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MSavagliani
11-07-2008, 05:44 PM
hi, I have a panasonic gs 400 with a ccd size of 1/4.7". I need to know my camera aperture in inches to do a matchmoving in maya. How do I figure that out? I don't know what this ccd value mean. Thanks

AroundTheFur
11-07-2008, 06:53 PM
The CCD measurement is the size of the sensor, the aperture is how open the shutter is and would only effect the amount of light going into the camera. The aperture would not have any effect on a camera track calculation as far as i know. What you want is the focal length, and on that camera according to Google, the zoom lens can go from min focal length 3.3 mm to max focal length 39.6 mm.

Hope that helps,
-S

vander
11-07-2008, 09:30 PM
You need to know the focal length and the Film Back (this is the CCD size in mm/inches of your digital camera - very difficulty to know, because they don't put this information in the manual), but if you don't have de Film Back, no problem, your software will do the job. Most important is the focal length, lens distortion, image aspect ratio and pixel aspect ratio.
The focal length you know, because is your camera.
The image and pixel aspect ratio the matchmove software will put to you (only verify if the numbers are correct).
To know the lens distortion you can shoot a chart with horizontal and vertical lines (a big chart) before shoot your scenes. With this chart you can correct the lens distortion in your matchmove software.

MSavagliani
11-08-2008, 12:34 AM
thank you guys for answering...I have this gnomon workshop dvd about matchmoving and the guy said that is really important to know the camera aperture to put in maya and the focal length...theres very few tutorials about the subject and its kind of hard to learn alone.
so knowing my film aspect ratio and my focal length am I good to go? how do I know pixel aspect ratio? To do a matchmoving its better not ro use the zoom? good lighting is also a must to tracking the data right? thank you

vander
11-08-2008, 02:11 AM
thank you guys for answering...I have this gnomon workshop dvd about matchmoving and the guy said that is really important to know the camera aperture to put in maya and the focal length...theres very few tutorials about the subject and its kind of hard to learn alone.
so knowing my film aspect ratio and my focal length am I good to go? how do I know pixel aspect ratio? To do a matchmoving its better not ro use the zoom? good lighting is also a must to tracking the data right? thank you

Ok... I don't know speak english very well, but I think that you will understand.

Commonly the images has this rules:

HD 1920 x 1080 - pixel aspect ratio 1x1 (square pixel) - image aspect ratio 1,78.
NTSC 720 x 486 - pixel aspect ratio 0,91 - image aspect ratio of 1,34.
PAL 720 x 576 - pixel aspect ratio 1,09 - image aspect ratio 1,37.

Zoom is a change of focal length when you are shooting a scene. If you know your initial focal length and your final focal length you can put this information in your matchmove software.

... but, Boujou, PFTrack, Syntheyes, Matchmover, etc.... can do the work without any extra information, in automatic mode (to easy scenes) - all this softwares detects automatically the image aspect ratio and pixel aspect ratio (if you know the correct film back / ccd size you can put it) - and don't forget the lens distortion parameter - without the correction of lens distortion is impossible to do the modeling of objects (builds, for example) after the matchmove.

Yes, good light is important, a scene without motion blur, without reflexion, without objects in movement, without noise, WITH paralaxe, but not ever we have perfect scenes (only in our dreams).

I recommend to you the book "matchmoving - the invisible art of camera tracking" - Tim Dobbert - It is an excellent book.

jhorsthuis
11-11-2008, 12:11 PM
I agree,

it's far too diffucult to find a good documentation on the exact size of various camera's ccd's.
I shot with the RED the other day, and knew the exact ccd size and lens (cos they have it documented precisely), and boujou (matchmoving) software worked better then ever. On previous shoots before I had to make it guess all the time on the focal lenght, and sometimes it just guessed wrongly.

There must be some documentation somewhere, or a handy tool that calculates ccd size for you, using lens info and angle info. (i'm thinking of something measuring the angle between left frame edge, nodal point, and right frame edge.) You'd only have to do that once with a camera and know the ccd size forever.

How about a big arc with degrees on and a midpoint for the nodal point of camera. You film the arc (with degrees written on the inside) and can see exactly what the field of view is.

lazzhar
11-11-2008, 12:55 PM
This guy (http://www.earlyworm.org/search/label/rebel%20cg)seems answering your request jhorsthuis.

Redsand1080
11-13-2008, 04:23 AM
I have this gnomon workshop dvd about matchmoving and the guy said that is really important to know the camera aperture to put in maya and the focal length




I think i can shed some light on this for you. The 'aperture' can mean a few things:

1) The opening in your camera (iris) that controls the apertures diameter which in turn regulates how much light enters in to hit the film or digital sensor.

2) It can refer to the 'film aspect ratio' which is derived by dividing the x and y measurements of your film back.

3) This is the meaning I believe the gnomon dude is reffering to. In CG, the term 'aperture' refers solely to the film gate's X and Y measurements...not the film aspect ratio OR the aperture's f-stop values. That's why he says it so important to know this...because it is the x and y measurements of the film gate.

Hope that helps!! :thumbsup:

jhorsthuis
11-13-2008, 02:21 PM
This guy (http://www.earlyworm.org/search/label/rebel%20cg)seems answering your request jhorsthuis.

Yeah great.

exactly what we need :)

thanx

MSavagliani
11-14-2008, 12:12 AM
thank you guys...the gnomon video explains a way to calculate the camera aperture with this ccd size, mine being 1/4,7"...but I really did not understand...boujou would work much better if I had that number....it would be nice to have a place here where everybody could put that information based on their camera...I bet every camera around has at least one guy who knows its ccd size, camera aperture...but I am trying some values until discover the closest one...try and error...

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