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What is this weird hatred of different focal lengths?



 
 
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  #31  
Old September 16th 12, 05:42 PM posted to rec.photo.digital.slr-systems,rec.photo.digital
David Dyer-Bennet
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Default What is this weird hatred of different focal lengths?

RichA writes:

On Sep 11, 3:19Â*pm, David Dyer-Bennet wrote:
Rich writes:
Alfred Molon wrote in
m:


In article c78ea956-44cd-4f57-80b8-85ef06d59896
@u19g2000yqo.googlegroups.com, RichA says...
On Sep 9, 1:43Â*pm, David Dyer-Bennet wrote:
"Trevor" writes:
Which is all rather amusing when you consider the more serious
photog
raphers
used an 85mm lens and a 35mm lens combination far more often than
any
thing
in the 40-70mm range. If anything a 58 mm lens was a little
better fo
r
portraits than a 50mm one at least, even if not by much. A fast
50mm
is a
much better lens now on a non FF sensor DSLR however IMO.


A 58mm is great on a 1.5X DSLR for portraits :-)


But does it behave the same way as say an 85mm on a FF for the same
subject matter?


Why shouldn't it? The only issue might be the different DOF.


How about the flattening effect (compression) of the focal length? Â*m4/3
and 50mm versus FF and 100mm, for instance. Â*Same effective area coverage
but would it look different, even if DOF was compensated for by using
different apertures?


Thre is no flattening effect or compression caused by focal length.

Perspective (which technically means the relationships between objects
in the rendered image) is controlled by camera location. Â*If you take a
photo from the same place with the center of the frame pointing exactly
the same direction with a 24mm lens and 600mm lens, and crop the 600mm
angle of view out of the center of the 24mm image, the perspective will
be the same.


So, if we have two objects in a frame, at different distances from
the camera and we just frame them in a 500mm lens and then a crop from
a 50mm lens shot, the appearance between the two subjects in the
images will appear identical in both shots? No "telephoto
compression" will be visible making the two objects in the 500mm crop
seem closer to each other?


Exactly; if the 500mm and 50mm shots are taken from the same location.

A "place mat" showing this (pictures taken with every lens a particular
manufacturer made, all from the same location) used to be standard
furniture at every camera store, too (usually one from each major lens
manufacturer, in fact).

With a modern wide-range zoom it's very easy to take your own test
photos to compare yourself.
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  #32  
Old September 16th 12, 05:44 PM posted to rec.photo.digital.slr-systems,rec.photo.digital
David Dyer-Bennet
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Default What is this weird hatred of different focal lengths?

(Floyd L. Davidson) writes:

RichA wrote:
On Sep 11, 3:19Â*pm, David Dyer-Bennet wrote:
Thre is no flattening effect or compression caused by focal length.

Perspective (which technically means the relationships between objects
in the rendered image) is controlled by camera location. Â*If you take a
photo from the same place with the center of the frame pointing exactly
the same direction with a 24mm lens and 600mm lens, and crop the 600mm
angle of view out of the center of the 24mm image, the perspective will
be the same.


So, if we have two objects in a frame, at different distances from
the camera and we just frame them in a 500mm lens and then a crop from
a 50mm lens shot, the appearance between the two subjects in the
images will appear identical in both shots? No "telephoto
compression" will be visible making the two objects in the 500mm crop
seem closer to each other?


Yes.

The composition will be the same. That is, the size of the two object
will have the same relationship. If the nearer object appears to be twice
as tall as the far one, that will be true for both images.


That's called "perspective", though, not "composition". Composition
relates to how the objects, masses, colors, and such interact visually
to make a more or less pleasing picture. Perspective is the size and
position relationships of the objects in the picture.

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  #33  
Old September 16th 12, 11:00 PM posted to rec.photo.digital.slr-systems,rec.photo.digital
Floyd L. Davidson
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Default What is this weird hatred of different focal lengths?

David Dyer-Bennet wrote:

The composition will be the same. That is, the size of the two object
will have the same relationship. If the nearer object appears to be twice
as tall as the far one, that will be true for both images.


That's called "perspective", though, not "composition".


Perspective is an aspect of composition.

The composition will be the same is because there is no
change in the perspective. What I said was precisely
correct: the composition will be the same.

Composition
relates to how the objects, masses, colors, and such interact visually
to make a more or less pleasing picture.


Composition is *not* how things relate "to make them
visually pleasing or not". It is "the spatial property
resulting from the arrangement of parts in relation to
each other and to the whole" (WordNet's definition).
Whether composition affects how more or less pleasing an
image is it is incidental the definition.

Perspective is the size and position relationships of
the objects in the picture.


Hence it clearly affects composition.

--
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  #34  
Old September 17th 12, 12:48 AM posted to rec.photo.digital.slr-systems,rec.photo.digital
[email protected]
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Default What is this weird hatred of different focal lengths?

On Sat, 15 Sep 2012 20:31:36 -0700 (PDT), RichA wrote:



So, if we have two objects in a frame, at different distances from
the camera and we just frame them in a 500mm lens and then a crop from
a 50mm lens shot, the appearance between the two subjects in the
images will appear identical in both shots? No "telephoto
compression" will be visible making the two objects in the 500mm crop
seem closer to each other?



Any lens, within limits, will project an accurate image of the scene coming
through it. The only thing the focal length does is determine the final size of
the entire image. If you keep this in mind, you should see that if you crop any
part of the scene, you will end up with the same image regardless of the lens
you use, and how you crop it, either by sensor size or by post processing.

I proved this to myself a few years ago using a 500mm and a cropped 50mm shot of
the same scene. I had the comparison up on the web for a while.

A similar thing can be seen if you take an extreme wide angle lens, and take a
picture of a city, for example. All of the buildings will appear to be curved
and lean together, but if you crop out a very small part, you will be surprised
to see perfectly rectangular windows.

Lots of effects seem to depend on the large final image, not small parts of it.

  #35  
Old September 17th 12, 12:54 AM posted to rec.photo.digital.slr-systems
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Default What is this weird hatred of different focal lengths?

On Sat, 15 Sep 2012 20:19:53 -0700 (PDT), RichA wrote:



Modern optimization. No need for outsized image circles now because
new glass and curves mean image quality at the lens edge is good
enough with a smaller image circle. As you said, it has no bearing
on the angle of specific parts of an image on the sensor, which (if
the focal lengths were the same) would be the same.


One interesting thing I found is that with a DX type lens on my D700, I could
force the camera to use the full FF mode, and then crop a perfect square from
the image, gaining slightly in pixels compared to the factory standard 3x2
aspect. I like the 1x1 because you don't have to rotate the camera! 1x1 aspect
seems to be coming back from the old 2 1/4 days, my Panasonic also has a 1x1
option.

  #37  
Old September 17th 12, 03:16 AM posted to rec.photo.digital.slr-systems,rec.photo.digital
Trevor[_2_]
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Default What is this weird hatred of different focal lengths?


wrote in message
...
A similar thing can be seen if you take an extreme wide angle lens, and
take a
picture of a city, for example. All of the buildings will appear to be
curved
and lean together, but if you crop out a very small part, you will be
surprised
to see perfectly rectangular windows.


Not "perfectly rectangular windows" at all, but if their size is small
enough the distortion becomes difficult to see. It is impossible for the
building to be "tilted" and it's windows not to be.
(Well before manipulation in PS anyway! :-)

Trevor.


  #38  
Old September 18th 12, 12:13 AM posted to rec.photo.digital.slr-systems,rec.photo.digital
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Default What is this weird hatred of different focal lengths?

On Mon, 17 Sep 2012 12:16:37 +1000, "Trevor" wrote:


wrote in message
.. .
A similar thing can be seen if you take an extreme wide angle lens, and
take a
picture of a city, for example. All of the buildings will appear to be
curved
and lean together, but if you crop out a very small part, you will be
surprised
to see perfectly rectangular windows.


Not "perfectly rectangular windows" at all, but if their size is small
enough the distortion becomes difficult to see. It is impossible for the
building to be "tilted" and it's windows not to be.
(Well before manipulation in PS anyway! :-)

Trevor.


OK lets say the windows aren't as 'wonky' as the entire image suggests!

When I first used a very wide angle lens to take architecture pictures, I
thought they wouldn't be usable as scale examples, but small sections of them
were surprisingly linear.

  #39  
Old September 18th 12, 12:17 AM posted to rec.photo.digital.slr-systems,rec.photo.digital
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Default What is this weird hatred of different focal lengths?

On Mon, 17 Sep 2012 02:57:01 +0200, Mxsmanic wrote:

writes:

Any lens, within limits, will project an accurate image of the scene coming
through it. The only thing the focal length does is determine the final size of
the entire image.


Not quite. Focal length determines the field of view that will be projected
onto the film or sensor.


You're just looking at it another way... if you didn't have a camera but just 2
lenses of different FL, you would see they project different size variations of
the same scene... A picture of a house for example might project 2 inches wide
with one lens but 3 inches with the other.


 




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