GX7's C-AF up to task of tracking running kids?

Started Nov 22, 2013 | Questions
New Daddy Regular Member • Posts: 464
GX7's C-AF up to task of tracking running kids?

I'm also torn between GX7 and E-M1. I've been using Panny and like the form factor of GX7. One big lure of E-M1, though, is its faster C-AF with PDAF. But since I'm not going to shoot pro sports or motor sports, C-AF fast enough to track running kids will be good enough.

Does GX7 have C-AF that is good enough to track running kids? By way of comparison, with my GH1, I have about 20-30% keeper rate on running kids at a soccer game.

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chris_j_l Regular Member • Posts: 355
Re: GX7's C-AF up to task of tracking running kids?

Depends. Are they running (relatively) consistently? Then yes AF-C manages it easily. If they are running at random, it will have a job keeping up as the prediction will fail.

C

G1Houston Senior Member • Posts: 2,784
You should use face detection instead.

New Daddy wrote:

Does GX7 have C-AF that is good enough to track running kids? By way of comparison, with my GH1, I have about 20-30% keeper rate on running kids at a soccer game.

Are you using face detection and shoot in burst? I once used my GH1/14-140 to photograph my 4 yr old running around with a whole bunch of kids between water columns, and my keep rate was >80%. I was able to get him between other kids, and behind the splashing water. I have no doubt that the AF and face detection in GX7 are better than those in the GH1, but you should get much better keep rate if you use face detection and do so properly. The beauty with the face detection is that when a face is not detected, it defaults to auto-AF area, which focuses on object that is closest to you (and which is almost alway your kids any way). With the Panasonic, you can also have the camera memorize up to five faces so when you shoot your kids among other people, the face detection will focus on your kids first.

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Trevor Carpenter
Trevor Carpenter Forum Pro • Posts: 15,598
Re: GX7's C-AF up to task of tracking running kids?
2

New Daddy wrote:

I'm also torn between GX7 and E-M1. I've been using Panny and like the form factor of GX7. One big lure of E-M1, though, is its faster C-AF with PDAF. But since I'm not going to shoot pro sports or motor sports, C-AF fast enough to track running kids will be good enough.

Does GX7 have C-AF that is good enough to track running kids? By way of comparison, with my GH1, I have about 20-30% keeper rate on running kids at a soccer game.

How many times does this need to be said, good CAF isn't a prerequisite for shooting running kids. Take any m4/3s camera, set a decent shutter speed, point it at the kids and press the shutter button. Surprise, surprise you have a perfectly focused picture or your kids,

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Timur Born
Timur Born Veteran Member • Posts: 4,778
Re: GX7's C-AF up to task of tracking running kids?
1

Trevor Carpenter wrote:

How many times does this need to be said, good CAF isn't a prerequisite for shooting running kids. Take any m4/3s camera, set a decent shutter speed, point it at the kids and press the shutter button. Surprise, surprise you have a perfectly focused picture or your kids,

Running straight towards the camera, grass behind the target in focus!? One could speculate that the AF frame was too large and couldn't decide on focusing on the closer target. But anything closer than 5 meters is a real challenge to any camera, even more so without predictive AF-C.

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OP New Daddy Regular Member • Posts: 464
Re: GX7's C-AF up to task of tracking running kids?

Trevor Carpenter wrote:

New Daddy wrote:

I'm also torn between GX7 and E-M1. I've been using Panny and like the form factor of GX7. One big lure of E-M1, though, is its faster C-AF with PDAF. But since I'm not going to shoot pro sports or motor sports, C-AF fast enough to track running kids will be good enough.

Does GX7 have C-AF that is good enough to track running kids? By way of comparison, with my GH1, I have about 20-30% keeper rate on running kids at a soccer game.

How many times does this need to be said, good CAF isn't a prerequisite for shooting running kids. Take any m4/3s camera, set a decent shutter speed, point it at the kids and press the shutter button. Surprise, surprise you have a perfectly focused picture or your kids,

I don't see a picture of running kid in your picasa gallery.

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Trevor Carpenter
Trevor Carpenter Forum Pro • Posts: 15,598
Re: GX7's C-AF up to task of tracking running kids?

Timur Born wrote:

Trevor Carpenter wrote:

How many times does this need to be said, good CAF isn't a prerequisite for shooting running kids. Take any m4/3s camera, set a decent shutter speed, point it at the kids and press the shutter button. Surprise, surprise you have a perfectly focused picture or your kids,

Running straight towards the camera, grass behind the target in focus!? One could speculate that the AF frame was too large and couldn't decide on focusing on the closer target. But anything closer than 5 meters is a real challenge to any camera, even more so without predictive AF-C.

I don't get it.  How would good CAF have helped that it would just means that you had the same piece of grass in focus in multiple shots.  That is nothing less than operator error I do it all the time.  You aren't focused on the subject you are focused on the grass.

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Trevor Carpenter
Trevor Carpenter Forum Pro • Posts: 15,598
Re: GX7's C-AF up to task of tracking running kids?

New Daddy wrote:

Trevor Carpenter wrote:

New Daddy wrote:

I'm also torn between GX7 and E-M1. I've been using Panny and like the form factor of GX7. One big lure of E-M1, though, is its faster C-AF with PDAF. But since I'm not going to shoot pro sports or motor sports, C-AF fast enough to track running kids will be good enough.

Does GX7 have C-AF that is good enough to track running kids? By way of comparison, with my GH1, I have about 20-30% keeper rate on running kids at a soccer game.

How many times does this need to be said, good CAF isn't a prerequisite for shooting running kids. Take any m4/3s camera, set a decent shutter speed, point it at the kids and press the shutter button. Surprise, surprise you have a perfectly focused picture or your kids,

I don't see a picture of running kid in your picasa gallery.

That's because i have no interest in running kids but I take lots of moving objects. That picture is focused on the grass and has a shutter speed of 1/200. Focus on the boy and set a shutter speed of 1/1000 and it would have been a great shot. CAF has nothing to do with why this shot isn't very good.

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MrWalrusGumboot Regular Member • Posts: 260
Re: You should use face detection instead.

I second trying face detection on the Panny for your application.
It does a surprisingly good job of what you're asking.
As mentioned above, register your kids faces too and it will try to prioritize focus on them over other kids. Works in video too.
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OP New Daddy Regular Member • Posts: 464
Re: GX7's C-AF up to task of tracking running kids?

"Trevor Carpenter wrote:

New Daddy wrote:

Trevor Carpenter wrote:

New Daddy wrote:

I'm also torn between GX7 and E-M1. I've been using Panny and like the form factor of GX7. One big lure of E-M1, though, is its faster C-AF with PDAF. But since I'm not going to shoot pro sports or motor sports, C-AF fast enough to track running kids will be good enough.

Does GX7 have C-AF that is good enough to track running kids? By way of comparison, with my GH1, I have about 20-30% keeper rate on running kids at a soccer game.

How many times does this need to be said, good CAF isn't a prerequisite for shooting running kids. Take any m4/3s camera, set a decent shutter speed, point it at the kids and press the shutter button. Surprise, surprise you have a perfectly focused picture or your kids,

I don't see a picture of running kid in your picasa gallery.

That's because i have no interest in running kids but I take lots of moving objects. That picture is focused on the grass and has a shutter speed of 1/200. Focus on the boy and set a shutter speed of 1/1000 and it would have been a great shot. CAF has nothing to do with why this shot isn't very good.

And where is a photo of a moving object that requires the same kind of skill necessary to shoot a moving kid? A BIF or an airplane, with deep DOF on subject with good contrast from the background? You obviously do NOT have expertise in taking photos of moving kids. Better to remain silent than remove doubt about your ignorance.

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OP New Daddy Regular Member • Posts: 464
Re: GX7's C-AF up to task of tracking running kids?

Trevor Carpenter wrote:

Timur Born wrote:

Trevor Carpenter wrote:

How many times does this need to be said, good CAF isn't a prerequisite for shooting running kids. Take any m4/3s camera, set a decent shutter speed, point it at the kids and press the shutter button. Surprise, surprise you have a perfectly focused picture or your kids,

Running straight towards the camera, grass behind the target in focus!? One could speculate that the AF frame was too large and couldn't decide on focusing on the closer target. But anything closer than 5 meters is a real challenge to any camera, even more so without predictive AF-C.

I don't get it. How would good CAF have helped that it would just means that you had the same piece of grass in focus in multiple shots. That is nothing less than operator error I do it all the time. You aren't focused on the subject you are focused on the grass.

Duh!

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Timur Born
Timur Born Veteran Member • Posts: 4,778
Re: GX7's C-AF up to task of tracking running kids?

Trevor Carpenter wrote:

I don't get it. How would good CAF have helped that it would just means that you had the same piece of grass in focus in multiple shots. That is nothing less than operator error I do it all the time. You aren't focused on the subject you are focused on the grass.

Then let me explain to you: The focus is not on the grass, it's on an earlier position of the kid. The E-M5's AF-C was not able to keep up with the running kid and did not predict where it's going. In this shot it's even so bad that the camera did not decide on a focus point at all, there is no focus frame shown in camera playback.This is where predictive and especially PDAF based AF-C should help.

The 1/200s is irrelevant, because the shot is meant to demonstrate focusing issues, not stopping down issues. Again, with small DOF and close proximity targets this is hard for any camera, though.

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OP New Daddy Regular Member • Posts: 464
Re: You should use face detection instead.

MrWalrusGumboot wrote:

I second trying face detection on the Panny for your application.
It does a surprisingly good job of what you're asking.
As mentioned above, register your kids faces too and it will try to prioritize focus on them over other kids. Works in video too.
--
Let the light guide you...

Yes, I use face detection from time to time (and have face recognition set up for my family as well.) The first generation Pannys had face detection. But it doesn't really work unless the subject is (nearly) facing the camera. If the face is sideways or lowered, it doesn't work. When the camera fails to detect face, yes, like someone else mentioned, my Panny goes into "multiple" AF mode, and, no, it's not always my kids that the camera locks multiple AF point on. It becomes a real hit or miss.

Also, face detection doesn't work if the kid is moving fast, like in a soccer match.

So an improvement in face detection AF (in addition to improved C-AF) in the latest iteration of Panasonic will be useful. Does anyone know if GX7 has better face detection algorithm than the first generation? (e.g., detecting lowered face, etc.)

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Timur Born
Timur Born Veteran Member • Posts: 4,778
Re: You should use face detection instead.

I do like that the E-M5 falls back to whatever focusing mode you setup when it fails to detect a face (far too often). So if you setup single AF center (or wherever) it will use that one when no face is detected.

What's not so nice is that it gets confused too easily by anything hiding parts of a face, especially when eye-brows or the mouth are covered. And it keeps detecting face in things that don't even remotely resemble such. And in combination with AF-C I can show you an example where playback claims the focus to be on the clearly visible face on the side of an image, but the focal plane is on the far behind patch of grass or wall or whatever in the center (center point frame was setup when face is not detected).

That being said the Face Detection of my former Fujifilm X10 was really good in that it could quite reliably detect faces from the side as well.

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Trevor Carpenter
Trevor Carpenter Forum Pro • Posts: 15,598
Re: GX7's C-AF up to task of tracking running kids?

Timur Born wrote:

Trevor Carpenter wrote:

I don't get it. How would good CAF have helped that it would just means that you had the same piece of grass in focus in multiple shots. That is nothing less than operator error I do it all the time. You aren't focused on the subject you are focused on the grass.

Then let me explain to you: The focus is not on the grass, it's on an earlier position of the kid. The E-M5's AF-C was not able to keep up with the running kid and did not predict where it's going. In this shot it's even so bad that the camera did not decide on a focus point at all, there is no focus frame shown in camera playback.This is where predictive and especially PDAF based AF-C should help.

The 1/200s is irrelevant, because the shot is meant to demonstrate focusing issues, not stopping down issues. Again, with small DOF and close proximity targets this is hard for any camera, though.

I understand completely but my point is why use CAF and then complain that it doesn't work. Use AF-S and press the shutter again and the kid would have been perfectly focused.  As for 1/200 is irrelevant, moving subject,  (there are exceptions) use a high shutter speed,

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Timur Born
Timur Born Veteran Member • Posts: 4,778
Re: GX7's C-AF up to task of tracking running kids?

Trevor Carpenter wrote:

I understand completely but my point is why use CAF and then complain that it doesn't work. Use AF-S and press the shutter again and the kid would have been perfectly focused. As for 1/200 is irrelevant, moving subject, (there are exceptions) use a high shutter speed,

Well, and my reason to give AF-C that day a try was that in the past AF-S already failed repeatedly at the task at hand. Usually you get slight back-focus with AF-S on kids running towards you at close proximity. Likely an issue of still too much shutter lag once focus has been acquired, but again, a predictive AF-C system should be able to calculate that lag in and thus get the shot by focusing slightly in front to begin with.

1/200s in that shot is still irrelevant, because it still was meant to test and demonstrate how AF succeeds or fails to follow the running kid. The grass clearly shows that the focal plane fell behind the kid, that's got nothing to do with shutter speed.

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Timur Born
Timur Born Veteran Member • Posts: 4,778
Re: GX7's C-AF up to task of tracking running kids?

Now look at this: Seems like I did not use AF-C that whole evening, but switched to AF-S in between. I checked EXIF information on the shot and it happens to be shot in AF-S. So much for that advise.

One big problem with AF-S and running kids is that with "Release Priority" OFF it often takes too long until it decides to be in focus and then loses the moment. And with "Release Priority" ON you end up with shots like the one I posted, where the camera/EXIF says: "AF not used" and the effective focal plane is somewhere where the kid has been earlier.

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micksh6
micksh6 Senior Member • Posts: 2,613
Re: GX7's C-AF up to task of tracking running kids?
2

Trevor Carpenter wrote:

New Daddy wrote:

Trevor Carpenter wrote:

New Daddy wrote:

I'm also torn between GX7 and E-M1. I've been using Panny and like the form factor of GX7. One big lure of E-M1, though, is its faster C-AF with PDAF. But since I'm not going to shoot pro sports or motor sports, C-AF fast enough to track running kids will be good enough.

Does GX7 have C-AF that is good enough to track running kids? By way of comparison, with my GH1, I have about 20-30% keeper rate on running kids at a soccer game.

How many times does this need to be said, good CAF isn't a prerequisite for shooting running kids. Take any m4/3s camera, set a decent shutter speed, point it at the kids and press the shutter button. Surprise, surprise you have a perfectly focused picture or your kids,

I don't see a picture of running kid in your picasa gallery.

That's because i have no interest in running kids but I take lots of moving objects. That picture is focused on the grass and has a shutter speed of 1/200. Focus on the boy and set a shutter speed of 1/1000 and it would have been a great shot. CAF has nothing to do with why this shot isn't very good.

It has everything to do with C-AF. Use math. Typical S-AF focusing + shutter lag time can be as long as 300ms. A child running with 15km/h speed will pass about 1.2m (4 feet) in that time. This is about where Timur's shot is focused - 4 feet behind the child.

I got some photos of kids running towards me in my gallery. But, I didn't focus on them, CDAF is too slow for that. I prefocused on the grass in front. This is where high frame rate helps - it gives more chances for sharp shot when subject crosses focus plane. 8fps on E-PL5 is way better than 3fps on E-P3 or even 5fps on E-PM1 or GX7.

Capturing tangential motion can be easy with CDAF, motion towards you - not so much, unless focus distance is long and you got huge DOF with slow telephoto zoom.
Couple of examples.

1

2

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Trevor Carpenter
Trevor Carpenter Forum Pro • Posts: 15,598
Re: GX7's C-AF up to task of tracking running kids?

I try not to bite, go to bed I tell myself but I can't pull back. I like a nice friendly argument. As far as I can see this thread goes along the lines of

1. To prove that GX7 cannot shoot moving kids, here's a very bad picture I took earlier using CAF

2.  Perhaps you should have used AFS

3.  Well to be truthful it was using AFS

4.  So how does that prove CAF doesn't work on a GX7

5.  It doesn't but it was the best way I could explain to the OP that GX7 CAF does not work

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agachart Regular Member • Posts: 279
Re: GX7's C-AF up to task of tracking running kids?

use AFF,after G5 panasonic add this feature to all m4/3 camĀ 

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