Digital Photography Hacks [Electronic resources] نسخه متنی

Hack 12 T-Mounts and Other Threaded Tricks

Digital SLR users can connect their camera
bodies to a variety of bargain optical attachments by using one of
the most enduring adapters of all: the T-mount.

The best camera for photographer-hackers is certainly the
digital SLR (DSLR). From
outward appearances, these cameras look just like the 35mm single
lens reflex (SLR) models that photographers have been using for
decades. SLRs are distinguished by the ability to remove the lens
from the body and replace it with another type, which makes them
extremely versatile. The other advantage is that you view the picture
through the same lens you use to take the photo, so what you see is
what you get. DSLRs work the same way. The only difference is that
they have an image sensor instead of film.

DSLRs
are a lot of fun for hackers, because when you remove the lens, you
can attach just about any optical accessory to the camera body,
including microscopes, telescopes, slide copiers, and much more.

At first, you might hold the microscope in one hand and the camera
body in the other and wonder how the heck these two items can work
with each other. Generally, this happens via some type of adapter.
For example, telescopes have an adapter that replaces the eyepiece,
and you attach your camera to the adapter. The same goes for
microscopes and other optical goodies.

But you still need a way to connect your camera to the adapter. If
you don't want to shell out the big bucks for a
custom adapter made by your camera manufacturer, you can make this
connection by using a common photographic tool called a
T-mount.

T-mounts are simple devices, really nothing more than a thick metal
ring. On one side, there's a bayonet-styled mount
(like the one on the base of your camera lens) that attaches the ring
to your camera body. Inside the ring, you'll notice
there are threads. These are a standard size that most adapters in
the universe screw into snugly.

So, all you have to do is screw the optical adapter (as for a
telescope) into the T-mount, tighten it, and then attach the unit to
your camera body. You're in business! Now, your
camera will mount on whatever optical lens the adapter is designed
for.

It's a good idea to find a T-mount that works with
your digital camera. Once you do, just about any optical adapter you
find in the bargain bin will now mount on your state-of-the-art
camera. For example, my slide copier is over 20 years old, but it
works great on my state-of-the-art DSLR because I have a T-mount
to hook the two together, as illustrated in Figure 1-13.

Figure 1-13. T-mount with slider copier attachment

1.13.1 Adapters Made by Scope Manufacturers

Many spotting-scope and telescope
manufacturers provide camera adapters for their products. For
example, Kowa (http://www.kowascope.com) makes a
photo and video adapter (TSN-VA1); you
simply slide the camera lens into the adapter, tighten the mounting
screw, and connect it to a Kowa spotting scope. If your camera has a
filter ring, Kowa's TSN-DA1 adapter will screw into it.

Many other scope manufactures make similar adapters. If you plan on
buying a telescope or spotting scope, be sure to check the accessory
line for camera adapters.

1.13.2 The Simple Reversing Ring

T-mounts have a first cousin called the reversing
ring. A reversing ring looks similar a to
T-mount, but instead of having internal threads to attach a variety
of optical accessories, it has external threads that screw into the
filter ring on the front of your lens. This enables you to literally
reverse your lens so that the front optic is
mounted to the camera and the back optic is pointed out to the world.

Why the heck would you want to do such a thing? Well, when you turn
your lens around, you increase its magnification. So suddenly, thanks
to this little round piece of metal, you can get closer to your
subjects for some serious macro photography.

Some camera makers, such as Nikon, make special reversing rings for
their electronic cameras, with delicate contacts near the lens mount.
Make sure you get a reversing ring that's suitable
for your camera; otherwise, you might damage its electronics.

1.13.3 Extension Tubes

If you don't like the idea of having your lens
turned around, there's another economical way to
increase magnification for close-up photography. Extension
tubes are
"spacers" in different widths that
go between your camera lens and its body. The more you increase the
distance, the higher your magnification will be. Kenko makes
automatic extension tubes for a variety of camera models that are
readily available at many retail camera stores.

Extension tubes have the advantage of retaining some or all of the
camera's functionality, such as adjusting the
aperture, because they have the same contacts as your lens. Reversing
rings don't provide that functionality.

The major drawback of extension tubes is that the farther you move
the lens away from the camera body, the darker the image becomes, and
the more light you need for a good exposure. When using tubes in low
light, it can be hard to focus on your subject.

Most people invest in DSLRs so that they can change lenses more
easily. But the less obvious advantage is that, by using a few of
these simple adapters, you can mount your camera to just about
anything with a lens. And that opens up a whole new world of
photography.