Archived from groups: rec.photo.digital (More info?)
"Mark²" <mjmorgan(lowest even number here)@cox..net> wrote in message
news:Gp_xd.60904$ka2.26406@fed1read04...
>
> "Bill Tuthill" <can@spam.co> wrote in message
news:41c86c74@news.meer.net...
> "Mark²" <mjmorgan(lowest even number here)@cox..net> wrote:
> >
> > "A" <nospam@nospam.com> wrote in message
> >>
> >> If you shoot tall buildings at 17mm on digital (with 1.6 crop factor),
> you
> >> still get distorted pics just like 17mm lenses on 35mm film cameras.
> >
> > The "equivalents" really only apply to *field of view,* since you're
> really
> > just cropping out the middle portion of the normal 35mm film camera's
> image.
>
> Is it also true that if you take a portrait of a person with a big nose
> using a 50mm lens on your DSLR instead of an 85mm(*) lens on your SLR,
> the nose will look bigger in the DSLR picture?
>
> (*) The two aren't quite equivalent, 80mm would be.
-----------
My above post began here:
(for some reason, Bill's post didn't have ">" preceding it in my other
response to him)
> It would give you the same perspective because you would likely back away
to
> the same distance you would have if you used the 80mm on a film camera.
> Remember, the nose:face size ratio (big or smaller nose) is NOT determined
> by the focal length, but instead, the relative difference in distance to
the
> nose tip compared with the distance to the rest of the face.
>
> This is easier to conceptualize if you imagine an EXTREME close-up.
> Imagine yourself taking a picture of someone's face only one inch away
from
> a person's nose. If you did this, the nose would be one inch away, and
the
> rest of their face would be perhaps two inches and further away...TWICE
the
> distance away that their nose was from you.
>
> This will greatly exaggerate the size appearance of the nose because there
> is a nose:face distance ratio of 1:2. This difference will remain true
> regardless of what focal length you have mounted.
>
> Now imagine backing away from the nose/face. As you back away to a full
one
> foot (12 inches) from the nose, the ratio of distance from nose:face has
now
> changed to a far more similar 12:13 ratio (12 inches from the nose, and 13
> inches from the face). As you move back to 8 feet away (for example), the
> ratio of distance from nose vs. distance from face will become tiny
(96:97).
> You can see from this extreme example how the farther you back up, and
less
> out of whack the ratio of distance between (distance to) nose and
(distance
> to) face will become.
>
> **This ratio will remain consistent regardless of what lens you use. What
> WILL change is how much of your subject is visible within the frame.
> So...when you've got your 50mm lens attached, and you add the 1.6 crop
> factor, you will have to back up to a similar distance than you would with
> your ~80mm lens.
> --This will give you the same perspective.
>
> It's all about relative distance to the subject's closest attribute (in
this
> case, the nose) compared with the distance to the rest of the subject.
>
> You've probably seen those funny snap-shots taken of cows, or dogs, where
it
> seems like their nose stretches right out to you? -Those look that way
> simply because they were taken at such close range that the distance ratio
> was extreme...and that they used such a wide-angle lens, that you could
> still see the entire face/head to appreciate the distorted difference.
> -Mark
>
>
"Mark²" <mjmorgan(lowest even number here)@cox..net> wrote in message
news:Gp_xd.60904$ka2.26406@fed1read04...
>
> "Bill Tuthill" <can@spam.co> wrote in message
news:41c86c74@news.meer.net...
> "Mark²" <mjmorgan(lowest even number here)@cox..net> wrote:
> >
> > "A" <nospam@nospam.com> wrote in message
> >>
> >> If you shoot tall buildings at 17mm on digital (with 1.6 crop factor),
> you
> >> still get distorted pics just like 17mm lenses on 35mm film cameras.
> >
> > The "equivalents" really only apply to *field of view,* since you're
> really
> > just cropping out the middle portion of the normal 35mm film camera's
> image.
>
> Is it also true that if you take a portrait of a person with a big nose
> using a 50mm lens on your DSLR instead of an 85mm(*) lens on your SLR,
> the nose will look bigger in the DSLR picture?
>
> (*) The two aren't quite equivalent, 80mm would be.
-----------
My above post began here:
(for some reason, Bill's post didn't have ">" preceding it in my other
response to him)
> It would give you the same perspective because you would likely back away
to
> the same distance you would have if you used the 80mm on a film camera.
> Remember, the nose:face size ratio (big or smaller nose) is NOT determined
> by the focal length, but instead, the relative difference in distance to
the
> nose tip compared with the distance to the rest of the face.
>
> This is easier to conceptualize if you imagine an EXTREME close-up.
> Imagine yourself taking a picture of someone's face only one inch away
from
> a person's nose. If you did this, the nose would be one inch away, and
the
> rest of their face would be perhaps two inches and further away...TWICE
the
> distance away that their nose was from you.
>
> This will greatly exaggerate the size appearance of the nose because there
> is a nose:face distance ratio of 1:2. This difference will remain true
> regardless of what focal length you have mounted.
>
> Now imagine backing away from the nose/face. As you back away to a full
one
> foot (12 inches) from the nose, the ratio of distance from nose:face has
now
> changed to a far more similar 12:13 ratio (12 inches from the nose, and 13
> inches from the face). As you move back to 8 feet away (for example), the
> ratio of distance from nose vs. distance from face will become tiny
(96:97).
> You can see from this extreme example how the farther you back up, and
less
> out of whack the ratio of distance between (distance to) nose and
(distance
> to) face will become.
>
> **This ratio will remain consistent regardless of what lens you use. What
> WILL change is how much of your subject is visible within the frame.
> So...when you've got your 50mm lens attached, and you add the 1.6 crop
> factor, you will have to back up to a similar distance than you would with
> your ~80mm lens.
> --This will give you the same perspective.
>
> It's all about relative distance to the subject's closest attribute (in
this
> case, the nose) compared with the distance to the rest of the subject.
>
> You've probably seen those funny snap-shots taken of cows, or dogs, where
it
> seems like their nose stretches right out to you? -Those look that way
> simply because they were taken at such close range that the distance ratio
> was extreme...and that they used such a wide-angle lens, that you could
> still see the entire face/head to appreciate the distorted difference.
> -Mark
>
>
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