Something to ponder!

Because I get the same effect if I look through a pair of binoculars
that have 10X written on them and I don't get that effect if I look
through a cardboard tube. It's all to do with magnifying lenses.
It's also noticeable on car wing mirrors if they are magnifying
ones other cars look closer.

The effect is even seen in videos. In this one the rugby player
is running fast towards the camera, but because of tele compression
he doesn't look to be moving much.....

http://www.youtube.com/watch?v=ahR6qHcONu8

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But they wouldn't look any different taken with a wide angle lens, other than they'd be smaller in the frame. Crop the wide angle lens image to match and it would be the same as those.
Take a zoom lens. Take two images, one at the wide angle end, another at the tele end. Now crop the wide angle image to match the telephoto one and apart from image quality they'd be the same.
I agree using a tele lens appears to compress the subject, but its only an optical illusion as it isn't a natural view.

John K

It's certainly not an optical illusion. I don't know why photographers
can't see it. but the average Joe or Beryl can. If I give them a camera
with a 300mm lens to have a look through they immediately say
"It brings everything closer" which it does and it does it by
magnifying the image..... Like all magnification it does that
by making the distance look smaller than it actually is.
With a 10X magnification every step forward of 1M will look
like 0.1M through the viewfinder or binoculars. It can't
be achieved from magnifying a WA view because the distance
information isn't correct.

Horse racing on TV shows this up well. The stuff on Youtube
isn't as good, but this one shows the horses moving very
little approaching the camera and by much more as they
pass it.

http://www.youtube.com/watch?v=oHE_LQjfuuM

This one might be a bit better.....
http://www.youtube.com/watch?v=g-TEyesFK8g

So Tele lens shots are unique in that they have
normal 2D distance information L/R Up/Down but
compressed distance information Near/Far which
can be clearly seen on the horse videos.

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Have you tried taking those two images with a zoom lens yet?

John K

Algi. Try this with the two images in the flickr link:
1) Take the wide-angle image and crop just the bit of the bridge that is shown in the telephoto image.
2) Resize the crop so that it is the same size as the telephoto image. Ensure that you preserve the aspect ratio. It will look pretty rubbish due to the huge magnification factor (about 6x) but the key lines will still be there.
3) Compare the two images.
4) If you're still not convinced, try taking the telephoto image and shrink it (to about 1/6th of the size) and then overlay it on a copy of the wide-angle image and compare again.

Go on, give it a try

EM

PS don't post the results here as the image owner obviously doesn't want his images copied.

This video shows it done by a photographer with different lenses.
Not as good as the racing, but might help some people.
Notice that on the Tele shots (200mm) the crowd
behind don't look to have much room. You can't achieve
that by enlarging a WA shot.

http://www.youtube.com/watch?v=7Fzh9eQDhL4

Also note WA shots have a greater DOF.

All this was well covered on the TP Forum someone
took shots from high up looking down on a row of
terraced houses from the back showing a lot of
parallel lines including railway lines. They
enlarged the WA shots, but they were miles away from
being the same as the Tele shots. I can't find it
via Google and have a feeling that TP don't keep
everything in their archive. I never bookmarked it
because it only confirmed what I already knew.

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If I look at the calendar through my telephoto lens will pay day seem closer

You can't achieve the effect on this video by enlarging a WA shot because the various different shots have different perspective. This change in perspective occurs because the camera and/or the person moved between shots to ensure that the person stayed more or less the same size in the frame.

EM

OK, I feel a bit guilty as I started this, but Algi you are wrong. Look at the photos I took. Look at your sketches and spot the basic error of geometry (how can they be the same lines if they are at different angles?) All your examples have one thing in common - the photographer moved. (As an aside, I do explain to my son that the second best tool for a tog is his/her feet.)

Can this end now please?

That's no surprise given the relationship between depth of field and focal length, but it's got nothing to do with perspective.

I wonder if I keep telling everyone I'm a kangaroo for long enough that I'll actually believe it myself and manage to convince anyone else??

The Brightest thing to do is admit defeat when defeat is all you've got and fight a battle you can actually win, but hey what do I know I'm a kangaroo!

Enough! If anyone else posts I'll make them watch Strictly Come Dancing!!!

Or X-factor....


,,,cripes! That means I've got to watch,,,,,,AHHHHHHHHHHHHHHH!

I'm not quite sure what is being discussed here. If you have a photographer, foreground subject and background then:

1) Nothing moves but the photographer changes lenses and enlarges the 'cropped' wider shot to compensate. The apparent DoF may change due to the larger enlargement, the perspective remains the same (the relative distances are the same). Using the longer lens has the same effect as enlarging the photo more (the lens projects an enlarged image on the sensor).

2) The photographer shoots the wider shot closer to the subject than the longer shot, the background remains in the same place. The DoF may change due to the different subject distance. The perspective changes because the photographer to subject distance has changed relative to the subject to background distance.

There is much more to (2) than that, the wider/closer shot includes a lot more foreground in front of the subject as the change in perspective is progressively exaggerated the closer things are to the camera. At very short subject distances, depending on the viewing angle, different parts of the subject (at different distances) can be distorted relative to each other for the same reason.

John.

Algi, you are wrong.





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