Hey all

Im a bit confused…and I dont mean to confuse anyone else, but any help here will be very gratefully recieved.

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Ive been trying out some tests with projecting a matte-painting onto rough geometry to create a 2.5D mattepainting with great success in Houdini, and I now want to apply the technique with more precision to a more complex project.

Here comes the problem.. :?

I am looking to create a matte-painting in photoshop constructed of various manipulated photos, which I can then use to project onto geomtry in Houdini theoretically creating a photoreal, but cg environment (from a certain point of view).

I then want to use this environment to place a bluescreened, live action actor.

My question is mainly about houdini's camera set up…

Jeff and some others kindly explained to me a while back about how to match Houdini cameras to live action in a previous post (http://www.sidefx.com/forum/viewtopic.php?t=3608&highlight=camera [sidefx.com])

We established that in order for the focal length to be correct, the apeture setting had to be set in Houdini as well according to the format of the image capture…in the previous post it was on 2/3 ccd chip…

…ok..

…well assuming I constucted the matte-painting using photographs only taken on 35mm film, and taken with a 50mm lens….I am very much assuming this would make the overall perspective of the painting, even when stitched, a focal length of 50mm…but, if the painting is extended beyond the original 35mm photograph, to become a much larger painting…what is the apeture going to be so that it corresponds to the focal length?

There is theoretically no capture device, because it is a painting, but it still has a focal length….

I am guessing that if the size of the image is, say, 3000x4000, then the projection camera is set to this size…but what is the apeture?

If i am not being clear here, please let me know, but I am interested in how I can make sure that the projection camera is completely correct for my geometry.

Also, if anyone has any experience compositing live into a live/cg environment…
I assume I can then create another camera to move within that environment at the setting of the bluescreen camera, so that the live action matches up…even though the background was taken using a 50mm lens?

Anyway, to summarise, my main concern is what to set the apeture to.

Thanks

Hope I havent confused too many people

J