[Tfug] Way OT: optics mumbo jumbo

[Brian Murphy]

As a pro-am photographer, what you need to use is a flash diffuser.
Sometimes this is also known as a "softbox."

There are lots of home-made ways to build the softbox:

http://www.diyphotography.net/studio_lighting_diy_softboxing_the_world

On a small digital camera, experiment with different thicknesses of
fabric or thin paper to reduce the glare.  Medical gauze might be a
good item to try.

Brian



Quoting Jeremy D Rogers <jdrogers at optics.arizona.edu>:
> I like how Bexley hinted at the presence of "optics people" on the
> list.. Here and I have a PhD in optics and I am still trying to figure
> out how to get a good picture of my instrument. I think others got the
> math right below, but in my experience this kind of problem is less
> about the math and more about creativity.
> One suggestion that someone in my program made to me once (I wish I
> could remember who and give him credit) was to set a really long
> exposure like 10 to 30 second and then use a flashlight and walk
> around the subject with the flashlight lighting at different angles.
> This long exposure means you can use a small aperture and have a long
> depth of field and the integration of the moving light makes for
> really nice even illumination.
> It's worth trying a few times to get it right (try with room lights on
> or off, etc), but I have been happy with the result.
>
> JDR
>
> On 3/19/08, erich <erich1 at copper.net> wrote:
>> Bexley Hall wrote:
>>
>>  >Hi,
>>  >
>>  >This is *way* OT but it seems there are some folks
>>  >with more than a casual knowledge of optics (while
>>  >I have *less* than a casual knowledge!) so...
>>  >
>>  >I often take photos of things that I have built
>>  >(etc.) to show clients problems that I have
>>  >encountered (picture, 1000 words, etc.).
>>  >
>>  >But, I don't waste a lot of time thinking about
>>  >*how* I do this -- I just keep dicking around
>>  >with where I am standing, ambient lighting,
>>  >camera angle, etc. until I get something that
>>  >more-or-less shows what I want/need to show.
>>  >(much easier when you can click a dozen frames
>>  >"for free" instead of having to use Polariods!!)
>>  >
>>  >Dealing with the flash is almost always a PITA
>>  >for me.  It's always "too hot" and too much
>>  >reflected glare, etc.  Granted, I can change the
>>  >camera angle to eliminate this to some extent.
>>  >But, at other times, it just moves the reflection
>>  >to another surface, etc.
>>  >
>>  >Often, my solution is to back away from the item
>>  >(light falls off as the square -- or cube? -- of
>>  >the distance) until the reflections are manageable.
>>  >
>>  >
>>
>> Inverse 4th power (x^(-4)), because the light makes a round trip
>>  from a light-dispersing object.
>>
>>
>>  >Of course, this means the image is smaller  :-/
>>  >
>>  >
>>
>> The aparture is constant. So, the light gathering ability doesn't
>>  increase unless you physically move closer to the subject.
>>
>>
>>  >So, I crank up the (optical) zoom to make the
>>  >image large enough to be useful.
>>  >
>>  >
>>  >Now, my naive question:  by doing this, am I,
>>  >to some extent, counteracting the effect of
>>  >"moving away" from the target?  I.e., does
>>  >the magnification I am bringing in to play
>>  >*increase* the amount of light that strikes
>>  >the (digital) film?
>>  >
>>  >
>>
>> Is a thought experiment so necessary? Why not just test it for
>>  real? Choose a subject and chalk off distances from it. Use
>>  the same camera. Then view images on the same monitor screen.
>>
>>
>>  ><sheepish grin>  I've tried to construct a
>>  >"thought experiment" to convince myself one way
>>  >or the other but seem to just be thinking myself
>>  >in circles...
>>  >
>>  ><shrug>  I definitely won't lose any sleep over
>>  >this but it *is* amusing (to me) to think about
>>  >what's really going on...
>>  >
>>  >We now return you to your regularly scheduled
>>  >program...
>>  >
>>  >
>>  >      
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>
>
> --
> Jeremy D. Rogers, Ph.D.
> Postdoctoral Fellow
> Biomedical Engineering
> Northwestern University
>
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The opinions or statements expressed herein are my own and should not be
taken as a position, opinion, or endorsement of the University of
Arizona.