. There is usually sufficient time to establish some sort of direction of motion that can be predicted - at least until it does change. Then the AF needs time to adjust. That's a fact and a realistic limitation. You have to develop your technique to work within the limits of the equipment.

Dog on the run, shot today, probably tracked for a couple of seconds before firing. Some adjustment to levels but no sharpening adjustments.....

20101107_123527_3741_LR.jpg


100% crop, and from a 7D that is a big enlargement....
20101107_123527_3741_LR-2.jpg



Here's another from a week or two ago. This was with a 70-200 at 200mm, f/3.2....

20101024_130808_3644_LR-2.jpg


100% crop, again from a 7D....
20101024_130808_3644_LR.jpg


If you think the trick is in f/1.8 or f/2.8 glass then here's a similar shot from my 100-400 at 400mm and f/5.6. Light was poor, requiring 1600 ISO in order to achieve a 1/1600 shutter speed....

20100919_125351_2051_LR.jpg


100% crop from the 7D....

20100919_125351_2051_LR-2.jpg



Oh, one more thing - if you use a UV filter then try without. Those things have been known to cause abominable results with some long lenses.
 
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Good info the tdodd. im fine at keeping the focus point on the target i've got a steady hand and good reactions.
When i use AI servo i can see the focus working and i experience what you said about taking a little time to get there, but once it does it seems to struggle to be in focus for any length of time or enough times. When i track its like its OOF 80% of the time and in focus 20% of the time. At 3fps i might aswell just pop away with the shutter button and get all the shots in focus. I havnt experience the rise then level-out-ness you described with the focus, for me its more like a continuous sine wave instead. Also when shooting football, a second is way to long to wait for focus to 'lock-on', theres too many times when you have to just suddenly swing to a different part of the pitch and you might have half a second at the most to get focus ready for the tackle, header, save etc..


Edit: I seem to have hijacked this thread and at the same time turned my own thread into a clone of this one, Im sorry i'll just keep to my own thread from now on.
 
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I really dont see why you are having such a problem with AI Servo on the 400D... It doesnt take any time at all to focus (really it doesnt 'lock on' as such, it just continuously focuses to whatever you are pointing it at but it does try to pre determine the next movement - but this shouldnt slow it down), its as instant as one shot focus. It re-adjusts very quickly without any hunting - even with my 50mm 1.8 which I have used indoors at equestrian events with excellent results.

Shooting sports, I wouldnt use anything other than AI Servo on any body (dont get this confused with AI Focus, which is rubbish!).

AI servo on your 400D should provide you with instant, continuous focusing. If it doesnt, there is either a fault with the body or lens.

EDIT - you are only using the centre focus point right?
 
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Jim, i've now set up back-button focusing and AI servo, i'll see how that goes.


i was using centre point only,but now ive set to auto point selection becasue i've read that in AI servo it behaves differently to single shot. It uses the centre first then only uses the other points after its found focus....if needed, whereas single shot uses all points at the initial 'hunt' stage. Is this correct?

Lovely shot btw!
 
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