On Tue, 4 Mar 2008 17:02:32 -0000, "Focus" <focus@[EMAIL PROTECTED]
> wrote:
>
>"Ray Fischer" <rfischer@[EMAIL PROTECTED]
> wrote in message
>news:47cd7d03$0$36355$742ec2ed@[EMAIL PROTECTED]
>> Focus <focus@[EMAIL PROTECTED]
> wrote:
>>>"Buy_Sell" <werkspace@[EMAIL PROTECTED]
> wrote in message
>>
>>>> One problem that I think that I am seeing, is that you are using
>>>> normal mirrors to take the photo. If you could find a mirror where
>>>> the silvering is on the surface instead of the backside, you would
>>>> avoid that double image in the reflection.
>>>>
>>>
>>>AH! I see what you're talking about. I didn't even know those mirrors
>>>existed! Do you have any idea where you can find such mirrors? And how
are
>>>they called?
>>>What people use them and for what reason?
>>
>> As an alternative to a really expensive 1st-surface mirror I'd suggest
>> getting a roll of aluminized mylar and use soem spray adhesive to
>> attach it to a smooth board. It's not as optically flat but you won't
>> get the double reflections and it may well be good enough. And it
>> will be vastly cheaper and easier to deal with.
>
>Not sure if that will give the same quality, but I can always try. What
kind
>of business would sell that kind of stuff? I live in ****tugal so I would
>have to look here.
>Thanks for the tip!
No, don't glue it. There is absolutely no way to glue thin mylar flat
enough.
Even if you were to glue it to glass the glue-layer itself would cause
deformations in the surface. What you want to do is make a frame and
stretch it
as taught as possible. then lay that down on your "stage" and your
subjects on
the stretched mylar surface. Try to keep the distance between your stage
surface
and the taughtly-held silverized mylar as narrow as possible, otherwise
when you
set down your subject on your mylar-mirror to photograph it will deform
the
surface too much and show up as a distortion in the mirror image.
Silverized (aluminized) mylar can be found in any thrift store, often sold
as
"Space Blankets" for $1.00 or less. They have lots of creases in them from
being
folded but when stretched tight enough all creasing will disappear. This
generally needs a lot of pulling-power, but it can be done.
The best way I have found to stretch mylar flat enough is to use a small
ball-bearing or marble in each corner to make your "anchors" to tie to.
When out
in the field and having to employ this (for light reflectors) I'll use a
small
polished and smooth pebble from a stream or lake-shore. Just make sure
that it
has no sharp edges and a smooth surface. Form each mylar corner into a
small
pouch to contain the round object. Then wrap strong smooth line around it,
as if
you were tying up these round "anchors" like a gift in a bag, tying it
very
tightly so the mylar is spread evenly over your "anchor" object. Try to
make
this as smooth and even as possible and tie your line evenly so as not to
make
any stress points in the mylar when pulled. When the mylar is pulled tight
any
stress is distributed radially equally across the face of the sheet. Do
this on
all four corners. When pulled *very* tightly only the corner areas will
have any
creases in them where you tied your "anchors". With a large sheet of mylar
this
will give you a very large 1st-surface mirror area. While not as nice as a
real
1st-surface mirror (and ones of this size would be astronomic in costs) it
will
suffice. If you are careful when tying the corner-anchors you can apply at
least
100 lbs of pressure or more on the tension lines and still the mylar will
not
break. It is only when mylar's integrity is ruined by a small tear, small
stress-point, or perforation will it tear and rip easily.
You may have to experiment and go through a few sheets of mylar before you
learn
how to tie those corner anchors properly. If the pleats in the mylar
(right by
your tied anchor-lines) are not evenly spaced where the mylar goes into
the knot
and line-wraps it will be easy to tear the mylar without too much effort
when
pulled tight.
BTW: Mylar doesn't really "stretch" in the conventional use of the word, I
am
only using that word to describe trying to apply enough tension to pull
out
every last little wrinkle and crease in it.
When I was using a mylar-mirror as a light-reflector in this manner and a
strong
wind-storm brewed up. An 6x6 foot sheet of mylar withstood 50-70mph winds
face-on, until after half an hour of this abuse it finally snapped apart
with a
sound as loud as a shotgun going off. Startling everyone within 1/4th
mile.
That's how much stress it was under and still it did not break. I would
have
taken it down before the winds but I was done with my photo shoot. For a
$1.00
investment I was curious to see just how much stress it could take. I was
just
as startled as everyone else when it finally snapped, as well as how much
wind
force it was able to withstand.
You might be able to achieve the same effect by using a square frame and
carefully taping 2 of the adjoining edges to the frame, and then using the
tape
on the other two edges to carefully stretch and pull out all creases and
wrinkles. Mylar edges to frame edges, vs. corners.. But I found that this
4-corners method faster, can be used in more situations, and the mylar is
able
to be pulled much tighter and smoother.
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