Focus Issues at a Soccer Match at DVinfo.net

Julian Fox · October 30th, 2006, 04:23 PM

I recently filmed a semi-pro soccer match from the back of a stand using the PAL XL2. It was a bright and sunny day, although in the second half in particular the sun did hide behind cloud cover every now and then.

The power dial was on TV with the sports preset, I used 50i, shutter speed 1/120, iris 5.6, had -3db gain for the first half, and 0db for the second half, and used the ND filter ring. I used the outdoor white balance.

On the whole the result was pleasing. However ...

Knowing the problems autofocus can have with a number of players in view at any one time at different distances from the camera, I tried manually focusing on the furthest point (corner flag), and for part of the game the centre spot. Either way I was unable to keep every part of the pitch in focus as I was zooming in and out around the pitch following play. I presume this is a depth of field issue.

What could I have done differently?

Richard Hunter · October 30th, 2006, 06:35 PM

Hi Julian. A couple of obvious suggestions.

First, if you were in Tv mode at 1/120s, the iris would not be fixed at F5.6 but would fluctuate according to the subject and lighting conditions. This means that your depth of field would also vary. You could try going to Av mode at F8, or even fully manual, both of which would allow you more control over the depth of field. However I doubt whether you would be able to maintain focus when zooming in over the zoom range of the XL2 just by relying on depth of field alone.

The other suggestion is to keep adjusting the focus as you move the camera around, especially when you zoom in. With practice, you get to know which direction to turn the focus ring for nearer or farther subjects, and how much/how fast to turn it to maintain focus.

Richard

Julian Fox · October 31st, 2006, 03:29 PM

Thanks Richard. Think I'll try the AV mode at f8 suggestion next time out. I think it will be tough to continually adjust the manual focus whilst chasing the play around the field so the least I have to do that the better.

Mind you, the next game coming up will be a floodlit evening game. Do you think the same principal applies but simply use 3db gain?

Richard Hunter · November 1st, 2006, 03:36 AM

Hi Julian. I understand why you don't want to keep adjusting focus over such a long period. The problem is that the XL2 lens has such a long reach, the depth of field is pretty limited when you are zoomed in. And if you try to get more depth of field by closing down the lens to f11 or smaller, you then run into diffraction problems and the picture quality suffers. If you don't want to follow focus all the time, I would try not to zoom in too far, or at least look out for focus drifting off as you zoom in and then adjust as necessary. As long as you're not zooming all the time, that should be less workload for you.

For shooting under floodlights, I would try to go fully manual and use gain as required to maintain the aperture at f8 or so. I have been caught out in the past using Av mode in artificial light, and my footage suffered from a colour shift whenever the brightness of the image changed and the camera selected a different shutter speed. I believe this only happens with certain types of lights, but I've no idea if this includes floodlights or not. Anyway, something to be aware of.

Richard

October 30th, 2006, 04:23 PM	#1
Julian Fox New Boot Join Date: Jul 2006 Location: Ashford, Middlesex (England) Posts: 22	Focus Issues at a Soccer Match I recently filmed a semi-pro soccer match from the back of a stand using the PAL XL2. It was a bright and sunny day, although in the second half in particular the sun did hide behind cloud cover every now and then. The power dial was on TV with the sports preset, I used 50i, shutter speed 1/120, iris 5.6, had -3db gain for the first half, and 0db for the second half, and used the ND filter ring. I used the outdoor white balance. On the whole the result was pleasing. However ... Knowing the problems autofocus can have with a number of players in view at any one time at different distances from the camera, I tried manually focusing on the furthest point (corner flag), and for part of the game the centre spot. Either way I was unable to keep every part of the pitch in focus as I was zooming in and out around the pitch following play. I presume this is a depth of field issue. What could I have done differently?

October 31st, 2006, 03:29 PM	#3
Julian Fox New Boot Join Date: Jul 2006 Location: Ashford, Middlesex (England) Posts: 22	Focus Issues At Soccer Match Thanks Richard. Think I'll try the AV mode at f8 suggestion next time out. I think it will be tough to continually adjust the manual focus whilst chasing the play around the field so the least I have to do that the better. Mind you, the next game coming up will be a floodlit evening game. Do you think the same principal applies but simply use 3db gain?

October 30th, 2006, 06:35 PM	#2
Richard Hunter Trustee Join Date: Dec 2004 Location: Lipa City Batangas, Philippines Posts: 1,110	Hi Julian. A couple of obvious suggestions. First, if you were in Tv mode at 1/120s, the iris would not be fixed at F5.6 but would fluctuate according to the subject and lighting conditions. This means that your depth of field would also vary. You could try going to Av mode at F8, or even fully manual, both of which would allow you more control over the depth of field. However I doubt whether you would be able to maintain focus when zooming in over the zoom range of the XL2 just by relying on depth of field alone. The other suggestion is to keep adjusting the focus as you move the camera around, especially when you zoom in. With practice, you get to know which direction to turn the focus ring for nearer or farther subjects, and how much/how fast to turn it to maintain focus. Richard

November 1st, 2006, 03:36 AM	#4
Richard Hunter Trustee Join Date: Dec 2004 Location: Lipa City Batangas, Philippines Posts: 1,110	Hi Julian. I understand why you don't want to keep adjusting focus over such a long period. The problem is that the XL2 lens has such a long reach, the depth of field is pretty limited when you are zoomed in. And if you try to get more depth of field by closing down the lens to f11 or smaller, you then run into diffraction problems and the picture quality suffers. If you don't want to follow focus all the time, I would try not to zoom in too far, or at least look out for focus drifting off as you zoom in and then adjust as necessary. As long as you're not zooming all the time, that should be less workload for you. For shooting under floodlights, I would try to go fully manual and use gain as required to maintain the aperture at f8 or so. I have been caught out in the past using Av mode in artificial light, and my footage suffered from a colour shift whenever the brightness of the image changed and the camera selected a different shutter speed. I believe this only happens with certain types of lights, but I've no idea if this includes floodlights or not. Anyway, something to be aware of. Richard