Computing image size different lens, subject distance

Greetings,
My apologies for being somewhat off topic here, but in reading this
group for some time, I noticed there are certinaly a number of
compenent people who can probably answer my question.

In using medium format, or 35mm for that matter, can I compute the size
of my subject on film given:

h - the height of the subject
d - the distance between film/lens and subject
l - focal length of the lens being used

Perhaps this is merely a question of magnification. Can anybody point
me to a book or on-line resource that discusses the technical/
mathematical aspects of photography?


Thank you,
Tom

On 12 Aug 2004 08:47:50 -0700, (TWW) wrote:

Greetings,
My apologies for being somewhat off topic here, but in reading this
group for some time, I noticed there are certinaly a number of
compenent people who can probably answer my question.

In using medium format, or 35mm for that matter, can I compute the size
of my subject on film given:

h - the height of the subject
d - the distance between film/lens and subject
l - focal length of the lens being used

Perhaps this is merely a question of magnification. Can anybody point
me to a book or on-line resource that discusses the technical/
mathematical aspects of photography?

Here's a freeware program that does common photo calculations:

http://tangentsoft.net/fcalc/

Chris Ellinger
Ann Arbor, MI USA

My zone plate photos: http://www.ellingerphoto.com

On 12 Aug 2004 08:47:50 -0700, (TWW) wrote:

Greetings,
My apologies for being somewhat off topic here, but in reading this
group for some time, I noticed there are certinaly a number of
compenent people who can probably answer my question.

In using medium format, or 35mm for that matter, can I compute the size
of my subject on film given:

h - the height of the subject
d - the distance between film/lens and subject
l - focal length of the lens being used

Perhaps this is merely a question of magnification. Can anybody point
me to a book or on-line resource that discusses the technical/
mathematical aspects of photography?

Here's a freeware program that does common photo calculations:

http://tangentsoft.net/fcalc/

Chris Ellinger
Ann Arbor, MI USA

My zone plate photos: http://www.ellingerphoto.com

"TWW" wrote in message
om...
SNIP
In using medium format, or 35mm for that matter, can I compute
the size of my subject on film given:

h - the height of the subject
d - the distance between film/lens and subject
l - focal length of the lens being used

Perhaps this is merely a question of magnification.

Yes.

If the distances from the object to the lens and from the lens to the
image are S1 and S2 respectively, for a lens of negligible thickness
they are found by the thin lens formula:
1/S1 + 1/S2 = 1/f.
This is accurate enough for most applications, although at closer
distances the "thin lens" must be replaced by the unknown distance
between the front and back principal planes, adding to the total
subject to focal plane distance.

Can anybody point me to a book or on-line resource that discusses
the
technical/mathematical aspects of photography?

A quick Google search for "lens formula" and "magnification factor"
turns up:
http://www.wordiq.com/definition/Lens_(optics)#Imaging_properties

Bart

"TWW" wrote in message
om...
SNIP
In using medium format, or 35mm for that matter, can I compute
the size of my subject on film given:

h - the height of the subject
d - the distance between film/lens and subject
l - focal length of the lens being used

Perhaps this is merely a question of magnification.

Yes.

If the distances from the object to the lens and from the lens to the
image are S1 and S2 respectively, for a lens of negligible thickness
they are found by the thin lens formula:
1/S1 + 1/S2 = 1/f.
This is accurate enough for most applications, although at closer
distances the "thin lens" must be replaced by the unknown distance
between the front and back principal planes, adding to the total
subject to focal plane distance.

Can anybody point me to a book or on-line resource that discusses
the
technical/mathematical aspects of photography?

A quick Google search for "lens formula" and "magnification factor"
turns up:
http://www.wordiq.com/definition/Lens_(optics)#Imaging_properties

Bart

TWW wrote:
Greetings,
My apologies for being somewhat off topic here, but in reading this
group for some time, I noticed there are certinaly a number of
compenent people who can probably answer my question.

In using medium format, or 35mm for that matter, can I compute the
size of my subject on film given:

h - the height of the subject
d - the distance between film/lens and subject
l - focal length of the lens being used

Old aerial photo ratio of I:F::G:A can be used...Image size is to Focal
length as Ground is to Altitude. Using your letters...
X:l::d:h therefore, X = (l*d)/h

--
dadiOH
_____________________________

dadiOH's dandies v3.0...
....a help file of info about MP3s, recording from
LP/cassette and tips & tricks on this and that.
Get it at http://mysite.verizon.net/xico
____________________________

TWW wrote:
Greetings,
My apologies for being somewhat off topic here, but in reading this
group for some time, I noticed there are certinaly a number of
compenent people who can probably answer my question.

In using medium format, or 35mm for that matter, can I compute the
size of my subject on film given:

h - the height of the subject
d - the distance between film/lens and subject
l - focal length of the lens being used

Old aerial photo ratio of I:F::G:A can be used...Image size is to Focal
length as Ground is to Altitude. Using your letters...
X:l::d:h therefore, X = (l*d)/h

--
dadiOH
_____________________________

dadiOH's dandies v3.0...
....a help file of info about MP3s, recording from
LP/cassette and tips & tricks on this and that.
Get it at http://mysite.verizon.net/xico
____________________________

TWW wrote:
Greetings,
My apologies for being somewhat off topic here, but in reading this
group for some time, I noticed there are certinaly a number of
compenent people who can probably answer my question.

In using medium format, or 35mm for that matter, can I compute the
size of my subject on film given:

h - the height of the subject
d - the distance between film/lens and subject
l - focal length of the lens being used

Old aerial photo ratio of I:F::G:A can be used...Image size is to Focal
length as Ground is to Altitude. Using your letters...
X:l::d:h therefore, X = (l*d)/h

--
dadiOH
_____________________________

dadiOH's dandies v3.0...
....a help file of info about MP3s, recording from
LP/cassette and tips & tricks on this and that.
Get it at http://mysite.verizon.net/xico
____________________________