Pictures of my trip to the US (it's not as dull as it sounds) - Page 4

Colon™ · September 14, 2002, 00:28

Colon™ · September 14, 2002, 00:35

Find the air pollution

Ethelred · September 14, 2002, 00:40

Quote:

Originally posted by Colon
Barrel distortion? Use layman's words please.

I have an Ixus 300 made by Canon.

Barrel distortion is when lines that should be parrallel actually bow outwards. Pincushion is when the lines bow inwards. A lot of PC monitors have an adjustment for pincushion/barrel distortion so maybe you can play with that to see what it looks like. LCD monitors of course don't have that adjustment only CRTs.

Colon™ · September 14, 2002, 00:53

Find the Empire State Building (and that weasely Chrysler Building)

Colon™ · September 14, 2002, 01:00

Quote:

Originally posted by Ethelred

Barrel distortion is when lines that should be parrallel actually bow outwards. Pincushion is when the lines bow inwards. A lot of PC monitors have an adjustment for pincushion/barrel distortion so maybe you can play with that to see what it looks like. LCD monitors of course don't have that adjustment only CRTs.

Where exactly do you notice barrel distortion? Isn't it just the effect of perspectives?

Ethelred · September 14, 2002, 01:44

In SOME of the pictures there might be some bowing. I can't be sure. The perspective effect is called keystoning. If I was to look at one of those pictures in a photo editing program I could lay a straight line along a building edge and be sure, especially with a high resolution version of them. Since the distortion will change with the zoom it could be there in some photos and not in others. Avoiding such distortion is one of the reasons that zoom lens have so many different elements in them. The other big reason is to keep the colors from spreading. Most lenses are designed to keep control the red and blue light and the middle of the spectrum kinda goes along. Very expensive lenses called apochromates are designed to control the middle of the spectrum better which keeps the all the colors hiting the same point instead of spreading and losing sharpness.

Keystoning is what you get when you tilt the camera so that the back is not parrellel with the buildings. I say it that way because it IS possible to shoot up an keep the back parrellel with a view camera. Instead of tilting the camera you raise the lens that is on a board mounted on rails on in a track. Thats one of the reasons profesional studio and architecture photographers use those bit ungainly things besides the large film sheets. Of course now they are replacing the big film backs with big digital backs but they are still using the basic view camera with hideously expensive lenses like a Schneider 90 mm Super Angulon. I don't even want to think about what those things must cost today.

There now you have more information than you wanted to know.

DanS · September 15, 2002, 10:19

Ethelred: You're eyes aren't deceiving you. There is still some distortion in these digital cameras (cheap optics?). My camera maxes out at about 20 mm, if I recall correctly.

NB: There were two cameras that took these pictures. If you are sharp, you might even be able to tell the difference between the two.

Ethelred · September 15, 2002, 10:45

Quote:

Originally posted by DanS
Ethelred: You're eyes aren't deceiving you. There is still some distortion in these digital cameras (cheap optics?). My camera maxes out at about 20 mm, if I recall correctly.

Doesn't have to be cheap optics although that most likely has something to do with it. Its hard to counter barrel/pincushion distortion throughout the entire range of a zoom lens especialy when the zoom is more than three to one. My 100 to 300 lens outweighs my Canon EOS 620 body by a large margin. People usually aren't willing to accept a 4 to 6 pound camera. Most of the digital cameras only have the one built in lens and they way less than pound.