Photographing a mirror
carp
I would like to photograph a reflection in a mirror. The camera is
pointed head on at the reflection, lets say 40cm away from the mirror.
1) From which point of my lens should I measure the distance to the
mirror?
2) When trying to accurately measure the distance to the image (the
reflection) what range should I manually enter into the camera, if I
don't use auto-focus?
3) Would auto-focus work? (I want to get an un-blurred image of the
reflection.)
4) If I am aiming at 30 degrees to the mirror, rather than straight at
it, will that effect the calculation?
Thank you so much for your help!
Jürgen Exner
>I would like to photograph a reflection in a mirror. The camera is
>pointed head on at the reflection, lets say 40cm away from the mirror.
>
>1) From which point of my lens should I measure the distance to the
>mirror?
From the focal point of the lens, which depending on the design of the
lens is often but not always in the last third or quarter of the lens.
But why are you interested in the distance to the mirror? I though you
wanted to get a picture of the relection, not the mirror?
>2) When trying to accurately measure the distance to the image (the
>reflection) what range should I manually enter into the camera, if I
>don't use auto-focus?
>3) Would auto-focus work? (I want to get an un-blurred image of the
>reflection.)
Ultrasound measurement will not because if will measure the distance to
the mirror. Infrared, and any optical system should work without a
problem.
John McWilliams
Oh, my, you're making it way too hard. Just try it. Auto usually works
just fine.
--
John McWilliams
tony cooper
wrote:
I don't understand the question. Why do you want to measure?
I recently photographed a mirror. I wanted a shot of me taking a
picture. I had the camera on a tripod, swiveled it just enough to
allow the autofocus to focus on the frame, held the shutter half-way
down, and swiveled the camera back to straight-on and fired the
camera. Worked fine.
--
Tony Cooper - Orlando, Florida
Mark Thomas
> carp <yee...@gmail.com> wrote:
>> I would like to photograph a reflection in a mirror. The camera is
>> pointed head on at the reflection, lets say 40cm away from the mirror.
>>
>> 1) From which point of my lens should I measure the distance to the
>> mirror?
>
> From the focal point of the lens, which depending on the design of the
> lens is often but not always in the last third or quarter of the lens.
to use the sensor (or film) plane as the origin point?
> But why are you interested in the distance to the mirror? I though you
> wanted to get a picture of the relection, not the mirror?
>> 2) When trying to accurately measure the distance to the image (the
>> reflection) what range should I manually enter into the camera, if I
>> don't use auto-focus?
C - if you are focusing on the subject not the mirror, it is the total
distance. So camera-to-mirror *plus* mirror-to-subject.
>> 3) Would auto-focus work? (I want to get an un-blurred image of the
>> reflection.)
Yes, as long as mirror is clean, and not so small that the AF tries to
focus on the frame..
> Ultrasound measurement will not because if will measure the distance to
> the mirror. Infrared, and any optical system should work without a
> problem.
J - Apart from those old Polaroids, are there any mainstream cameras
that use ultrasound?
>> 4) If I am aiming at 30 degrees to the mirror, rather than straight at
>> it, will that effect the calculation?
C - Nope, as long as you use the method referred to in 2)
As they said, just use AF or manual focus - why do you need the distance?
Kennedy McEwen
<tony_co...@earthlink.net> writes
>
>I recently photographed a mirror. I wanted a shot of me taking a
>picture. I had the camera on a tripod, swiveled it just enough to
>allow the autofocus to focus on the frame, held the shutter half-way
>down, and swiveled the camera back to straight-on and fired the
>camera. Worked fine.
>
a fast aperture with shallow depth of field then that method would have
resulted in a sharp image of the mirror frame, smudges and dirt on the
mirror surface, but not of you!
You need to focus on the image of the reflection, if that is what you
want in prime focus, and that is the distance from the camera to the
mirror added to the distance from the mirror to the subject. If you and
the camera are the subject then it is twice the distance from you to the
mirror - NOT the distance to the mirror or its frame!
You can see this for yourself just by looking at the mirror - your eyes
change focus when you look at the frame and then at your reflection,
especially if you are close to the mirror in dim light, but not dark,
where the depth of field of your eye is less.
--
Kennedy
Yes, Socrates himself is particularly missed;
A lovely little thinker, but a bugger when he's pissed.
Python Philosophers (replace 'nospam' with 'kennedym' when replying)
bugbear
>
> You need to focus on the image of the reflection, if that is what you
> want in prime focus, and that is the distance from the camera to the
> mirror added to the distance from the mirror to the subject. If you and
> the camera are the subject then it is twice the distance from you to the
> mirror - NOT the distance to the mirror or its frame!
>
> You can see this for yourself just by looking at the mirror - your eyes
> change focus when you look at the frame and then at your reflection,
> especially if you are close to the mirror in dim light, but not dark,
> where the depth of field of your eye is less.
Yes - auto focus handles this just fine.
I took this shot:
http://i48.photobucket.com/albums/f234/bugbear33/pano_head.jpg
to show my camera in use. And I only have one camera ;-)
The shot was (of course) flipped in Gimp afterwards.
BugBear
tony cooper
<r...@nospam.demon.co.uk> wrote:
>In article <9s6kp4p7h3jq0a9mu...@4ax.com>, tony cooper
><tony_co...@earthlink.net> writes
>>
>>I recently photographed a mirror. I wanted a shot of me taking a
>>picture. I had the camera on a tripod, swiveled it just enough to
>>allow the autofocus to focus on the frame, held the shutter half-way
>>down, and swiveled the camera back to straight-on and fired the
>>camera. Worked fine.
>>
>But you were only in focus because of the depth of field! Had you used
>a fast aperture with shallow depth of field then that method would have
>resulted in a sharp image of the mirror frame, smudges and dirt on the
>mirror surface, but not of you!
Why would you do that, though? Use a shallow DOF and fast aperture?
You'd have to choose the setting to do that, and no one would.
>
>You need to focus on the image of the reflection, if that is what you
>want in prime focus, and that is the distance from the camera to the
>mirror added to the distance from the mirror to the subject. If you and
>the camera are the subject then it is twice the distance from you to the
>mirror - NOT the distance to the mirror or its frame!
That doesn't make sense to me. The reflected image in the mirror is
at the same distance, +/- a millimeter or so, as the frame. That is
what shows in the photograph. The reflected image is what is being
photographed. Not the person.
>You can see this for yourself just by looking at the mirror - your eyes
>change focus when you look at the frame and then at your reflection,
>especially if you are close to the mirror in dim light, but not dark,
>where the depth of field of your eye is less.
--
Dudley Hanks
"tony cooper" <tony_co...@earthlink.net> wrote in message
news:c3hlp4dhs65harh28...@4ax.com...
For an even more dramatic demonstration, sit in your car. Then, focus on
the frame of your rear-view mirror. Once focused, look at the image in the
mirror and compare it to both the frame and parts of the door which are
visible in your viewfinder.
Afteryou've checked out the image by focusing on the frame, focus on the
image in the mirror and check out the frame of the mirror / visible parts of
the door.
There is no such thing as the "image in the mirror. There is only the
mirror's surface and the light reflected by it.
Take Care,
Dudley
Floyd L. Davidson
>On Tue, 17 Feb 2009 08:24:33 +0000, Kennedy McEwen
><r...@nospam.demon.co.uk> wrote:
>>In article <9s6kp4p7h3jq0a9mu...@4ax.com>, tony cooper
>><tony_co...@earthlink.net> writes
>>>
>>>I recently photographed a mirror. I wanted a shot of me taking a
>>>picture. I had the camera on a tripod, swiveled it just enough to
>>>allow the autofocus to focus on the frame, held the shutter half-way
>>>down, and swiveled the camera back to straight-on and fired the
>>>camera. Worked fine.
>>>
>>But you were only in focus because of the depth of field! Had you used
>>a fast aperture with shallow depth of field then that method would have
>>resulted in a sharp image of the mirror frame, smudges and dirt on the
>>mirror surface, but not of you!
>
>Why would you do that, though? Use a shallow DOF and fast aperture?
>You'd have to choose the setting to do that, and no one would.
If you want the reflection of the person to be in focus
and the mirror's frame (plus the dirt/smudging on the
mirror surface) to be out of focus, use a fast aperture
with a narrow DOF.
If you want both the person's reflection and the mirror
frame to be in focus, stop the lense down as you did,
but set the camera to manual focus and adjust the focus
at about 1/3rd the distance from the frame to the
person.
>>You need to focus on the image of the reflection, if that is what you
>>want in prime focus, and that is the distance from the camera to the
>>mirror added to the distance from the mirror to the subject. If you and
>>the camera are the subject then it is twice the distance from you to the
>>mirror - NOT the distance to the mirror or its frame!
>
>That doesn't make sense to me. The reflected image in the mirror is
>at the same distance, +/- a millimeter or so, as the frame. That is
The distance to the reflected image is the distance from
the camera to the mirror *plus* the distance from the
mirror to the person.
That is because the image is *reflected* from, not
*projected* on, the mirror's surface.
>what shows in the photograph. The reflected image is what is being
>photographed. Not the person.
The *person* is being photographed.
Don't believe it? Use a relatively fast lense that can
focus relatively close (a 105mm f/2.8 macro lense will
really show this effect, but so will almost any lense
that is at least f/4 or so), and get up about as close
to a mirror as the lense can focus.
Focus on the edge of the frame. Note what the lense's
scale says the distance is (say 2 feet, or whatever).
Make an exposure so that you can verify that the frame
was in fact in focus, but do this with the lense wide
open. Then aim through the mirror at some object
reflected from least 5 to 10 feet distant from the
mirror, and focus on that. Again, take an exposure and
note the distance on the scale.
The image focused on the frame will show a very close
distance (the 2 feet or whatever) while the image
focused on the distant object will indeed show as some
significant distance. And in each case the other object
will be significantly out of focus due to the narrow
DOF.
You are not taking a picture of a *projected* image on
the mirror's surface, you are imaging a *reflected*
image.
>>You can see this for yourself just by looking at the mirror - your eyes
>>change focus when you look at the frame and then at your reflection,
>>especially if you are close to the mirror in dim light, but not dark,
>>where the depth of field of your eye is less.
That is exactly the same experiment, with your eyes, as
I described above for a camera. Try it!
--
Floyd L. Davidson <http://www.apaflo.com/floyd_davidson>
Ukpeagvik (Barrow, Alaska) fl...@apaflo.com
Jürgen Exner
>On Tue, 17 Feb 2009 08:24:33 +0000, Kennedy McEwen
><r...@nospam.demon.co.uk> wrote:
>
>>In article <9s6kp4p7h3jq0a9mu...@4ax.com>, tony cooper
>><tony_co...@earthlink.net> writes
>>>
>>>I recently photographed a mirror. I wanted a shot of me taking a
>>>picture. I had the camera on a tripod, swiveled it just enough to
>>>allow the autofocus to focus on the frame, held the shutter half-way
>>>down, and swiveled the camera back to straight-on and fired the
>>>camera. Worked fine.
>>>
>>But you were only in focus because of the depth of field! Had you used
>>a fast aperture with shallow depth of field then that method would have
>>resulted in a sharp image of the mirror frame, smudges and dirt on the
>>mirror surface, but not of you!
>
>Why would you do that, though? Use a shallow DOF and fast aperture?
Because you want to direct the viewers attention to the single object
that is in focus, not on items in the background?
>You'd have to choose the setting to do that, and no one would.
Actually many people would. It is standard practise for any
photographer.
>That doesn't make sense to me. The reflected image in the mirror is
>at the same distance, +/- a millimeter or so, as the frame.
No, it isn't. There is no real object to be photographed in the mirror,
it's only a virtual image, i.e. a reflection.
Therefore the total distance, which is relevant for the optical path is
the sum of distance from camera to mirror and from mirror to object.
jue
Keith Nuttle
When you take a picture in a mirror you are practically adding another
element in the lens system of the camera. The difference is that the
auxiliary mirror is not figured into the calibrations on the lens and in
the camera.
It is basic physics that the apparent distance an subject is from the
viewer is the sum of the distances of the viewer to the mirror and the
mirror to the subject. This assumes there is no curvature in the
mirror. To focus the camera to take the picture using a mirror set the
distance on the lens to that sum of the two.
Depending on how the range finder works in the camera, the automatic
focus may or may not work.
The following site deals with basic laws of reflection.
http://physics.bu.edu/~duffy/PY106/Reflection.html
Dudley Hanks
"Keith Nuttle" <keith_...@sbcglobal.net> wrote in message
news:BTAml.18011$c45....@nlpi065.nbdc.sbc.com...
Focusing manually can help make the experiment even more dramatic.
When you are sitting in your driver's seat, your camera should be fairly
close to the rear-view mirror. If you are parked on a street, you should
have a nice vista behind from which to extract different focus points. By
focusing on the mirror frame, the mirror's surface will be generally out of
focus, with the exception of some reflected parts from your car. As you
start to focus farther away, the car's door will slowly slip into haziness,
and the mirrored reflection will start to sharpen, starting with the region
right behind the car and slowly moving down the street to infinity...
Keep in mind that, if you could actually focus on "the image in the mirror,"
it would be impossible to build a mirrored supertelephoto lens or telescope,
since the mirror would screw up the focusing mechanism of the lens.
Take Care,
Dudley
Pat
> Jürgen Exner wrote:
> > carp <yee...@gmail.com> wrote:
> >> I would like to photograph a reflection in a mirror. The camera is
> >> pointed head on at the reflection, lets say 40cm away from the mirror.
>
> >> 1) From which point of my lens should I measure the distance to the
> >> mirror?
>
> > From the focal point of the lens, which depending on the design of the
> > lens is often but not always in the last third or quarter of the lens.
>
> J - ? Just nitpicking, but aren't lens focus distance scales supposed
> to use the sensor (or film) plane as the origin point?
I don't remember seeing them lately (but then again I havene't
looked), but back in "the day" there was a mark on the camera that
showed where the focal plane was. IIRC, it was a circle with a line
going through it (like overlaying a O and a ---
Pat
The autofocus and everything should work as long as you set the focus
point inside the mirror, not outside the mirror. Most autofocus
systems will select the NEAREST item to focus on, so if you have one
focus point on the subject in the mirror and another one on the wall
next to the mirror, the system will select the wall every time.
Generally you can shut off the "all focus points" and select a single
one. Select a single on in the middle of the viewfinder and point
that at your subject and you'll be fine. The camera won't even know
the mirror is there.
You do need to pay attention to a few things. You are shooting a
person who is standing next to you. The mirror is leaning against the
wall with the bottom sticking out a foot. Say you are focusing on the
person's belt buckle. Due to the angle of the mirror, the face will
be farther away from you than the belt buckle and the feet will be
closer (because of your distance to the mirror). Theoretically, with
a large aperture, you could have areas out of focus.
Finally, the other thing your introduce into the equation is the
mirror itself. Any flaws in the mirror will show up in the final
picture.
Good luck with it.
GregS
>Just remember that because the mirror coating is on the back of the
>mirror, you will get some diffraction through the glass on the front of
>the mirror. If you're at a distance you might not notice much but that
>is why astronomical and dental mirrors are "front surface".
And SLR and laser mirrors.
grge
Chris Malcolm
> On Feb 16, 9:23?pm, Mark Thomas <mark.thoma...@gmail.com> wrote:
>> J?rgen Exner wrote:
>> > carp <yee...@gmail.com> wrote:
>> >> I would like to photograph a reflection in a mirror. The camera is
>> >> pointed head on at the reflection, lets say 40cm away from the mirror.
>>
>> >> 1) From which point of my lens should I measure the distance to the
>> >> mirror?
>>
>> > From the focal point of the lens, which depending on the design of the
>> > lens is often but not always in the last third or quarter of the lens.
>>
>> to use the sensor (or film) plane as the origin point?
> I don't remember seeing them lately (but then again I havene't
> looked), but back in "the day" there was a mark on the camera that
> showed where the focal plane was. IIRC, it was a circle with a line
> going through it (like overlaying a O and a ---
At least most of the more expensive Sony cameras have that mark. I
don't know about all lenses, it may be too small a difference to
matter for longer distances, but it's certainly the distance from that
mark that macro lenses are calibrated to.
--
Chris Malcolm
Mark Thomas
> When you are sitting in your driver's seat, your camera should be fairly
And here's a random example:
http://vwkombi.com/photos/beetle-bash-bug-jam-etc/Images/0.jpg
Obviously the 'image' is not at the same distance as the mirror itself.
Paul Furman
Fun to disassemble old hardware like that. I have a pentamirror from a
D70 and some nice long narrow mirrors from old scanners & fax machines.
They are so much brighter & sharper than a rear coated mirror, it's
surprising.
But yeah, the focus is according to the light path which of course
includes the full reflected distance.
Now that that's clear I'll describe a much more confusing scenario: the
'ground glass' viewfinder focusing aid in an SLR camera. In that case
you focus on the projected image on the frosted glass 'movie screen'
surface plus it is partly transparent so you get some additional detail
from the clear view through. Now first you might think that's too close
and the background would be out of focus but it's set up so your eye is
focusing to a virtual distance of (if I recall correctly) about 18
inches. The human eye is more like a web cam than a 35mm imager so the
depth of field is big in decent light, so there is still more detail at
infinity than the 'huge' 35mm system can manage. In order for our eyes
to be at a similar scale to a 35mm camera, we would need something like
4-inch diameter eyes.
--
Paul Furman
www.edgehill.net
www.baynatives.com
all google groups messages filtered due to spam
carp
> carp <yee...@gmail.com> wrote:
> >I would like to photograph a reflection in a mirror. The camera is
> >pointed head on at the reflection, lets say 40cm away from the mirror.
>
> >1) From which point of my lens should I measure the distance to the
> >mirror?
>
> From the focal point of the lens, which depending on the design of the
> lens is often but not always in the last third or quarter of the lens.
>
> But why are you interested in the distance to the mirror? I though you
> wanted to get a picture of the relection, not the mirror?
>
lost between these two.
carp
> In article <9s6kp4p7h3jq0a9muk6qc6tt16k0m1r...@4ax.com>, tony cooper
> <tony_cooper...@earthlink.net> writes
>
> >I recently photographed a mirror. I wanted a shot of me taking a
> >picture. I had the camera on a tripod, swiveled it just enough to
> >allow the autofocus to focus on the frame, held the shutter half-way
> >down, and swiveled the camera back to straight-on and fired the
> >camera. Worked fine.
>
> But you were only in focus because of the depth of field! Had you used
> a fast aperture with shallow depth of field then that method would have
> resulted in a sharp image of the mirror frame, smudges and dirt on the
> mirror surface, but not of you!
>
> You need to focus on the image of the reflection, if that is what you
> want in prime focus, and that is the distance from the camera to the
> mirror added to the distance from the mirror to the subject. If you and
> the camera are the subject then it is twice the distance from you to the
> mirror - NOT the distance to the mirror or its frame!
>
> You can see this for yourself just by looking at the mirror - your eyes
> change focus when you look at the frame and then at your reflection,
> especially if you are close to the mirror in dim light, but not dark,
> where the depth of field of your eye is less.
What a clear explanation of the problem! Thank you :)
carp
Nice shot. I like the backcloth.
carp
Mark, I love that photo! Thank you for posting it. It is also a clear
example of the image and mirror frame being in different focus.
John McWilliams
Excellent!
--
john mcwilliams
Kennedy McEwen
<tony_co...@earthlink.net> writes
>On Tue, 17 Feb 2009 08:24:33 +0000, Kennedy McEwen
><r...@nospam.demon.co.uk> wrote:
>
>>Had you used
>>a fast aperture with shallow depth of field then that method would have
>>resulted in a sharp image of the mirror frame, smudges and dirt on the
>>mirror surface, but not of you!
>
>Why would you do that, though? Use a shallow DOF and fast aperture?
To isolate your image FROM the dirt and smudges on the mirror, as well
as normal photographic creativity of shallow DoF!
>You'd have to choose the setting to do that, and no one would.
Fortunately, I have been away for a few days and in that time quote a
few people have posted links to photographs showing that plenty of
people do precisely that!
>>You need to focus on the image of the reflection, if that is what you
>>want in prime focus, and that is the distance from the camera to the
>>mirror added to the distance from the mirror to the subject. If you and
>>the camera are the subject then it is twice the distance from you to the
>>mirror - NOT the distance to the mirror or its frame!
>
>That doesn't make sense to me.
That's your problem, nobody else can fix your sense!
> The reflected image in the mirror is
>at the same distance, +/- a millimeter or so, as the frame.
No matter how many times you repeat it, it doesn't make it right. Since
it isn't right, every time you repeat it makes you more idiotic.
> That is
>what shows in the photograph. The reflected image is what is being
>photographed. Not the person.
And the reflected image is ALWAYS further away than the mirror itself.
This animation should make it obvious why, even for you!
http://www.glenbrook.k12.il.us/GBSSCI/PHYS/mmedia/optics/ifpm.gif
If you place yourself and camera at the position of the first yellow dot
on the left of the animation, then the reflected image that you see and
photograph is at the second yellow dot on the right, which is at twice
the distance to the mirror, shown by the black vertical line.
C J Campbell
> Hello!
>
>
> I would like to photograph a reflection in a mirror. The camera is
> pointed head on at the reflection, lets say 40cm away from the mirror.
>
> 1) From which point of my lens should I measure the distance to the
> mirror?
You measure it from the film or sensor plane, to the mirror, then to
the subject. You never measure focus distance from the lens.
>
> 2) When trying to accurately measure the distance to the image (the
> reflection) what range should I manually enter into the camera, if I
> don't use auto-focus?
Total distance of camera to mirror to subject.
>
> 3) Would auto-focus work? (I want to get an un-blurred image of the
> reflection.)
Depends. Some auto-focus systems are fooled by mirrors. Most modern
ones are not. Check your camera's manual.
>
> 4) If I am aiming at 30 degrees to the mirror, rather than straight at
> it, will that effect the calculation?
It "affects" the calculation, not "effects" it. If it effected the
calculation, it would do the calculation for you. :-) In any case, it
all depends on what you mean by whether it affects the calculation.
Wedding and portrait photographers do this shot all the time. Seems
like every bride wants a picture of herself getting ready in the
mirror. Your biggest problem is not focal distance, but getting rid of
unwanted reflections, such as flash.
--
Waddling Eagle
World Famous Flight Instructor
Frank ess
I always believed my tenth-grade science teacher, so when he said,
"Remember: the image is as far behind the mirror as the object is in
front of it", I did, and it has always worked out for my version of
the world.
--
Frank ess
Robert Coe
wrote:
: On Feb 16, 9:23 pm, Mark Thomas <mark.thoma...@gmail.com> wrote:
: > Jürgen Exner wrote:
: > > carp <yee...@gmail.com> wrote:
: > >> I would like to photograph a reflection in a mirror. The camera is
: > >> pointed head on at the reflection, lets say 40cm away from the mirror.
: >
: > >> 1) From which point of my lens should I measure the distance to the
: > >> mirror?
: >
: > > From the focal point of the lens, which depending on the design of the
: > > lens is often but not always in the last third or quarter of the lens.
: >
: > J - ? Just nitpicking, but aren't lens focus distance scales supposed
: > to use the sensor (or film) plane as the origin point?
:
: I don't remember seeing them lately (but then again I havene't
: looked), but back in "the day" there was a mark on the camera that
: showed where the focal plane was. IIRC, it was a circle with a line
: going through it (like overlaying a O and a ---
My Canons (50D and 400D) have that mark.
Bob