Digiscoping is the process of taking photos with a digital camera, either still
or video, through a spotting scope.
Until recently, the only way to get photos of birds was to use a traditional film
camera, either with a long lens built for the camera, or by adapting the camera
to a spotting scope. With the advent of digital cameras and camcorders, and their
vast improvements in photo quality, many alternatives are now available. The choice
that is best for you will depend on how you want to use and display the photos.
Digital vs. Film
Resolution is the amount of information contained in an image. Film resolution is
measured in line pairs per millimeter, and is the result of the number of grains
of silver or chromatic dyes within the frame. In digital images, light is sensed
by a matrix of red, green, and blue sensors. A set of one of each color sensor is
called a picture element, or pixel. In digital still cameras, the sensed image is
stored on various kinds of memory chips; in digital video cameras, images are usually
stored on magnetic tape, though some new cameras put images into a buffer, which
is then written to a CD or DVD disk. In either case, resolution is measured in pixels,
or its larger unit, megapixels (MP). The knock on digital used to be that it lacked
the resolution of film. This is no longer the case. Today's highest resolution professional
digital single lens reflex (SLR) cameras have more resolution at 11 MP than 35mm
film. At that resolution, you can make 4x5-foot posters that look as good as film.
At 5 MP, you can make 8x10 inch-prints that are of film quality. If the final destination
for the photo is a website, a 3-MP camera will meet your needs.
Store the equivalent of 15 rolls of film on a device the size of a quarter.
Easily store your photos on your computer. No scanning required.
Ease of post-processing
No processing mistakes
Instant feedback - delete bad photos immediately
Lower cost per photo with reusable flash memory
- Easier airline security check-in
- Lower battery requirements
Scopes vs. Long Lenses
Before addressing the relative benefits here, we define magnification to facilitate
comparison. In film cameras, binoculars, and scopes, the "X" in the magnification
rating means "times normal". In film cameras, 50mm is considered normal, so a 400mm
lens would be 8X. In digital cameras and camcorders, the "X" means "times the shortest
focal length" or zoom range. Say two cameras claim 10X zoom lenses. One has a wide-angle
35mm equivalent of 28mm while the other has a 35mm wide-angle equivalent of 35mm.
The maximum magnification on the first camera is 10 x 28 = 280mm, which is 5.6X.
The second camera goes up to 350mm, which is 7X. For photographing scenery, the
first camera would be better. The second, while not really sufficient, would be
better for photographing birds.
Now we can compare scopes and long camera lenses. Scope magnification ranges from
10X to 75X. In film equivalence, this converts to 500mm - 3750mm. Film camera lenses
used by bird photographers are usually 600mm - 800mm, sometimes used with a 2X-telextender,
thereby doubling that focal length. A 400mm f/2.8 lens weighs over 10 lbs. A 600mm
f/4 lens can weigh 15 lbs. These lenses gather more light than scopes, but do so
at enormous weight increases. The problem is that to carry only one lens (and 2
would be a nightmare!), there is no way to turn a large camera lens into a scope,
and even at 1200mm, the desired magnification isn't there. Simply put, to study
birds as well as photograph them, shooting through a scope is the way to go.
Built-ins vs. Components
Recently, some scope makers have announced scopes with built-in digital cameras.
While this is an interesting solution, there are certainly some caveats. The only
two scopes that have built-in cameras so far have objective lenses in the 55mm to
60mm range. Scope views will not be of 80mm quality. Also, the digital sensors have
resolutions around 3.1 MP, which is on the small side. Worse, to upgrade either
the camera or the scope, you have to upgrade both. The only advantage of having
a scope with a built-in camera is that the camera is ready to go faster than when
you use separate parts.
Selecting a digital camera for digiscoping is different than picking one for general
use. Excluding the professional digital SLR cameras, the best cameras for general
use have large objective lenses with large apertures. For digiscoping cameras, however,
large objective lenses lead to one of the biggest problems in digiscoping - vignetting.
Vignetting is the effect caused when the entire frame of the image is not illuminated,
leaving a circular image with surrounding black. It occurs when either the objective
lens of the camera is larger than the exit pupil of the scope, or when the curvature
or mounting of the objective lens of the camera is farther away from the eyepiece
of the scope than the scope's eye relief. For this reason, most digiscopers prefer
cameras with small objectives, which can be brought very close to the scope's eyepiece.
In general, pocket-sized digital cameras with large zoom ranges are also problematic,
as their zooming lens elements recede from the eyepiece when zooming to larger magnifications.
The only way to solve the vignetting problem without changing the physical parameters
of the camera and scope is to crop the image. Cropping can be done in a photo-editing
program, which reduces the size of the image, or by zooming in with the camera while
taking the photo. Zooming in maintains full resolution of the image file, but lowers
Mating Cameras to Scopes
Before digiscoping, people shooting through scopes attached SLR cameras to scopes
using special adapters that used the camera's lens mount and a tube that connects
the camera to the scope's eyepiece socket. The limitation here is that there is
no ability to zoom either the scope or the camera.
In the beginning of digiscoping, everybody just held the digital camera up to the
scope's eyepiece. This has speed advantages, but photos taken this way could be
blurry due to camera shake. Soon, camera-to-scope mating devices began appearing
in the field. Now, scope makers are designing them for their scopes. To accommodate
the wide variety of digital cameras around, these tend to be collars that mount
to the eyepiece and accept cameras with adapter plates that screw into the filter
thread on the camera's lens. Thus, for a camera lacking a filter thread, you need
another solution. The other problem with this mounting system is that it isn't good
for camcorders, which weigh much more than still cameras. You certainly do not want
to hang a 1.5-lb weight to a scope eyepiece.
The solution to this is a mounting bracket design that supports
cameras without filter threads and can be adjusted to align the axis of the eyepiece
to the axis of the camera lens. Three scope makers, Kowa, Nikon, and Zeiss offer
brackets that mount between the scope and the tripod. These have vertical and horizontal
adjustments that facilitate alignment. Each has its own method for adapting to straight
and angled scopes. The Kowa and Nikon brackets will fit most scopes and cameras,
but the Zeiss bracket is less adaptable. Swarovski, and now Kowa, have brackets
that mount directly to the scope body. These are designed to swing into place behind
the eyepiece and then swing back out of the way when the camera is not in use. With
the exception of the new Kowa TSN-DA4, none of the brackets allow for shooting a
vertical format photo as the collar-type systems do, although with the Swarovski
DCB you can achieve the same result by rotating the scope. Since birds do not wait
to pose, setup time is of the essence. Get a mount system that deploys quickly.
A more recent technique involves holding a digital SLR up to the eyepiece. To avoid
vignetting, you must use a 50mm lens and only zoom with the scope eyepiece. It might
seem that this will also work with film SLRs, but the circle of illumination is
not large enough to cover a 35mm frame.
Digital Film (Memory)
Digital movie film is magnetic videotape. It comes in two sizes: Digital 8, which
is the same size as standard 8mm videotape, and MiniDV, which is a smaller cassette.
Both hold the same amount of data. Digital 8 costs less while MiniDV is about half
the size and therefore easier to carry.
Digital still film is a memory chip generically known as removable flash memory.
These chips come in various shapes, sizes, and capacities. Older forms include SmartMedia
(SM), Compact Flash (CF), and Sony Memory Sticks. SmartMedia is becoming obsolete,
Sony Memory Sticks are proprietary (only used by Sony products), but Compact Flash
is still going strong. Some reasons for the strength of CF is it has the largest
capacities - up to 2GB, are increasing write speeds with the same interface, and
it is compatible with IBM MicroDrives (miniature hard drives that fit in a CF slot)
which now go up to 4GB. New forms of memory media include Secure Digital, Reduced-size
MultiMediaCard, and xD-Picture Card. Each of these new formats is aimed at smaller
size and faster memory transfer. Some of the new formats have adapters to allow
them to fit into older cameras and card reading adapters. When purchasing your camera,
check out the current prices and capacities of flash memories and make sure the
camera is compatible with the type you want.
Most cameras accept one or two types of flash memory. One of the decisions upon
which to base a camera purchase is the type of flash memory you want to use, which
may be based on the number of photos it can store. When comparing prices, divide
the price by the memory size to get the price per MB. Frequently, the highest capacity
cards are not as cost effective as the next size down. The number of images your
flash memory can hold depends on its capacity, the resolution of your image file,
the file type, and the amount (if any) of compression with which the file is stored.
Digital cameras require a lot of power. Most digital cameras use AA batteries, so
your choice is just of which kind to get. The only two real alternatives are Nickel
Metal Hydride (NiMH) and Lithium Ion rechargeables. Use of alkaline batteries is
discouraged for several reasons. First is that some cameras will not work with them.
But more importantly, they are both the most expensive and the most polluting. With
rechargeable batteries you will get hundreds of repeat uses instead of the one shot
with alkalines. And, even if alkalines could be used for as long a period as the
rechargeables, they contain 10 times as much polluting chemicals as either of the
rechargeables. As birders who should be concerned with conservation of habitat,
this should be a deciding factor even if all the other factors were equal. To determine
how long a battery will last, look at the battery's power rating, which is measured
in milliamp-hours (mAh). The higher the number, the longer the battery will last
on a single charge. Current longest-lasting AA NiMH batteries are rated at 2600mAh.
Most digital cameras have two ways of composing an image - the viewfinder and the
LCD screen. On many small digital cameras, however, the viewfinder does not provide
a through-the-lens (TTL) view, and is useless in composing the image or in focusing.
For these cameras, you will need to use the LCD screen on the back of the camera.
Since these screens can be difficult to see in bright light, viewing hoods have
been designed to help. A less expensive (and perhaps even better) alternative is
to use a plastic slide viewer that can be trimmed of the slide holder and placed
over the LCD. These slide viewers have 2x lenses that can also aid in seeing the
LCD for focusing purposes. If you would rather use the viewfinder, you will need
to get a camera with a TTL or direct electronic viewfinder.
This is one of the trickiest parts of digiscoping. Theoretically, an autofocus camera
should be able to compensate for a slightly unfocused image projected by the scope
and produce a sharply focused image. But, because the camera is not all that easy
to place at the focal point of the scope, a different technique is often used. What
many people do is to set the camera to focus on infinity, and then to manual focus.
Then, using the scope's focusing knob, get the best focus possible. Finally, turn
the autofocus back on and let the camera do the ultimate fine-tuning.
In general, you should be able to use autoexposure (AE) most of the time. As long
as you have average scenes with average subjects, any exposure mode will do. Often,
spot metering will produce a good exposure. However, when your subject is a Great
Egret or a Great-tailed Grackle, you will need to compensate to get a properly exposed
image. If you're not sure of your exposure, you can always bracket, delete the shots
that don't work, and choose the best exposure for the rest of your shots.
In optical zoom mode, the camera records all the pixels in the sensor. The camera's
lens resizes the image. In digital zoom, however, the camera records only a portion
of the pixels in the sensor (cropping into the image), resizes the image back to
full size, and then interpolates the image data to approximate what the interstitial
pixels would be. You can perform this process in your image editing software much
better than the camera can do it. We recommend that you turn off digital zoom, forget
it's there, and never use it.
When digiscoping, zoom the camera, not the scope. Leave the scope at minimum zoom.
When you zoom the scope, you reduce the exit pupil of the scope, which reduces the
light reaching the camera, and you increase the vignetting. Zooming the camera improves
vignetting and keeps the exit pupil of the scope constant.
Selecting a Spotting Scope
As previously discussed, the optimum digiscoping scope has a big objective lens
with high quality glass. With one of the new 65m scopes, the high quality glass
is even more important. This is not to say that good photos are unobtainable with
smaller scopes, but it is more difficult and the quality will be lower.
For those who want the flexibility to build their digiscoping system with complete
freedom in their camera choice, it might be best, at least for now, to select a
scope from a manufacturer that doesn't make cameras. At this writing, except for
the universal mount system brackets mentioned above, most companies that make both
scopes and cameras make digiscoping adapters that only fit their own cameras. Be
sure to investigate compatibility issues before you buy.
Selecting a Digital Camera
As more people have tested more cameras for digiscoping, the perception of what
works best has changed. We now know that cameras with large optical zooms tend to
have more vignetting problems, as do cameras where the zooming lens element moves
away from the subject when going to larger magnification. For best results with
point-and-shoot cameras, look for cameras that do not exceed 4x optical zoom, or
that have internal zoom elements.
A common problem with early digital cameras that is improving with newer cameras
is a delay between the time that you press the shutter button and the time the camera
takes the photo. If this is too long, you can lose the bird.
Older cameras took a long time to write the image file to memory. Newer designs
can not only write quickly, but also shoot several shots rapidly (known as burst
Digiscoping systems (camera, scope, and tripod) are inherently susceptible to vibrations.
These can result from wind or hand shake, and are worsened at increasing magnifications.
The best way to avoid these is to use a remote camera shutter release. Some cameras
are capable of accepting an electronic cable release. Others have wireless remotes.
Finally, some digiscoping adapters, such as the Kowa TSN-DA4 allow use of an old-style
mechanical cable release that is placed over the shutter button by an adjustable
positioning arm. Electronic cable releases are the best solution. Wireless remotes
often have a built-in delay of up to three seconds.
Some characteristics of cameras good for digiscoping are:
3x - 4x optical zoom
External zoom elements
Lenses with filter threads
Minimum 3-MP sensor - more is better
LCD screens that swivel independently from the lens
Flash memory slot
Full manual capability
Fast write speed
Little or no shutter lag
- Cable or wireless shutter release
For a list of digital cameras that do not vignette or can eliminate vignetting by
use of the optical zoom,
see this list compiled by Roy Halpin of Swarovski and Jeff Bouton of Leica.
One of the biggest benefits of digital photography is the ability to edit image
files on a computer. Exposure and contrast, color saturation, image sharpness and
background alteration can all be improved after taking the photo. You can even remove
branches that block part of the bird. Artistic effects, copyright notices, watermarks,
captions, photographic data, and just about anything else can be added. Digital
videos can also be edited to add various types of scene changes like fades, cuts,
and other fancy effects seen on TV. Video frames can be converted to stills.
These three articles, written by Clay Taylor of Swarovski, give an excellent overview
of the current state of the art in digiscoping.
Digiscoping offers a quality image using lighter and less expensive equipment than
Better scopes give better photos
Mount systems give sharper photos than hand-holding and leave your hands free to
focus and shoot.
NiMH batteries are the cheapest and the most environmentally friendly
Get the largest economical size flash memory available for the camera
Bracket the exposure, take the photo, view it, then correct if necessary
Photo editing programs let you correct a multitude of problems.
When you are unsure of a proper exposure, take the photo, view it, then correct
- Photo editing programs let you correct
a multitude of problems.
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