Canon G5 camera and camera matching

[pailhead]

Sorry if im posting this in the wrong place.

 

I've recently bought a this camera, and yesterday i tried shooting a scene to practice camera matching in max. I've set up some items on a table, measured a wodden box like thing as accuratly as i could. Then i built that same box in max, made 5 tracking points, made a camera and set its focal lenght to the lenght i read in the image's properties, it said 7.19mm which seemed kinda odd compared to the result in max, maxs FOV seems much wider than the photos. Anyway when i tried matching with "freeze FOV" turned on, the results were pretty bad, it totally neglected some point positions and i couldnt get the error below 65.

 

Then i made a couple more points, so i had 7 total, when it finally matched right max's camera said that focal lenght is about 37mm.

 

So i concluded that these two things are not the same, but how can i use that focal lenght information on the picture?

[William Alexander]

A focal length changes depending upon zoom and wide angle aspects. The default or stock measure maybe 7mm but between the optical [physical] and digital enhancements it gets all over the place.

 

Here is a site that might help. There is also at least one other thread on CGA about this.

 

www.outsight.com/hyperfocal.html#digital

 

rgrds

WDA

[alexg]

Hi

 

Here's a link to previous discussion of the same problem in this forum.

http://www.cgarchitect.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=1;t=000739

 

Cheers

[pailhead]

Thanks a lot and sorry for double posting about the same problem.

[Eric]

I'm not sure what kind of distance you're shooting from, but I assume it's pretty close. At the wider field of view, zoomed all the way out, there is a considerable amount of barrell distortion. That causes the image to distort quite a bit. Could this be some cause for your calculation errors? I also have a G5. Love the camera, by the way! You might try standing a bit further back from your objects, and zoom in slightly. This will cut down on some of the distortion.