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Using Binoculars to see at distances

Digiscoping


Why Digiscope?


Definition

Digiscoping is the process of taking photos with a digital camera, either still or video, through a spotting scope.

Photography Alternatives

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.

Digital Benefits

  • 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

Film Benefits

  • Old familiar
  • 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.

Vignetting

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 image brightness.

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.

Swarovski DCBThe 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.

Batteries

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.

Shooting Techniques


Composing

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.

Focusing

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.

Metering

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.

Zooming

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 mode).

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.

Post Processing

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.

Reference Material

These three articles, written by Clay Taylor of Swarovski, give an excellent overview of the current state of the art in digiscoping.

Conclusions

  • Digiscoping offers a quality image using lighter and less expensive equipment than film
  • 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 if necessary
  • Photo editing programs let you correct a multitude of problems.

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