LW camera vs Real world camera help

[squeegie]

I do a lot of comping LW items into digital photos from clients. Can anyone explain how to set my LW camera to match the same lens as the digital camera the image was taken with? I know what the lens of the digital camera is ( f=6.0 60.00mm 1:2.8 Ø52) , but I have no idea what it means, or how to use that data in the LW camera. I have just been using the grid & "eyeballing" it to get it close, but the perspective always looks a little off.
Any help in this matter would be greatly appreciated.

[faulknermano]

( f=6.0 60.00mm 1:2.8 Ø52) , but I have no idea what it means, or how to use that data in the LW camera. I have just been using the grid & "eyeballing" it to get it close, but the perspective always looks a little off.
Any help in this matter would be greatly appreciated.

not sure why F is at 6.0, but it is most likely your f/stop, which has nothing to do with perspective. 60mm is your focal length, which is relevant. 1:2.8 if your lens ratio between opening and length so it's not directly relevant. Ø52 is just your filter size. so forget about that. ;)


the problem is not that simple. you must know your aperture height because knowing focal length without knowing aperture height is still useless. there's probably a mathemetical way to figure out aperture height based on fixed factors like taking a photo of an object of a known height at a known distance and at a known focal length (in your case 60mm).

but i suggest you eyeball this part. i recommend the following. take a picture of a real life object of some size (maybe 1 meter in height / length). then distance yourself from this object enough to take a picture of the whole of it with your lens. back in LW set your camera to 60mm and make an LWO representing the real object. situate it as you would when you do your compositing and adjust your aperture height to match (instead of your focal length). so, i guess it goes without saying (but i'm saying it anyway), that you should take note the dimensions of everything in the scene, including height of camera when you took the picture. preferably you take the test picture perfectly horizontal (so you dont have to rotate the LW camera and thus get rid of the rotation factor). additionally, measure the distances of surrounding objects and reproduce it in LW so you can get a better solution.

again, all of this is to simply how to get the aperture height. if your camera has a zoom lens this will prove to be more useful. for once you have the aperture height correct, simply match the focal length in your digital camera for every picture you take.

EDIT: also depending on the quality of the lens you may experience spherical abberation, which is basically distortion, which will throw off apparent perspective. there may be utilities out there that may fix that, but i dont know about them.