Macro question and calculation

Do you know a equations on how to calculate magnicication with the focal
length and subject distance for macro and non-macro lenses (or a good
softwar to do that)?

I would like to know something.

With a sigma 180mm macro, if my subject is at 0,46 m (the minimal working
distance), the magnification will be 1:1. If the distance between my lense
and the subject increase, the magnification will decrease. I would like to
know how to calculate the distance between the subject and the lense to get
a magnification of 1:2, 1:3, etc or at a give distance, which magnification
will I have...

I have the Canon EF 70-300 IS USM and if I remember, the maximum
magnification is 0,25X at 1,5 m of working distance and 300mm of focal
lenght. At which distance of the subect, the Canon EF 70-300 begin to have a
higher magnification ?? At 1,5 meter, will I have a greater magnification
with the Sigma 180 mm than with the Canon 70-300 ?? at 10 meters ??

Well... I suppose it is not simple ! I will be very glad if someone can help
me !

Thank you very much for your time !

"Jonathan Sylvestre" wrote in message
. ..
Do you know a equations on how to calculate magnicication with the focal
length and subject distance for macro and non-macro lenses (or a good
softwar to do that)?

I would like to know something.

With a sigma 180mm macro, if my subject is at 0,46 m (the minimal working
distance), the magnification will be 1:1. If the distance between my lense
and the subject increase, the magnification will decrease. I would like to
know how to calculate the distance between the subject and the lense to
get a magnification of 1:2, 1:3, etc or at a give distance, which
magnification will I have...

I have the Canon EF 70-300 IS USM and if I remember, the maximum
magnification is 0,25X at 1,5 m of working distance and 300mm of focal
lenght. At which distance of the subect, the Canon EF 70-300 begin to have
a higher magnification ?? At 1,5 meter, will I have a greater
magnification with the Sigma 180 mm than with the Canon 70-300 ?? at 10
meters ??

Well... I suppose it is not simple ! I will be very glad if someone can
help me !

Thank you very much for your time !


Here is a web site with a magnifaction calculator:

http://hyperphysics.phy-astr.gsu.edu...lenseq.html#c1

However there is a problem with using a formula like this in that it is
difficult to determine the object distance with real lenses.
The formula used is the "thin lens" formula which assumes that the lens is
infinetly thin, whereas in real life the lens is not. For
long subject distances this can be neglected, but for closer up it is
significant. Some prime (non-zoom)lenses have a mark on the
lens barrel which indicates the "thin lens" equivalent. Also some lenses
come with a table that shows magnification at
various focus distances.

Jonathan Sylvestre wrote:
Do you know a equations on how to calculate magnicication with the focal
length and subject distance for macro and non-macro lenses (or a good
softwar to do that)?

I would like to know something.

With a sigma 180mm macro, if my subject is at 0,46 m (the minimal working
distance), the magnification will be 1:1. If the distance between my lense
and the subject increase, the magnification will decrease. I would like to
know how to calculate the distance between the subject and the lense to get
a magnification of 1:2, 1:3, etc or at a give distance, which magnification
will I have...

I have the Canon EF 70-300 IS USM and if I remember, the maximum
magnification is 0,25X at 1,5 m of working distance and 300mm of focal
lenght. At which distance of the subect, the Canon EF 70-300 begin to have a
higher magnification ?? At 1,5 meter, will I have a greater magnification
with the Sigma 180 mm than with the Canon 70-300 ?? at 10 meters ??

Well... I suppose it is not simple ! I will be very glad if someone can help
me !

Thank you very much for your time !

In a "pure" lens formula the distace from the subject to the nodal
point of the lens should be the same as the focal length of the lens.
So this formula is dashed immedeately with the distance of .46m for a
180mm lens. You may just have to test this out, the lens does have
magnification markings. The distance at 1:2 should be 2x of 1:1. But
with macros for 35mm or dslrs manufacturers seem to have a sliding
scale, or focal length changes as the lens expands. I know on my view
camera at 1:1 my 120 macro lens is 120mm from the subject, and the
distance to trhe film plane is 240mm, at 1:2 the distance to the
subject is 240mm and the lens to film plane is 180mm. The lens at
infinity is 120mm from lens to film plane. The constraints of making
lenses for DSLRs makes these calculations difficult. Testing is the
best way to handle it.

Tom

Jonathan Sylvestre wrote:
Do you know a equations on how to calculate magnicication with the focal
length and subject distance for macro and non-macro lenses (or a good
softwar to do that)?

I would like to know something.

With a sigma 180mm macro, if my subject is at 0,46 m (the minimal working
distance), the magnification will be 1:1. If the distance between my lense
and the subject increase, the magnification will decrease. I would like to
know how to calculate the distance between the subject and the lense to get
a magnification of 1:2, 1:3, etc or at a give distance, which magnification
will I have...

I have the Canon EF 70-300 IS USM and if I remember, the maximum
magnification is 0,25X at 1,5 m of working distance and 300mm of focal
lenght. At which distance of the subect, the Canon EF 70-300 begin to have a
higher magnification ?? At 1,5 meter, will I have a greater magnification
with the Sigma 180 mm than with the Canon 70-300 ?? at 10 meters ??

Well... I suppose it is not simple ! I will be very glad if someone can help
me !

Thank you very much for your time !


Try this web site it may help.
http://www.dofmaster.com/dofjs.html

tomm42 wrote:

lenses for DSLRs makes these calculations difficult. Testing is the
best way to handle it.

Yes, photograph a ruler.