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DPChallenge Forums >> Tips, Tricks, and Q&A >> focusing on a reflection
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09/25/2002 01:17:03 PM · #1
I have an idea for the reflection challenge, but I'm having a hard time executing the shot. I want to take a shot of reflection in my watch crystal, but I can't get the camera to focus correctly. Either the watch face is is focus, or the reflection is... any tips? FWIW... the camera is a Sony DSC-S85. It does not have a manual focus mode, but I can set the focal distance which would act as a pseudo-manual focus mode.
09/25/2002 01:19:23 PM · #2
You'll probably need a tripod to pull this one off. You'll want to use the smallest aperature you can (f11, f22, etc.) to try to get everything in focus. Hope it turns out well for you!
09/25/2002 02:02:52 PM · #3
You need to use maximum depth of field... The largest F number you can achieve.

when photogrphing a reflection, your depth of field must be deep enough to cover the distance between the reflective surface AND the object that is being reflected...


* This message has been edited by the author on 9/25/2002 2:01:26 PM.
09/25/2002 02:47:26 PM · #4
when photogrphing a reflection, your depth of field must be deep enough to cover the distance between the reflective surface AND the object that is being reflected...

Does this imply that the reflection and the original object must both be in the photograph?



* This message has been edited by the author on 9/25/2002 2:45:57 PM.
09/25/2002 02:58:47 PM · #5
Originally posted by mcrael:
[i]when photogrphing a reflection, your depth of field must be deep enough to cover the distance between the reflective surface AND the object that is being reflected...

Does this imply that the reflection and the original object must both be in the photograph?

[/i]

No...

This is an interesting phenomenon of photography. You would normally think that a shallow depth of field would work since your reflecting surface and the reflection are on the same plane. However, the object that is creating the reflection on that plane may be difficult to bring into focus WITH the reflecting surface.

You have distance between these two objects. you will be photographing the reflective surface... not BOTH objects.

If you were photographing, for instance, both of these objects, and one is farther away than the other, you would need a certain depth of field setting to get both objects in focus since they are not on the same plane. You will need the SAME depth of field to photograph the reflective surface if you want the surface and the object's reflection to both be in sharp focus.

I'm not sure if i'm making sense here or not... :(
09/25/2002 03:24:55 PM · #6
John,

Riddle me this:

If I want to photograph the reflection of an object in a mirror and I set my focal distance manually, should I set it to

a) the distance from my camera to the mirror PLUS the distance from the mirror to the object, or...
b) just the distance from my camera to the mirror?

Basically, I guess my (and some others, apparently) assumption was that whatever is reflected in a mirror is considered to be in the same plane as the mirror itself (i.e. if you have the mirror in focus, the reflection should also be in focus). I've never tried photographing a mirror reflection, though... but it sure does bring up some interesting topics! :-)


09/25/2002 03:37:45 PM · #7
Focal length and depth of field (aperture setting) are not the same thing... They are related to each other though...

Let's say, for instance, that you want to photograph a mirrored reflection... The revlection has two elements that you want to be in focus. The first element is 10 feet from the mirror and the second element is 20 feet from the mirror. Since the mirror itself is not the object being photographed, you would need to have a depth of field setting that would cover the distance from the mirror to the farthest object that you want to be in focus.

In the original question here, jack wanted to deal with the surface of a wristwatch. he wants the hands of the watch to be in focus along with the reflection on the watch crystal. In this case, his depth of field needs be the same as the mirror example... he needs enough depth of field to cover the distance between the watch face and the object in the reflection... The surface of the watch is like the surface of the mirror...

09/25/2002 06:00:57 PM · #8
I also found this brief article useful...

Reflections How-To
09/25/2002 06:24:52 PM · #9
You can see this looking at anything in a mirror that has something
written on it 'e.g an 'objects in the mirror may be closer than
they appear' (which is again an indication of the problem.

Just looking, no camera - you can focus on the thing being
reflected, or you can focus on the writing - its hard to focus on
both at the same time, if the reflected thing is far enough away

Same problem here, when you point a camera at it - it has to
have sufficient depth of field to resolve the reflection source and
the reflected item.

Photographing things in a 'perfect mirror' works, as you usually
don't care about the mirror being in focus, just the thing being
reflected. The problems occur when you want to have both in focus

[Aside]
On the car mirror thing, when you look in the mirror, objects appear
to you to be the distance between you and the mirror + the distance
from the mirror to the object away.

This is why passenger mirror have the warning, as the effect is more
pronounced in that side (being further from the driver)

* This message has been edited by the author on 9/25/2002 6:24:45 PM.
09/25/2002 07:11:44 PM · #10
Jak the scaned articale is not readable on my screne. :(
09/25/2002 07:24:19 PM · #11
Originally posted by aelith:
Jak the scaned articale is not readable on my screne. :(

Sorry! It isn't my article so I can't fix it. It looks pretty good on my machine, though, so I am not sure what the problem might be.


09/25/2002 07:33:32 PM · #12
Originally posted by aelith:
Jak the scaned articale is not readable on my screne. :(

Your browser might be resizing it to fit the available page -
if you have internet explorer, wave your mouse over the pic, and
particularly in the lower right corner - if you get an 'expand'
type icon click it and you might be able to see it.

Alternatively, save the image off and open it in a graphics viewer
and zoom it...
09/25/2002 07:37:41 PM · #13
thanks
09/26/2002 12:09:10 AM · #14
Would someone mind putting this in Mavica Language I can understand? The fine people at Sony have not provided me with f-stops to adjust, only focus distance (which I learned in an earlier post has nothing to do with f-stops- mine always seem to come out to f3.8).

Someone please give me an example using the Mavica focus settings of Macro, .5m, 1m, 3m, 7m and infinity. Logic tells me that if I chose inifinity, then all things in teh whole frame regardless of distance should be in focus, no? This doesn't seem the case in trial and error.
09/26/2002 12:22:19 AM · #15
Originally posted by jacksonpt:
I have an idea for the reflection challenge, but I'm having a hard time executing the shot. I want to take a shot of reflection in my watch crystal, but I can't get the camera to focus correctly. Either the watch face is is focus, or the reflection is... any tips? FWIW... the camera is a Sony DSC-S85. It does not have a manual focus mode, but I can set the focal distance which would act as a pseudo-manual focus mode.

If your camera is too close to the watch, try activating the macro mode.
09/26/2002 12:37:55 AM · #16
Originally posted by TechGuy:
Originally posted by jacksonpt:
[i]I have an idea for the reflection challenge, but I'm having a hard time executing the shot. I want to take a shot of reflection in my watch crystal, but I can't get the camera to focus correctly. Either the watch face is is focus, or the reflection is... any tips? FWIW... the camera is a Sony DSC-S85. It does not have a manual focus mode, but I can set the focal distance which would act as a pseudo-manual focus mode.


If your camera is too close to the watch, try activating the macro mode.[/i]

I think from all the discussions and articles and general physics involved
that macro mode is entirely the wrong end to be at - infinity focus
might be closer to what you want, to get the largest depth of field.

But play with it, and take a couple of shots each way - and then let
us know which works the best!
09/26/2002 01:37:20 AM · #17
Originally posted by GordonMcGregor:
[Aside]
On the car mirror thing, when you look in the mirror, objects appear
to you to be the distance between you and the mirror + the distance
from the mirror to the object away.

This is why passenger mirror have the warning, as the effect is more
pronounced in that side (being further from the driver


I thought the warning was there because most of those mirrors are convex (to try and see into the "blind spot") and therefore make objects appear smaller, and thus farther away -- I don't think the extra 3-4 feet across the car interior makes much difference.
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