Z5/1000 Autofocus-The Anti-Christ of Face Detection? at DVinfo.net

Ken Ross · February 16th, 2009, 06:57 AM

Obviously I'm being a bit flip with the title, but it does bring into 'focus' (sorry for the bad pun) an issue both I and a friend who also has the Z5 have been experiencing.

It seems these cams just don't like faces in the autofocus mode. In fact, I can't recall ever having a camera that had such a tough time with faces. More often than not the camera seems to prefer to focus on the background and ignore the face. In looking at the scenes where this occurs, it becomes obvious that any background that's 'busy' in the least way will take preference over a face in the foreground with the Z5 autofocus.

My friend and I were comparing notes last night and he mentioned that he was focusing on a face that filled up 70% of the frame and the cam still refused to focus on the face. I've had the same thing occur to me. Now give it some time and the autofocus will eventually catch up, but man, that can seem like an eternity.

Now yes, you can surely disengage autofocus, use the 'one push' autofocus or use the focus assist on the Z5, but what happens when you have a face in motion? What happens when you have a face moving toward the camera? For you event guys I can see this being a real issue.

Now for most other situations I see few issues with the autofocus and it seems pretty reliable. But when you think about the 'face detection' feature on consumer cams, it seems the Z5/1000 have 'anti-face detection'.

Since it's happening on both my Z5 and my friend's Z5, it's hard to believe this is an isolated camera issue. This is the only real disappointment I've had with the camera. So how are you guys dealing with this?

Michael Wisniewski · February 16th, 2009, 07:37 AM

This is a normal problem with digital passive auto-focus systems. The AF systems look for high contrast areas of the image in order to focus. The higher the contrast the more likely it will focus on that area. Faces can be a problem if a busy background provides a lot more contrast, and as you've noticed, moving faces can be difficult as well as they can become a fast changing low contrast area. The normal work arounds are: 1. manual focus 2. zoom in, lock focus, then zoom out 3. turn the camera sideways to help it lock focus (many AF systems look for vertical contrast, turning it sideways, helps it see the eyebrows, mouth, nose as vertical contrast lines) this is a trick from still cameras, obviously it's not as useful on video cameras 4. if possible place your subject in lighting that casts a shadow across their face, once again to create a vertical high contrast area 5. use as a high a gain as you can in low light situations. These are all compromises, but then that's the nature of passive AF systems.

Some cameras have a dual active/passive system like the XH A1 which uses both to help it catch focus. I don't know enough about the Z5/1000 to know if it does that.

Hope that helps a little.

Jean Rousseau · February 16th, 2009, 11:18 AM

You guys are absolutely right about the autofocus, My FX1000 does it too. Its perfect outside but inside where the background is a bit overexposed compared to a face, it focus on the background . The thing that I dont like is that my FX1 wasnt giving me any problems. Its really annoying because Im trying to record my 8 months old son running towards me but struggling with the focus! Hope it wont be too much of a pain for my wedding days :s
Im also dissapointed with the huge iris difference from wide to telephoto. You zoom in to someone but lose so much light that the zooming option become almost obsolete. It becomes way too dark to be accceptable. Only use for it is to zoom in, adjust the exposure and then record. Or maybe if you put the iris to a smaller aperture from wide, then it stays at the same focal opening for the whole zooming distance.

Wayne Nakamura · February 16th, 2009, 02:17 PM

I have to agree. My Z5 was used to shoot a ballroom dance. The lighting wasn't great but still exposed ok. But many times I found the camera losing focus and then struggling to get it back. Very unimpressive performance. My previous experience recording these dances at this same venue was with a TR900 and I don't recall any focus issues with that camera.

Martin Duffy · February 16th, 2009, 04:30 PM

Quote:

Originally Posted by Wayne Nakamura

I have to agree. My Z5 was used to shoot a ballroom dance. The lighting wasn't great but still exposed ok. But many times I found the camera losing focus and then struggling to get it back. Very unimpressive performance. My previous experience recording these dances at this same venue was with a TR900 and I don't recall any focus issues with that camera.

And everyone just a few weeks ago bagged me out for giving Sony a hard time ago on such issues.

Guys this is absolutely terrible stuff that is happening here. They have brought out a camera with very basic flaws. To anyone that's about to post along the lines of "professionals should always be in manual focus" well I say get up with it.

Auto focus has become a very useable function and seasoned cameramen from the old school are now seeing the benefits of it. On cameras such as Sony's TRV900/VX2000/PD170's etc it were just brilliant. In even lowish light one could rely on auto focus. Auto focus can be great in the heat of the moment especially if you are like alot of us who are cameraman/ producers/directors/audio monitors all at the one time.

A camera with good Auto focus is one less thing to think about but now we have a camera that does not auto focus as good as a camera that is 10 years old like the TRV900.

I am over Sony and their two steps forward one step back and are seriously thinking of selling my FX1000 and looking around for something better.

Like many of us video is my life and passion but why should we be expected to just put up with this garbage and disappointments.

If I had known about the auto focus issue and 4 second rec/pause/rec issue then there is no way I would have purchased a FX1000/Z5.

But no its taken 2 months for everyone to shoot and edit and examine and well lets face it some of the results are pretty disappointing.

I am over it and going either Canon or Panasonic.

Khoi Pham · February 16th, 2009, 04:50 PM

HD focus must be dead on, with SD you have some room, if a shot in SD is a litttle bit out of focus, it is still acceptable and hard to noticed, but with HD, a little out of focus then you can clearly see it, I don't think it is getting worse, it just that HD is different and required exact focus with no room for mistake.

Ken Ross · February 16th, 2009, 05:33 PM

I think the Canon AF systems are unquestionably better, but I also think the new 1000/Z5 picture is the best out there. I've got my first shoot with the Z5 this week, so I'll see how it goes in actual use.

Wayne Nakamura · February 16th, 2009, 05:43 PM

I just read Igor's thread about auto focus assist. I tried it out and it seems to be a solution, albeit a little messy to the losing focus problem.

Khoi Pham · February 16th, 2009, 05:53 PM

Quote:

Originally Posted by Ken Ross

I think the Canon AF systems are unquestionably better, but I also think the new 1000/Z5 picture is the best out there. I've got my first shoot with the Z5 this week, so I'll see how it goes in actual use.

Don't think so, I have the Canon A1, and the auto focus sucks too, I hardly use it, similar to the Sony, the normal AF use vertical line/contrast to focus, the instant focus use infrared, you can combine the 2 system and it still sucks, it will hunt, and so best not to use them at all, you guys just need to get use to and good at manual focus in Hd world.

Ken Ross · February 16th, 2009, 05:59 PM

Wow Khoi, I didn't realize the Canon was just as bad! If the larger Canon couldn't get it right, I doubt that any of the larger prosumer cams can. My experience with the small consumer HD cams like the Canon HV20 and my newer HG21 is just superb. Those autofocus systems seem to always 'know' what to focus on...so much so that it's almost uncanny.

But I think something happens to these autofocus systems when mated to larger lenses. Even my Sony SR12 that I sold for the HG21 had a much better autofocus than my Z5. So there must be something about the larger lens and perhaps a narrower depth of field that adversely affects the autofocus.

Martin Duffy · February 16th, 2009, 06:06 PM

[QUOTE=Khoi Pham;1013140]Don't think so, I have the Canon A1, and the auto focus sucks too,

Well I have a friend who has the Canon and says its auto focus is great.

All I know is that my Canon 1/6 CCD MD225 ($220US) has a better "snap" auto focus in good light than the FX1000.

It's a pretty sad situation.

Ken Ross · February 16th, 2009, 07:09 PM

Martin, if you think about it, your Canon is not only SD but it has small 1/6" chips which give it a huge depth of field. That's what I was alluding to when mentioning the smaller HD cams. Their smaller lens and sometimes smaller chips give them a larger depth of field which makes autofocus so much easier for the camera. It's hard to screw up focus when almost everything is in focus no matter what you do.

When you have a smaller depth of field, then focusing errors are much more possible. I'm just saying it might be an explanation.

Jean Rousseau · February 16th, 2009, 07:48 PM

I also realized that the focus seem to be more accurate on the edge of the face instead of the center. Same thing when shooting an object, looks like it focus on the edge instead of the middle. Its weird because my FX1 was focusing without problems. And about the longer lense, I agree BUT the problem occurs at wide angle too! That is not good at all!

Martin Duffy · February 16th, 2009, 07:56 PM

Quote:

Originally Posted by Jean Rousseau

I also realized that the focus seem to be more accurate on the edge of the face instead of the center. Same thing when shooting an object, looks like it focus on the edge instead of the middle. Its weird because my FX1 was focusing without problems. And about the longer lense, I agree BUT the problem occurs at wide angle too! That is not good at all!

A camera that has focus issues. My god!

It's like the bad old days of the Canon XL1. This is a joke. I am out of here Sony.

Pedanes Bol · February 16th, 2009, 08:58 PM

I remember reading in one of the threads in HV20-40 forum that auto focus does not work well (more focus hunting) when the optical image stabilization is ON. Do you usually shoot OIS on? You may try to turn it off and see whether auto-focus improves.

February 16th, 2009, 06:57 AM	#1
Ken Ross Trustee Join Date: Jan 2005 Location: New York Posts: 1,945	Z5/1000 Autofocus-The Anti-Christ of Face Detection? Obviously I'm being a bit flip with the title, but it does bring into 'focus' (sorry for the bad pun) an issue both I and a friend who also has the Z5 have been experiencing. It seems these cams just don't like faces in the autofocus mode. In fact, I can't recall ever having a camera that had such a tough time with faces. More often than not the camera seems to prefer to focus on the background and ignore the face. In looking at the scenes where this occurs, it becomes obvious that any background that's 'busy' in the least way will take preference over a face in the foreground with the Z5 autofocus. My friend and I were comparing notes last night and he mentioned that he was focusing on a face that filled up 70% of the frame and the cam still refused to focus on the face. I've had the same thing occur to me. Now give it some time and the autofocus will eventually catch up, but man, that can seem like an eternity. Now yes, you can surely disengage autofocus, use the 'one push' autofocus or use the focus assist on the Z5, but what happens when you have a face in motion? What happens when you have a face moving toward the camera? For you event guys I can see this being a real issue. Now for most other situations I see few issues with the autofocus and it seems pretty reliable. But when you think about the 'face detection' feature on consumer cams, it seems the Z5/1000 have 'anti-face detection'. Since it's happening on both my Z5 and my friend's Z5, it's hard to believe this is an isolated camera issue. This is the only real disappointment I've had with the camera. So how are you guys dealing with this?

February 16th, 2009, 07:37 AM	#2
Michael Wisniewski Wrangler Join Date: Jul 2002 Location: Makati, Metro Manila Posts: 2,706 Images: 32	This is a normal problem with digital passive auto-focus systems. The AF systems look for high contrast areas of the image in order to focus. The higher the contrast the more likely it will focus on that area. Faces can be a problem if a busy background provides a lot more contrast, and as you've noticed, moving faces can be difficult as well as they can become a fast changing low contrast area. The normal work arounds are: 1. manual focus 2. zoom in, lock focus, then zoom out 3. turn the camera sideways to help it lock focus (many AF systems look for vertical contrast, turning it sideways, helps it see the eyebrows, mouth, nose as vertical contrast lines) this is a trick from still cameras, obviously it's not as useful on video cameras 4. if possible place your subject in lighting that casts a shadow across their face, once again to create a vertical high contrast area 5. use as a high a gain as you can in low light situations. These are all compromises, but then that's the nature of passive AF systems. Some cameras have a dual active/passive system like the XH A1 which uses both to help it catch focus. I don't know enough about the Z5/1000 to know if it does that. Hope that helps a little. __________________ "Ultimately, the most extraordinary thing, in a frame, is a human being." - Martin Scorsese

February 16th, 2009, 04:50 PM	#6
Khoi Pham Major Player Join Date: Nov 2004 Location: Dallas Posts: 747	HD focus must be dead on, with SD you have some room, if a shot in SD is a litttle bit out of focus, it is still acceptable and hard to noticed, but with HD, a little out of focus then you can clearly see it, I don't think it is getting worse, it just that HD is different and required exact focus with no room for mistake. __________________ Khoi Pham www.proeditproductions.com

February 16th, 2009, 06:06 PM	#11
Martin Duffy Regular Crew Join Date: Jan 2006 Posts: 156	auto focus [QUOTE=Khoi Pham;1013140]Don't think so, I have the Canon A1, and the auto focus sucks too, Well I have a friend who has the Canon and says its auto focus is great. All I know is that my Canon 1/6 CCD MD225 ($220US) has a better "snap" auto focus in good light than the FX1000. It's a pretty sad situation.

February 16th, 2009, 08:58 PM	#15
Pedanes Bol Regular Crew Join Date: May 2007 Location: Boston MA Posts: 167	OIS Effect I remember reading in one of the threads in HV20-40 forum that auto focus does not work well (more focus hunting) when the optical image stabilization is ON. Do you usually shoot OIS on? You may try to turn it off and see whether auto-focus improves.

February 16th, 2009, 11:18 AM	#3
Jean Rousseau Regular Crew Join Date: Jun 2005 Posts: 38	You guys are absolutely right about the autofocus, My FX1000 does it too. Its perfect outside but inside where the background is a bit overexposed compared to a face, it focus on the background . The thing that I dont like is that my FX1 wasnt giving me any problems. Its really annoying because Im trying to record my 8 months old son running towards me but struggling with the focus! Hope it wont be too much of a pain for my wedding days :s Im also dissapointed with the huge iris difference from wide to telephoto. You zoom in to someone but lose so much light that the zooming option become almost obsolete. It becomes way too dark to be accceptable. Only use for it is to zoom in, adjust the exposure and then record. Or maybe if you put the iris to a smaller aperture from wide, then it stays at the same focal opening for the whole zooming distance.

February 16th, 2009, 02:17 PM	#4
Wayne Nakamura New Boot Join Date: Aug 2008 Location: Toronto, Canada Posts: 14	I have to agree. My Z5 was used to shoot a ballroom dance. The lighting wasn't great but still exposed ok. But many times I found the camera losing focus and then struggling to get it back. Very unimpressive performance. My previous experience recording these dances at this same venue was with a TR900 and I don't recall any focus issues with that camera.

February 16th, 2009, 05:33 PM	#7
Ken Ross Trustee Join Date: Jan 2005 Location: New York Posts: 1,945	I think the Canon AF systems are unquestionably better, but I also think the new 1000/Z5 picture is the best out there. I've got my first shoot with the Z5 this week, so I'll see how it goes in actual use.

February 16th, 2009, 05:43 PM	#8
Wayne Nakamura New Boot Join Date: Aug 2008 Location: Toronto, Canada Posts: 14	I just read Igor's thread about auto focus assist. I tried it out and it seems to be a solution, albeit a little messy to the losing focus problem.

February 16th, 2009, 05:59 PM	#10
Ken Ross Trustee Join Date: Jan 2005 Location: New York Posts: 1,945	Wow Khoi, I didn't realize the Canon was just as bad! If the larger Canon couldn't get it right, I doubt that any of the larger prosumer cams can. My experience with the small consumer HD cams like the Canon HV20 and my newer HG21 is just superb. Those autofocus systems seem to always 'know' what to focus on...so much so that it's almost uncanny. But I think something happens to these autofocus systems when mated to larger lenses. Even my Sony SR12 that I sold for the HG21 had a much better autofocus than my Z5. So there must be something about the larger lens and perhaps a narrower depth of field that adversely affects the autofocus.

February 16th, 2009, 07:09 PM	#12
Ken Ross Trustee Join Date: Jan 2005 Location: New York Posts: 1,945	Martin, if you think about it, your Canon is not only SD but it has small 1/6" chips which give it a huge depth of field. That's what I was alluding to when mentioning the smaller HD cams. Their smaller lens and sometimes smaller chips give them a larger depth of field which makes autofocus so much easier for the camera. It's hard to screw up focus when almost everything is in focus no matter what you do. When you have a smaller depth of field, then focusing errors are much more possible. I'm just saying it might be an explanation.

February 16th, 2009, 07:48 PM	#13
Jean Rousseau Regular Crew Join Date: Jun 2005 Posts: 38	I also realized that the focus seem to be more accurate on the edge of the face instead of the center. Same thing when shooting an object, looks like it focus on the edge instead of the middle. Its weird because my FX1 was focusing without problems. And about the longer lense, I agree BUT the problem occurs at wide angle too! That is not good at all!

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search