Chip position
 

Aimed more at the techie set:

Does anyone know how far in the GL2 body the CCD is situated? I'm assuming it's a fixed position (i.e. not part of the zoom mechanics) but I can't find any specs that mention it.

I'm working on a motion-control system for use in animation and I'd ideally like to have it operate around the camera's nodal point. I'd take that to be where it backfocuses, rather than trying to accommodate the three actual light-sensitive surfaces (as I understand the process).

Any input would be appreciated. Thanks in advance!


-j

Jay,
Short answer: no, I don't know exactly where it's positioned in the camera. (Yes, it is in a fixed position in the camera, not the lens.)

BUT, last year I recall a lengthy thread somewhere here that concerned exactly the same subject. Someone needed to know the CCD's exact position in order to do an animation. I'm completely in the dark on why this is important (as well as blissfully ignorant on animation) but I'll bet that a Search on "animation" will eventually lead you to that thread. (I do not recall whether the thread concerned the GL2 or an XL1.)

Good luck!

i thought that in animation/motion control the nodal point changes depending on your closest object to lens and your furthest object in the shot ???

on set - i just see them making adjustment sometimes when shots are changed and when i ask what's taking so long they say they are adjusting NODAL

You might try contact Canon, you will hve to work you way past the phone answering service people to find the real technical people, but you may find someone at Canaon USA who can answer the question.

A service manual might provide answers for this. Canon should
be able to get you that I'd say.

I haven't been able to find that old thread. I'll try Canon directly. Thanks for the help, guys.

If I find out I'll post it for future reference.


-j

If you know the "normal" lens of the camera then you know the distance. The normal lens on my film camera is 50mm so the distance is 50mm from the object lens.

Focal length is the distance, in mm, from the Rear Nodal Plane to the Principal Focal Point, when the lens is focused to infinity. In many lenses the rear nodal plane is determined mathematically, and it is not easy to physically measure the distance.

Look on the top of the camera, near the lens mount for a circle with a line through it. The line should be parallel to the front of the lens. This marking indicates the location of the chip (Principal Focal Point). Canon marks many of their 35mm and digital cameras with this symbol. I'm not sure if the GL1/GL2 has this symbol or not.

It's got the symbol, but it appears right at the end of the lens housing. In full, the info reads:

CANON VIDEO LENS 20x ZOOM 4.2-84mm 1:1.6-2.9 L IS @ 58

@ = funny circle with a line through it.

Nothing useful there, and no parallel line anywhere. I'm guessing that since you can't remove the GL2 lens (unlike with the still cameras) they don't feel it's necessary info.

On the mathematical approach: I'm not so good with wrapping my head around focal lengths just yet - is there a way I might approximate the chip position by setting the camera to min/max zoom, min/max focus and measuring where it focuses in front of the lens?

Thanks again for all the help.


-j

No, the symbol would be on the camera body (not the lens). The symbol on the end of the lens (circle with a diagonal line through the circle) is indicating the filter size in mm. In your case the lens uses a 58mm filter.

The symbol your looking for would be just behind the lens, where it attaches to the camera, with a horizontal line parallel to the front of the lens.

Sorry - I didn't explain myself very well. I looked all over the camera and there's no line or symbol.

Canon has already responded to me but unfortunately only to say:

"...the exact position of the camcorder's internal components
is not published information. We regret this inconvenience."

Based on the lens, I can make a pretty good position measurement on two of the three axis. The third I'll just have to make a reasonable guess at (like just slightly forward of the ND button).

Thanks, everybody.


-j