Is digiscoping a good alternative to using a super-telephoto lens for birding?

Question

While I was researching bird photography, I noticed some people suggest using a spotting scope in front of digital camera instead of a super-telephoto lens - this technique is called digiscoping.

So far, I've understood there are such major differences when compared to using a super-telephoto (400+ mm) lens:

• a much longer focal length (1200+ mm);
• lower price;
• smaller weight;
• manual focusing only;
• zoom option when shooting through zoom eyepiece;
• smaller maximum aperture (f/8 seems to be common);
• support (e.g. tripod) is a must, which makes the equipment less maneuverable;
• need equipment for attaching and/or adapting the camera to spotting scope;
• some spotting scopes come with angled ocular - good for minimizing neck fatigue, but makes hard to follow action.

Are there any other important factors to bear in mind when deciding which way to go about birding?

I am aware of the option to get the birds closer with bait, but this question is more about photos in action other than gathering food (in air, on nest), so I'm afraid a short focal length will not do.

Answer 1

spotting scopes can be useful and you can get publication-caliber images from them with practice (just check the birdwatching magazines). The downside is the lenses are relatively slow (F8 or slower) so they are useful in good lighting conditions but not nearly as good in marginal conditions. They are manual focus, and setup/use can be cumbersome and doing it well can require practice. The manual focus and slow speed mean they are useful primarily for stationary or mostly stationary birds. Since most birds aren't stationary most of the time, you are going to be trading off time setting up for a shot and being patient for the bird to step into the frame against a more flexible lens that might lend itself more to catching the bird in action.

The images are going to be softer, too. The lens quality just isn't up to the top end lenses, although on the higher end the quality is quite good.

So, cheaper, but slower, less flexible, and softer. And sometimes, it's the only way to get the magnification needed to get a shot without winning the lottery and hiring a forklift... it's a viable option, but realize that if you research the guys getting published using scopes, their rigs are probably closer to $3,000 US than $1,000. I don't think I've seen a scope i'd consider capable of publication quality images for under $1,000 US, although if everyhing goes just right, you might get one here and there. But predictably?

Answer 2

Expanding on chuqui's answer slightly, Roger Cicalia of LensRentals.com did a comparision of a high-end digiscope (Swarovski) against some high-end Canon lenses in 2012. Summarising the results briefly:

• In the centre of the frame, the sharpness of the digiscope compares well with the sharpness of the Canon lenses.
• Away from the centre of the frame, the Canon lenses have a significant sharpness advantage.
• In real-world shots, the digiscope doesn't do so well - Roger's belief is that this is due to diffraction softening.
• On the other hand, the digiscope is cheaper, smaller, lighter, has greater magnification and is waterproof in a way that even the high-end Canon lenses aren't.