Kowa TSN-EX16 Extender Review


Kowa TSN-EX16 Extender

Kowa TSN-EX16 1.6x extender

Kowa TSN-EX16 1.6x extender.

Kowa America recently released the TSN-EX16 Extender. The extender is placed between the body of a Kowa TSN-880 or TSN-770 spotting scope 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 photo.

Photo on the left uses the TSN-EX16 at 25x on the eyepiece. Photo on the right is at 40x without the extender.

The first test answers the above questions. I took photos without the 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). I took both photos 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 the Extender


Best exposure using the TSN-EX16 @ 25x.

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. The 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 I don’t have one here. I was able to determine that photography at 96x will require the most stable of tripods. 96x magnification compresses depth of field significantly. It is more difficult to achieve a good focus 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. There is a slight loss of light, but there is no degradation of sharpness or clarity. In conclusion, the Kowa TSN-EX16 Extender is a useful addition to any TSN-880 or TSN-770 spotting scope.