Focus mode/other tips for super shallow DOF telephoto (135L) shots?

Hi guys,

So I generally take pictures of things that don't move at wide angles (landscapes, city scapes, architecture, etc). However, lately I've been getting into street photography and fast lenses, culminating in the purchase of my 135L.

However, I'm having trouble nailing shots, and I think it's partially because of my movements...the depth of field is so shallow (truly, we're talking about an inch or less) that I think between focusing and tripping the shutter I move the camera just enough (and most likely the subject moves too, as I usually shoot people) to introduce a slight blur/misfocus.

I've always used One Shot focus (partially because I often focus/recompose, and partially because that mode is perfect for everything else I do)...however, I think I may be better off using AI Servo for shots like this, right? Any other tips for me?

Thanks and Happy New Year!
- Tamas

LowriderS10 wrote in post #15424889
...however, I think I may be better off using AI Servo for shots like this, right? Any other tips for me?

Thanks and Happy New Year!
- Tamas

Yes
Learn to focus with the back button instead of the shutter button. That way you can do your focus/recompose as well as these moving shots, all on AI Servo.

Happy New Year to you as well!
Dave

With moving subjects, AI Servo is definitely the "mode of choice".

When the subject is stationary, the only question is to whether your movement can throw the focus off. If so, a faster shutter speed will really be your only recourse. However, I find that it's good to have a narrow enough aperture with a wide enough depth of field to cover a little "jiggle" for street photography. Using an aperture of f/4-f/5.6 will typically suffice. But, if you are going for the shallow depth-of-field "look", well, it's a balancing act.

I guess I should say that another factor that helps me with hand-held shooting is that I've used IS lenses for quite some time. For subject movement you still need a "capable" shutter speed, but IS helps with the jiggly hands!

tracknut wrote in post #15425075
Yes
Learn to focus with the back button instead of the shutter button. That way you can do your focus/recompose as well as these moving shots, all on AI Servo.

Happy New Year to you as well!
Dave

Thanks, I was thinking that exact same thing (moving to back-button focusing...I tried it a while ago, but saw no advantage - since I usually shoot landscapes, etc), but this may be a compelling reason...I can set up a Custom mode to have back-button focusing while the other has half-shutter press focusing, right?

tonylong wrote in post #15425675
With moving subjects, AI Servo is definitely the "mode of choice".

When the subject is stationary, the only question is to whether your movement can throw the focus off. If so, a faster shutter speed will really be your only recourse. However, I find that it's good to have a narrow enough aperture with a wide enough depth of field to cover a little "jiggle" for street photography. Using an aperture of f/4-f/5.6 will typically suffice. But, if you are going for the shallow depth-of-field "look", well, it's a balancing act.

I guess I should say that another factor that helps me with hand-held shooting is that I've used IS lenses for quite some time. For subject movement you still need a "capable" shutter speed, but IS helps with the jiggly hands!

Thanks, it's actually not the camera movement that's an issue (ie: something that can be corrected with IS), the problem is that they're live targets and I'm not a tripod...the DOF is so shallow that if he moves a half an inch and I move a quarter of an inch, then we've thrown focus completely off where it was intended to be. Would AI Servo pick up on minute changes like that?

Yeah, I knew stopping down was an option, but I'm loving the look of pictures wide open...I tend to use my fast lenses wide open only, so I'm trying to work around that...

You don't have to stop down much, you just want to take it from an inch to a couple of inches. AI Servo will keep updating until you hit the release, so assuming you are moving outside of it's natural margin for error, yes it should keep up. You only really have a problem if the DoF is inside the AF systems margin of error, as then of course the number of Hits to Misses will be down to the statistical distribution of that error.

Alan

What are you having a problem shooting? (A problem image with EXIF would be nice to see?)

I do use AI Servo, but w/out back button focusing when the subject is moving since I want focusing to continue right up until the shutter trips.

PhotosGuy wrote in post #15426910
I do use AI Servo, but w/out back button focusing when the subject is moving since I want focusing to continue right up until the shutter trips.

Frank, there's an implication in this, that back-button focusing does not continue right up until the shutter trips? Would you mind explaining that?

Dave

tracknut wrote in post #15427171
Frank, there's an implication in this, that back-button focusing does not continue right up until the shutter trips? Would you mind explaining that?

Dave

The AF-ON button functions no differently than a half shutter press.

If you and your subject are both standing still, don't use AI-Servo. The AF system will be expecting your subject to move much more than just an inch or two, and may actually cause a misfocus by predictively hunting!

In my experience using one-shot and tripping the shutter as soon as focus is confirmed seems to be the most effective method. Note that there's nothing wrong with "spamming focus" in one shot mode (pressing AF-ON rapidly over and over). The effect is similar to AI-Servo without the possibility of errent hunting.

LostArk wrote in post #15427349
The AF-ON button functions no differently than a half shutter press.

That's been my experience too, which is why I was asking Frank about his statement.

Dave

PhotosGuy wrote in post #15426910
What are you having a problem shooting? (A problem image with EXIF would be nice to see?) I do use AI Servo, but w/out back button focusing when the subject is moving since I want focusing to continue right up until the shutter trips.

I'll try to get a shot up, but I don't really have anything yet, I usually just delete them when I'm not happy haha.

LostArk wrote in post #15427349
The AF-ON button functions no differently than a half shutter press.

If you and your subject are both standing still, don't use AI-Servo. The AF system will be expecting your subject to move much more than just an inch or two, and may actually cause a misfocus by predictively hunting!

In my experience using one-shot and tripping the shutter as soon as focus is confirmed seems to be the most effective method. Note that there's nothing wrong with "spamming focus" in one shot mode (pressing AF-ON rapidly over and over). The effect is similar to AI-Servo without the possibility of errent hunting.

Hmm...well that's the thing, is that "standing still" is a relative term...we both may be standing/sitting, but humans are rarely as still as telephone poles. And just the natural movement of two people (as I've said, half an inch from one person, a quarter from the other) is enough to achieve incorrect focus with such a shallow DOF.

So if AI Servo isn't the answer (or the whole answer) I think I might try putting the camera on burst mode and rattling off a few shots, and hoping that one will be bang on. Of course, the problem is that I'm trying to go as unnoticed as possible, and a camera firing away at +/- 4 fps won't help with that haha

I think another problem of mine is that I don't always focus and trip the shutter right away...sometimes I focus and then make sure the composition looks good/I get a facial expression I like and then I trip the shutter...with that, I think Servo would be much better...I'll definitely work on that...

tracknut wrote in post #15427171
Frank, there's an implication in this, that back-button focusing does not continue right up until the shutter trips? Would you mind explaining that?

Dave

No, sorry. Back button focusing is usually used if/when you want to turn focusing on & off. So when I just want "normal" focusing to take place, I don't see any reason to use the back button for it.

LowriderS10 wrote in post #15426731
Yeah, I knew stopping down was an option, but I'm loving the look of pictures wide open...I tend to use my fast lenses wide open only, so I'm trying to work around that...

Yeah, which is why I keep things a bit stopped down with a wide aperture lens with those situations!

That being said, I have done some "creative experimentation", although with mixed results.

Here are a couple decent shots taken at f/1.2 (with my 5DC and the 85 f/1.2L) at an event last year, just because I felt that the composition/subject could benefit from the wide aperture (but I was sitting down and concentrating on a steady shot):

tracknut wrote in post #15427171
Frank, there's an implication in this, that back-button focusing does not continue right up until the shutter trips? Would you mind explaining that?

Dave

Back button focusing works "differently" for different people. Frank is describing the fact that back-button focus can be "inconvenient" if you want to quickly shift from focusing, focus lock, and taking the shot, since you are "juggling" two buttons.

In practice, I do like to use the shutter button focus and One Shot AF for stationary subjects when it's convenient, but I do tend to leave the camera in rear-button focus -- to lock, I just take my thumb off the button and I find the focus pretty reliable. If I think of it and it's appropriate I'll switch to AI Servo, and really rarely get around to switching to shutter button AF, but yeah, Frank's comment has merit!

LowriderS10 wrote in post #15428734
Hmm...well that's the thing, is that "standing still" is a relative term...we both may be standing/sitting, but humans are rarely as still as telephone poles. And just the natural movement of two people (as I've said, half an inch from one person, a quarter from the other) is enough to achieve incorrect focus with such a shallow DOF.

So if AI Servo isn't the answer (or the whole answer) I think I might try putting the camera on burst mode and rattling off a few shots, and hoping that one will be bang on. Of course, the problem is that I'm trying to go as unnoticed as possible, and a camera firing away at +/- 4 fps won't help with that haha

First off, I try to make a habit of good "steadying" techniques...I'll either lean on things and tuck my elbows in, crouch or sit and lean elbows on my thighs, or whatever, unless I'm in good light and can get the right exposures. I've done a lot of street photography where "on the fly" photographing is pretty much a "rule of the road". Those are scenarios where I very much depend on an f/5.6 aperture!

And, for me, another "rule of the road" for a lot of my photography is short "bursts" -- 2-or-3-shot bursts are not "cheating" or "spraying and praying", it is simply a technique when hand-held shooting of difficult scenes to give you the best chance of capturing your vision!

Yeah, an ongoing challenge and "balancing act"! It's all about "judgement calls" that become effective from a lot of experience and learning by "trial" and, especially, "error"!

I agree. I can bench rest 3 shots into a dime at 100 meters, but when I only have human support, I've found that the second longer exposure shot of a series is better than the first: "Pre-Cruise" at 1/15 seconds - 7/28/12