I would also like to know what bob has asked.  
I imported a series of images in to imagemodeler 3 and it created different camera devices that I didn't want with different focul lenghts and it was impos.sible to calibrate. I just wanted to use the default  amera device so  im3 could work out the parameters

Hello,
ImageModeler creates more than one camera device if the imported images have not the same sizes in terms of pixels. It's probably your case.
If the images have all the same size, there will be only one camera device.
Anyway, if you double click on the picture, you can assign the camera device you want and remove the one that ImageModeler created which are useless.
Be careful, if you have one camera device for all the pictures, it's better to set the focal length Variable because, it probably changed a little during the shots (autofocus), even if you did not zoom.