Focal length in pixels
 

Hey any body out there who can help me transform focal length in mm to
focal length in pixels. to be precise am trying to get 24mm to pixels
for scanned areal photos with dimensions 4992 x 3328 pixels. and for
153mm with dimensions 7242 x 7263 pixels.

Thanks.

Re: Focal length in pixels
 

orelza@gmail.com wrote:
> Hey any body out there who can help me transform focal length in mm to
> focal length in pixels. to be precise am trying to get 24mm to pixels
> for scanned areal photos with dimensions 4992 x 3328 pixels. and for
> 153mm with dimensions 7242 x 7263 pixels.
>
> Thanks.
>
I know SFA about the subject but a Google search of the term "focal
length in pixels" turned up millions of hits.

Results 1 - 10 of about 1,410,000 for focal length in pixels. (0.09 seconds)

What couldn't you find? Couldn't anybody in any of the photography or
affiliated groups help?

Re: Focal length in pixels
 

On Wed, 11 Apr 2007 09:53:01 -0700, orelza wrote:

> Hey any body out there who can help me transform focal length in mm to
> focal length in pixels. to be precise am trying to get 24mm to pixels
> for scanned areal photos with dimensions 4992 x 3328 pixels. and for
> 153mm with dimensions 7242 x 7263 pixels.
>
> Thanks.

Lionel?


--
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#1 Usenet Asshole, March 2007
#1 Bartlo Pset, March 13-24 2007
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Pierre Salinger Memorial Hook, Line & Sinker, June 2004
COOSN-266-06-25794

Re: Focal length in pixels
 

On Wed, 11 Apr 2007 13:39:31 -0400, Google Tech Support
<meat@meatplow.local> wrote:

>On Wed, 11 Apr 2007 09:53:01 -0700, orelza wrote:
>
>> Hey any body out there who can help me transform focal length in mm to
>> focal length in pixels. to be precise am trying to get 24mm to pixels
>> for scanned areal photos with dimensions 4992 x 3328 pixels. and for
>> 153mm with dimensions 7242 x 7263 pixels.
>>
>> Thanks.
>
>Lionel?

There's no such thing as "focal length in pixels", so the question
doesn't have an answer. 'Focal length' on a camera lens relates to the
distance between the front of the lens & the plane where the image is
projected:
<http://en.wikipedia.org/wiki/Focal_length>

If the OP explains in more detail what s/he is trying to actually
achieve, I might be able to come up with a more helpful answer.

--
W "Some people are alive only because it is illegal to kill them."
. | ,. w ,
\|/ \|/ Perna condita delenda est
---^----^---------------------------------------------------------------

Re: Focal length in pixels
 

Lionel wrote:
> On Wed, 11 Apr 2007 13:39:31 -0400, Google Tech Support
> <meat@meatplow.local> wrote:
>
>> On Wed, 11 Apr 2007 09:53:01 -0700, orelza wrote:
>>
>>> Hey any body out there who can help me transform focal length in mm to
>>> focal length in pixels. to be precise am trying to get 24mm to pixels
>>> for scanned areal photos with dimensions 4992 x 3328 pixels. and for
>>> 153mm with dimensions 7242 x 7263 pixels.
>>>
>>> Thanks.
>> Lionel?
>
> There's no such thing as "focal length in pixels", so the question
> doesn't have an answer. 'Focal length' on a camera lens relates to the
> distance between the front of the lens & the plane where the image is
> projected:
> <http://en.wikipedia.org/wiki/Focal_length>
>
> If the OP explains in more detail what s/he is trying to actually
> achieve, I might be able to come up with a more helpful answer.
>
STFU kiwi fagg0t

Re: Focal length in pixels
 

On 2007-04-11, orelza@gmail.com <orelza@gmail.com> wrote:
> Hey any body out there who can help me transform focal length in mm to
> focal length in pixels. to be precise am trying to get 24mm to pixels
> for scanned areal photos with dimensions 4992 x 3328 pixels. and for
> 153mm with dimensions 7242 x 7263 pixels.
>
> Thanks.

What are you actually trying to do?

In so far as the question has any meaning at all (one might as well ask for
a focal length in ounces or gallons), perhaps this is the answer, from
<http://www.worldserver.com/turk/quicktimevr/calculators.html>:

Field of View from EXIF Data

In the images captured by some digital cameras, there is some data that
is useful to determine the field of view for stitching panoramas.

Ideally, this would be the focal length in pixels, but unfortunately
the focal length is given in millimeters. In order to determine the
field of view, it is necessary to know the density of pixels (in
pixels per millimeter) on the virtual imaging sensor associated with
the image. Again, this pixel density is usually given in pixels/inch,
so conversion to pixels/mm is needed as well. The pixel density may be
different for the horizontal and vertical directions.

From the focal length in pixels, and the number of pixels in each
dimension of the image, it is possible to compute the field of view in
each dimension.

To convert from focal length in mm to focal length in pixels, where
pixel density is given in pixels/inch, use:

focalPixels = focalMM * pixelDensity / 25.4

To compute the field of view from focal length in pixels, use:

fov = 2 * atan( (H - 1) / (2 * focalPixels) )

where H is either width or height, for the field of view in the
respective direction. These equations are encapsulated into the
calculator below.

(there is a 'calculator' there apparently designed to perform the
calculations described). I won't try to comment on what that page is
trying to do or how it does it.

--
-- ^^^^^^^^^^
-- Whiskers
-- ~~~~~~~~~~

Re: Focal length in pixels
 

"Whiskers" <catwheezel@operamail.com> wrote in message
news:20070411184710.1977.a.NOFFLE@ID-107770.user.individual.net...
> On 2007-04-11, orelza@gmail.com <orelza@gmail.com> wrote:
>> Hey any body out there who can help me transform focal length in mm to
>> focal length in pixels. to be precise am trying to get 24mm to pixels
>> for scanned areal photos with dimensions 4992 x 3328 pixels. and for
>> 153mm with dimensions 7242 x 7263 pixels.
>>
>> Thanks.
>
> What are you actually trying to do?
>
> In so far as the question has any meaning at all (one might as well ask
> for
> a focal length in ounces or gallons), perhaps this is the answer, from
> <http://www.worldserver.com/turk/quicktimevr/calculators.html>:
>
> Field of View from EXIF Data
>
> In the images captured by some digital cameras, there is some data that
> is useful to determine the field of view for stitching panoramas.
>
> Ideally, this would be the focal length in pixels, but unfortunately
> the focal length is given in millimeters. In order to determine the
> field of view, it is necessary to know the density of pixels (in
> pixels per millimeter) on the virtual imaging sensor associated with
> the image. Again, this pixel density is usually given in pixels/inch,
> so conversion to pixels/mm is needed as well. The pixel density may be
> different for the horizontal and vertical directions.
>
> From the focal length in pixels, and the number of pixels in each
> dimension of the image, it is possible to compute the field of view in
> each dimension.
>
> To convert from focal length in mm to focal length in pixels, where
> pixel density is given in pixels/inch, use:
>
> focalPixels = focalMM * pixelDensity / 25.4
>
> To compute the field of view from focal length in pixels, use:
>
> fov = 2 * atan( (H - 1) / (2 * focalPixels) )
>
> where H is either width or height, for the field of view in the
> respective direction. These equations are encapsulated into the
> calculator below.
>
> (there is a 'calculator' there apparently designed to perform the
> calculations described). I won't try to comment on what that page is
> trying to do or how it does it.
>
Dang - atan = ancient history! I totally forgot everything they ever tried
to teach me in trig class!

Re: Focal length in pixels
 

On 2007-04-11, WhzzKdd <frack_this@email_is.invalid> wrote:
> "Whiskers" <catwheezel@operamail.com> wrote in message
> news:20070411184710.1977.a.NOFFLE@ID-107770.user.individual.net...
>> On 2007-04-11, orelza@gmail.com <orelza@gmail.com> wrote:

snip

> Dang - atan = ancient history! I totally forgot everything they ever tried
> to teach me in trig class!

You can get the same result by drawing the triangles to scale and
measuring the angles with a protractor, if you can draw accurately enough.

--
-- ^^^^^^^^^^
-- Whiskers
-- ~~~~~~~~~~

Re: Focal length in pixels
 

"Whiskers" <catwheezel@operamail.com> wrote in message
news:20070411193916.1977.c.NOFFLE@ID-107770.user.individual.net...
> On 2007-04-11, WhzzKdd <frack_this@email_is.invalid> wrote:
>> "Whiskers" <catwheezel@operamail.com> wrote in message
>> news:20070411184710.1977.a.NOFFLE@ID-107770.user.individual.net...
>>> On 2007-04-11, orelza@gmail.com <orelza@gmail.com> wrote:
>
> snip
>
>> Dang - atan = ancient history! I totally forgot everything they ever
>> tried
>> to teach me in trig class!
>
> You can get the same result by drawing the triangles to scale and
> measuring the angles with a protractor, if you can draw accurately enough.
>

My thoughts exactly <g>! And NOTHING I'd build would require any more
accuracy than that.