Back Focus Revisited, more weird questions. at DVinfo.net

Go Back   DV Info Net > Sony XAVC / XDCAM / NXCAM / AVCHD / HDV / DV Camera Systems > Sony XDCAM EX Pro Handhelds

Sony XDCAM EX Pro Handhelds
Sony PMW-300, PXW-X200, PXW-X180 (back to EX3 & EX1) recording to SxS flash memory.


Reply
 
Thread Tools Search this Thread
Old December 20th, 2009, 12:02 AM   #1
Major Player
 
Join Date: Sep 2008
Location: East Bay Cali
Posts: 563
Back Focus Revisited, more weird questions.

I have seen all over the forum the "focus" and or backfocus issues.
because of that i have been looking for a camera with a lens that has a Manuel backfocus flange on the back of the lens itself. (cant afford a 10K lens so. . .)
I have my usual strange questions, because what i am reading doesnt make sence from what i have learned the hard way.

Then i read pages apon pages of this backfocus stuff and trying to set the Auto using various charts and distances and such, some of which are successfull.
It still doesnt sound like I and my camera persons or my customers would be happy with a camera that goes out of focus in the middle of thier event, and it sounds like that might happen.

All this has made me paranoid, and then i read this:
60Feet away the pic is going out of backfocus when they wide out.
BUT
i also see that according to the instructions were supposed to set this backfocus at 3 meters? Well to me that doesnt make any sence at all.

having worked very LITTLE with cameras with actual Manuel backfocus , and having disassemble set the backfocus (the hard way) on various pro-sumer cameras throughout the ages i learned this:

you set the backfocus for the Range you will be working in.
so when we are shooting horses, the furthest distance that the camera would reach in that Arena would be where we would set the backfocus.
when shooting indoor church say, the furthest distance in the church which existed is where the backfocus would be set for.
when shooting stage the cams had a prime backfocus location that would keep them in focus when doing any zoom backs from on the stage, at that distance.
if your outside shooting landcsapes 700yards away, you set the backfocus so that mountain is sharp when wide.

now i see people trying to "fix" an auto backfocus for 60 feet distances at 3 meter distances. if you see what i am saying , stop reading now, and help me out here.

why would i set an "AUTO" backfocus at a distance that i am not shooting at?
Does not the maintance auto backfocus setting set the Back focus on the camera BY adjusting the backfocus itself when in the WIDE position by (back) focusing with the camera wide ON the stuff it is aimed at , AT the distance that stuff is at?

are these Auto Backfocus things that are occuring , totally unlike a manuel flange adjustement on a broadcast type lens that has a manuel flange adjustment?

If this happened to me once during a shoot, and i softed a whole shoot, i would toss the camera in the trash and go home :-) so i have this need to know this kind of thing. there is no Take 2 in most of my jobs.
__________________
----------------sig-----------------
Re-learning everything all over again, one more time.
Marty Welk is offline   Reply With Quote
Old December 20th, 2009, 12:43 AM   #2
Major Player
 
Join Date: Feb 2008
Location: Cardiff, Wales, UK
Posts: 410
On a manual lens the standard procedure is to alter the flange when focussed at 10 feet with aperture wide open, ideally using a Siemens star chart. You don't chose a zone to be in focus as the back focus procedure leaves you confident that all will be in sharp focus when starting on a full telephoto shot and then pulling back to a wide.

Like many others my EX1 calibration was out on delivery but by following the procedures posted here by Paul Kellet and Matt Davies if I remember correctly, all has been well since lining up my camera back in February 2008. All you need is to be 10 feet back from a neutral wall with some photocopies of the star chart. I would have thought that Sony would have got their act together by now but back then sharp pictures were not I think a priority!
Bruce Rawlings is offline   Reply With Quote
Old December 20th, 2009, 12:57 AM   #3
Major Player
 
Join Date: Sep 2008
Location: East Bay Cali
Posts: 563
ok so the NON-sucessfull stories of this were being 3-5 feet away, trying to get a tiny leetel chart in the picture?
but 10feet or 3meters , works, that corelates with other users who got it to work finally.

so i could assume that people just werent doing things right?
or
that Stuff Happens, and the thing could go wackey at the worst moment?
__________________
----------------sig-----------------
Re-learning everything all over again, one more time.
Marty Welk is offline   Reply With Quote
Old December 20th, 2009, 04:43 AM   #4
Major Player
 
Join Date: Feb 2008
Location: Cardiff, Wales, UK
Posts: 410
I can't remember a post where it has suddenly gone off but you will have to search for that. The Paul Kellett system (and others) was to have a block of 6 or 8 Siemens stars in a block on a neutral wall so that the camera would have no distractions when Auto Flanging or what ever it is called. The main thing is to check the result on a high def monitor. The more care taken the better the result. The thought of wide shots being out of focus is not something to have to contemplate.
Bruce Rawlings is offline   Reply With Quote
Old December 20th, 2009, 05:55 AM   #5
Trustee
 
Join Date: Aug 2005
Location: Berkshire, UK
Posts: 1,562
Quote:
Originally Posted by Marty Welk View Post
but 10feet or 3meters , works, that corelates with other users who got it to work finally.
Backfocus, or Flange Back, requires you to focus as near as dammit on infinity, so there's no way it can work on anything other than a fair old distance (2-3 meters is a bare minimum I guess).

On the two occasions I've needed to do BackFocus on my EX1 (once after purchase, once after sending it to Sony for the standard fixes), it's worked perfectly. Check the following before/after shots:

Untitled Page

Worked first time, each time, with perfect results. Note the distance. I think it's the distance and something contrasty to focus on that's important, not the number or the type of focus chart.
__________________
Director/Editor - MDMA Ltd: Write, Shoot, Edit, Publish - mattdavis.pro
EX1 x2, C100 --> FCPX & PPro6
Matt Davis is offline   Reply With Quote
Old December 20th, 2009, 06:53 AM   #6
Major Player
 
Join Date: Sep 2008
Location: East Bay Cali
Posts: 563
cool well thanks for your replys.

focusing problems with this new Stuff IS a huge issue, a limited web search for "focus problems lens" brings up 67MILLION hits, for only this past year :-) that is more hits than george bush problems :-)
search for the same thing in Jan 1, 2007–Jan 1, 2008 and only 2 million hits, so either everyone got a camera, or there is a lot more digital lens problems than before.
backfocus problems 758million hits ,just in the past year, oh my!.

but mainly when scouring the web about these new digital (auto) cameras, every one of them except the ones with Manuel controls, had lots of stories about problems. AUTO backfocus problems dont seem to be limited to any specific brand or model of camera.
that is why i am asking.
__________________
----------------sig-----------------
Re-learning everything all over again, one more time.
Marty Welk is offline   Reply With Quote
Old December 20th, 2009, 12:11 PM   #7
Major Player
 
Join Date: Apr 2008
Location: Malibu, CA
Posts: 480
I'm not sure if your problem is similar to the original back focus problems that the early EX1 cameras had/have with ND filters but here is a link to a solutions page on Adam Wilt's website that was posted almost 2 years ago but should still be relevant.

ProVideo Coalition.com: Camera Log by Adam Wilt | Founder | Pro Cameras, HDV Camera, HD Camera, Sony, Panasonic, JVC, RED, Video Camera Reviews

Most of the pertinent information is on page 2 of the article including the secret handshake to get the hidden maintenance menu to display. I performed this operation once back then and it's kept the back focus in perfect harmony with or without the internal ND's engaged since then. Having the newest firmware also seems to help the issue as I'm told by Sony maintenance people.

The poster with the picture above has the right idea, but I would even eliminate the shrubs and any foreground objects as well as put the chart(s) on a blank neutral wall with no conflicting vertical or horizontal lines. As long as they are on the same focal plane as the charts it shouldn't be a problem though.
Bruce Schultz is offline   Reply With Quote
Old December 20th, 2009, 12:11 PM   #8
Trustee
 
Join Date: Jun 2004
Location: Denver, Colorado
Posts: 1,866
The focus scale is logarithmic, so the reason for doing the procedure at 10 feet is it puts the camera safely away from the minimum focus distance, and zeros the focus at the near end where the focus scale has more resolution.

Out near infinity, there are only just a few degrees of rotation of the focus ring separating 30 feet from infinity. That's a large range of distance to pack between the marks. At the close end of the scale, a few degrees of rotation corresponds to mere inches. That's why you want the back flange procedure to happen up closer, where there is finer resolution of the scale.

My own experience is that a brick wall 10 feet away from the camera is all you need, star charts are not even necessary, but do what makes you comfortable.
Tom Roper is offline   Reply With Quote
Old December 20th, 2009, 12:38 PM   #9
Major Player
 
Join Date: Mar 2008
Location: All over, USA
Posts: 512
Can anyone verify whether removing the lens on the EX-3 throws the backfocus out?

Having to do a backfocus everytime I switch from the W/A to the standard is a big pain when location shooting.
Ed Kukla is offline   Reply With Quote
Old December 20th, 2009, 12:49 PM   #10
Sponsor: Westside AV
 
Join Date: Dec 2008
Location: Mount Washington Valley, NH, USA
Posts: 1,365
Yes I have had to redo back focus on every change.

Sometimes my EX3 will forget BF on the first restart after setting BF, but then seems to hold it fine. I think the EX3 is supposed to remember the lens ser# and the settings for each compatible lens. There may be a setting for this, I have a vague memory of something like that in the manual.
Olof Ekbergh is offline   Reply With Quote
Old April 13th, 2010, 05:04 AM   #11
Regular Crew
 
Join Date: Jul 2004
Location: Berlin, Germany
Posts: 169
Sorry for highjacking this thread, but its related.

I woke up in this thread that maybe I should check my backfocus from time to time. I always use full manual focus and film most times at Z0, full width, with Sonys WA VCL-0877, using zooming in-zooming out to find best focus in distance.

My questions are:
How do I check if backfocus is ok, without doing a flange focus adjust? If I don't need one I try to avoid entering the service menu of my EX1R and doing something, which I do not understand fully.
I can check the focus on a 50'' Kuro Plasma, but it is very difficult to judge at full width end (filming out of my window against roofs/houses/trees in 100 m distance), if the sharpness is really 100% or maybe 80-90% only. Probably I could not judge this out-of-focus without having the mouseover controll. Can I check against a Siemens star indoor at 3 m/10 foot distance at Z0 and if it looks there 100% sharp, then it will be 100% even at far distances of 200-400m?

Do I have to do a flange focus adjust for using the Sony WA VCL-0877, which is zoom through?

Thanks for any hint,
Markus
Markus Klatt is offline   Reply With Quote
Old April 13th, 2010, 08:42 AM   #12
Major Player
 
Join Date: Feb 2008
Location: Cardiff, Wales, UK
Posts: 410
Once your back focus is ok then there is no alteration needed for the Sony W/A adaptor - I use one without problems.
Bruce Rawlings is offline   Reply With Quote
Old April 13th, 2010, 08:56 AM   #13
Regular Crew
 
Join Date: Aug 2009
Location: Buenos Aires, Argentina
Posts: 73
Markus:

Record, max zoom in, focus, max zoom out, stay there for a moment and then slowly move your focus ring towards one end. Repeat procedure doing this towards the other end. Check your footage on a 1080p display, such as PC monitor. It should be fairly easy, using a Siemens Star, to check if it's correctly focused or not.

As said, with me doing it at 3 meters worked, I even ran several tests to confirm it... but yesterday I checked my backfocus and it was off again... ... ... =/ Any insight on this? I remember someone stated in one of the big backfocus threads that he had to repeat the procedure several times as well, but I still don't get why.

EDIT: anybody has the siemens star pdf around? I can't find one on the web and I'm planning to use more stars this time... thanks.

EDIT2: found it. http://dsclabs.com/free_charts.htm

Last edited by Ivan Gomez Villafane; April 13th, 2010 at 06:46 PM.
Ivan Gomez Villafane is offline   Reply With Quote
Old April 13th, 2010, 12:17 PM   #14
Major Player
 
Join Date: Jun 2006
Location: San Diego, CA
Posts: 203
Quote:
Originally Posted by Markus Klatt View Post
Sorry for highjacking this thread, but its related.
My questions are:
How do I check if backfocus is ok, without doing a flange focus adjust?
Can I check against a Siemens star indoor at 3 m/10 foot distance at Z0 and if it looks there 100% sharp, then it will be 100% even at far distances of 200-400m?
Markus -

This advice is for the EX1R only. My EX1 PUSH AF was worthless. On my EX1R it is dead accurate. EX1/EX3/EX1R are all different animals with different requirements. My EX1R came out of the box with the back focus wrong.

Because you have an EX1R, you can test the back focus with a star chart at 10 feet on a smooth, plain wall or photo backdrop and the PUSH AF (momentary auto focus) button. Leave the WA VCL-0877 off.

1 Connect you EX1R to your big monitor. Set the Focus Ring forward to AF/MF and the FOCUS switch forward to Manual. Set IRIS switch forward to Manual and the Iris wide open. Set the Macro switch forward to Off. Setup and light the star chart.
2 Adjust the lighting for wide open iris. Even slight underexposure is OK. Don't let the lens stop down. This is important for an accurate check.
3 Zoom in to Z99 on the star target. Center the target in the finder center marks. Manually focus on the star watching the big monitor.
4 Now let's test your PUSH AF system. With the best focus you can achieve manually, watch the monitor while you press the PUSH AF button.

If the focus doesn't change, you and the PUSH AF are both working correctly. If the focus gets softer, my EX1R is an anomaly and you don't have to read any further. If the focus gets sharper, well ... practice more.

5 If you are still reading, the PUSH AF must be as good or better than your manual focus zoomed in. Great. Now zoom back to Z0. Watch the monitor carefully while you press PUSH AF.

If the focus doesn't change this time, the back focus is correct. If the image gets sharper, your back focus is off. Time to go into the service menu. If the image gets softer, the background is too busy (reread the part above about a smooth, plain wall) or your PUSH AF is whacked.

You can easily repeat this sequence several times to see that you get consistent results.

Then check with the WA VCL-0877. The chart will be smaller and softer with the 877, but the image shouldn't get sharper when you press PUSH AF.

There is a legend floating around the web that you have to perform the Auto FlangeBack adjustment three times, one for each filter wheel setting. According to Sony Tech Support, there is only one FlangeBack memory buffer on the EX1 and EX1R so only one filter wheel position needs to be set.
George Strother is offline   Reply With Quote
Old April 13th, 2010, 12:32 PM   #15
Trustee
 
Join Date: Dec 2003
Location: Malvern UK
Posts: 1,931
I find that the EX auto flange back adjustment works better with the back focus chart supplied with Doug Jensens book than some of the others I have tried. Might be because it is higher contrast.
Simon Wyndham is offline   Reply
Reply

DV Info Net refers all where-to-buy and where-to-rent questions exclusively to these trusted full line dealers and rental houses...

Professional Video
(800) 833-4801
Portland, OR

B&H Photo Video
(866) 521-7381
New York, NY

Z.G.C.
(973) 335-4460
Mountain Lakes, NJ

Abel Cine Tech
(888) 700-4416
N.Y. NY & L.A. CA

Precision Camera
(800) 677-1023
Austin, TX

DV Info Net also encourages you to support local businesses and buy from an authorized dealer in your neighborhood.
  You are here: DV Info Net > Sony XAVC / XDCAM / NXCAM / AVCHD / HDV / DV Camera Systems > Sony XDCAM EX Pro Handhelds

Thread Tools Search this Thread
Search this Thread:

Advanced Search

 



Google
 

All times are GMT -6. The time now is 04:12 PM.


DV Info Net -- Real Names, Real People, Real Info!
1998-2017 The Digital Video Information Network