Focal range in ArtLantis....what is it exactly?

[Anonymous]

I'm building a model of a house and I have taken photos of the real background, just a normal work flow...

The photos were taken with a Canon S40 digicam. When I place the background in ArtLantis and I want to adjust the camera settings I firstly try to do it "scientifically"...that is entering the value of the focal range of 35 mm (I'm not sure here...some say I should multiply the digicams focal range with 4 which gives a focal range of 28mm while Canons specs says the focal range (in 35mm measures) is 35-105mm so I go with the Canon specs). I can see from the preview that this value is just nuts! I manually tweak the camera settings to match the castle and I get a focal range of 52 mm.

If I stick to what I found myself the focal range is 28 mm and then I realize that 90-28=52....hmmmmm....

All of this can be seen in the attachment.

Am I missunderstanding something about focal range in ArtLantis?

Learning by doing wrong is boring....

[Djordje]

mathome wrote:
Am I missunderstanding something about focal range in ArtLantis?

The trick here is to get the EXACT conversion table of the 35mm focal lengths to your digital camera, AND knowing what lens you used when you took the photos. The zoom range is not of much help, except giving you the maximum and the minimum values. It is not so linear as it might sound.

Art•Lantis IMHE usually guesses the focal lenght quite OK provided you give him the base point, X and Y directions and the Z value.

[Anonymous]

Djordje wrote:
The trick here is to get the EXACT conversion table of the 35mm focal lengths to your digital camera, AND knowing what lens you used when you took the photos. The zoom range is not of much help, except giving you the maximum and the minimum values. It is not so linear as it might sound.

Well, in this case the camera was set to the widest focal range so it should be correct with 35 mm according to Canons specs. When I take the photos myself I use my own real SLR-stuff...should do it more often...
I linked the attachment...I forgot that when I posted my question.

Anyway the 52 mm which seemed correct in ArtLantis has nothing to do do with the focal range the image was taken with so my question remains.

Mats

[Anonymous]

Hello Mathome,

Can you try to match your model with the background using the "Insertion" tool (Available in the Edit Points of View editor).
To acquire the tool please follow the tutorial 7 present on the Art*lantis CD.

You make coresponding one axis X, Y, Z in the Preview window (on the background) and the other one in the Projected View window (on the model), then launch the calculation, once done move the focal slider more or less to refine the fitting. All his in real time. So no need to know about your camera focal.


Alain Picard
Abvent SA