Photography Optics – Keystone Distortion & Perspective Control 05


today we’re going to talk about Keystone
Distortion if you’re not familiar with Keystone Distortion it’s basically when
you take a photo and the buildings and the straight lines should be vertical
but instead they come out looking like a trapezoid or just slanted like
eventually the lines are going to converge at some points
this is Keystone Distortion now let’s pretend this is my camera and let’s
pretend this is a telephone pole or a tree or maybe a building anyways if you
take a picture at a 90 degree angle that is the sensor or your film is going to
be parallel to the building or the power lines or the trees then you’re going to
get perfectly straight lines so a building is going to look square or
rectangle the way it should however if you take if you tilt your camera
downward at an angle now the sensor or the film is going to be at an angle it’s
not parallel to your subject so this is the power line and your sensor is now
tilted down like this it’s not 90-degree angle that’s going to cause the lines in
your picture to come out crooked or tilted or distorted same thing happens
if you point the camera up so basically any degree that’s not 90 degrees is
going to cause you to get a picture where the lines do not come out straight
here’s the same concepts just in different pictures you have a camera
straight you have perfectly vertical lines you tilt it just a few angle
or even just one like one degree and you’re going to get a store the picture
now what’s funny is that if it’s a small change like this people catch on really
quick and they don’t like it if you do it at an angle that’s more than 30
percent and people perceive it as being on purpose so then they’re more than
happy with that photo so if it looks like it’s done on purpose then people
don’t usually complain now please take a look at this picture I try to show you
something called a column at camera it’s basically just an old camera and the
good thing about this camera is that you can actually shift the lens upwards and
this way you can keep the sensor or the film parallel to your like your pole or
your power line or your building or your tree so here is a camera that is 90
degrees but the lens can actually be shifted upwards and the film plane
things parallel now people don’t use color map cameras anymore these days
you’re probably going to use a tilt shift lens now or perspective control
lens that allows you to move the lens upward while keeping the back the film
plane parallel to your subject so how do you deal with Keystone Distortion
the answer is get a tube shift lens shift the lens upward and keep the angle
at 90 degrees you have to make sure that the sensor or the film is parallel to
your vertical lines and that’s all there is to it – See you

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