Focus Lock On Second Shots Seems Suspect (AF-S)

[BackdoorArts]

I've been using the D7100 almost exclusively this week at Musikfest and I've experienced some wild deviations in getting focus lock on a second consecutive shot. I've been shooting outdoors and in bright light with a 24-120mm f/4, so the conditions shouldn't be an issue. I have it set to back button focus and am using AF-S with 5 points (center point almost always active) and Focus Priority set to Focus Lock, so it will not fire unless focus has been achieved.

Here's what is happening. I'll be looking through the view finder, focus and shoot, and immediately move the camera to a new spot (usually as the subject is moving) and re-engage the back button to focus a second time. At this point it will sometime not focus at all and the shot will be missed. Other times it just takes a long time before it locks and finally fires.

I'm also running into wild variations in the display of the image on the back screen after a shot using a SanDisk Extreme 92Mbps card, so speed shouldn't be an issue, shooting one image at a time. It was a refurb, and all this stuff screams ,"Send it back and get it checked while you're still in the 90 day window!!", but I thought I'd check here first to see if anyone else has had similar experiences.

 

[Horoscope Fish]

I've been using the D7100 almost exclusively this week at Musikfest and I've experienced some wild deviations in getting focus lock on a second consecutive shot. I've been shooting outdoors and in bright light with a 24-120mm f/4, so the conditions shouldn't be an issue. I have it set to back button focus and am using AF-S with 5 points (center point almost always active) and Focus Priority set to Focus Lock, so it will not fire unless focus has been achieved.

I'm not sure it's relevant, but if you're in AF-S mode, it sounds like you're selecting one focus point (that's an "S" for single focus point), not "five" focus points.

Even so, this behavior sounds odd to me. I used BBF for a while, though I also used AF-C/d21 when I did so...

Not sure any of this helps either. I could try re-enabling BBF, using your settings and see what happens though.

...

 

[Eyelight]

s = stationary

Actually means single-servo, but fairly certain the intent is for subjects that don't move.

 

[BackdoorArts]

You guys are both spot on for what AF-S is about. What I'm doing is primarily street photos, where I...

1. grab the subject at the chosen (center) focus point
2. engage auto-focus with the back button
3. fire a single frame
4. re-aim the camera, either at the same subject, or a new one elsewhere in the frame, releasing the back button as I do this
5. re-engage the back button auto-focus
... and wait as it attempts to lock on the new subject.

Sure, I could go to AF-C with dynamic points, but that's not what I want, particularly in a crowded street where I want a specific target to be in focus. I'm not looking to track a single target, but even if I did I am releasing and re-engaging the back-button (which I may not have been clear about in the initial post), so it shouldn't matter if it's the same subject or something new. Regardless, it would seem that I get an issue either way.

Could it have something to do with disengaging and re-engaging the focus system so quickly?

 

[Horoscope Fish]

s = stationary

Actually means single-servo, but fairly certain the intent is for subjects that don't move.

When referring to the *mode* AF-S is Auto Focus Single Servo, yes... But again, that's the AF-Mode.

Then there are the number of focus points being used while IN that particular AF-Mode. In AF-S Mode, you can choose to use a "S"ingle focus point, or you can select "Auto" and let the CPU decide which focus points are used to achieve focus-lock. AF-S Single Point is used for stationary subjects (so sayeth the manual).

...

 

[BackdoorArts]

Once again, I'm either not making myself clear, or you're not hearing what I'm typing. I've readeth the manual!!

I am in AF-S mode, with the single point focus selected (I neveruse AUTO for anything but ISO). I am not asking it to track, I am asking it to release and re-engage. It's on the re-engage that it seems to be struggling.

I did some testing on the deck today (nothing worth seeing tonight, and these old bones can use a night off) and here's what I'm finding. As before, first frame locks just fine and fires perfectly. Second frame seems to lock, or at least stop searching for a lock, but does not fire. This happens not all the time, but some times, and usually when the second subject is not high contrast (when it is, this doesn't seem to be an issue). It pauses, and fires about 1-2 seconds later if I hold the shutter button down. It may be a technique issue, as I may be pressing the shutter button before lock is achieved, so the camera is struggling to figure out whether or not to fire or focus. It's a technique I've not really had to use before, and I may be better off in another mode. I'm going to keep this in mind when I head back out tomorrow, if only to concentrate on when I'm pressing what.

 

[Horoscope Fish]

You guys are both spot on for what AF-S is about. What I'm doing is primarily street photos, where I...

1. grab the subject at the chosen (center) focus point
2. engage auto-focus with the back button
3. fire a single frame
4. re-aim the camera, either at the same subject, or a new one elsewhere in the frame, releasing the back button as I do this
5. re-engage the back button auto-focus
... and wait as it attempts to lock on the new subject.

I don't see why that wouldn't work... By my understanding it SHOULD. I'm going to enable BBF on my D7100 and see if I can duplicate your issue.

I'm assuming you're just re-assigning the AE-L/AF-L button for focus, correct? And you're using AF-S with a single focus-point. Give me a minute to experiment and get back to you with what I find out.

...

 

[Horoscope Fish]

Once again, I'm either not making myself clear, or you're not hearing what I'm typing. I've readeth the manual!!

I wasn't asking you to read the manual I was explaining to Eyelight what the manual says about AF-S Single Point vs. AF-S Auto.

I am in AF-S mode, with the single point focus selected (I neveruse AUTO for anything but ISO). I am not asking it to track, I am asking it to release and re-engage. It's on the re-engage that it seems to be struggling.

I understand this perfectly.

In an attempt to answer your question I have re-enabled Back Button Focus on my D7100.

So far I am having no trouble getting it to focus lock as you seem to want it to. I focus use the back-button, release the button after getting the shot, re-compose and press the back button again all within, say, half a second. So far no issues with getting a focus lock.

I apologize if I'm misunderstanding you.

...

 

[Eyelight]

The first sentence in the manual describing Autofocus Mode AF-S is: "Single-servo AF: For stationary subjects."

Best I understand and seems to bear out in practice, AF-S does not like movement either by camera or subject.

I suggest using AF-C, AF-Area single point, with AF-C Priority set to focus. You get the benefit of continuous focus on the subject you choose. The snag is you can't lock focus and swing off center while using the back button to initiate focus.

 

[PapaST]

I have my D7100 set for back button focus and I mimicked your other settings. I did not experience anything like that either. I tried focusing on an object about 20yds away and releasing, then panning remove and rengage the back focus and got lock quickly (and subsequent release).

 

[Horoscope Fish]

Could this be related to the (Custom Settings Menu) a3: Focus Tracking with Lock-on setting I wonder?

Edit: Going to rule this out as well, based on my own experiments.

Seems to me you should be getting a snappy AF-lock each and every time you press the AE-L/AF-L button, regardless... That's what I'm getting.

....

 

[hark]

Once again, I'm either not making myself clear, or you're not hearing what I'm typing. I've readeth the manual!!

I am in AF-S mode, with the single point focus selected (I neveruse AUTO for anything but ISO). I am not asking it to track, I am asking it to release and re-engage. It's on the re-engage that it seems to be struggling.

I did some testing on the deck today (nothing worth seeing tonight, and these old bones can use a night off) and here's what I'm finding. As before, first frame locks just fine and fires perfectly. Second frame seems to lock, or at least stop searching for a lock, but does not fire. This happens not all the time, but some times, and usually when the second subject is not high contrast (when it is, this doesn't seem to be an issue). It pauses, and fires about 1-2 seconds later if I hold the shutter button down. It may be a technique issue, as I may be pressing the shutter button before lock is achieved, so the camera is struggling to figure out whether or not to fire or focus. It's a technique I've not really had to use before, and I may be better off in another mode. I'm going to keep this in mind when I head back out tomorrow, if only to concentrate on when I'm pressing what.

Even I was stymied by your earlier post where you said you were using 5 focus points. That might be what caused some confusion.

When I first got my D610, I had a similar problem with the shutter not firing--I think I even mentioned it to you as I wondered if it was because I was using a Sigma lens. What I eventually noticed is the little green focus dot inside the viewfinder wasn't lit even though it seemed that the camera/lens had achieved focus. My suggestion is to keep watch of the little dot and see if focus is confirmed. And having a low contrast image did seem to affect mine, too.

 

[Rick M]

It may be a technique issue, as I may be pressing the shutter button before lock is achieved, so the camera is struggling to figure out whether or not to fire or focus. I

Then that would be happening with your other bodies also.

 

[nickt]

Could it be a lens or contact problem causing af to be intermittent? With that in mind, I would be curious if this presents in af-c as well. Try both holding focus on (with a3 off) while panning around as well as quickly engaging/disengaging it as you are doing now.

Another thought, could the back button be intermittent? Was there any problem with half press shutter button focus? You could test the back button in the dark in af-s by watching to see if the af assist lamp responds quickly to your presses. Or you could eliminate the back button entirely by programing your fn button to af-on.

That's all I got.

 

[PaulPosition]

...
I suggest using AF-C, AF-Area single point, with AF-C Priority set to focus. You get the benefit of continuous focus on the subject you choose. The snag is you can't lock focus and swing off center while using the back button to initiate focus.

If you set AF-C priority to shutter, however, you can grab focus, release the AF-on button then compose (or focus, release af-on, swing off center, grab spot exposure values with shutter half-press, then frame the composition you wish for).

 

[Krs_2007]

Check the focus delay Jake, mine is turned off. I had issues with this in the beginning . If it's off then I don't what else could cause that.