How will I know if i am going to get perspective distortion with my ultrawide?

Hi all -

I've been shooting with my Tamron 17-35 for about 3 months now. There are times that when shooting at 17-18mm, I get distortion and there are times that I do not. Sometimes when I do get the distortion, it's on one side and not the other (or t least it appears to be) . . . am I supposed to be able to identify ahead of time what photos are going to have perspective distortion? If so . . . any tips on how? 98% of my shots are of people if that helps.

Is this a dumb question? Sorry if it is.

I will try to get you some examples of what I am seeing.

Thanks, in advance, for your input.

I would imagine you should be able to see any distortion through the viewfinder.

Perspective is controlled totally by distance between the viewer (or camera) and the subject. If you are too close to a subject and not viewing it straight on, you will see the "distortion" that I think you are describing.

An ultra-wide lens is not the appropriate lens to use for photos of people unless you are deliberately trying to make an image with the "distortion".

31mm is the focal length of a "normal" lens for a 20D (and all its other APS-C DSLR sisters). If you stay close to that focal length or somewhat longer, you will have much better people photos. Something around 22mm (equivalent field of view to a 35mm lens on a 35mm film camera) is about as wide as I would dare go for people photos.

Like Bill said, you should be able to analyse the framing of the image in the viewfinder.

thanks for the explanation, Skip. I usually just frame, focus, and shoot. I guess I need to pay more attention to my distance to my subjects and then to the actual view in the viewfinder.

I got the lens becuase I couldn't fit the larger groups in my frame with my 28-75.

Mark,

Thanks for asking this question. I've been wondering the same thing (I have a 350D and the Canon 10-22).

And thanks Skip for explaining it an understandable way!

If the subject is parallel to the camera and you keep the camera level, you should get no distortion. Tilt the camera up or down or to the side and there will be distortion.

I find that's not entirely true with wide angle shots. Especially as your subjects get closer, a subject at the top of the frame (ie the head) may be for instance 3 feet away from the lense, their chest which is centered will be maybe 1 foot away, and the legs will be 3 feet again, by the sheer virtue of wide angle emphasizing perspective you will get distortion, even though the subject is technically "straight" relative to the lense.