Focus problems at DVinfo.net

Simon Glidewell · July 6th, 2009, 04:27 PM

In addition to the noise problems I had recently with the XL-H1A I've now noticed that certain wide angle shots appear soft (whilst viewing in FCP version 5.1.4 after capture). It could be a back focus issue but it doesn't happen on all wide angle shots which one would expect if it was a back focus problem; yesterday I took two similar full wide angle views in the country; one was soft the other was very sharp, and both were very sharp in the camera's viewfinder. The problem is not evident in CU or MCU which are both very sharp. The viewfinder diopter is adjusted correctly for my eyesight and I am very careful about checking focus before a shot. The problem is most obvious when shooting landscapes and vegetation (trees, grass, etc) at full wide angle. I am shooting at 1080/25p in cine 2 gamma mode. Also the viewfinder frame seems narrower than the lens frame so the 16:9 aspect ratio matte box appears in wide angle captured footage but not in the viewfinder. Any advice or suggestions regarding the above would be most welcome!

Cheers
Simon

Doug Bennett · July 24th, 2009, 09:57 AM

You can't judge critical focus of a wide shot in the EVF - but at full wide you have a lot of depth of field. Could it be a diffraction problem caused by too small an aperture?

Chris Soucy · July 24th, 2009, 10:17 PM

I'm an XH A1 man, so this may not translate to a XL H.

It's possible on an A1 to push the lens past infinity to infinity+, at least in manual, can't say for Auto as I rarely use it.

Infinity+ is definately less sharp than infinity.

Could be the problem, if the XL H can do the same thing.

Can't offer any advice on the matte box tho'.

CS

Tony Davies-Patrick · July 28th, 2009, 10:23 AM

Quote:

Originally Posted by Chris Soucy

...It's possible on an A1 to push the lens past infinity to infinity+, at least in manual, can't say for Auto as I rarely use it.

Infinity+ is definately less sharp than infinity.

Could be the problem, if the XL H can do the same thing.

CS

ALL lenses focus to just beyond the infinity mark. This is to allow for slight expansion and contraction of glass elements during extreme temperature variations.

Regarding wide shots. Are you using the 20X or 6X and which aperture/iris settings are you most often using?

On the subject of back-focus. Have you re-adjusted the back-focus lately? It might be worth doing quick lens adjustment using the back-focus control.

If all the other footage taken at various telephoto settings are sharp, then I doubt that it is actually a back focus issue.

July 6th, 2009, 04:27 PM	#1
Simon Glidewell Regular Crew Join Date: Mar 2009 Location: Manosque (France) Posts: 94	Focus problems In addition to the noise problems I had recently with the XL-H1A I've now noticed that certain wide angle shots appear soft (whilst viewing in FCP version 5.1.4 after capture). It could be a back focus issue but it doesn't happen on all wide angle shots which one would expect if it was a back focus problem; yesterday I took two similar full wide angle views in the country; one was soft the other was very sharp, and both were very sharp in the camera's viewfinder. The problem is not evident in CU or MCU which are both very sharp. The viewfinder diopter is adjusted correctly for my eyesight and I am very careful about checking focus before a shot. The problem is most obvious when shooting landscapes and vegetation (trees, grass, etc) at full wide angle. I am shooting at 1080/25p in cine 2 gamma mode. Also the viewfinder frame seems narrower than the lens frame so the 16:9 aspect ratio matte box appears in wide angle captured footage but not in the viewfinder. Any advice or suggestions regarding the above would be most welcome! Cheers Simon

July 24th, 2009, 10:17 PM	#3
Chris Soucy Inner Circle Join Date: Feb 2007 Location: Fairfield, Dunedin, New Zealand Posts: 3,691 Images: 18	Hi............ I'm an XH A1 man, so this may not translate to a XL H. It's possible on an A1 to push the lens past infinity to infinity+, at least in manual, can't say for Auto as I rarely use it. Infinity+ is definately less sharp than infinity. Could be the problem, if the XL H can do the same thing. Can't offer any advice on the matte box tho'. CS

July 24th, 2009, 09:57 AM	#2
Doug Bennett Major Player Join Date: Oct 2004 Location: NYC Posts: 260	You can't judge critical focus of a wide shot in the EVF - but at full wide you have a lot of depth of field. Could it be a diffraction problem caused by too small an aperture?