As Thomas Edison once said, "Genius is 1% inspiration and 99% perspiration". Focus takes practice and lots of it. As you've discovered, turning the focus ring clockwise moves the focus point closer to the camera and turning it counter-clockwise moves the focus point farther away. Once you've gotten that so into your head that you don't even have to think about it anymore you'll be operating much more smoothly. Practice before the show starts; follow other techies as they move around the stage while setting up.

Zooming in to get clear focus is usually a good idea as you can see finer details and poor focus is easier to see. If you have a true zoom lens then you shouldn't have to adjust focus while zooming as long as the subject remains at a constant distance. If that lens is made for that manual focus camera then most likely it is a true zoom. Unfortunately, many lens manufacturers will build cheaper "vari-focal" lenses for autofocus cameras which are not true zooms. The difference is that true zooms maintain correct focus when changing focal length but vari-focals don't. Of course, the reason for making vari-focal lenses is because they're cheaper to manufacture, and on an autofocus camera it's not a big problem since the camera adjusts the focus for you. However, putting a vari-focal lens on a manual camera can cause headaches because you'll loose focus when you zoom in or out. It should be easy to tell what type you have though. Zoom in as far as you can on a distant, high contrast object and focus sharply. Then zoom all the way out without touching the focus ring. If the object is still as sharp as possible without refocusing then you have a true zoom. If you have to adjust the focus after zooming out then you have a vari-focal lens.

What if you find that your lens is vari-focal? Well, it's not a disaster, but you do have to keep it in mind when zooming and be prepared to adjust focus every time.

Techniques? Learn the show in advance if possible. Be prepared in advance for changes and be ready to adjust focus immediately (or sooner if possible). If in doubt, zoom out. Lack of perfect focus is less noticeable on a smaller subject than on a larger one. Also, the depth of field will be greater when zoomed out so you have a better change of having the subject in focus.

Practice, practice, practice. ;)

The downside is of course until you have practiced any manual adjustment of focus especially when zooming is going to look like #$%%#( because until you have practiced a lot the typical user will over correct and the image for a second or two will be badly out of foucs resulting in a handful of frames that will be much worse that the auto focus would have delivered. :-)

You are right BillyBoy; unfortuantaley makers of high end lenses don't offer an autofocus option.

The problem with a lot of camcorders these days is that the focus ring does not directly connect to the lens, but rather sends a series of pulses to the focus mechanism, which then directs the focus motor. The result is that the ring cannot be calibrated to show distance. In your case, however, I would assume that your Sony model has an expensive lens with a manual focus lens calibrated for distance.

The Hollywood crowd traditionally has had a person, called a "focus puller" or something like that, ride along with the (film) camera operator. They run through the shot and make notes on a piece of tape attached to the focus ring. Then when they do an actual "take," the focus puller's job is to constantly adjust the focus by using those marks he made earlier. Makes for a full-employment Hollywood industry.

Thanks for your answers.

The backfocus is correctly adjusted and everything works fine when zooming, I was just asking...
And the focus is not servo-controled. Its an old studio camera, but fully professional.

Well, I got it: practice, practice and a lot of practice XD

Thanks !

THe DXC D30 isn't THAT old. It hit the market in 1996, just 7 years ago. It was replaced by the D35WS, which in turn was just replaced by the DXC D50 we bought last week. Sony has a mission: recapture market share. I paid 19K CAD @ for the D30 heads in 1997 and 18K CAD for the D50WS in 2003.

That Fujinon lens has to have a zoom servo, mate. Look underneath for a little lever labelled "servo/manual" within reach of your thumb. I haven't seen a manual only lens for that type of camera since the late 70s.

Peter