Back button focus vs shutter button focus for BIF

I have complained several times about poor focus (searching) when using BBF for BIF. This is with the Canon 5D3 and several lenses, from the 300 f/2.8 IS to the 600 II. (AI Servo, of course.) I think I have pinpointed the problem, at least in my case, and am curious for other input. I was using BBF and recently followed someone's advice here (sorry, I don't remember who) and switched back to linking focus to the shutter button and now I get focus holding much steadier. Before it would start wandering with no obvious reason -- not enough to see in the viewfinder and warn me to bump focus, but enough to see at 100% in LR.

Possibly I have a dirty connection with the back button. As I recall, I've tried both the AF-ON button and the * button. Or possibly I'm not managing to hold them down firmly enough but I doubt that. Going back to the shutter button gives much more reliable results, so I'll stay with that for BIF situations. Will still use one of the BB options for recomposing still subjects -- focus in that case has been extremely accurate, which does puzzle me.

Same results, comparing front button to back button, hold whether on a tripod or hand-holding. As I've said, the issue is not gross focus searching, but a slight softening at 100% that makes an image a reject, for me. Then the next frame will generally be sharp again. No logic to it by where the subject is relative to the focus sensor (I'm using the middle sensor for BIF, without the 4 surrounding points).

Just curious about others' experiences, and with other bodies. I could believe that it's some issue with my particular body, but maybe the 5D3 just has a limitation in that regard. I've tried to take as much load as possible off the processor -- I'm in M exposure mode, and turning IS off didn't seem to make any difference (not that I can see why it would).

Hi Diane,
I have not given BBF a fair trial as I always fall back to the more familiar shutter button focus for 'mission critical' work. However, I have some experiences similar to yours. I use a 5DIII with 300 mm f/2.8L II and 600 mm f/4L II and focal length extenders as required. I mostly use the AF custom case settings recommended by Arthur Morris and others and for some time I used the neutral setting for second shot priority in high speed continuous shooting. However, I found the second frame was invariably slightly out of focus and the third frame was often worse. This prompted me to change to focus priority for the second shot and I have had much better results. I think the relatively slow frame rate (6 fps) of the 5DIII allows sufficient time between frames for the focus to drift off when using the neutral setting. With the 1Dx ( 12 fps) this seems not to be a problem.
Regards, Ian

I use shutter release and have never even tried BBF, so I can't tell you if there's a difference in the functionality on my 5D3 or not.

I feel no handicap using the shutter release, finding it very intuitive. I use a back button if I want to lock and recompose.

I've read (on camera internet forums) many claims that back button focus is superior to using the shutter button, but I spent quite some time trying it on my 7D and concluded it provided no advantage whatsoever. I agree with David that using the shutter release button is intuitive and natural, particularly when hand-holding a large lens.

John

Hi Diane-as you know I don't yet have the 5DIII so I can't comment on that aspect. Have changes been made to other parameters (such as sensitivity, speed or focus point and type) or is it strictly a button change that shows the increased softness?

I do use BBF exclusively on the 7D, I find it indispensable for picking a subject out of a group and quickly recomposing with single shot. It's also very useful for zone focus techniques where tracking a subject towards a pre-determined spot and firing off a small burst as it passes through is desired. As for BIF- I've found my keeper rate improved only slightly; from miserable to frustratingly low. As for stills on a tripod-there might not be much of a benefit using BBF other than for focus and recompose situations. The biggest benefit (for me) is that it eliminates the possibility of misfires when bump focusing as I track a moving subject. It took quite some time for BBF to become intuitive, using a SB now feels awkward.

I only changed the button, and got a noticeably higher percentage of sharply-focused shots. (Same location and subjects -- flying egrets -- same day and same improved results the next day.) I had been using the back button (had tried both the AF-ON and * at different times, was currently using the *) and holding it down for focus tracking (camera on AI Servo and focus disconnected from the front button). High speed burst mode. Changing the focus back to the shutter button and disabling both back buttons (while muscle memory tried to forget them) gave better focus more of the time. When I say poor focus I mean just slightly unsharp at 100% -- not grossly OOF. Not enough to see in the VF to know to bump focus. But enough to toss them out.

So I've gone back to shutter button focus and using * to lock focus for still subjects when I want to focus and recompose. I think I'll continue to get better focus but I'll whine again if I don't -- the egrets will be a target-rich environment for another month or more. I thought I was getting accurate focus with the * button for still subjects, and the issue was with moving ones. Could do a more scientific study, I guess. With shutter button focus I do have a pretty consistent issue with the first frame being soft, but I can deal with that in burst mode if the rest are good.

Diane, do you have any shots showing images taken with BBF and shutter button focus? I'm curious to see the difference. I've always used BBF and haven't had much problems. I like to "bump" quite a bit, so maybe that has something to do with it?

Many of both, but posting a few wouldn't show much as it's a statistical thing. I was getting more with what I judge to be poor focus when I linked focus to the BB instead of the shutter button. Saw some improvement when I linked to the shutter. The difference is really only apparent at 100%, but that's important to me. I want things tack sharp at 100%. And shooting a fine tree branch would alwys give me tacj sharp -- it is moving subjects that are the issue. They are typically moving on a path toward me at maybe 30 degrees off the focus plane.

The flight path I'm shooting now is good because there is a catchlight in most shots, making it easy to distinguish poor focus from motion blur. DOF issues are a little harder to sort out.

I normally don't have enough focus excursion to bump focus and haven't been doing it unless things get off enough to see, which is WAY off.

Im a bit late on this thread but I thought I would throw my two cents in. I shoot allot of BIF stuff and I use the shutter button to focus. It feels more natural for me and I feel more locked in to the flight shot.
I see a downside to back focusing for my style of BIF shooting. I brought this up to a group of BPN photographers at a lunch break on my trip to Florida a month ago.
Doug Brown uses back focusing and some of the others did also, so we started taking about the pros and cons.
I then realized that if you are using your thumb to focus, and you use your index finger to depress the shutter button, then how can you change exposure settings without taking your thumb off the focus button and your finger off the shutter button? You cant. I use the back dial to control my shutter speed with rolling my thumb, and then focus and hit the shutter with my index finger, never missing something by having to remove my finger from the shutter to turn the dial on top. I am able to shoot one species as it flies by and then lock on to a darker species and change exposures as I am shooting and focusing all at the same time. The group did see what I meant and realized that there was a con to back focusing for BIF and changing exposure settings.
It may seem trivial to remove your finger off the shutter and change the exposure with the top dial, but with quick action BIF stuff, it can mean missing the killer wing position or loosing your tracking and concentration.
Now, for shooting portrait and perched birds, it's great and I like the ability to focus and then recompose. I change between the two modes depending on what I am shooting, BIF or BOAS (bird on a stick)
Not that any one style is right or wrong, just maybe whats best for your shooting situation.

David

Yes, that's an advantage. I think you -- or someone -- pointed this out in an earlier thread, which was part of my motivation to "switch back" -- although a higher percentage of sharply focused shots is my main concern right now.

I think it's pretty obvious which way you need to be doing it based on your own results :)

I've tried it with my 5DIII and was fine until we got into the heart of our waterfowl season when the temps drop and the gloves go on. At that point my keeper rate goes to heck simply because of not being able to feel the buttons as firm as barehanded. It's not even a debate for me anymore our winters are just too cold and it make zero sense to shoot one way part of the year then switch. With the 5DIII I do much better just using the joystick to move the focus point anyway on static shots. And that works quick once you get use to it.

Quote:

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Originally Posted by David Salem

I use the back dial to control my shutter speed with rolling my thumb, and then focus and hit the shutter with my index finger, never missing something by having to remove my finger from the shutter to turn the dial on top. I am able to shoot one species as it flies by and then lock on to a darker species and change exposures as I am shooting and focusing all at the same time. The group did see what I meant and realized that there was a con to back focusing for BIF and changing exposure settings.
It may seem trivial to remove your finger off the shutter and change the exposure with the top dial, but with quick action BIF stuff, it can mean missing the killer wing position or loosing your tracking and concentration.

David

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David I've often thought about this myself. So you reversed the Default TV/AV dials for Manual exposure mode?
Did you just reassign the TV & AV buttons in the Custom Controls Menu, or did you use the Dial Direction CFn from 0: Normal to 1: Reverse direction?

Hi Bobby,

Yes to everything you just asked.

I changed the default setting so that the TV was controlled by the dial in the back and the AV was controlled by the small dial on top. Simple enough. Then I reversed the dial on the back, and you can control it which ever way you are most comfortable with, so that I can speed up the TV when I roll right and slow it down as I roll left. It is mostly used for exposure control as apposed to actual shutter stopping power
You may ask why not assign it to the AV and keep the SS constant? With shooting BIF stuff, and with a location with allot of action, you want to keep the SS as high as you reasonably can, so the AV is wide open, or almost wide open most of the time. This being the case, you don't have any more room to change to a lower exposure. I have heard of some using the ISO to change exposure on the fly but I dont like bumping up the ISO too much unless I have to.
I set my self up at a location, with the sun at my back, and set my exposure to meet a neutral colored bird, say a Mallard. On a sunny day this is usually about 1/2500 at f6.3 to 5.6.
Now I know where the mallard exposes well, so when a Avocet flies in from the right I can lock on and use two clicks of the dial to the right and I am at 1/4000th and probably exposing proper. Same thing when a Cinnamon Teal comes smokin in from the left, I can dial a click or two to the left and expose the Teal better. Sometimes I am doing this as I am firing away because when the action happens it's easy to forget to change your setting because you are busy enough just trying to get locked on, then I remember to dial in SS as I am composed and shooting at 12fps. You cant do this with Back focusing. Its usually better in color and sharper when a BIF is exposed well. I have learned this from trial and error and have shown this many photography friends over the years. It has made a big difference in my ability to get well exposed flight shots. Hope this answers your question. Try it out and see how you like it. It takes a bit of practice and constant reminding yourself to dial up or down, but when you get it figured out, it will make a big difference on your keeper rate and you wont have to try to bring a dark frame back to grainy life;)

David

Hi David,
I was using back focusing recently. Prior to that I was using the shutter release for focusing and the * for focus stop and recompose.
Now as per your suggestion, I switched back to front focusing. I also changed the dials just like you suggested.
I have questions I you may help me.
For BIF my setting currently is; Tracking sensitivity: -2 Accel/decal: +1 AF pt switching +1.
AF Servo first image priority: Release
A I Servo 2nd point priority: Speed.
My camera is 5DM3 somewhat similar to 1D X.
Thanks.

Hello David
my english is very bad and I would be happy if you could give me more details about your setting as up explained.
I have a 5D III and 1Dx .
At the moment I use for focus * and Af button but I think could be fine return to the normal setting and use * only to recompose stopping the focus.
But I no undestood your other setting..could you help me ?
Thanks

Hello Ian
about the seconf frame which is your right setting with Dx?
Thanks
Gio

I've made another observation in my quest for improving focus with the 5D3 for birds in flight. I've seen people say here that birds flying parallel to the sensor are more successful subjects, and have now found that for myself. (I learn the hard way.)

In my BIF shooting, up until the last few days, there was often a significant component of the bird flying toward me -- at angles between 0 and 60 degrees. In the last few days I found birds at our local rookery (my practice grounds) flying on a reliable track carrying nesting material between two trees, almost parallel to the sensor. It's a short path and I hadn't tried to shoot it before, but with hand-holding the 300 + 1.4X I concentrated on that path and got some nice shots with more reliable focus holding than I had been getting with longer tracks that were coming more toward me. I was using the center sensor only and was able to hold focus as the birds flew in front of BG trees at the two ends of the flight path, as well as against sky. (The trees are very close to the birds and not pretty but were a good check.)

I couldn't follow the bird perfectly and sometimes focus drifted, but in most of them I could see that there was a DOF issue as focus shifted from front wing to back wing to head. I tried it yesterday with the 600 on the Wimberley and got similar results, but with more DOF issue with the birds larger in the frame.

I've gone back to focus with the shutter button -- probably won't bother to do a "statistical study" to see if the back button gives degraded focus behavior.