I am trying to make a mesh of someone’s head from reference photos. Despite being super careful to get the front and side images the same distance from the lens etc I can’t seem to get them to marry up on a front and side view in Blender. I was wondering if anyone had any tips on what lens to use etc as I am pretty sure this is down to lens distortion. I have been told a 50mm lens would be best for this. I have a Canon 7D as my disposal and am willing to purchase a lens to solve this issue.
Any tips for taking ideal reference photos, greatly appreciated.
The portrait lens for 35mm film format is 105mm and not 50mm. 50mm suppose to give you the same angular view as a human eye. There are lots of distortions with that lens.
Matching front and side view is difficult. If a subject moves even a little to reposition front to side shot you will never get the same pose. To keep head still, you could put the subject on a swiveling chair. So you can shoot multiple views by spinning the subject around while they keep still. Camera needs be on tripod and it should not be moved.
Comparing visual landmark for the shot helps as well. Most noticeable visual landmarks are eye to ear, ear to nose, ear to mouth. Look at this image. The front and side view don’t match:
Put a straight edge between the bottoms of ear on front shot. The straight edge almost touches his bottom of nose. Now look at the side view. Place the straight edge by the bottom of the ear and project it to the bottom of nose. Its not lining up! Its ether his head tilted or camera height changed.
Note also that the front shot nose is almost long as his ear. Side view is quite different. His ear appears taller than his nose. This is what happens using 50mm close up shot. The object that is closer to the lens project larger. His nose is closer to the lens, and its image gets larger than other parts of the head. To get proper proportion you need longer lens, 105mm.
Actually the Canon 7D has an APS-C size sensor, with a crop factor of 1.6X. So that means the 50mm lens has the same field of view as an 80mm lens on a 35mm film camera. That’s actually a pretty decent portrait lens. I think if the OP uses the techniques that ridix described, he should be fine.
Thanks very much for a detailed an thorough answer. I really appreciate the time you lengths you went to, to explain.
Oddly we did exactly as you described but obviously with an 18-130 lens at 18. We used the swivel chair method and tripod in our initial go at this. But as you say just the fact that elements of the face will be at slightly difference distances from the lens has caused distortion.
I will try with the same lens at 130 (although I will have to be a fair way from the subject - although I have this room available). I also have a 35-80 which I will try but sounds like the 130 may be the way to go.
Thanks once again for all your help, and I’ll drop a message back here in the next day or two once we have done the new reference photos.
