FAQ FAQ  Forum Search   Events   Register Register  Login Login

Video - Our SLT/mirrorless experiences

Page  <1 3456>
Author
QuietOC View Drop Down
Senior Member
Senior Member

Joined: 28 February 2015
Country: United States
Location: Michigan
Status: Offline
Posts: 2334
Post Options Post Options   Quote QuietOC Quote  Post ReplyReply Direct Link To This Post Posted: 14 March 2019 at 02:41
Originally posted by Photosopher Photosopher wrote:

a6300 + LA-EA3 adapter + ZA24/2 for A-Mount.
...
Video:
Allows only AF-S, and only when stills shutter button is pressed. Otherwise no AF at all.
No other AF modes are available.
Pressing stills shutter button to engage AF is reasonable speed, obviously CDAF, very accurate, and confirms Face Detect with green box. It will not track AF-C by keeping shutter button pressed.
Releasing stills shutter button disengages all AF, and reverts to manual focus only.
Pressing stills shutter button engages AF for new target, with new AF-S lock on, but no tracking.

This is how the non-SLT adapters have worked in video mode on all cameras: contrast-detect AF-S only.
Sony A68 A6000 A7II LA-EA3 LA-EA4 MC-11
Minolta Maxxum 600si
Pentax Q7 5-15 15-45/2.8
 



Back to Top
windhorse View Drop Down
Senior Member
Senior Member

Joined: 11 February 2013
Country: Australia
Location: Mexico&Denmark
Status: Offline
Posts: 338
Post Options Post Options   Quote windhorse Quote  Post ReplyReply Direct Link To This Post Posted: 14 March 2019 at 02:57
Wow looks like lots of possible combos to explore, all with strengths and weaknesses. My next step will be to experiment with wide focus area and face detection with the native FE prime lenses I already have, to see how well that solves the problem that got me going, and find out what new problems it brings.
Back to Top
Canopus View Drop Down
Newbie
Newbie

Joined: 26 November 2018
Status: Offline
Posts: 3
Post Options Post Options   Quote Canopus Quote  Post ReplyReply Direct Link To This Post Posted: 14 March 2019 at 16:48
Yes, you are right.
Sony mirrorless + adapters + lenses + plenty firmwares + plenty of focusing modes + plenty bugs/features …
It should be called “Sony construction toys” similar to “Lego construction toys”.
It is heavy overpriced! But still very nice set to play with
Back to Top
windhorse View Drop Down
Senior Member
Senior Member

Joined: 11 February 2013
Country: Australia
Location: Mexico&Denmark
Status: Offline
Posts: 338
Post Options Post Options   Quote windhorse Quote  Post ReplyReply Direct Link To This Post Posted: 14 March 2019 at 22:03
Originally posted by Canopus Canopus wrote:


It should be called “Sony construction toys” similar to “Lego construction toys”.


Wow, toys can also drive you nuts!

I am messing around trying to figure out more about how face detect autofocus works for filming video on my A7RII, since I have not found much useful information about this, either in the manual or on the internet yet. Maybe I am not looking in the right direction?

As mentioned earlier, I did come across a useful blog that told me this combo only works in wide area focus mode, you see a white box around the face, and when the box turns green it means the face is in focus right?

OK, so I set the camera to video mode+M+AF-C (as usual) +face detect+wide area focus - just like the doctor ordered - and sure enough there is that dancing white box around the face... then what?

WELL, I find (by experimenting randomly) that if I depress the main shutter button that white box does turn green (great) but only for as long as I depress the main shutter button, and as soon as I take my finger off the main shutter button that green box goes away and the dancing white box comes back again.

Hmmm, does this mean the only way to get confirmed focus on a face via face detect in video mode is to depress the shutter button, and keep it held down so the autofocus doesn't refocus on whatever else it decides ought to be in focus?

Does it also mean the focus stays exactly where it was when I first depressed the shutter button to confirm face detect autofocus, as long as I keep holding it down, even if the face moves, or not?

Then, just for fun, I thought, why not see what happens when I switch from wide angle area to center focus, that according to the blog I reverently referred to earlier, would supposedly stop face detect from working?

Well, face detect did work, the same as it did in wide area focus mode, the only difference being that it ONLY did this if the face happened to be close to the center of the frame, in which case the box around the face appears, but if the face was not close to the center of the frame, the camera would as expected focus on whatever happens to be in the center of the frame, not the face!

NOW HERE IS MY POINT (apart from wanting to give satisfaction to those who insist that MF is the only viable way to do this): I have not been able to find good documentation anywhere that explains how, when, and with what settings, face detect works????

Does this mean either:
(1) Comprehensive detailed documentation about how face detect autofocus in video mode works is available somewhere but I just haven't found it yet?
(2) the camera is so complex with so many different variables interacting that not even the people who designed it know exactly how face detect autofocus works?
(3) So much pressure to get the product to market nobody has had time to write it down and release instructions?
(4) Face detect autofocus is so experimental that how it works may vary depends on the phase of the moon etc
(5) It is only intended as a toy function but not to be taken seriously?
(6) Or....

Unfortunately, when it does work it works great, though as others here have pointed out, how useful is that if you cannot be sure when, where and how it will work?

At the moment the best focus workflow for videoing talking heads I can think of may be to use face detect to get the camera focussed on the face of the subject, then slip the camera into manual focus mode, use peaking to monitor if the subject stays in focus, and if s/he goes out of focus, then wait for a convenient moment to slip the camera back into AF and repeat the same process again. Or for me to get new eyes?

    

Edited by windhorse - 14 March 2019 at 22:32
Back to Top
stiuskr View Drop Down
Moderator Group
Moderator Group

Joined: 01 September 2006
Country: United States
Location: West Virginia
Status: Offline
Posts: 11167
Post Options Post Options   Quote stiuskr Quote  Post ReplyReply Direct Link To This Post Posted: 14 March 2019 at 22:59
Watch the first 8 minutes or so of this Gary Friedman video about focus modes for the a7iii/a7riii and using Center Lock On AF for video.

https://www.youtube.com/watch?v=HG0lS5C1PZQ&t=286s

Here's a Peter Gregg video that should be useful.
https://www.youtube.com/watch?v=CZENiq3U1oc

Just finished watching it and the Peter Gregg video will give you all you need for a7RIII Face Detection/tracking with video anywhere in the frame all the way to the edges. You haven't mentioned what file format you were using and I suspect that's what gave you problems to start with. Gary covers that also.

Edited by stiuskr - 14 March 2019 at 23:50
Rob Suits Jr.
a99M2 a99 a77 a700 KM7D|Min24/2.8 Min35/2 So50/1.4 So50/2.8 Min85/1.4G Tam90/2.8 Tam180/3.5|Tam17-50 CZ24-70G2 KM28-75D So70-200G1 So70-300G So70-400G1| SonyF60 AD200R2
Back to Top
windhorse View Drop Down
Senior Member
Senior Member

Joined: 11 February 2013
Country: Australia
Location: Mexico&Denmark
Status: Offline
Posts: 338
Post Options Post Options   Quote windhorse Quote  Post ReplyReply Direct Link To This Post Posted: 15 March 2019 at 05:14
Originally posted by stiuskr stiuskr wrote:

Watch the first 8 minutes or so of this Gary Friedman video about focus modes for the a7iii/a7riii and using Center Lock On AF for video.

https://www.youtube.com/watch?v=HG0lS5C1PZQ&t=286s

Here's a Peter Gregg video that should be useful.
https://www.youtube.com/watch?v=CZENiq3U1oc

Just finished watching it and the Peter Gregg video will give you all you need for a7RIII Face Detection/tracking with video anywhere in the frame all the way to the edges. You haven't mentioned what file format you were using and I suspect that's what gave you problems to start with. Gary covers that also.


Very useful indeed!

It is good to get new insights from old timers like these two that maybe most normal people already know but I didn't. For example, I did not realise that while shooting video in AF-C mode the face detect box is doing its job and is in focus when it is white, and does not switch to green like it does in other modes to confirm it is in focus... Perhaps this is mentioned some place in the instructions, which I overlooked, so maybe I should have taken an earlier coffee break before I got to that page?

As these two useful links were about A7RIII autofocus, I decided to look for more about the A7RII and came across this Youtube video with 28,910 views by Dave Dugdale about "A7RII Interview Face Detection."

He refers twice to the "focus hunting" as (sigh) "focus breathing."   
 



Back to Top
windhorse View Drop Down
Senior Member
Senior Member

Joined: 11 February 2013
Country: Australia
Location: Mexico&Denmark
Status: Offline
Posts: 338
Post Options Post Options   Quote windhorse Quote  Post ReplyReply Direct Link To This Post Posted: 15 March 2019 at 05:31
Originally posted by stiuskr stiuskr wrote:

You haven't mentioned what file format you were using and I suspect that's what gave you problems to start with.


My guess is what gave me problems to start with was I had the camera set in face detect and center focus rather than wide area mode, so even though the camera did pick up and track the face of the subject most of the time, even though the face was not in the center of the frame, the camera got momentarily confused (apparently when the hands of the subject in the center of the frame started moving) then refocussed on the face, resulting in a tiny but very annoying moment of hunting.

This refocussing ( I think as the camera switched from face detect to center focus and back again) is what I would expect to happen if something like a moving hand had blocked the view of the subject's face, or the head of the subject had turned away for a moment, but this did not happen.

To be quite sure, I have to try and replicate this problem, which I have not done yet.

Edited by windhorse - 15 March 2019 at 05:37
Back to Top
stiuskr View Drop Down
Moderator Group
Moderator Group

Joined: 01 September 2006
Country: United States
Location: West Virginia
Status: Offline
Posts: 11167
Post Options Post Options   Quote stiuskr Quote  Post ReplyReply Direct Link To This Post Posted: 15 March 2019 at 12:03
Originally posted by windhorse windhorse wrote:

...As these two useful links were about A7RIII autofocus, I decided to look for more about the A7RII and came across this Youtube video with 28,910 views by Dave Dugdale about "A7RII Interview Face Detection."

He refers twice to the "focus hunting" as (sigh) "focus breathing."   


Actually that is an example of focus breathing, where there is a small change in the field of view as the focus is adjusted from minimum to maximum focus distance without changing the focal length.
Rob Suits Jr.
a99M2 a99 a77 a700 KM7D|Min24/2.8 Min35/2 So50/1.4 So50/2.8 Min85/1.4G Tam90/2.8 Tam180/3.5|Tam17-50 CZ24-70G2 KM28-75D So70-200G1 So70-300G So70-400G1| SonyF60 AD200R2
Back to Top
windhorse View Drop Down
Senior Member
Senior Member

Joined: 11 February 2013
Country: Australia
Location: Mexico&Denmark
Status: Offline
Posts: 338
Post Options Post Options   Quote windhorse Quote  Post ReplyReply Direct Link To This Post Posted: 15 March 2019 at 18:15
Originally posted by stiuskr stiuskr wrote:

Actually that is an example of focus breathing, where there is a small change in the field of view as the focus is adjusted from minimum to maximum focus distance without changing the focal length.


No wonder they say ignorance is bliss!

Here is a link to crop from the video clip I am talking about. As you can see the autofocus is hunting and also the edge of the frame is moving, even though the camera is fixed on a tripod.

Any idea what is causing this?

Just a thought: is it possible this problem has nothing to do with either focus breathing or hunting and is caused by the camera's in-built stabilising system that is switched on, even though the camera is stationary? However if that were the case, would not the movement be continuous rather than once in a while? And would I not see it in other clips recorded in the same way which I usually don't?

Edited by windhorse - 15 March 2019 at 18:18
Back to Top
stiuskr View Drop Down
Moderator Group
Moderator Group

Joined: 01 September 2006
Country: United States
Location: West Virginia
Status: Offline
Posts: 11167
Post Options Post Options   Quote stiuskr Quote  Post ReplyReply Direct Link To This Post Posted: 15 March 2019 at 19:13
That is focus breathing caused by focus hunting, why is the focus hunting is the question that needs resolved. Might be easier to answer if we could see the whole frame but from what I can see is that is a very animated subject, hands are moving almost non stop and he is rocking side to side from one foot to the other, the rocking motion shouldn't be enough to cause Face Detection to lose focus but it does look like the focus hunting is happening when his hands are moving. With the hands being the closest thing to the camera that's what it's picking up on when it loses FD. Thinking about what Peter Gregg says in that video, image stabilization could one of the contributing factors, the more things the camera has to process the less it can contribute to lock on face detection.

Edited by stiuskr - 15 March 2019 at 19:16
Rob Suits Jr.
a99M2 a99 a77 a700 KM7D|Min24/2.8 Min35/2 So50/1.4 So50/2.8 Min85/1.4G Tam90/2.8 Tam180/3.5|Tam17-50 CZ24-70G2 KM28-75D So70-200G1 So70-300G So70-400G1| SonyF60 AD200R2
Back to Top
sybersitizen View Drop Down
Senior Member
Senior Member

Joined: 04 August 2006
Country: United States
Location: California
Status: Offline
Posts: 14113
Post Options Post Options   Quote sybersitizen Quote  Post ReplyReply Direct Link To This Post Posted: 15 March 2019 at 19:14
Originally posted by windhorse windhorse wrote:

Here is a link to crop from the video clip I am talking about. As you can see the autofocus is hunting and also the edge of the frame is moving, even though the camera is fixed on a tripod.

Any idea what is causing this?

The focus is rapidly changing (hunting) which results in the sudden changes in angle of view (breathing). Stop the hunting and you also stop the breathing. Or use a lens that is designed to have no breathing ... a focus change would still be evident, but no breathing would occur.

Just a thought: is it possible this problem has nothing to do with either focus breathing or hunting and is caused by the camera's in-built stabilising system that is switched on, even though the camera is stationary?

I think that would look different. But you can test it by keeping stabilization enabled and shooting a similar scene using both autofocus and fixed manual focus.
Back to Top
windhorse View Drop Down
Senior Member
Senior Member

Joined: 11 February 2013
Country: Australia
Location: Mexico&Denmark
Status: Offline
Posts: 338
Post Options Post Options   Quote windhorse Quote  Post ReplyReply Direct Link To This Post Posted: 15 March 2019 at 19:38
Thanks a lot for this clear diagnosis!

If this is the case, is not the most plausible explanation that face detect autofocus was not engaged, the focus hunting was caused by the moving hands in the center focus area of the frame, and the focus breathing was caused by the focus hunting?
Back to Top
stiuskr View Drop Down
Moderator Group
Moderator Group

Joined: 01 September 2006
Country: United States
Location: West Virginia
Status: Offline
Posts: 11167
Post Options Post Options   Quote stiuskr Quote  Post ReplyReply Direct Link To This Post Posted: 15 March 2019 at 21:10
From what I understand if Face Detection is enabled it will always be engaged if it can detect a face and it will focus on the next closest thing when it loses detection until it detects the face again. There are many variables that can cause it to lose detection or not engage in the first place such as video file format (no more than 60p and less is better), AF area used, locking sensitivity, Wi-Fi on and tethered to HDMI. What I've learned the most here is that the more the camera has to process the more likely it is to lose detection, have you tried Peter Gregg's settings, they seem to work very well.
Rob Suits Jr.
a99M2 a99 a77 a700 KM7D|Min24/2.8 Min35/2 So50/1.4 So50/2.8 Min85/1.4G Tam90/2.8 Tam180/3.5|Tam17-50 CZ24-70G2 KM28-75D So70-200G1 So70-300G So70-400G1| SonyF60 AD200R2
Back to Top
Photosopher View Drop Down
Senior Member
Senior Member
Knowledgebase Contributor

Joined: 13 June 2010
Country: United States
Location: St. Louis Mo
Status: Offline
Posts: 4145
Post Options Post Options   Quote Photosopher Quote  Post ReplyReply Direct Link To This Post Posted: 15 March 2019 at 21:19
At :17 at the beginning of video, Dave says: "I'm not saying this is something you should try on an interview..." First advise of the video.

Just out of curiosity, with all the effort spent on watching videos and corresponding with Dyxxum etc... Have you watched any of the How To Talking Head videos I linked? Have you practiced any manual focus? Have you looked into the camera manual?

Earlier you mentioned that one of your considerations was to use AF to target the face, and verify it was accurate with focus peaking. I question why not just do that, and/or just use manual focus with focus peaking to do the same?

You'll notice that Gary and Dave videos only show hunting/breathing when they are demonstrating the technology. But the phenomenon doesn't show when they are making regular videos. I propose that's because they don't use face detection AF for their day to day professional workflow. Perhaps they use it for family videos though.
Back to Top
Dyxum main page >  Forum Home > Equipment forums > Camera Talk Page  <1 3456>

Forum Jump Forum Permissions View Drop Down



This page was generated in 0.078 seconds.

Monitor calibration strip

Dyxum.com - Home of the alpha system photographer

In memory of Cameron Hill - brettania

Feel free to contact us if needed.