Friday, June 13, 2014

Digiscoping Challenges


"I hate cameras. They interfere, they're always in the way. I wish: if I could work with my eyes alone."

~ Richard Avedon

"The camera is my tool. Through it I give reason to everything around me."

~ André Kertész

"All my digiscoped images are blurry. Why can’t I get sharp images like I see on the web?"

~ New Digiscoper

Though digiscoping has solidified itself as a legitimate method of photography (especially by birders), it comes with inherent challenges, chief among them an extremely poor focal ratio. A long focal length and small aperture translates to an optically slow photographic lens system. Add poor lighting to the equation and you have a recipe for blurry images. What follows is a list of the most common digiscoping focus challenges I know of, but it's probably not exhaustive.

Distance

The greater the distance between you and your subject, the less sharp your digiscoped images will be. If you’re going for close-up subject portraiture, I recommend a digiscoping distance of 25 to 35 feet for small sparrow-sized songbirds. For larger birds like raptors, owls, and herons, I try to be at least 50 to 75 feet away depending on the size of the bird. If you're unable to get closeup portraiture, try to to improve the shot with creative composition.

Too Much Magnification

Many new digiscopers attempt to photograph something like an eagle's nest or other large birds at distances up to several hundred yards. Because even large birds will appear rather small in the frame, the novice will instinctively increase eyepiece magnification. Unfortunately, this taxes the optics by decreasing the exit pupil and shutter speed, thereby reducing overall potential image quality. Digiscoping at such distances may be acceptable for documenting rarities, but it isn’t advisable for quality portraiture. I recommend digiscoping at the lowest eyepiece setting that's available. If you can’t get close enough for the shot you’re after, it's probably best to move on. There will be opportunities another day.

Low Optical Quality

Though I'm a firm believer that photography skill is acquired by practice and not by price, spotting scope optical quality does correlate with price. All else being equal, the best possible results will come from more expensive spotting scopes. World-class digiscopers generally use high-end spotting scopes to obtain the sharpest images. One can certainly digiscope with less expensive spotting scopes, but as the price goes down, so too will image sharpness. Having said that, I've seen great digiscoped images from comparably inexpensive spotting scopes, and poor images taken from the most expensive ones on the market; recalling the adage that it's the photographer that takes good photographs, not the camera.

Improper Autofocus

Spotting scopes do not autofocus. Any digiscoping setup that uses a camera body without a lens will have to be focused exclusively from the spotting scope (see ‘Manual focusing problems’ below). When autofocusing is available, it can help bring an image into sharp focus, but problems can arise. Digital cameras are not designed to focus on images projected through a spotting scope, so autofocusing might yield inconsistent results. The focal depth can be extremely narrow for the autofocusing to choose true focus and it might select something other than the bird’s face, like a nearby twig. If you’re going to use autofocusing, it’s best to use manual spot-area and select the bird’s face.

Improper Manual focus

My Swarovski ATX 85, Nikon 1 V1, and TLS-APO adapter is a manual focus configuration. The TLS-APO is essentially a 30mm fixed-focus lens coupled to the scope’s ocular. The Nikon 1 V1 has an Electronic View Finder (EFV), plus a magnifying focus assist mode that makes manual focusing considerably easier. Without an EVF, the digiscoper must manually focus by looking at the image displayed on the LCD monitor. This can be very challenging if the camera has a small LCD monitor or bright lighting makes the LCD difficult to see.

A common misconception is that one can look through the scope’s eyepiece, establish perfect visual focus, and then attach the camera to take a digiscoped photograph. The trouble is that the camera’s focal plane might not match what your eye sees when looking through the eyepiece. You can get an approximate focus through the eyepiece, but you will likely need to adjust the focus after attaching the camera. You’re going to need to focus in order to accommodate the camera lens rather than your eye.

Poor Light

As I previously mentioned, digiscoping has an optically slow lens speed. In terms of f-number (focal ratio), a typical digiscoping focal length of 1,200mm and aperture of 85mm objective renders f/14. It gets even worse when increasing the eyepiece magnification. Fast shutter speeds can be difficult to achieve in poor light. The magic shutter speed is 1/125th of a second. If the shutter speed is slower, images are likely to be blurred from camera or tripod movement.

Many of today’s digital camera sensors allow you to increase the ISO setting without much degradation in image quality. My strategy is to digiscope on sunny days, especially an hour or so after sunrise or a few hours before sunset. I also have a remote shutter release for my Nikon 1 V1, but it isn’t especially useful for birds that are constantly on the move like warblers, flycatchers, and vireos. You can also try using a self-timer delay for birds that are sitting still like a resting owl or heron.

Cold Weather

When bringing a spotting scope from a warm environment to a cooler one, it can take up to an hour for the temperature inside the spotting scope to equalize with the outside air. Until it equalizes, there can be turbulent currents inside the scope that can reduce image sharpness or render inconsistent results.

Heat Effects

Wobbling or shimmering images from mirage, heat haze, or air distortion will profoundly hinder one’s ability to get sharply focused digiscoped images. Whether during summer or winter, sunlight heats air, especially close to the ground. Distance and magnification plays a role and heat haze will be more pronounced with high magnification or the further away you are from your subject.

Diopter Setting

Cameras that have a view finder often have a diopter that needs to be calibrated to your vision. If the diopter isn't calibrated properly, you might not be able to tell when the image is properly focus.

Camera/Tripod movement

If your tripod isn't stable, bumps and vibrations will impede your ability to get crisp images. Investing in a sturdy tripod will go a long way in your pursuit of obtaining quality images. Mirror slap with DSLR cameras should not be a problem if your shutter speeds are at least 1/125th of a second.

Subject Movement

If your subject (presumably a bird) makes an abrupt movement, various elements in the frame might be in focus, but not the bird. If branches or twigs at the same focal plane as the bird are sharp, but the bird is blurry, then it might have moved during the exposure. The same advice for digiscoping in low light applies here.

In conclusion, mastering any kind of photography requires patience, dedication, and most importantly, practice. Knowing the potential and limitations of your gear and how it responds in the field under a variety of situations and lighting is all part of the learning process. But always remember, as Doug Bartlow said, “No matter how sophisticated the camera, the photographer is still the one that makes the picture.”

Experiment! Be creative! And practice, practice, practice!

2 comments:

  1. Thank you, Sir,
    Mike very appreciate your valuable time saving information.
    James R Lara

    ReplyDelete