Canon IS with Back Button Focus
Apr 9, 2015 09:25:49 #
Silvermeteor
Loc: South Carolina, USA
I have been reading the discussion on IS. As a result I also consulted the manual for my T3i which says:
IS is activated by pressing the shutter half way down. Oh boy!
I had converted to Back Button Focus primarily because I kept forgetting to press-pause-press when taking a picture.
So I figured that I would separate the two functions, which I like, but now it seems that some of the fuzzy images I continue to get may be operator error.
So now it seems that I still need to press-pause-press when using Back Button Focus without a tripod at shutter speeds below 1/500.
Comments or clarifications would be welcome.
IS is activated by pressing the shutter half way down. Oh boy!
I had converted to Back Button Focus primarily because I kept forgetting to press-pause-press when taking a picture.
So I figured that I would separate the two functions, which I like, but now it seems that some of the fuzzy images I continue to get may be operator error.
So now it seems that I still need to press-pause-press when using Back Button Focus without a tripod at shutter speeds below 1/500.
Comments or clarifications would be welcome.
Apr 9, 2015 09:32:00 #
Canon customer service was very friendly and helpful the one time I called:
http://www.usa.canon.com/cusa/consumer/standard_display/contact_by_phone
http://www.usa.canon.com/cusa/consumer/standard_display/contact_by_phone
Apr 9, 2015 09:53:26 #
Silvermeteor wrote:
I have been reading the discussion on IS. As a res... (show quote)
I don't think it should matter. It is the lens focusing that activates it I believe. If you have the switch turned to on when the lens focuses it should work.
Jim D
Apr 9, 2015 09:54:29 #
IS is not reliant on AF so whether you use BBF or SBF the IS is governed by the shutter button just like the exposure. Do your BBF and when you press the shutter button both exposure and IS are calculated. Hope this helps.
Apr 9, 2015 10:27:03 #
Silvermeteor
Loc: South Carolina, USA
big-guy wrote:
IS is not reliant on AF so whether you use BBF or SBF the IS is governed by the shutter button just like the exposure. Do your BBF and when you press the shutter button both exposure and IS are calculated. Hope this helps.
While it may clarify it does not help. lol
My main reason for utilizing BBF was because I kept forgetting to press-pause-press when activating the shutter thus creating my own blurriness.
If what you say is correct, and the manual appears to support that, then I am right back where I started.
It would seem that the only solution that would allow me to operate the camera as I would like is to buy lenses with f/.01 and never shoot below 1/500. Hmmmmm. I'm afraid that is not a viable option.
Apr 9, 2015 11:41:26 #
amfoto1
Loc: San Jose, Calif. USA
I've been shooting with a variety of Canon IS lenses for almost 15 years now. I almost never turn off IS, use BBF almost exclusively and I average around 97-98% of my shots acceptably in-focus. The missed focus I do get, I figure about half of them are my fault, only a very few do I blame on the camera & lens.
BBF merely uses one of the back buttons to activate and control AF.
Pressing EITHER the shutter button (half-press) OR the back button OR both will start IS running, as well as activate the camera's metering system. So it really doesn't matter.
I have no idea what you mean by "press-pause-press". Maybe you are referring to the half-press of the shutter release button? It is true that shooting too quickly with AF can trip the shutter before the camera has time to achieve focus and/or before IS has done it's job. However, AF and IS operate concurrently and starting things running in advance with BBF allows pretty instantaneous shot taking.
If still having issues with "fuzzy pictures", it's most likely caused by missed focus for some other reason. And there are several possibilities.
Depending upon the lighting conditions and contrast detail of the subject you're trying to focus upon, the AF may take a moment to achieve focus.
The lens' focus drive also makes a difference in how quickly AF achieves focus. Cheaper "micro motor" (aka "piezo" motor) lenses are the slowest focusing. STM or "stepper motor" are a bit faster, while USM or "ultrasonic motor" are the fastest and best tracking moving subjects. If shooting video, STM may be preferable because they are the smoothest and quietest focusing.
Camera setup is also important. You might already know, One Shot is for still subjects and AI Servo for moving subjects. (Using BBF allows you to use AI Servo as your default mode. It is better to use One Shot if not using BBF, if using SBF or shutter button based focusing.) I don't recommend using AI Focus at all. It's not really a focus mode, but is more automation where the camera is supposed to decide for you whether or not the subject is moving, then use One Shot of AI Servo, as appropriate. I haven't tried it in many years, but when I did test it, I found it caused a bit more delay and sometimes chose the wrong mode, resulting in far more missed focus shots. It might be a hint that the most pro-oriented Canon cameras don't have AI Focus mode... they only have One Shot and AI Servo.
So I recommend not using AI Focus and choosing between One Shot and AI Servo modes yourself. Note: I mostly shoot sports/action, moving subjects, so I use AI Servo most of the time... and, again, when combined with BBF it's possible to use AI Servo by default, even with stationary subjects and even if "focusing and recomposing".
One of the most common mistakes I notice when other photographers are shooting nearby is that they are in the wrong focus mode. In One Shot (and it's equivalent in other camera systems), the focus runs, achieves focus, stops and locks, then gives you Focus Confirmation with a green LED in the viewfinder and, if it's enabled, an audible "beep". AI Servo mode, on the other hand, is continuous focus. It runs and continuously updates focus as long as you maintain pressure on the BB (or half-press of the SB). Since it never stops and locks, there is no Focus Confirmation in AI Servo. It happens quite often when I'm shooting a sporting event... I hear the cameras of other photogs "beeping", which tells me that they are in the wrong focus mode and that most of their images of moving subjects will miss focus.
In addition, a lens with larger max aperture rating will give better AF performance. f/2.8 or better allows some AF points to give their top performance... on your camera the center one only (on my 7Ds, all 19 AF points are enhanced, but center one is even higher rated). But f3.5 or f/4 lenses are better focusing than f/5.6 or f/6.3, simply because they allow more light in to the AF sensors in the camera.
However, some lenses simply aren't designed to be fast focusing. For example, most macro lenses are a lot slower focusing. Even with USM and other things to help with focus performance, macro shooting often involves very shallow depth of field that demands very precise focus, so macro lenses are often designed with an emphasis on accuracy, as opposed to speed.
Other lenses are designed to focus very quickly... all of Canon's 70-200s are examples of these.
Another thing to be aware of is that many modern AF zoom lenses are "varifocal" designs. This means they don't maintain focus when you zoom to a different focal length. If using One Shot, after you zoom the lens you MUST release focus and restart it, to update the focus. If using AI Servo, the camera automatically corrects focus (yet another good reason for using AI Servo & BBF as default settings).
I think the Canon 70-200s are "parfocal" (or at least nearly so), meaning they maintain focus when zoomed. Not so sure about any other Canon zooms. I'd bet some or even most of the cheaper ones are varifocal.
Finally, there are some things you can do to improve your chances of getting good focus results. One is simply practice with your camera and lens. The more you use it, the better you will be focusing with it.
Also mostly do not use multi-point AF (your camera has All Points/Auto Selection), which can choose incorrectly. Set the camera to Single Point/Manual selection and try to use the center point as much as possible (the other 8 points in your camera are lower performance type). This makes every shot you take have the subject centered, so I suggest also try to frame the subject slightly loosely so that you can crop the image later, to be more off center, if you wish to do so.
There are occasions when the multiple AF point mode All Points works well.... such as tracking a bird flying against a plain sky, where there is little or no other detail to distract the AF. It also can be fine when using a wide angle lens stopped down, with a whole lot of depth of field. But otherwise, All Points will usually focus on whatever is closest and covered by one of the AF points... and that might not be what you want the camera focusing upon. So it's usually better to take charge by using Single Point.
If you have a "protection" filter on your lens, try shooting without it. You might find your AF works better and your images are sharper (the original Canon 100-400mm really gets "soft" with any filter on it, for example).
And, always use a properly fitted and matched lens hood. It protects your lens better than any filter ever could, plus might help AF performance by keeping oblique light off the lens, increasing contrast.
Also don't be overly critical of your images when reviewing them on your computer. On most modern monitors, viewing an image from your 18MP camera "at 100%", is like making a five foot wide print of the image and then viewing it from about 18" away. Anything viewed that large can easily look like crap. Back off to 50% or, even better, 33% to be more reasonable evaluating your images. Or, best, consider what size the image will be in the end. An image might be more than good enough for an 8x12" print or online display in smaller size, but not usable at a larger size.
Your T3i doesn't have Micro Focus Adjustment, like some other Canon cameras do. This allows the user to fine-tune the focus of their cameras and lenses. However, your camera and lenses can be calibrated. If you have a whole lot of problems with AF, it's possible it's out of adjustment. You'll have to have that done by a repair technician, though. You should do a series of test shots with your different lenses to see if focus seems out of calibration. Ask us for more info about how to do that, if you think it's needed.
Finally, stop your lens down a little whenever you can. For one thing, most lenses get sharper one or two stops down from wide open. But this also makes for more depth of field, which can cover or eliminate minor missed focus problems.
Hope this helps!
BBF merely uses one of the back buttons to activate and control AF.
Pressing EITHER the shutter button (half-press) OR the back button OR both will start IS running, as well as activate the camera's metering system. So it really doesn't matter.
I have no idea what you mean by "press-pause-press". Maybe you are referring to the half-press of the shutter release button? It is true that shooting too quickly with AF can trip the shutter before the camera has time to achieve focus and/or before IS has done it's job. However, AF and IS operate concurrently and starting things running in advance with BBF allows pretty instantaneous shot taking.
If still having issues with "fuzzy pictures", it's most likely caused by missed focus for some other reason. And there are several possibilities.
Depending upon the lighting conditions and contrast detail of the subject you're trying to focus upon, the AF may take a moment to achieve focus.
The lens' focus drive also makes a difference in how quickly AF achieves focus. Cheaper "micro motor" (aka "piezo" motor) lenses are the slowest focusing. STM or "stepper motor" are a bit faster, while USM or "ultrasonic motor" are the fastest and best tracking moving subjects. If shooting video, STM may be preferable because they are the smoothest and quietest focusing.
Camera setup is also important. You might already know, One Shot is for still subjects and AI Servo for moving subjects. (Using BBF allows you to use AI Servo as your default mode. It is better to use One Shot if not using BBF, if using SBF or shutter button based focusing.) I don't recommend using AI Focus at all. It's not really a focus mode, but is more automation where the camera is supposed to decide for you whether or not the subject is moving, then use One Shot of AI Servo, as appropriate. I haven't tried it in many years, but when I did test it, I found it caused a bit more delay and sometimes chose the wrong mode, resulting in far more missed focus shots. It might be a hint that the most pro-oriented Canon cameras don't have AI Focus mode... they only have One Shot and AI Servo.
So I recommend not using AI Focus and choosing between One Shot and AI Servo modes yourself. Note: I mostly shoot sports/action, moving subjects, so I use AI Servo most of the time... and, again, when combined with BBF it's possible to use AI Servo by default, even with stationary subjects and even if "focusing and recomposing".
One of the most common mistakes I notice when other photographers are shooting nearby is that they are in the wrong focus mode. In One Shot (and it's equivalent in other camera systems), the focus runs, achieves focus, stops and locks, then gives you Focus Confirmation with a green LED in the viewfinder and, if it's enabled, an audible "beep". AI Servo mode, on the other hand, is continuous focus. It runs and continuously updates focus as long as you maintain pressure on the BB (or half-press of the SB). Since it never stops and locks, there is no Focus Confirmation in AI Servo. It happens quite often when I'm shooting a sporting event... I hear the cameras of other photogs "beeping", which tells me that they are in the wrong focus mode and that most of their images of moving subjects will miss focus.
In addition, a lens with larger max aperture rating will give better AF performance. f/2.8 or better allows some AF points to give their top performance... on your camera the center one only (on my 7Ds, all 19 AF points are enhanced, but center one is even higher rated). But f3.5 or f/4 lenses are better focusing than f/5.6 or f/6.3, simply because they allow more light in to the AF sensors in the camera.
However, some lenses simply aren't designed to be fast focusing. For example, most macro lenses are a lot slower focusing. Even with USM and other things to help with focus performance, macro shooting often involves very shallow depth of field that demands very precise focus, so macro lenses are often designed with an emphasis on accuracy, as opposed to speed.
Other lenses are designed to focus very quickly... all of Canon's 70-200s are examples of these.
Another thing to be aware of is that many modern AF zoom lenses are "varifocal" designs. This means they don't maintain focus when you zoom to a different focal length. If using One Shot, after you zoom the lens you MUST release focus and restart it, to update the focus. If using AI Servo, the camera automatically corrects focus (yet another good reason for using AI Servo & BBF as default settings).
I think the Canon 70-200s are "parfocal" (or at least nearly so), meaning they maintain focus when zoomed. Not so sure about any other Canon zooms. I'd bet some or even most of the cheaper ones are varifocal.
Finally, there are some things you can do to improve your chances of getting good focus results. One is simply practice with your camera and lens. The more you use it, the better you will be focusing with it.
Also mostly do not use multi-point AF (your camera has All Points/Auto Selection), which can choose incorrectly. Set the camera to Single Point/Manual selection and try to use the center point as much as possible (the other 8 points in your camera are lower performance type). This makes every shot you take have the subject centered, so I suggest also try to frame the subject slightly loosely so that you can crop the image later, to be more off center, if you wish to do so.
There are occasions when the multiple AF point mode All Points works well.... such as tracking a bird flying against a plain sky, where there is little or no other detail to distract the AF. It also can be fine when using a wide angle lens stopped down, with a whole lot of depth of field. But otherwise, All Points will usually focus on whatever is closest and covered by one of the AF points... and that might not be what you want the camera focusing upon. So it's usually better to take charge by using Single Point.
If you have a "protection" filter on your lens, try shooting without it. You might find your AF works better and your images are sharper (the original Canon 100-400mm really gets "soft" with any filter on it, for example).
And, always use a properly fitted and matched lens hood. It protects your lens better than any filter ever could, plus might help AF performance by keeping oblique light off the lens, increasing contrast.
Also don't be overly critical of your images when reviewing them on your computer. On most modern monitors, viewing an image from your 18MP camera "at 100%", is like making a five foot wide print of the image and then viewing it from about 18" away. Anything viewed that large can easily look like crap. Back off to 50% or, even better, 33% to be more reasonable evaluating your images. Or, best, consider what size the image will be in the end. An image might be more than good enough for an 8x12" print or online display in smaller size, but not usable at a larger size.
Your T3i doesn't have Micro Focus Adjustment, like some other Canon cameras do. This allows the user to fine-tune the focus of their cameras and lenses. However, your camera and lenses can be calibrated. If you have a whole lot of problems with AF, it's possible it's out of adjustment. You'll have to have that done by a repair technician, though. You should do a series of test shots with your different lenses to see if focus seems out of calibration. Ask us for more info about how to do that, if you think it's needed.
Finally, stop your lens down a little whenever you can. For one thing, most lenses get sharper one or two stops down from wide open. But this also makes for more depth of field, which can cover or eliminate minor missed focus problems.
Hope this helps!
Apr 9, 2015 11:56:12 #
Silvermeteor wrote:
I have been reading the discussion on IS. As a res... (show quote)
There is a very easy to check. Manually move the focus ring all the way to 1 extreme or the other. Then press the backbutton and see if the lens comes into focus. If it does then you will know.
Apr 9, 2015 14:18:23 #
Silvermeteor
Loc: South Carolina, USA
Wow! Thanks for taking the time to respond. I'm pleased if a little overwhelmed. I even copied this and sent it to a friend. Great information and appreciated.
Apr 10, 2015 08:00:58 #
Silvermeteor wrote:
I have been reading the discussion on IS. As a res... (show quote)
What lens are you using?
Apr 10, 2015 08:30:10 #
From your response I get the feeling that you have the dreaded "quick shot" syndrome. (slapping the shutter button which moves the camera which gives burred results) Can you try a simple technique when shooting; do your BBF and before clicking the shutter button, take a deep breath and slowly exhale then gently squeeze (don't press) the shutter button. The deep breath lets you relax, if only for a second or two, helping to keep your body calm and steady. Give it an honest try for a session or two and gauge your results.
Squeezing the shutter entails using pressure on your finger and thumb which tends to balance the forces exerted on the camera. Yes, exactly like shooting a gun. By pressing the shutter you tend to push the camera down as the shot is taken.
Squeezing the shutter entails using pressure on your finger and thumb which tends to balance the forces exerted on the camera. Yes, exactly like shooting a gun. By pressing the shutter you tend to push the camera down as the shot is taken.
Silvermeteor wrote:
While it may clarify it does not help. lol br br ... (show quote)
Apr 10, 2015 09:04:58 #
Silvermeteor wrote:
I have been reading the discussion on IS. As a res... (show quote)
Maybe this report will help you out. I explains BB focus and how to use it......http://www.learn.usa.canon.com/resources/articles/2011/backbutton_af_article.shtml
Apr 10, 2015 09:46:29 #
boberic wrote:
There is a very easy to check. Manually move the focus ring all the way to 1 extreme or the other. Then press the backbutton and see if the lens comes into focus. If it does then you will know.
No, this misses the point. If you use BBF, of course pressing the back button will snap the lens into focus. That tells you nothing about IS activation.
amfoto1: Nicely done, Alan. :thumbup:
Apr 10, 2015 10:07:30 #
RRS
Loc: Not sure
Silvermeteor wrote:
I have been reading the discussion on IS. As a res... (show quote)
You don't have to "press-pause-press"at all! Keep your thumb on the BBF button and don't let up and your lens will maintain focus. Use your finger to activate the shutter when you like the composition. I use BBF for BIF and when you bring up a file right click the mouse and click on AF Point. If you have done it right your focus point should show up as a red square. When shooting a stationary subject, bird or etc, I let up with the BBF as long as the subject doesn't move and on my file when doing as I said I will see my focus pattern but not the red square. On your fuzzy files check to see if in fact you actually activated BBF at all.
Apr 10, 2015 11:12:50 #
Silvermeteor
Loc: South Carolina, USA
amfoto1 wrote:
Pressing EITHER the shutter button (half-press) OR the back button OR both will start IS running, as well as activate the camera's metering system. So it really doesn't matter.
One of my main concerns was that both were activated with BBF. I am using BBF because it forces me to acknowledge that there two steps. One to set focus and activate the light meter and one to release the shutter. I did notice yesterday the movement in the viewfinder was reduced when IS kicked in.
amfoto1 wrote:
The lens' focus drive also makes a difference in how quickly AF achieves focus. Cheaper "micro motor" (aka "piezo" motor) lenses are the slowest focusing. STM or "stepper motor" are a bit faster, while USM or "ultrasonic motor" are the fastest and best tracking moving subjects. If shooting video, STM may be preferable because they are the smoothest and quietest focusing.
I am using a Canon EF-S 55-250 mm f/4.0 - 5.6 STM lens.
amfoto1 wrote:
Camera setup is also important. You might already know, One Shot is for still subjects and AI Servo for moving subjects. (Using BBF allows you to use AI Servo as your default mode.
I have been using AI Focus on the assumption that it allowed the best of both worlds. Guess not. I will shift to AI Servo and give that a try. You still get the red dot indicating engaged focus points when in AI Servo and using BBF. It would be nice if Canon left the red dots live at all times when BBF was active so you would get a continuous indication of what was catching the camera's attention.
amfoto1 wrote:
If using AI Servo, the camera automatically corrects focus (yet another good reason for using AI Servo & BBF as default settings).
Since AI Servo is essentially a continuous focus process is it reasonable to believe that this might also have some benefit for camera shake?
amfoto1 wrote:
Also mostly do not use multi-point AF (your camera has All Points/Auto Selection), which can choose incorrectly. Set the camera to Single Point/Manual selection and try to use the center point as much as possible (the other 8 points in your camera are lower performance type). This makes every shot you take have the subject centered, so I suggest also try to frame the subject slightly loosely so that you can crop the image later, to be more off center, if you wish to do so.
What about focus with the center point and recompose? With AI Servo enabled will the camera still maintain focus on the original point? It seem like it would but . . .
amfoto1 wrote:
And, always use a properly fitted and matched lens hood. It protects your lens better than any filter ever could, plus might help AF performance by keeping oblique light off the lens, increasing contrast.
I have a collapsible rubber lens hood that I use. I am assuming that you do not feel that this is sufficient.
amfoto1 wrote:
Also don't be overly critical of your images when reviewing them on your computer.
I believe this may be part of my problem too but not all.
Just some background to help the process.
While in the military I took numerous pictures of the Thunderbirds using my Pentax 35mm and an off brand 400 mm lens mounted on a modified rifle stock.
Now I find myself, at 72, almost overwhelmed with the variety of adjustments available on even my down scale T3i.
I'm certainly not as steady as I was at 24. lol
I am forced to rely on the in camera focus. With or without my glasses I am unable to adjust the diopter far enough to give me a clear view of the viewfinder so automation is my best friend.
I have attached a series of four images that I took yesterday.
Shutter: 1/1000
f/ Stop: 8.0
ISO: Automatic
Auto Focus: AI Focus - Center Focus Point
I varied the focal length to see it there was a sweet spot.
Thanks for you thoughtful and comprehensive response. I look forward to your thoughts on my comments.
Apr 10, 2015 11:20:43 #
Silvermeteor
Loc: South Carolina, USA
big-guy wrote:
IS is not reliant on AF so whether you use BBF or SBF the IS is governed by the shutter button just like the exposure. Do your BBF and when you press the shutter button both exposure and IS are calculated. Hope this helps.
It does. Thanks.
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