Camera versus Digiscope - Initial Tests
Inspired by a 2012 PetaPixel.com article that compared the telephoto abilities of the premium Swarovski ATX 95 spotting scope with the super-premium Canon 800mm lens, I recently did some tests with my own gear. One difference is that for the digiscoping setup I used an iPhone 7 Plus attached to the ATX 95 by an adapter from PhoneSkope.com. The apps Pro Camera (for stills) and Filmic Pro (for video) were needed to manually access the "2x" (56mm equiv.) lens on the iPhone. My "birding camera" is a crop-frame Canon 7D mark II to which is attached a Canon 100-400 f/4.5-f/5.6 Mark II, both with and without Canon's EF 1.4 III Extender. The Canon combo is a very popular, "fantastic value for the money" option for non-professionals. A further test was done comparing the Swarovski ATX95/iPhone7Plus combo with the addition of the "Swarovski ME 1.7x Extender for ATX/BTX/STX"*, courtesy of Dez Hughes.
*(I mistakenly refer to it as BTX in two images. Thanks Dez for the correction.)
Technical details (feel free to skip): I kept test conditions consistent to the extent possible, and the comparisons were conducted under "good" to "fair" atmospheric conditions. All images are "SOOC" (Straight-Out-Of-Camera), with no sharpening or correction of Chromatic Aberration (CA), the latter of which was tested to be easily corrected in Lightroom. The scope and camera in turn were mounted on a very stable Manfrotto 535 Carbon Fibre tripod with HD502 video head. Camera photos taken with miror lock-up and 2-second delay; iPhone photos taken as 3-image burst at 0.5 sec intervals, with best image chosen. Please note the 14.5 mm on the chart scale is relevant only at 27m; in pictures a) and b), manually drawn centimetre markers across the top and right hand side are also visible.
Here's the reference image I used, downloaded from the site shown. I laser-printed it as 1200dpi on A4 paper, and pinned it 27m (88.6ft) away from the camera / scope (the distance from my back fence to my front fence).
< Click the images to open them full-screen >
I kept hand-written notes as took the images, to make sure all settings that weren't contained in the EXIF files were noted. I then took 1:1 screen captures of the images from Lightroom. I determined the maximum resolution to be where I could conservatively still count all nine (9) lines on the vertical, ever-narrowing 6-20 scale. My main difficulty in presenting them here is trying to ensure 1:1 image representation. The original screen captures are all 1888 x 917 pixels.
Comparison 1: Camera vs Scope
a) Canon 100-400 @ 400mm: Max. Resolution = "3"
This is what I normally use for taking pictures of birds. Super quality up close, but at a distance of 27m I'm really pushing my luck for capturing small subjects in any detail.
b) Canon 100-400 @ 400mm with Canon EF 1.4 III Extender: Max. Resolution = "4"
This is my next way to "level up". I thought this might sort my "distant shorebird" problem, but alas it did not.
c) Swarovski ATX95 @ 30x / iPhone 7 Plus 2x (56mm equiv) lens: Max. Resolution = "8"
This is the minimal zoom on the scope, and is what would typically be used when viewing a scene. My birding life changed when I bought this scope! As for resolution, it seems a lot better than the camera/lens options I have available to me.
d) Swarovski ATX95 @ 70x / iPhone 7 Plus 2x (56mm equiv) lens: Max. Resolution = "13"
This is as big as it gets, and is normally only used under perfect conditions for very far objects, or for spotting very fine detail. Resolution of 13! At this level of magnification, I can distinguish individual 0.5mm lines at 27m.
Comparison 2a: ATX95 plus ME 1.7 Extender at maximum magnification
Tested on a different day, atmospheric conditions for the test of the Swarovski ATX95 vs the ATX95 + ME 1.7 extender at the Western Treatment Plant were only "fair", as there was some minor heat haze. The target distance was the same (27m) as in the tests previously conducted at my home. Thanks again to Dez Hughes for lending me his ME extender for the tests!
Let's start where we finished off previously - the ATX95 @70X. Due to the slightly worse conditions, a resolution of "12" was the best I could determine, compared to "13" previously. That means we should consider this comparison as relative, not absolute.
a) Swarovski ATX95 @ 70x / iPhone 7 Plus 2x (56mm equiv) lens: Max. Resolution = "12"
b) Swarovski ATX95 / ME 1.7 @ 120x (70x x 1.7) / iPhone 7 Plus 2x (56mm equiv) lens
Adding the ME 1.7 extender improved things markedly. The result of "15" was the best obtained so far.
Comparison 2b: ATX95 versus ATX95 / ME 1.7, each at 50x
a) Swarovski ATX95 @ 50x / iPhone 7 Plus 2x (56mm equiv) lens: Max. Resolution = "11"
b) Swarovski ATX95 / ME 1.7 @ 50x (30x x 1.7) / iPhone 7 Plus 2x (56mm equiv) lens: Max. Resolution = "10"
I wasn't entirely sure if my technique was as good on this test, and the atmospheric conditions had deteriorated marginally by this time. While the results are similar ("11" vs "10"), and I should probably re-test it sometime, keeping the ME 1.7 extender on at lower magnifications would only be done for convenience. For best results I'd stick to basic ATX95 scope, except where you need the extra reach.
My best camera/lens combination is no competition for my Swarovski ATX95 scope + iPhone 7 Plus in terms of resolution at great distances. The ability to capture 4K video in the iPhone is an additional bonus.
This system works for days when you can't get close to small, distant subjects such as shorebirds, and where the atmospheric-haze is minimal. Don't forget that you need to have a great tripod/head, and good technique just to get adequate results. It certainly does not replace a good camera and lens in most circumstances.
The ME 1.7 Extender @120x was surprisingly good! Something that isn't captured in these tests is what the view looks "between" the wobbles of heat-haze; the ME seemed subjectively better beyond what is shown in these tests. Hard to explain, and I think it warrants further investigation. Nonetheless, if you need the extra reach, the Swarovski ME 1.7 Extender might be just what you need.
Caveats: This article is a very rough draft, so that I can share some of my initial tests with some interested parties. At this point I have not included any comments regarding ease-of-use, cost-comparison etc., all of which are highly significant points to consider. Additional comparisons were done with Panasonic's Lumix GX85 (micro four-thirds format) and a Canon 70D, which I believe uses the same sensor as the 7D Mark II. This latter test utilised that Swarovski TLS APO adapter (30mm, 35mm equivalent) as used in the PetaPixel article. More on these points, if I get back to it.