Perspective is not a distortion, if you accept that a distortion is a failure of an optical system to render a view accurately. We humans think that vertical perspective is a distortion because we are gravity bound creatures incapable of naturally controlling our movement through vertical space. Vertical displacement is irrelevent data that is largely disregarded by our brains. When we see an accurate photo featuring vertical perspective we are often surprised by something that was always there to be seen, but which we instinctively chose to ignore.
The additional fact that our eyes have a spherical image plane, and that our brains selectively interpret what our eyes see could also be a factor. Sometimes being a photographer means opening your eyes to the visual assumptions we make all the time. regards, Anthony Farr On 10/11/2007, [EMAIL PROTECTED] <[EMAIL PROTECTED]> wrote: > I can't call this a stupid newbie question, because I am not a newbie > anymore. ;-) > > Previously I have not shot much with wide angles. I used my Canon 17-40 in > Yosemite and thought I noticed some trees leaning in slightly in some shots. > But only slightly. > > I have noticed a lot of distortion using the 16-45 on the K100D. While > sometimes I don't mind this, other times I have been annoyed because I wasn't > taking it into account. I am also reassessing the lens. > > However, I realize I am not all that clear on the difference between barrel > distortion and perspective distortion. > > I also realize that getting more in the frame than normal perspective would > allow must mean something will happen. > > I am curious if there is a formula for when perspective distortion will not > occur, or some focal length at which it will not occur? Would about 45mm be > the cut off point -- it won't occur at 45mm? As for barrel distortion, it > seems to be depend on the lens. It seems people use brick wall to test for > barrel > distortion. Is that true, some wide angles have barrel distortion and some > do not? Or do they all to some degree? > > As you can tell, I am not quite sure how to phrase this question. > > Basically what I want to know is when I shoot with the 16-45 when I will get > some distortion and when I am likely not to. So I can take it into account > and plan for it. And use the 16mm end or zoom in a bit more to avoid it when > I > want to avoid it. > > And anyone who wants to expound more on the difference between barrel > distortion and perspective distortion, too, feel free. I am pretty clueless > on the > whole topic. > > I think this is perspective distortion... (which I don't mind in this case, > but this is not the strongest example, just one I have shown) > > http://members.aol.com/eactivist/PAWS/pages/temple2.htm > > I think this was may be barrel distortion. When I looked at it I found the > lamp post leaning in, so I straighten the picture in Elements 5 with > Transform/Skew. Hence the distortion isn't showing anymore, but it was > there. > > http://members.aol.com/eactivist/PAWS/pages/bars.htm > > I can go back and look at exitf if needed, but I think the top was shot at > 16mm and the lower one longer. > > TIA for anything you want to offer, Marnie aka Doe :-) > > --------------------------------------------- -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
