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What is this weird hatred of different focal lengths?



 
 
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  #11  
Old September 10th 12, 07:09 PM posted to rec.photo.digital.slr-systems,rec.photo.digital
David Dyer-Bennet
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Posts: 1,814
Default What is this weird hatred of different focal lengths?

Alfred Molon writes:

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 photographers
used an 85mm lens and a 35mm lens combination far more often than anything
in the 40-70mm range. If anything a 58 mm lens was a little better for
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.


You're not using the edges, so vignetting and edge quality issues
(common in ultra-fast lenses) are less important.

The DOF is different (at any given aperture), yes. I don't find this
actually matters in practice, but that'll depend on kind of photos and
personal taste, it's a real difference. The DOF formulas work with real
focal length not "equivalent". You also have to pick a circle of
confusion, which depends partly on your standards for "sharp" and partly
on the degree of enlargement planned and the viewing distance planned --
and the degree of enlargement is greater for smaller sensors.
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  #13  
Old September 11th 12, 01:26 AM posted to rec.photo.digital.slr-systems
[email protected]
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Posts: 210
Default What is this weird hatred of different focal lengths?

On Mon, 10 Sep 2012 09:59:23 +1000, "Trevor" wrote:


wrote in message
.. .
On Sun, 9 Sep 2012 13:51:59 -0700 (PDT), RichA
wrote:
On Sep 9, 1:43 pm, David Dyer-Bennet wrote:
"Trevor" writes:
Which is all rather amusing when you consider the more serious
photographers
used an 85mm lens and a 35mm lens combination far more often than
anything
in the 40-70mm range. If anything a 58 mm lens was a little better for
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 :-)


That was my point.


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


The 85mm lens bends the light rays less than the 58mm lens does, that
might make
a differance... you need to try it!


Since you are only using the centre part of the focus plane on a non FF
sensor, the "bend" should be the same for the area used.

Trevor.


No matter what sensor you have, an 85mm focal length lens bends light at less of
an angle than a 58mm lens.

  #14  
Old September 11th 12, 04:06 AM posted to rec.photo.digital.slr-systems
Robert Coe
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Posts: 4,901
Default What is this weird hatred of different focal lengths?

On Mon, 10 Sep 2012 20:25:17 -0400, wrote:
: On Sun, 09 Sep 2012 15:46:48 -0800,
(Floyd L. Davidson) wrote:
:
: wrote:
: On Sun, 9 Sep 2012 13:51:59 -0700 (PDT), RichA wrote:
:
: On Sep 9, 1:43*pm, David Dyer-Bennet wrote:
: "Trevor" writes:
: Which is all rather amusing when you consider the more serious photographers
: used an 85mm lens and a 35mm lens combination far more often than anything
: in the 40-70mm range. If anything a 58 mm lens was a little better for
: 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?
:
:
: The 85mm lens bends the light rays less than the 58mm lens does, that might make
: a differance... you need to try it!
:
: Unless of course you use the 85mm of a full frame
: sensor, in which case it has to bend the light rays
: *exactly* the same as a 56.7mm lens does on a APS-C
: sized sensor.
:
: No matter what sensor you have, an 85mm focal length lens bends light
: at less of an angle than a 58mm lens.

A lens of any focal length bends light at a continuum of different angles. The
significance of each of those angles depends on the sensor size.

Bob
  #15  
Old September 11th 12, 05:03 AM posted to rec.photo.digital.slr-systems
Floyd L. Davidson
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Posts: 5,138
Default What is this weird hatred of different focal lengths?

wrote:
On Sun, 09 Sep 2012 15:46:48 -0800,
(Floyd L. Davidson) wrote:

wrote:
On Sun, 9 Sep 2012 13:51:59 -0700 (PDT), RichA wrote:

On Sep 9, 1:43*pm, David Dyer-Bennet wrote:
"Trevor" writes:
Which is all rather amusing when you consider the more serious photographers
used an 85mm lens and a 35mm lens combination far more often than anything
in the 40-70mm range. If anything a 58 mm lens was a little better for
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?


The 85mm lens bends the light rays less than the 58mm lens does, that might make
a differance... you need to try it!


Unless of course you use the 85mm of a full frame
sensor, in which case it has to bend the light rays
*exactly* the same as a 56.7mm lens does on a APS-C
sized sensor.


No matter what sensor you have, an 85mm focal length lens bends light at less of
an angle than a 58mm lens.


When you frame the exact same image, using an 85mm lens
on a 36mm wide sensor, the angle is the same as when you
use at 56.7mm lens to place that image on a 24mm wide
sensor.

Use the FOV calculator at this site to see the relationship:

http://www.tawbaware.com/maxlyons/calc.htm

And note that the two images will *not* be taken with the same
camera to subject distance.

--
Floyd L. Davidson http://www.apaflo.com/
Ukpeagvik (Barrow, Alaska)
  #16  
Old September 11th 12, 05:04 AM posted to rec.photo.digital.slr-systems
Floyd L. Davidson
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Posts: 5,138
Default What is this weird hatred of different focal lengths?

wrote:
On Mon, 10 Sep 2012 09:59:23 +1000, "Trevor" wrote:


wrote in message
. ..
On Sun, 9 Sep 2012 13:51:59 -0700 (PDT), RichA
wrote:
On Sep 9, 1:43 pm, David Dyer-Bennet wrote:
"Trevor" writes:
Which is all rather amusing when you consider the more serious
photographers
used an 85mm lens and a 35mm lens combination far more often than
anything
in the 40-70mm range. If anything a 58 mm lens was a little better for
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 :-)


That was my point.


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


The 85mm lens bends the light rays less than the 58mm lens does, that
might make
a differance... you need to try it!


Since you are only using the centre part of the focus plane on a non FF
sensor, the "bend" should be the same for the area used.

Trevor.


No matter what sensor you have, an 85mm focal length lens bends light at less of
an angle than a 58mm lens.


Not to cover a smaller sensor it doesn't.

--
Floyd L. Davidson http://www.apaflo.com/
Ukpeagvik (Barrow, Alaska)

  #17  
Old September 11th 12, 06:59 AM posted to rec.photo.digital.slr-systems,rec.photo.digital
Rich[_6_]
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Posts: 1,081
Default What is this weird hatred of different focal lengths?

Alfred Molon wrote in
:

In article c78ea956-44cd-4f57-80b8-85ef06d59896
@u19g2000yqo.googlegroups.com, RichA says...
On Sep 9, 1:43*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? m4/3
and 50mm versus FF and 100mm, for instance. Same effective area coverage
but would it look different, even if DOF was compensated for by using
different apertures?
  #18  
Old September 11th 12, 08:19 PM posted to rec.photo.digital.slr-systems,rec.photo.digital
David Dyer-Bennet
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Posts: 1,814
Default What is this weird hatred of different focal lengths?

Rich writes:

Alfred Molon wrote in
:

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? m4/3
and 50mm versus FF and 100mm, for instance. 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. 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. (With that big a crop, there will probably be visible
noise/sharpness issues, but the perspective will be the same.)

(In the real world, one either picks a lens for a position you want to
shoot from to get the framing you want, or else picks a position that
gives the framing you want for the lens you have; the decisions are
often made intertwined, not independently.)
--
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Snapshots: http://dd-b.net/dd-b/SnapshotAlbum/data/
Photos: http://dd-b.net/photography/gallery/
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  #20  
Old September 12th 12, 12:47 AM posted to rec.photo.digital.slr-systems
[email protected]
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Posts: 210
Default What is this weird hatred of different focal lengths?

On Mon, 10 Sep 2012 23:06:18 -0400, Robert Coe wrote:

On Mon, 10 Sep 2012 20:25:17 -0400, wrote:
: On Sun, 09 Sep 2012 15:46:48 -0800,
(Floyd L. Davidson) wrote:
:
: wrote:
: On Sun, 9 Sep 2012 13:51:59 -0700 (PDT), RichA wrote:
:
: On Sep 9, 1:43*pm, David Dyer-Bennet wrote:
: "Trevor" writes:
: Which is all rather amusing when you consider the more serious photographers
: used an 85mm lens and a 35mm lens combination far more often than anything
: in the 40-70mm range. If anything a 58 mm lens was a little better for
: 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?
:
:
: The 85mm lens bends the light rays less than the 58mm lens does, that might make
: a differance... you need to try it!
:
: Unless of course you use the 85mm of a full frame
: sensor, in which case it has to bend the light rays
: *exactly* the same as a 56.7mm lens does on a APS-C
: sized sensor.
:
: No matter what sensor you have, an 85mm focal length lens bends light
: at less of an angle than a 58mm lens.

A lens of any focal length bends light at a continuum of different angles. The
significance of each of those angles depends on the sensor size.


The shorter the lens, the more the light bends, simple fact. The more the light
bends, the more distortion.

http://www.pbase.com/flintstonestudi...me_things_work

 




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