infinity mark is off at DVinfo.net

Leonard Levy · March 11th, 2008, 01:28 PM

I've notice that my EX lens (when I have it slipped into manual mode) seems to roll right through the real infinity focus point well before I reach the end of the focus barrel travel or even the infinity mark on the barrel.

Anyone else have the same experience? Is it normal. It would be a big problem except the color peaking is so good i can clearly see where I need to be.

Bill Ravens · March 11th, 2008, 01:33 PM

It's normal. The mechanical stop goes beyond infinity to allow for temperature changes in the environment...the focus shifts when the temperature changes.

Eric Pascarelli · March 11th, 2008, 01:35 PM

Sounds like a backfocus issue.

Though I don't have too much faith in those lens markings - they seem like an approximation to me. Otherwise they'd be more committal and have withness marks like a Panavision lens rather than nebulous numerals.

Alister Chapman · March 11th, 2008, 02:13 PM

Bill is correct. All true pro lenses go through infinity to allow for temperature changes and the use of adapter lenses. It is not a fault.

Leonard Levy · March 11th, 2008, 02:26 PM

Thanks, that's what was wondering.
I'm used to it a teeny bit but this seems more noticeable though. No back focus problem though as far as i have seen.

Eric Pascarelli · March 11th, 2008, 03:37 PM

Quote:

Originally Posted by Leonard Levy

... seems to roll right through the real infinity focus point well before I reach the end of the focus barrel travel or even the infinity mark on the barrel...

Leonard,

Bill and Alister are correct that all pro lenses, including still camera lenses go a bit past infinity to allow for any slight mechanical variations - however the problem you descibe is that the lens is focused at infinity before reaching the mark - not that the lens can go past the mark.

So that's why I think it's a (slight) backfocus issue.

Leonard Levy · March 15th, 2008, 01:17 PM

Well I've discovered what my problem is . My backfocus and my infinity mark are exactly where I would expect with no filter in plsce. As soon as I roll in an ND filter my back focus completely goes to hell and my infinity focus rolls in around 30'. Very very bad news. I don't think the back focus adjustment would fix it because its OK without filter.

. Didn't notice the back focus problem till I looked on a big monitor.

Beware out there. It goes back to Sony on monday. Perhaps there is a software fix for this.

Also I've discovered lots of CA when I am fully zoomed in. very distressing.

Lenny

Bob Grant · March 15th, 2008, 03:32 PM

Perhaps somebody could try doing the backfocus calibration procedure for each of the ND filter settings. It's possible the camera stores a different set of values for each position of the ND filter wheel.

I'd try this myself but I suspect I don't have enough light to light up a back focus chart with the NDs engaged.

Graeme Fullick · March 15th, 2008, 04:29 PM

Bob,

You could use the back focus chart outdoors. Its pretty sunny today!

Pavlos Symeon · March 15th, 2008, 04:48 PM

Both of my EX1s are going back to UK with backfocus and slight vignetting problems.

March 11th, 2008, 01:28 PM	#1
Leonard Levy Trustee Join Date: Feb 2006 Location: USA Posts: 1,684	infinity mark is off I've notice that my EX lens (when I have it slipped into manual mode) seems to roll right through the real infinity focus point well before I reach the end of the focus barrel travel or even the infinity mark on the barrel. Anyone else have the same experience? Is it normal. It would be a big problem except the color peaking is so good i can clearly see where I need to be.

March 11th, 2008, 02:13 PM	#4
Alister Chapman Inner Circle Join Date: Dec 2005 Location: Bracknell, Berkshire, UK Posts: 4,957	Bill is correct. All true pro lenses go through infinity to allow for temperature changes and the use of adapter lenses. It is not a fault. __________________ Alister Chapman, Film-Maker/Stormchaser http://www.xdcam-user.com/alisters-blog/ My XDCAM site and blog. http://www.hurricane-rig.com

March 15th, 2008, 04:29 PM	#9
Graeme Fullick Major Player Join Date: Mar 2005 Location: Newcastle, Australia Posts: 337	Bob, You could use the back focus chart outdoors. Its pretty sunny today! __________________ Graeme

March 11th, 2008, 01:33 PM	#2
Bill Ravens Join Date: Nov 2001 Location: santa fe, nm Posts: 3,264 Images: 10	It's normal. The mechanical stop goes beyond infinity to allow for temperature changes in the environment...the focus shifts when the temperature changes.

March 11th, 2008, 01:35 PM	#3
Eric Pascarelli Major Player Join Date: Nov 2007 Location: Los Angeles, CA Posts: 498	Sounds like a backfocus issue. Though I don't have too much faith in those lens markings - they seem like an approximation to me. Otherwise they'd be more committal and have withness marks like a Panavision lens rather than nebulous numerals.

March 11th, 2008, 02:26 PM	#5
Leonard Levy Trustee Join Date: Feb 2006 Location: USA Posts: 1,684	Thanks, that's what was wondering. I'm used to it a teeny bit but this seems more noticeable though. No back focus problem though as far as i have seen.

March 15th, 2008, 01:17 PM	#7
Leonard Levy Trustee Join Date: Feb 2006 Location: USA Posts: 1,684	Well I've discovered what my problem is . My backfocus and my infinity mark are exactly where I would expect with no filter in plsce. As soon as I roll in an ND filter my back focus completely goes to hell and my infinity focus rolls in around 30'. Very very bad news. I don't think the back focus adjustment would fix it because its OK without filter. . Didn't notice the back focus problem till I looked on a big monitor. Beware out there. It goes back to Sony on monday. Perhaps there is a software fix for this. Also I've discovered lots of CA when I am fully zoomed in. very distressing. Lenny

March 15th, 2008, 03:32 PM	#8
Bob Grant Trustee Join Date: Nov 2005 Location: Sydney Australia Posts: 1,570	Perhaps somebody could try doing the backfocus calibration procedure for each of the ND filter settings. It's possible the camera stores a different set of values for each position of the ND filter wheel. I'd try this myself but I suspect I don't have enough light to light up a back focus chart with the NDs engaged.

March 15th, 2008, 04:48 PM	#10
Pavlos Symeon Regular Crew Join Date: Nov 2007 Location: Athens, Greece Posts: 48	Both of my EX1s are going back to UK with backfocus and slight vignetting problems.