Nuke's camera tracker focal length can always be set as "unknown constant" or "unknown varying" and then it will figure out the proper focal length. If though there isn't enough paralax change in the shot it can help to set the camera tracker to "Approximate Constant" or "Approximate Varying". You do need to input the equivilent cropped focal length here.
-deke On Tue, May 29, 2012 at 2:02 PM, Nathan Rusch <[email protected]>wrote: > Going back to the origin of this discussion, it really doesn’t matter > one way or another... the reason the tracking software asks for the film > back is so it can calculate the equivalent "cropped" focal length and thus > an accurate field of view. Unless the process has changed significantly in > the last two years, you shouldn’t ever have to include crop factor in your > parameters when solving for a camera. > > -Nathan > > > *From:* Diogo Girondi <[email protected]> > *Sent:* Tuesday, May 29, 2012 1:47 PM > *To:* Nuke user discussion <[email protected]> > *Subject:* Re: [Nuke-users] Arri Alexa sensor size - camera tracking > question > > I'm not familiar with Nikon lenses, but Canon ones even if designed for > APS-C sensors are still named disregarding any compensation for crop > factors. Personally I never heard of lenses that state their focal lengths > compensated by a certain crop factor since that tends to vary from camera > to camera and it's not a characteristic of the lens it self. > > Canon EF-S lenses are a good example of this, they are designed to only > mount on EF mounts of bodies with APS-C sensors (1.6x crop factor) but > their focal lengths are still stated "1:1" taking a full frame if you will > as base, so you still have to multiply their focal lengths by 1.6. My EF-S > 10-22mm for instance when mounted on my 7D is becomes a 16-35mm and not the > 10-22mm written on the lens. > > > > On Tue, May 29, 2012 at 5:28 PM, Howard Jones <[email protected]>wrote: > >> The crop factor was based on the original question. Not my maths. A >> 100 mm lens on cropped back will give an equivalent lens angle (not actual) >> of a longer lens, with the original question this was 1.5. >> >> You are both agreeing with by stating the film back size gives a >> different fov (but not focal length - agreed) >> >> However, >> 1. If you can't get a 100mm lens that is designed for a crop film back, >> ie compensates for the sensor size, then you are correct that in this case >> the focal length is the same, regardless of sensor size, however the fov is >> different. >> >> However if you can buy a lens that has compensated for the sensor size >> and gives the same fov as a 35mm lens then there is a discrepancy. >> >> I'm under the (mis)understanding that the latter is available, however I >> can quite believe I'm mistaken. >> >> 2. We are all assuming nuke behaves correctly in this fashion. In the >> back of my mind, if you put the focal length into the camera tracker and >> then change the film back, it changes the focal length, but you can then >> change it back. >> >> I can't check this last point until tomorrow, but if it's the case then >> what does this mean for the solve? If its not the case then it's because >> I'm getting on and the mind plays tricks. >> >> Cheers >> H >> >> > > _______________________________________________ > Nuke-users mailing list > [email protected], http://forums.thefoundry.co.uk/ > http://support.thefoundry.co.uk/cgi-bin/mailman/listinfo/nuke-users >
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