Photographic Lenses, Perspective,
Yes, another in the series about lenses, perspective, and distortion. This time it is about wide angle lenses used up close. For example, if you photograph a group of people with a short lens and fill the horizontal frame with the group you will find that the people on the right and left appear to be stretched out.
Pop quiz! Why does this happen? Do you think it is the wide angle lens causing the situation? Or is it the distance between the camera and the group of people?
I think the popular answer is going to be "the lens," but I also think that with a few photographs I can show that the lens is NOT the issue. In these photos, the (full frame) camera was stationary with a 16mm lens on a tripod. I photographed the mannequin head straight on, then I moved it to the left and right sides of the frame, still facing straight forward. I then combined the three in Photoshop. The images are layered straight over each other, with no cropping or other manipulation.
You can clearly see the distortion of the mannequin head when moved out to the far edges of the frame. And, of course, our first inclination is to blame the use of a wide angle lens. But is the lens to blame? Let's look at another set of images...
We start with the same image that ended the first series of photos for reference. Then we see a photo with a PRINT of the original photo in the same position as the head on the left. Take note that the head in the print does NOT show the "wide angle" distortion that the actual head shows.
This shows us that the distortion is not from the lens. The reason we see the distortion on the three-dimensional head is that we are so close to those people on the edge of the frame and at such an acute angle that the lens is seeing both the front and the side of their heads at the same time. The 2-dimensional print, in the same position as the head is rendered straight--there isn't a side of the head to show in the print.
This is something you can easily try for yourself. Hang a photograph on your wall. Put your widest lens on your camera. Position the camera straight on to the wall with the photograph centered and take a photo of the photo. Then move laterally to the left or right so the hanging photograph is on the edge of your frame. Make sure the camera is still positioned straight on to the wall and take another photo. Repeat the same with a 3-dimensional object (a lamp, a statue, etc.). Do you see the same amount of distortion in the 2-dimensional photo as in the 3-dimensional item?
If I was to keep the same 16mm lens on the camera and backed up to a suitable distance I would not be at that strong of an angle and would only see the faces straight on. The distortion would be gone, but the people in the image would be much smaller with a lot of empty space around them. The fix for that? Use a longer lens, which will magnify the people more to fill the frame. The longer lens doesn't fix the distortion we saw with the short lens, it just magnifies the scene when you are further away from the subject by providing a narrower angle of view.
So..., what do you do if you are in that situation where you have a group of people to photograph and you can't move back? Have the people on each end of the group turn in towards the other subjects so that they are more straight on to the camera. It won't be perfect, but will help. Next time try to arrange to take the photo in a larger space that allows you to back up.
This goes back to the basics of perspective in photographs. The camera to subject distance determines the perspective (the relationship between items in the photo) and the lens focal length determines the magnification or how the subject fills the frame. One of the best descriptions of how this all works is in a book from the 1930s called Pictorial Composition in Photography by Arthur Hammond. A good read if you can find a copy. Check out Chapter V on "Linear Perspective."
Here is a list of some of my previous articles on lenses and perspective:
Seeing Ourselves In Photos
Seeing Ourselves Part 2
Depth of Field
Aperture and Depth of Field
Aperture and Portraits