2.2 Point-and-shoot Cameras: Digiscoping

For many birdwatchers, the easiest way to get your feet wet with digital bird photography is via what has come to be known as digiscopingi.e., using a small, point-and-shoot camera in conjunction with a spotting scope in order to capture magnified images of birds as they appear through the scope.  Since many birdwatchers already own spotting scopes, this is often a very economical way to try out bird photography: if after trying it out for a while you decide that you get more enjoyment out of merely looking at the birds (without all the fuss and bother of also trying to photograph them), you won’t have wasted much money on specialized photographic gear.
    Figure 2.6 illustrates the basic concept of digiscoping.  Upon finding a bird, you would focus your spotting scope on the bird by looking directly into the eyepiece and adjusting the scope’s focusing mechanism until the bird appears to be in focus.  You then remove your eye from the eyepiece and place your camera (typically an inexpensive point and shoot, or P&S, camera) up to the eyepiece where your eyeball had been just a moment ago. Finally, you press the shutter-release button on the camera and snap the photo.  Alternatively, you might watch the LCD screen on the back of the camera while holding the camera up to the eyepiece, to wait for the bird to do something interesting, before snapping the photo.

Fig. 2.6: The concept of digiscoping. A simple, point-and-
shoot camera is held up to the eyepiece of a spotting scope
 in order to capture the image as seen through the eyepiece.
This is the TTE (through-the-eyepiece) form of digiscoping.

There are a number of important things to note about the figure above.  First, I have not depicted the manner in which the camera is held up to the eyepiece of the scope.  In traditional digiscoping, this is accomplished by simply holding the camera in your hands; this obviously requires steady hands, since any significant movement or tremor during the exposure will result in a blurry image. As we will discuss shortly, there are more reliable alternatives to simply holding the camera in your hand during digiscoping.
    There is also the issue of magnification. A spotting scope will provide considerable magnification beyond what any P&S camera will be natively capable of providing. Most spotting scopes have a zoom control, which varies the magnification as seen through the eyepiece, but the camera itself may also provide some zooming capability
whether optical zoom or digital zoom (or both).  Generally speaking, digital zoom (in the camera, not on your computer) is a gimmick that should be avoided entirely; all this feature does is to blow up the pixels and make them larger, which you can easily do (and with more control) later in software (i.e., after you’ve uploaded the photos from the camera into the computer).

Fig. 2.7: An astronomical telescope (left) versus a typical spotting scope (right).
The astronomical scope is a 150mm Orion Maksutov, which runs about $600 US;
the spotting scope is a 77mm Leica Televid APO, which runs about $1500 US.
Note that when the diameter doubles, the light-gathering capacity quadruples.

    The magnification through a spotting scope typically ranges from 20x to 60x. For birds further away
such as the bald eagle nest shown below in Figure 2.8, which was about three football-field lengths away from the cameramore magnification is needed.  For magnifications in the 100x to 300x range, an astronomical telescope can be an effective and economical solution.  Maksutov or Schmidt-Cassegrain telescopes with a 5 or 6 inch diameter can be had for about $500 US, and these collect enough light to support magnifications of over 100x (via a combination of eyepieces and 2x barlows), though they are bulky and heavy and can therefore be very difficult to lug out into the field.

    Fig. 2.8: Bald eagle nest photographed through an astronomical telescope. The nest was about
three football-field lengths away. A 6-inch Maksutov telescope was used to obtain high
magnification without losing light
Nikon D50 (6 megapixels) with Sigma 50mm lens.
The camera’s lens was hand-held against the scope’s eyepiece.

     Keep in mind that higher magnifications generally result in a narrower field of viewthat is, as you increase the magnification you see more detail on the bird, but you see less and less of the surrounding landscape due to the telescoping effect.  You also reduce the brightness of the image.  In the case of astronomical telescopes (and a number of high-end spotting scopes), eyepieces can be exchanged as easily as lenses on a DSLR camera, and this provides the preferred means of changing magnification. Zoom eyepieces may be convenient for framing the shot (i.e., choosing the zoom level which gives the most pleasing magnification and field of view), but they tend to degrade image quality; a non-zoom eyepiece will generally give you a sharper image than a zoom (and we’ll see in section 3.2 that this is also generally true of zoom versus prime lenses in the case of true DSLR lenses).  In terms of the amount of light collected by the telescope, even large-diameter Maksutov and Schmidt-Cassegrain scopes can provide too little light for effective bird photography on cloudy days or in shade, as many of them operate in the neighborhood of f/12 (we haven’t defined f-numbers yet, but will do so in section 3.1).
    A major difficulty in digiscoping is that of holding the camera steady. A number of manufacturers now sell mounting hardware that you can use to firmly fix your P&S camera in the appropriate position over the eyepiece of the scope.  This solves the steadiness issue (for the camera, at least, though not for the telescope) but renders the entire rig somewhat less convenient when bird watching is the primary objective and bird photography only the secondary objective, since frequently mounting and unmounting of the camera can become tiresome. An additional advantage, however, is that with the mount you may be less likely to damage either the telescope’s eyepiece or the camera’s lens by inadvertently grating the two together. The prices for these mounts range from about $15 US to $350 US.
    When the camera being used for digiscoping is a DSLR rather than a simple P&S model, there is an additional (and potentially very significant) advantage to using a specialized camera mount. In traditional digiscoping, the light path passes through a very considerable amount of glass: there is the main objective lens of the scope as well as any other lenses, prisms, or mirrors within the main body of the telescope; then there is the eyepiece, which may comprise 10 or more individual glass elements in the case of zoom eyepieces; and then there is the built-in lens on the body of the P&S camera, which may utilize a number of distinct glass elements. Every time the light path passes into yet another glass element, some of the light is lost due to reflection, resulting in both diminished brightness and also loss of image quality; also, since all of those glass elements have to be precisely aligned at the factory during manufacturing, systems with larger numbers of optical elements tend to show greater variability in alignment accuracy (and resulting image quality), and may be more vulnerable to being knocked out of alignment during normal use in the field.

Fig. 2.9: Eyepiece (left) and T-adapter (right). By removing the eyepiece from a
telescope and installing a T-adapter and T-ring (not shown), the telescope will
directly mount onto a DSLR just like a normal lens (minus autofocus capability)

    Special camera mounts are available for many scopes which allow you to remove both the scope’s eyepiece and the camera’s lens (if it’s a DSLR), so that the scope body (minus eyepiece) acts as a dedicated camera lens. This often reduces quite substantially the number of glass elements through which the light path must pass, and results in noticeable improvements in image quality.  In the case of astronomical telescopes, these mounts are typically known as T-rings (which attach to the camera) and T-adapters (which attach to the scope); the T-ring firmly attaches to the T-adapter, so that the camera and scope are firmly fixed together. In addition to reducing camera shake, these mounts also help to ensure that the camera’s focal plane is properly aligned to the scope’s focal plane, which is extremely difficult to ensure when simply holding the camera up to the eyepiece with your hands.

Fig. 2.10: Mourning Dove digiscoped using a Nikon D50 (6 megapixels) attached
to a 6-inch Maksutov telescope (fixed aperture f/12) via a $15 T-ring. The camera’s
lens and the telescope’s eyepiece were removed from the light path, producing a
sharper image
. Effective focal length was 1800mm (not counting the camera’s 1.5x
crop factor).  1/200 sec, ISO 400.

    Figure 2.10 shows a Mourning Dove (Zenaida macroura) photographed through a 6-inch Maksutov telescope with the camera attached directly via T-ring/T-adapter (i.e., with the camera’s lens and the telescope’s eyepiece removed from the light path).  Note that this image has been processed in Photoshop; nevertheless, it provides some indication of the amount of detail which can be captured via digiscoping.  Mourning doves are among the easiest of birds to photograph, since they tend to remain perfectly still for long periods of time, and are often quite tame.  Digiscoping of birds in motionespecially birds in flightis a challenge I have not personally been able to successfully meet.

Fig. 2.11: A Canon 30D camera (at left) attached to a 6-inch astronomical
telescope via a T-ring and T-adapter. An enormous rig like this must be
tripod-mounted due to weight and optical leveraging.

An additional note is in order, regarding the large magnifications achievable via digiscoping. Because spotting scopes and astronomical telescopes generally do not offer any sort of image stabilization (section 3.5) feature such as those found on high-end camera lenses from Canon, Nikon, and other manufacturers, the use of high-magnification scopes can result in frequent image blur due to the phenomenon of optical leveragingi.e., the fact that small vibrations due to hand tremors or even the slightest breeze get magnified into large shakes that blur the image, with the magnitude of the resulting shake being a direct effect of the magnification factor of the scope.  The issue is, unfortunately, compounded by the fact that higher magnifications are accompanied by an increased need for light, so that on any but the brightest of days, the camera will be forced to resort to slow shutter speeds to gather enough light for a proper exposure.  A complete discussion of light, shutter speed, and image blur is postponed to Chapter 6.  For the time being, note simply that obtaining tack-sharp, properly exposed images via digiscoping can require substantially more skill, effort, and luck than via traditional telephoto lenses, especially those supporting autofocus and image stabilization functions.
    A few more examples of images digiscoped through my 6-inch Maksutov telescope with a 6 MP camera are shown below.  Note that the strange background artifacts in the second image are the result of using a mirror lens (see section 3.14).

Fig. 2.12: Eastern Bluebird (Sialia sialis) photographed through a $600 astronomical
telescope (1800mm focal length) with a 6 MP camera (Nikon D50).  This was one of
my favorite early photos, and I still have a large, framed print of it in my home.

Fig. 2.13: Belted Kingfisher (Megaceryle alcyon) photographed through Maksutov
telescope with 6 MP camera.  Background artifacts (doughnuts, etc.) like those visible
here are also seen when using cheap, mirror lenses.  1800mm, f/12, 1/250 sec, ISO 400.