focus distance

[Sam Diego]

Hi,
I just received my GL2 and found it a wonderful camcorder. I already shoot 4 mini-dv of my kids sports. My question is does the focal length make a difference in the clarity of the video images? I was shooting a basketball game and had the up close video that looked super but when in wide angle the images suffered. The video lacked sharpness and were somewhat blurrily. I was using a tripod in all cases.

Has anyone experience this before or has an explaination?

Thanks for the great forum!

[Ken Tanaka]

Hello Sam,
Hard to say what went wrong but something was definitely not right. Do you recall what mode you were using (green box, Av, Tv, et.al) and whether or not you were using manual or auto focus?

[Sam Diego]

I was using frame mode and auto focus. I played back both videos through the GL2 to my Sony TV. I am somewhat worried as I noticed a great deal of clarity degradtion. I haven't set the white balance yet as I am just getting started to learn the GL2.

However, I am now thinking that I shot the first video (with normal mode and longer focal length) and the second in frame mode and wide angle.

Thanks,

[Ken Tanaka]

Hmmm. Well here are a couple of off-the-cuff tips.

Try to manually set white balance whenever in artifical lighting, especially the light typically found in gymnasiums and arenas. Use a preset (ex: tungsten, daylight) when appropriate. Try not to use auto white balance. It's not faulty but it's inherently flakey on all video cameras.

It is possible that your GL2's lens' back focus is out of calibration. "Back focus" is a zoom lens' ability to maintain a set focus throughout its zoom range. This should be determined before proceeding, since it may save you a great deal of time and frustration.

To test this possibility do the following.

1. Set the camera on a tripod (very important).

2. Set the camera in Manual mode and adjust your eposure (iris, shutter) appropriately.

3. Set the lens for Manual Focus.

4. Select a well-lit stationary subject perhaps 30-40 feet away. The ideal subject will have high contrast to make this task easier.

5. Zoom into the subject as close as possible. Use the focus ring to get the best focus possible. (You can also press the Auto-Focus button to let the camera pull focus for you, but be sure to set it back to Manual Focus before proceeding.)

6. Shoot 10 sec of footage.

7. Zoom out to the widest setting taking care not to change the lens' focus setting or the camera's exposure settings in any way.

8. Now shoot 10 more secs. of footage.

9. Review your footage on a professional monitor or a high-quality tv. If the main subject in the wide shot appears to be out of focus with respect to the close shot the camera needs to be sent to Canon service for back-focus calibration. (The GL2's back-focus cannot be owner-calibrated.)

If this exercise shows consistent focus then something else, probably user-related <g>, is to blame.

Let us know your results.

[Sam Diego]

Thank you, Ken!
I will try your suggestion and will provide some feed back within a few days.

[Barry Goyette]

Sam

Just want to throw out the old adage about DV, which is that in general, the DV format looks somewhat less sharp in wide shots than it does when zoomed in. This is a limitation of the format, and is one that can be made worse by use of the frame mode, which lowers vertical resolution by 25%. I've found that by increasing the in-camera sharpness control on wide shots that you can more closely match the apparent sharpness of closer shots.

Without seeing your footage, it's hard to tell whether this is your problem or not, and in fact the gl2, I feel, is much better in wide shots than other members of the Canon dv family, but it's something to consider.

Barry

[Steve Nunez]

Barry-

I think you're incorrect about the 25% drop in vertical resolution in frame mode. On page 50 of the GL2 user's manual it states, " ... the vertical resolution of the image is improved by 1.5X "

[Barry Goyette]

Steve

Canon's manual, while truthful, is misleading on this point.

The 1.5x increase refers to a comparison of a still image taken from an interlaced field and a frame mode field. When you combine two interlaced fields into a single frame the interlaced resolution is double that of a single field. Frame mode fields are identical, thus when combined into a frame, there is no net increase in resolution...thus a frame of "frame mode" footage has 25% less vertical resolution.

The effect is apparent to the eye when switching between modes on normal subject matter. I've photographed several resolution charts with a variety of canon cameras in both frame and interlaced modes, and the loss of vertical resolution in frame mode has been confirmed in every case. The the gl2, due to it's higher head resolution, exhibits less of a loss than the lower resolution xl1s.

Barry

[Steve Nunez]

Great explanation....and yes i agree- very misleading....but the way you've explained, makes the confusion totally understandable- thanks for the clarification.