Kowa Sporting Optics

Category Archives: Product Reviews

Steve Blain reviews the Kowa TSN-EX16 1.6x extender

Steve has been digiscoping for around twenty years, when he first started trying video cameras up against his scope to capture what he was seeing. His digiscoping evolved from video tape, to the first Nikon Coolpix’s, then through a succession of advancing cameras up to his present day setup which includes a Panasonic GX7, 20mm f1.7 lens, and a Kowa 883 ‘scope. He also dabbles digiscoping with his mobile phone and currently uses an iPhone 6. He has digiscoped over 1000 species of birds on five continents including 600 species alone from two years spent in Ecuador.


Kowa 1.6 extender review | Steve Blain
June 2016

I originally purchased my Kowa scope in August 2015 after comparing all the top scores at the BirdFair. It was clear to me that the Kowa 883 was an awesome scope – bright, very sharp, and almost no chromatic aberrations that I could discern. However what really swung it for me was the new 1.6 extender they were debuting. This pumped their top of the range scope and 25-60x wide angle eyepiece up to an astonishing 96x. The view through it was simply stunning, especially compared to other high-powered rivals. It was very sharp, bright and contrast was good too. I was itching to get one.

It wasn’t until early in 2016 that I managed to get myself a 1.6 extender to use for an extended period of time. I have managed to use it in a variety of situations, from watching thousands of gulls on my local rubbish tip, to blistering views of Northern Parula in the pine woods of Florida. Below are my findings, split in to two areas, birding and digiscoping.

The extender is around an inch long, very lightweight at just 105 grams, and blends seamlessly on to the body of the scope. Eyepieces attach using a standard bayonet mount and the extender attaches to the body of the scope securely via a threaded mount. This is really good news because you can do something astonishing with them because of it – stack them. Yes, that’s right, you can use multiple extenders to double your magnification. That means if you attach two extenders to their 25-60x eyepiece it has a top magnification of around 156x! No other birding scope can even come close to matching that.


After just a couple of trips out leaving the extender on the scope I’d almost forgotten that it was there. The view, although starting at around 40x instead of 25x, was still easy to use and find birds with. The view is still bright, and the field of view is large enough to make you forget it is there. As you zoom up through the magnification brightness only really drops away around 50x (that’s around 80x), but the sharpness is still excellent. One thing I did notice was a slight drop-off in contrast, and some chromatic aberrations in high contrast situations – but you have to look for it. This is perhaps not too surprising as almost all photographic extenders suffer similar traits, and Kowa would have to pull off a miracle for this extender not to show any flaws at this price point.

The detail you could achieve using the extender was exceptional. I could see superb detail of a Yellow-legged Gulls eye ring on my local rubbish tip at around 100 meters, and reading colour rings all of a sudden became a lot easier too with the extra boost in magnification, coupled with the clarity of the Kowa 883 and the magic 25-60x zoom eyepiece.

Adding a second extender was also something of an eye opener. The base magnification (around 64x) I found a bit too much for scanning through gulls at around 100 meters, however for more distant birds it was truly impressive. I could easily pick out a hybrid drake Pochard x Tufted Duck amongst a flock of Tufties at around one kilometre! I found adding the second extender obviously made the resulting image duller, and at the maximum zoom (approx a staggering 153x) it was very dull indeed, especially on a dreary UK winters day. However, the image was still very sharp, something that surprised me considering how much glass you have now added to your original scope. Contrast also drops again adding a second extender, and a little more chromatic aberration creeps in too, but nothing that detracts from its overall usability and still super impressive. Set at around 50x on the zoom (roughly 128x with both extenders) the view was comfortable and I thought offered an excellent compromise on brightness and magnification. The only thing you have to watch are vibrations – you are going to need a solid tripod to use two extenders, especially at magnifications over 100x.

As I also have the 30x eyepiece I was pleased to see the extender worked with this too. The view again is excellent, and makes your 30x in to a 48x eyepiece instead. If you only have the 30x and cannot justify upgrading to the zoom for your scope, the 1.6 extender maybe what you’re looking for. Again, very sharp and bright, with minimal CA, the view through this setup was very nice indeed, and personally I preferred it to using it with the zoom. I could imagine this being a favourite with seawatchers very quickly – the exceptional field of view for the magnification makes it a joy to look through.

Once you have attached the extender the eyepiece is, understandably, a little longer, this means the stay-on case only just fits over the eyepiece and attaches via the poppers. No real issue it is just going to be a little tight. When you attach two extenders you can forget about trying the poppers!

So, with the birding views being so good using the extender I wondered what the digiscoping possibilities were using it.

The extra boost in base magnification was obviously the first bonus. The light loss from using it without the extender is minimal and the sharpness, especially at lower zoom ranges is very good. As you move up through the zoom range the sharpness slightly decreases and light loss naturally increases. At the far end of the zoom range conventional digiscoping still images gets difficult, especially birds. However if you are after a record shot of that distant rarity or especially if you are using video, the increase in magnification and extra reach is again superb and very usable. The extender will be a fantastic addition if you are in to phonescoping – the increase in magnification will really benefit you as most mobile phones don’t have an optical zoom lens, so the edge the extender offers you means closer phonecoped shots.

Focal length comparison


There are a couple of characteristics which you will notice when digiscoping with the 1.6 extender attached – the first is the slightly shallower depth of field. This is most noticable at close range. You will see from the images below (See the Greenfinch and Brambling shots) the heads are sharp and the tails are out of focus – slightly more so if you simply used the 25-60x at a similar magnification. This issue gets less noticable as your targets get further away. The second thing you are going to have to contend with is the slight increase in chromatic aberrations – and although the Kowa’s have some of the best glass in optics today, CA still creeps in when you attach the 1.6. However, remember at the price point which this is being pitched at, there will not be any fancy flouride coatings on this optic, so the small amount of CA showing up is still astonishingly low. And besides, with modern day software CA can easily be removed, especially if you shoot RAW images. The third thing you will notice, and which especially affects digiscopers, is the increase in shake because of the higher magnifications used. Perhaps an obvious one, but unless you have a good solid tripod for your ‘scope, vibrations will cause you an issue when digiscoping using the 1.6. When you add a second 1.6 vibrations are very noticeable when viewing and digiscoping becomes much more difficult, but still possible with the right setup (see peregrine shots above).

Images digiscoped by Steve Blain using Kowa TSN-EX16 1.6x extender


Bottom line
Overall I was extremely impressed with the Kowa 1.6 extender. If your birding involves scrutinising birds at distance then it’s a no-brainer – get one. The boost this gives your zoom or 30x eyepiece, especially for the price, is incredible value. If you’re interested in digiscoping then there are certain applications you will find the 1.6 very useful too, especially if you are a phonescoper or in to video. Overall the 1.6 extender is a very impressive addition to the Kowa range and at a bargain price. I won’t be parting with mine for a long while yet!