"Bill Pragnell" <bil### [at] hotmailcom> wrote:
> As an aside, I have recently ordered some mirrored spheres from a garden centre
> (of all places!) to do exactly what you described, or at least attempt it. I
> suspect the actual photography will be the difficult part. My camera's not an
> SLR, so I hope it's up to the task... oh well, good excuse to buy me a new toy
> if it's not!

Good luck and have fun!
I have made a few in the past
(http://barberofcivil.deviantart.com/gallery/#HDR-Light-Probes) using a regular
digital camera (Canon S2, with 12X optical zoom though) and steel balls (those
chinese stress balls ~2" diameter).  I used HDRSop and followed the tutorials
to assemble them (http://gl.ict.usc.edu/HDRShop/tutorial/tutorial5.html).

A few pointers for you:

- Make sure you use a good dynamic range.  Check your scene beforehand with your
camera, decrease stops until the scene is mostly dark and light sources are as
dim as possible, then increase until the scene is mostly saturated

- You can make a usuable HDR with as little as 3 exposures, two as noted above,
plus one in between at a balanced exposure.  However, more exposure can be
helpful in ensuring a good dynamic recreation and minimize errors from noise.

- Try to make sure the perpendicular shots are taken from the same distance if
possible to minimize the parallax/perspective difference.  Also try to get
camera as far away from the ball as possible to minimize overall perspective
effects (this is where large zoom can help), however this is not critical so
long as you have sufficient distance.  It also makes a much smaller
camera/photographer reflection to be removed.

- adjust the shutter speed only for exposures.  Aperture and ISO have other
photographic effects that will impact the HDR assembly.

- keep the camera still and stationary.  This makes assembling the HDRs easier,
however, jitter can be adjusted for if necessary, it can just be tedious

- make sure there is minimal movement of background objects (ie, cars driving,
people walking, even fast moving clouds) as this can be quite evident and cause
visual errors in assembling the HDR.

Most of all, have fun!  Try to pick scenes which will produce interesting
reflection or lighting effects.  And by all means post them where I can get
them, I'm always looking to expand my collection.

One further item of interest.  If you have a Canon camera, you may want to check
out CHDK (http://chdk.wikia.com/wiki/Main_Page). I have it installed on my
cameras and it installs easily and doesn't harm the camera at all.  It can give
you a few advantages such as the scripting ability so you can setup your camera
push a button once and wait, minimizing jitter (look in the user-made scripts
section, I actually have a couple in there myself that are for HDR usage).
Also it makes shutter speeds available beyond those avaiable in the standard
camera (available shutter speeds from 64s to as fast as 1/32000 or possibly
even faster, yes that is three zeros) it can make a point and shoot Canon
camera far more powerful than any DSLR money can buy!

-tgq

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