flange back problems with XF300

[Reinhard Kungel]

Shure I did. But unfortunatelly they couldn´t reproduce the problem.

[Alex Footman]

I know I'm jumping in a little late here, but this revelation about parfocal problems really dampens my enthusiasm for the XF300. In my work I need to trust that focus will stay sharp, and given the extreme lighting situations where I am I routinely shoot fully open and as closed down as possible plus ND filters.

Given that I won't be able to trust manual focus to stay sharp through the zoom range, how have you found the autofocus? Is it useable or does it hunt? I still use an XHA1 and AF mode is useless because of hunting issues.

[Reinhard Kungel]

Hi Alex,

I´m one of these old-fashioned guys who only use manual focus. I never trust in automatic, never. But as you say: if theres is no guarantee in manual focus, than it becomes difficult.

Reinhard

[Robert Turchick]

The AF really depends on the situation. As with all cameras, light makes a huge difference. I have mostly been using mine in full daylight or controlled lighting shoots. I shot a series of auditions for a tv show and just for grins decided to try the face detection AF mode. Not a critical shoot so wasnt concerned if it messed up. To my amazement, it never missed. I mean not once! I then used it for a greenscreen TelePrompTer shoot where the actor would be walking around a bit. Dead perfect! This is the real deal and not a gimmick! Not saying I'd use it all the time but for certain types of shoots, it makes life insanely easy! On a recent shoot, my XF found itself flying on a glidecam 4000 and I suggested to the operator to leave it in face detection AF mode. Worked great!
Since discovering how well it does work, the only times the AF had a problem were in unlit indoors situations (chasing my kids around the house) and one shoot where the background was too bright (used the backlight feature and it helped) So in extreme lighting conditions, use manual. But give the face detection mode a try (I use the instant mode) and as long as the white box is around your talent, you are perfectly focused!

[Doug Jensen]

Robert, I agree 100% with your assessment of face detection. It's not for everyday use, but it really does work in the right situation.

[James Miller]

Doesn't adding a nd behind the rear element change the lens characteristics? I know if I use anything thicker than a gelatine filter behind the lens the lenses does not function as parafocal.

Are all these issues found after ND's are flicked on? Are the ND's too thick?

[Alex Footman]

Robert,

Thank you for testing this out and posting about it. I have no shame in declaring that this feature will make my life easier. Given the situations I shoot in (no preparation, managing sound levels and ad-libbing interview questions on the spot) trusting in auto-focus would take a big load off my mind. Starting to take this camera seriously, especially if there's a good telephoto adapter on the market. Also, a trustworthy AF takes a lot of the sting out of the single-ring configuration.

[Brian Drysdale]

In cameras with built in ND filters, there is always a piece of optical glass in the image path otherwise you will get back focus problems. The rear ND filters have to be manufactured to a tight specification to avoid thickness variations, although this doesn't mean that one or more sub standard NDs got into the system.

This would be best tested by shooting with a fully open aperture and testing each ND filter for back focus variations. You'll need to control the lighting level for the correct exposure,

If there appears to be a variation between ND filters I'd send the camera back to Canon.

[James Miller]

Brian, yes sorry I didn't account for the clear optics in the image path, still if it not a problem before switching to the inbuilt ND's the ND's are at fault. You would have thought this would have been tested when the camera went in for service.

I had a bad copy of a Canon 2.8 70-200mm IS that had slight play (about 1mm) on the zoom ring not the focus ring, and would shift a pin sharp image out of true just by rocking the play.

I wonder if you are finding any slack on these lenses?

[Alister Chapman]

I've experienced similar problems on my EX cameras after bumpy journeys or shipping, clearly rough handling and shocks can upset the focus tracking. With the EX it's just a matter of running the back focus routine in the service menu to restore accurate focus tracking.