Kowa TSN-EX16 Extender Review

Kowa TSN-EX16 Extender exploded

Kowa TSN-EX16 Extender (exploded view)

Kowa TSN-EX16 Extender

Kowa America recently released the Kowa TSN-EX16 Extender. The extender is placed between the body of a Kowa TSN-880 or TSN-770 spotting scope body and the eyepiece and multiplies the standard magnification by 1.6x. This is analogous to photographic lens extenders that mount between a camera’s lens and body. With the current 25-60x zoom eyepiece (Kowa TE-11WZ) that fits these spotting scopes, the resultant magnification becomes 40-96x!

But what about the historical downsides of extenders? How does the optical quality hold up? Is there much loss of light? What about sharpness and clarity? I took out my trusty TSN-884 and Panasonic Lumix G6 to find out. An accommodating Peregrine Falcon stayed long enough for me to get some test shots.


Comparison with and without Kowa TSN-EX16 Extender

Comparison of exposures (25x + extender) vs. 40x (no extender)

The first test was meant to answer the above questions. I took photos without the Kowa TSN-EX16 Extender and the zoom set to 40x (right hand portion of the photo to the right) and then with the extender mounted and the eyepiece at 25x for a resultant 40x magnification (left portion).   Both photos were taken in manual exposure mode at the same exposure. This  demonstrates the amount of light lost due to the extra lenses in the extender. As you can see in the comparison photo, there is about 1/2 f/stop lost due to the extender, but the photo is still quite usable, especially for documentation purposes.  There is no loss in clarity. Feather edges are sharp in both photos.

Best exposure with Kowa TSN-EX16 Extender, zoom at 25x.

Best exposure with TSN-EX16, zoom at 25x.

Best Exposure with the Extender

The final test was to see how good a photo I could get with the extender using automatic exposure. You can see that the proper exposure gives a very close match to the photo without the extender. Color, crispness, and clarity are all within the desired range.

Of course, I just had to try the scope and extender combination at the full 96x (60x * 1.6). I was too close to the Peregrine for a good photo, so none is shown here. I was able to determine that photography at 96x will require the most stable of tripods. Depth of field gets very compressed at 96x, so obtaining a good focus increases in difficulty as magnification rises. Not unexpectedly, in the heat of the day, the extra magnification does exacerbate heat shimmer, but you’ll see the same effect once you get to the upper range of the zoom eyepiece without the extender.


The extra magnification provided by the TSN-EX16 Extender will get you views of distant birds you would not otherwise obtain. While there is a slight loss of light, there is no degradation of sharpness or clarity. The bottom line is the Kowa TSN-EX16 Extender is a useful addition to any TSN-880 or TSN-770 spotting scope.

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