Re: Newbie question about macro with DSLR
- From: floyd@xxxxxxxxxx (Floyd L. Davidson)
- Date: Tue, 29 Apr 2008 01:32:07 -0800
tony cooper <tony_cooper213@xxxxxxxxxxxxx> wrote:
On Mon, 28 Apr 2008 19:41:18 -0800, floyd@xxxxxxxxxx (Floyd L.
Davidson) wrote:
For the OP, don't get sidetracked by Tony and I discussing
all this techie crap at the beginning of this article. Go
down to the end, if you didn't do so when you read Tony's
article to start with, and check out the URL he provided
for an example camera/microscope combination.
It appears to be the perfect match!
The feature you'll want to look for is the ability to
mount it in a way that you can use your X-Y stage (which
is not true of all metallurgical scopes). Another
feature, which is almost universal though there is a
chance you don't need it, is episcopic (or "epi" for
short) illumination. That uses a beam splitter to
illuminate the object through the same optical path that
you view it. (That is probably _very_ useful to you.)
Floyd, I was a dealer for Zeiss microscopes for 30 years. I've been
to the Zeiss facilities in Germany. I've sold hundreds of microscopes
and beam splitters. The beam splitter splits the optical path. It's
Yes, that it does. Typically one path has a light
attached, and the other has an eyepiece. That is how
epi-illumination is typically provided.
used to provide a view for a second observer or for photography. The
That is, also, a not uncommon use for a beam splitter;
but does not negate the fact that episcopic illumination
is also done with a beam splitter.
field of view is illuminated coaxially with the prime viewer
completely independent of the beam splitter.
The coaxial illumination is done with a beam splitter,
that is entirely distinct from another beam splitter
used to provide a camera port, or another beam splitter
used to provide binocular viewing! There are beam
splitters galore!
The observer or camera
is seeing the same field of view as the prime viewer, and that field
is illuminated.
The observer/camera is not looking at the illuminator
though, which is the reason for using a beam splitter.
viewing eye
V
| (beam splitter)
|/
/
aligning eye < ====/ ==== < light source
/ |
|
objective lense
The light source shines into the beam splitter from the
right side, and is split between one path going down
(through the objective lense) to light the object being
viewed and a path that goes straight through to the
"aligning eye". Some designs actually have a port that
can be visually observed to align the beam splitter and
the light source, but most do not and just block that
path.
Light which reflects from the object being viewed shines
upward into the beam splitter and is also divided into
two paths. One goes straight upwards towards the
"viewing eye" and the other shines into the light source
port (where it is useless of course).
The prefix "epi" means "above". There are two types of episcopes:
The prefix "eip" means
"A prefix, meaning upon, beside, among, on the
outside, above, over. It becomes ep-before a vowel, as
in epoch, and eph-before a Greek aspirate, as in
ephemera"
Note that "episcopes" is a different word than
"episcopic".
Regardless, epi-illumination is so called because the
source of illumination is generally above the object
being viewed, rather than below it as with transmitted
light microscopy.
(I see in a second post from you that this has been
figured out. Do note that I did not choose the
terminology, it standard terminology that the OP will
need to be familiar with if he chooses to research this
topic farther. Also note that while epi-illumination
via the microscope is one method to provide reflected
light illumination, it isn't the only one. Hence I said
it is likely to be very useful, but might not be. With
"dissecting" style microscopes it is more common to see
ring lights and various forms of fiber optic
illuminators.) If some particular light shading is
necessary or useful to make the images show topographic
detail better, it might not be epi-illumination that
works best.
one projects light from above for surface viewing, and the second -
and the most common use of "episcope" - is a device that projects an
image using a mirror.
Do you see the connection with epi-illumination?
An overhead projector is an episcope. The kind most of us are
familiar with, though, is:
http://www.stds.fr/boutique/images_produits/vAT01-AR225-481.jpg When
we were kids, we used these to project an image - usually the comic
pages - on a piece of paper taped to the wall - so we could trace over
it.
Wonderful, but with no significance to the OP or too my
discussion.
Microscopes can be very expensive, but it is unlikely
that you need a fancy one. It should be fairly easy to
find an older used model that will do fine. They often
are available on eBay at reasonable prices, as are the
parts and pieces such as objectives and "relay lenses"
for photography. Keep in mind that objective lenses are
matched to the eye pieces (and to the relay lenses used
for projecting into a camera), and hence should not
necessarily be mixed and matched between manufacturers.
I can't figure out what you're saying here, and I'm pretty familiar
with microscopes. I have no idea what "relay lenses" are.
That is an alternate term for "projection lense". Some
might also call it a "camera lense" or a "photo lense",
but those would be very rare. It replaces the ocular
on a normal microscope when a camera is to be attached
rather than a human observer.
Here is a URL that I gave previously. It goes into
detail.
http://krebsmicro.com/relayDSLR/relayoptics1.html
There are
two ways to photograph through a microscope: (1) You attach a camera
body to a port of the beam splitter. (2) You attach a camera body in
place of an eyepiece.
No, the camera body is not usually "in place of an
eyepiece", though that can be done, it is rare. It is
in _addition_ to *changing* the "eyepiece" (the ocular
lense) to a projection (aka relay) lense. Otherwise the
image will not likely "cover" the camera's sensor in a
useful manner at the same point where the image is also
in focus on the sensor.
See the above URL. It's a complex subject.
Some microscopes have built-in beam splitters
with a single port, and some use a beam splitter that goes between the
microscope body and the binoculars.
I don't know what you mean by matching objective lenses to eyepieces.
Naturally you have to have compatibility of manufacturer, but a
microscope can be set up with several combinations of objective lenses
and eyepieces. The combination determines the viewer's magnification
and the field of view.
There are at least two ways that oculars need to be
matched to the objectives. One is due to dependency on
the length of the tube and the other is to match
compensation for optical aberration between the ocular
and the objective lenses.
Older microscopes were all based on a specific tube
length, and the objective lenses are matched to that
length (typically 160mm but sometimes a bit more or
less). It can be a problem if an objective designed for
a 160mm tube is used on a 210mm tube, for example. And
modern microscopes are all designed for an "infinite"
tube, which allows any length of tube to be used, but
also requires that the objective and the ocular be
matched. (The purpose is to allow addition of multiple
optical devices into the optical path without changing
the objective or ocular lenses. Again, they do need to
be matched though, so only accessories from the same
manufacture are likely to work together.)
The second manner in which the objective and ocular
lenses need to be matched is in regard to the
compensation for optical aberration. Typically,
oculars that have a 'C' or a 'K' in the designator are
"compensating" oculars. For example, Zeiss KPL oculars
have -1.4% compensation while Leitz uses -0.75% and
Olympus used -0.7%. Nikon, near as I can tell, tended
to use 0%, but I've never fully been able to confirm
that. Whatever, it is clear that mixing oculars and
objectives of those manufacturers will degrade the
optics of a microscope.
I haven't been able to figure out, from the postings I've read, if he
even really needs a camera body. There are systems available that
send the image direct to a computer, and the computer captures the
image.
He might be able to work with an instrument like the digital boom
microscope at
http://www.microscope.com/omano-ezvuv7-digital-articulated-zoom-boom-microscope-p-194.html
because it doesn't appear that he needs to view the field through
eyepieces at all. This would provide 7x to 45x magnification, or up
to 90x with the Barlow lens. It could swing over his stage.
I have no idea about the re-sale aspect of this type of instrument,
but he could check with the company and see if an arrangement could be
made. They may buy back the instrument at an agreed-on price if they
can re-sell it.
While $1,700 seems like it's over his budget, he'd might be spending
$1,000 on a camera system with macro accessories that doesn't do what
he wants done.
Bingo. You've hit what the OP needs dead on!
At least, it sure looks like it. That assumes there is
no other, unmentioned, need for a DSLR. I can't see how
it can be done better for less money if new equipment is
purchased.
--
Floyd L. Davidson <http://www.apaflo.com/floyd_davidson>
Ukpeagvik (Barrow, Alaska) floyd@xxxxxxxxxx
.
- References:
- Newbie question about macro with DSLR
- From: Eric Smith
- Re: Newbie question about macro with DSLR
- From: Floyd L. Davidson
- Re: Newbie question about macro with DSLR
- From: tony cooper
- Newbie question about macro with DSLR
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