Kowa Telephoto Lens Scope Review

The huge cost involved in setting up an SRL camera with a high quality and powerful telephoto lens, has led many people, including myself to look for alternative methods to get as close as possible to our subjects. One option was to sacrifice camera and picture quality and go for a superzoom bridge camera, another was to connect you camera to a spotting scope (digiscoping), which for serious birders and wildlife enthusiasts, was very appealing as you could also use the scope for general observation.

So because of this, it is no surprise that digiscoping has become very popular and you can now connect most spotting scopes to either your digital compact or SLR camera, using a whole range of adapters. The best digiscoping setups can work very well, but because spotting scopes are not designed specifically for photography, there are compromises and it can be a bit fiddley and often confusing to set it all up.

In response to this, Kowa has produced a new telephoto lens for super telephoto shooting (350mm, 500mm or 850mm), that can also be used as a spotting scope (so the other way round) meaning that you can use this high-performance camera lens as a spotting scope as well. This is achieved by simply connecting it to the optional prism unit and eyepiece using a bayonet mounting system, this makes the switch between photography and observation a fairly quick simple operation. What is more, the Kowa Lens/Scope is smaller, weighs less and is cheaper than the equivalent "standard" SLR telephoto lenses on the market.

Sounds fantastic and when I first saw the Lens/Scope before it's official release at the British Birdwatching Fair, it looked great, but how does it work in practice? Well I was lucky enough to get my hands on one for a month to test and so below is my full review of the Kowa Telephoto Lens Scope:

The Main Body (TP556)

Build Quality
I have not been able to find out exactly what the main housing on the Kowa TP556 Telephoto Master Lens is made from, my guess is a Magnesium alloy which Kowa use on many of their top of the range spotting scopes, but whatever the case, it looks to be very well made, feels as solid and robust as any telephoto lens out there and is pretty light (see the section on weight below). Unlike many spotting scopes, the main body is not covered in a rubber armour (apart from the focussing rings), this makes it look more like a camera lens than a scope and has the advantage of keeping the weight down, but obviously it wont be protected as well as a rubber coated scope. All this exposed metal also won't dampening down any sounds made from an object like your watch or a ring connecting with the body when grabbing hold of it, which could frighten away some birds and other wildlife.

Mounting on a Tripod
The mounting foot is nice and long (13cm) and so offers plenty of support and manoeuvrability that enables you to get your setup nicely balanced. It's design also allows it to be mounted directly to quick release plates of some tripod heads manufactured by Manfrotto and GITZO without the need of the quick release plate. This makes mounting and release from the tripod head very easy and the system can be used without worrying about the quick release plate coming loose. If like me, your tripod won't accept the mounting foot directly, you can still mount it on most other tripod heads as the standard 1/4" threads are supported.

The mounting foot is attached to the lens/scope via a collar that goes right round the barrel that allows you to rotate the mounting plate around the body, effectively changing the orientation of the eyepiece, or for photography, allowing you to rotate your camera and shoot either portrait or landscape shots.

The objective lens its almost 10mm inside the end of the body, which will provide some protection to the lens, you can also obviously attach the included hood (see accessories below) and there is a 95mm filter thread. Kowa also make a Protective Filter (TP-95FT) that can be screwed onto this thread and which has water and oil repelling coatings for easy removal of fingerprints and water droplets.

Waterproof?
Whilst the main master lens is not fully waterproof, Kowa mention that the objective lens and focusing units have rubber O-rings to seal the housing of the lens that enhances dust and weatherproofing. So my guess is that it is weather protected as opposed to being fully waterproof.

Focusing
Like most quality spotting scopes, the Kowa Telephoto Lens/Scope has a Dual speed focussing mechanism. Unlike most standard spotting scopes, where focusing is achieved via two small knobs on the body of the scope, to focus the Kowa Telephoto Lens/Scope, you turn one of two focusing rings that wrap around the whole body of the lens, the same as you usually fined on standard telephoto lenses for photography. The quick focusing ring that you use more often is larger (wider) than the fine focusing ring and sits closer to your camera body. I found that focusing using these rings was excellent, when using the lens as a spotting scope or for photography. The mechanism is very smooth and both focusing rings turn very easily - I often found myself focusing with one finger and because they wrap around the whole body of the lens, they can be easily reached with either your left or right hands. The rings themselves have a rubber covering that is deeply grooved to help with grip.

Using the quick focusing ring, it takes just less than half a turn to go from the near focus to infinity. This nice and aggressive gearing means that it is very quick to go from one extreme to another and rather surprisingly I did not find it that difficult by just using the quick focusing ring to get a correct focus, but when I had time and the pesky birds would stay still, it was nice to have the fine focusing ring to get a more detailed focus adjustment with the fine focusing ring.

Those used to using a spotting scope for observation or indeed for digiscoping will be used to not having an auto focus, but perhaps those who's only interest is in photography may not be as used (these days) to having to manually focus on an object. Manual focusing is perhaps one of the compromises that you have with this Kowa lens as opposed to standard telephoto lenses, but there are some situations where a manual focus is better and indeed faster and more reliable than an auto focusing lens - for instance when a bird is in a bush or tree and your auto focus keeps on wanting to focus on branches or leaves in front of your subject. Also worth noting is that it is really obvious and simple to see when the subject is correctly in focus.

Rating for Body Construction Quality: 9/10

Weight
One of the really big benefits of this super-telephoto lens, when compared to standard telephoto lenses is that the Kowa TP556 Telephoto Master Lens weighs less than 2kg (4.34 lbs / 69.4 oz.), which is very light. Obviously you have to add the weight of the mount adapter that you are using: the 500mm TX10 Mount weighs 180g, the 350mm TX07 weighs 235g or the 850mm TX17 weighs 480g. So if you are using the heaviest 850mm mount adapter, the total weight of the lens comes to 2.48kg's.

To put this into context take a look at the weights of some comparable lenses below:

• Sigma 800mm f5.6 EX DG weighs 4.9kg's
• Canon EF 800mm f5.6L IS USM - 4.5kg's
• Nikon 600mm f4.0G ED AF-S VR - 5kg's
• Canon EF 600mm f4.0L IS II USM Super Telephoto Lens weighs 3.9kg's
• Canon EF 500mm f4L IS II USM weighs 3.2kg's
• Sigma 500mm f4.5 EX DG APO HSM weighs 3.15kg's
• The much smaller Canon EF 400mm F4 DO USM IS still weighs 1.9kg's.
• Tamron 200-500mm f5-6.3 SP Di LD weighs 1.23kg's

As a spotting scope, you need to add the weight of the Prism unit (410g) to the main body, giving you a total weight (without eyepieces) of 2.41kg's. This means that the weight of the Kowa Lens/ Scope also compares fairly well to other large diameter spotting scopes:

• Kowa TSN-883 Spotting Scope - This 88mm scope weighs 53.6oz (1520g)
• Celestron Regal 100 F-ED - This 100mm scope weighs 89ozs (2523g)
• Nikon EDG Fieldscope 85-A: - This 85mm scope weighs 71.6ozs (2030g)
• Acuter DS20-60X80A - This 80mm scope weighs 63.5ozs (1800g)
• Barr & Stroud Sahara 20-60x80 This 80mm scope weighs 47.97ozs (1360g)

Length: Another advantage of the Kowa Lens over standard photographic telephoto lenses is that it's compact size makes it very portable. It has a length of only 25cm / 9.8 in (when the mount adapter is removed), this means that the lens can easily be carried in a small backpack. The fact that the lens can be broken down into smaller parts also really helps if you want to carry a super telephoto lens with you on an aircraft for example and so I would say this makes an ideal travel telephoto lens and perfect for taking on safari!

As a spotting scope, the length of the body, with the prism attached is still a very compact 34cm / 13.4in. Adding the TE-10z 20x-60x Zoom Eyepiece, this length increases to 42.5cm /16.7in which once again compares well to most other 80 - 85mm spotting scopes.

Rating for Body Stats: 9/10

The video below highlights some of the Lens/Scope's main features especially just how compact it is - it was taken whilst it was still a prototype at the Rutland Birdfair in 2010:

Kowa Prominar Optics

Within the main master PROMINAR telephoto lens, Kowa have used one pure fluorite crystal lens and two XD (extra-low-dispersion) lenses:

Objective Lenses
Kowa's very special Prominar pure fluorite crystal lenses, which use an achromatic lens design to limit the effects of chromatic and spherical aberrations and is actually composed of two individual lenses, one concave lens that has a relatively higher dispersion, while the other, a convex element which has a lower dispersion and then joined together.

The convex lens element is made from Fluorite which concentrates and directs the wavelength of light very effectively and thus is known to have extremely low dispersion that cannot be found in standard optical or even ED (extra low dispersion) glass and is the key to eliminating color fringing (chromatic aberrations).

Kowa then go another step further as in place of ordinary glass on the concave lens element of the achromatic lens, they use their XD glass that also has special dispersion properties to reduce the chromatic aberrations even more.

The combination of the two enables Kowa to eliminate color blur almost completely even at higher magnifications, which dramatically improves resolution and contrast. This effect cannot be duplicated by a normal achromatic lens used on other lenses and scopes.

Fully Multi-Coated
Kowa have also fully multi-coated their lenses, which means all air-to-glass surfaces have received multiple layers of anti-reflective coatings which increases light transmission to produce a brighter image and therefore better low light performance.

Anti-reflective coatings can make large difference on the brightness of the image produced. It is not uncommon for a lens or scope with a smaller objective lens, but high quality anti-reflection coatings to outperform one with a much larger objective lenses, but with fewer or no coatings. Beware of these lower quality optics that will often only add multiple anti-reflection coatings to the outer surfaces of the lenses (Multi-Coated) and cheaper still are scopes that only have a single layers of anti-reflection coating added to the outer lenses (Coated). The very cheapest optics have no anti-reflective coatings at all and I highly recommend staying well clear of these.

The table below shows the amount of transmittance you can expect by the amount of anti-reflection coatings:

Rating for Optical Components Quality: 9/10

Kowa Lens/Scope Eyepieces and Mount Adapters

Depending on how you wish to use the lens/scope, there are a number of different options available to you:

As a Telephoto Lens

The standard package comes with the master lens and the TX10 mount adapter (500mm / F5.6) that enables you to attach the lens to your camera. This adapter is currently available with Canon, Nikon, Pentax and Micro Four Thirds fittings. Also available is the TX07 (350mm / f4) mount adapter and the YX17 (850mm / F9.6) mount adapter.

These mount adapters connect to the master lens with a bayonet mounting system, to prevent it from falling out accidentally. This works really well and it is very simple to attach by lining up a red dot on the lens one on the mount adapter, inserting and then twisting clockwise. To remove, you just press a small button on the mount adapter and twist anti-clockwise.

350mm, 500mm or 850mm Mount Adapters
The standard package comes with the TX10 mount adapter that makes the lens have a focal length of 500mm (F5.6), but by using the optional mount adapters (TX07 or TX17) it is possible to change the focal length of the lens so that it can be used as a brighter 350mm F4 lens or as a longer telephoto 850mm F9.6 lens.

* With Nikon mount and without hood

For the test, I had all three Mounts, but unfortunately the 350mm one was for a Pentax fitting and so could not use it. You can see some of my sample photographs below.

As a Spotting Scope

If you wish to use this lens as a spotting scope, you need to get the TP-88EC1 Prism unit, which will then accept the standard Kowa TSN 880 and 770 eyepieces. TSN-660/600 series spotting scope eyepieces can also be used with the additional TSN-EC3 eyepiece converter.

As with most top end scopes, the eyepieces are also not included with the scope and must be purchased separately. The advantage of this is that you can get the right eyepiece(s) to suite your particular needs.

Like the mount adapter, the Prism unit connects to the master lens with a bayonet mounting system, to prevent it from falling out accidentally. This works really well and it is very simple to attach by lining up a red dot on the lens one on the prism unit, inserting and then twisting clockwise. To remove it, you just press a small button and twist anti-clockwise.

Prisms
I have not been able to find out too much about the Kowa Prism unit, apart from the fact that it uses a porro prism design where the internal prisms are off-set (as opposed to the aligned in roof prisms). This porro prism bends the light rays inside the unit to produce the image. Porro prisms often provide greater depth perception and generally offer a wider field-of-view than most roof prisms and because there is total internal reflection, no expensive phase correction coatings are necessary.

Kowa TSN 880 and 770 eyepieces

All Kowa eyepieces are multi-coated to help increase the light transmission through the lenses and are completely waterproof and filled with dry nitrogen gas to prevent them from fogging up.

Model	TE-10Z	TE-17W	TE-20H
Magnification	22 - 66X, ZOOM	33X, WIDE	28X, LER
Real Field of View	2.0°- 0.95°	2.2°	1.9°
Exit Pupil	4 - 1.3mm	2.7mm	3.2mm
Relative Brightness	16 - 1.8	7.1	10.2
Eye Relief	17 - 16.5mm	20mm	32mm
Field of View at 1000m	34.9 - 16.6m	38.4m	33.2m
Field of View at 1000ft	104.7 - 49.7ft	115.2ft	99.5ft

TE-10z 20x-60x Zoom Eyepiece

This is the eyepiece that I used for the review and I was highly impressed with. It has 10 lens elements in 6 groups and uses an aspherical lens to increase the field of view, which has traditionally been a drawback of zoom eyepieces. This design ensures a wide field of view through the entire zoom range and a flat field all the way to the edge of the lens. The newly developed optical design reduces the deterioration of the image at high magnifications.

Field Of View
Using the 22x-66x Zoom Eyepiece the field of view at 20x magnification is 2° and 0.95° when using the eyepiece at full 60x magnification (34.9 - 16.6m at 1000m). To try and put this into some sort of context, the FOV of the Kowa TSN-883 Spotting Scope with the same TE-10z eyepiece ranges from 2.2° to 1.1° (38.4 - 19.3m at 1000m). The equivalent Nikon FEP-20-60x eyepiece attached to the very top of the range Nikon EDG Fieldscope 85-A, has a field of view ranging from 38-19m @ 1000m.

Close Focusing Distance
This Kowa TSN-880 series scope has a minimum close focussing distance of 5m (16.4ft) which is very good - for comparison the Acuter DS20-60X80A Spotting Scope has a minimum focusing distance of 6.5m (21.3ft).

Eye-Relief:
This eyepiece has a twist up eyecup that looks to be made of metal and has a soft rubber coating that that is really comfortable even when pressed quite firmly against your face. Depending on the magnification you are using, there is about 17mm of eye-relief that should be more than enough for most eyeglass wearers to be able use the scope without having to remove their glasses and still get the full field of view without any vignetting.

The twist-up mechanism on the eyecup is really smooth and works well. They also have two fixed intermediate stops which helps those who do wear glasses to get exactly the right amount of eye relief for them. Non-eyeglass wearers will just use the eyecup in the fully extended position.

Rating for Optical Stats: 8/10

TE-17W 33x WIDE Eyepiece

This eyepiece design has 7 lens elements in 5 groups provides easy viewing with an eye relief of 20mm and field of view approximately 10% wider than conventional eyepieces. This wide field of view is extremely useful when searching for subjects that you want to bring into view. The 20mm eye relief allows you to see the entire field of view, even when wearing eyeglasses.

TE-20H 28x LER

This eyepiece design has 7 lens elements in 4 groups has an extremely long eye relief of 32mm. This extra eye relief is extremely useful when wearing eyeglasses or for a digiscoping system. *Suitable for 4X zoom cameras and cameras with large-diameter objective lenses. Vignetting may not be eliminated in some cameras.

As mentioned earlier, TSN-660/600 series spotting scope eyepieces can also be used with the additional TSN-EC3 eyepiece converter:

Digiscoping with the Kowa TP556 Telephoto Lens/Scope

If the maximum of 850mm is not large enough for you, you can also connect a compact or even SLR digital camera to the lens when it is configured for use as a scope - as you would for standard digiscoping. In this way it is possible to achieve focal lengths of 1000-3000mm & more, allowing for photography of subjects at very long distances which would not otherwise be possible. To do this you can use the standard digiscoping accessories that are compatible with the Kowa TSN-880 series scopes:

• Kowa TSN-DA10 Digital Camera Adapter - For TSN-880/770 Series
  It threads on the eyepiece and is used to connect the digital camera to the spotting scope. Note you will also need the TSN-DA4 or Adapter Ring.
  
• Kowa TSN-DA4 universal camera adapter used for compact digital cameras
• Kowa TSN-VA1 is a specially designed adapter for use with high power optical zoom digital cameras.
• Kowa TSN-VA2 is a specially designed adapter for use with high power optical zoom digital cameras with a large objective lens.

Image Quality & Sample Photos

As a Telephoto Lens

I am very grateful to Kowa for lending me their Telephoto Lens Scope for a whole month, but it was during winter and so I only had a small amount of days where the weather and light were good enough for decent photography. To ensure that I did at least get some pictures, I decided to cheat a little and position myself not far from some of the bird feeders in my garden! So whilst I don't usually like to publish photos of birds at feeders, for this review I have included them:

Photos taken with the 500mm (F5.6) Mount Adapter (TX10)
Medium (1000x665) | Large: (2000x1330)	Medium (1000x665) | Large: (2000x1330)
Medium (1000x665) | Large: (2000x1330)	Medium (1000x665) | Large: (2000x1330)
Photos taken with the 850mm (F9.6) Mount Adapter (TX17)
Medium (1000x665) | Large: (2000x1330)	Medium (1000x665) | Large: (2000x1330)
Medium (1000x665) | Large: (2000x1330)	Medium (1000x665) | Large: (2000x1330)
Medium (1000x665) | Large: (2000x1330)	Medium (1000x665) | Large: (2000x1330)
Medium (1000x665) | Large: (2000x1330)	Medium (1000x665) | Large: (2000x1330)

As a Spotting Scope

Image Brightness
When using the device as a spotting scope and with the TP-88EC1 Prism Unit and TE-10z 20x-60x Zoom eyepiece, I thought that in terms of image brightness, this Kowa was extremely impressive. To my eyes it was quite a bit brighter than my 80mm benchmark spotting scope at both 20x and at 60x magnifications, which in a way was expected as this Kowa Telephoto Lens Scope has far higher quality lenses and coatings.

More about Image Brightness & Low Light Performance
Good light gathering ability is important because quite often you will find yourself in situations where the lighting is sub-optimal, especially in thickly wooded or forested areas, early in the morning just before or at sunrise or late afternoon when most birds and other animals are at their most active. Scopes with larger objective lenses have the potential to take in more light and therefore have the potential to produce a brighter image.

You also need to take into account that the exit pupil will change depending on which magnification you are using - with the magnification set at 20x the exit pupil is 4mm, whilst at 60x it reduces right down to 1.3mm.

But no matter how much light your spottingscope gathers, it is no good if that light is not passed onto your eyes (transmittance) and this depends hugely on the quality of the glass and optical coatings and not just the size of the objective lens. Good coatings on the lenses and the prisms can in some cases double the amount of light that gets through the scope, when compared to those that have none or poor quality coatings and as we have already discovered this Kowa used the best quality glass and coatings, so it is no wonder that it produces such a bright image.

Color Fringing
Kowa make a lot about the fact that they use fluorite crystal lenses in a achromatic lens design to limit the effects of chromatic aberrations (color fringing) and so I was expecting them to be excellent in this area. I was not disappointed, to check for any color fringing, I focus on light coloured and white objects sitting in front of a dark backgrounds and I could not see any color fringing at all at any magnification. Very impressive.

Softening
Using the 20-60x zoom eyepiece, there is a very small amount of softening of the image at the edge of the view and you only actually notice it when you are really looking for it.

Contrast & Colour Reproduction
I thought that the amount of contrast was excellent, which really helps to make objects jump out at you and feel more three dimensional. The colors that are produced also look and feel natural and are as vivid as on any scope that I have ever used.

Overall the quality of the image produced was far superior to that of my entry-mid range benchmark and definitely has one of, if not the best views of any scope that I have had the pleasure to look through.

Rating for Image Quality: 9/10

Included Extras & Attention to Detail:

TP-100LH Lens Hood
The Kowa Scope/Lens comes with a good quality and very long lens hood (13.9cm) as a standard accessory. The metal hood mounting screw has a special shape that allows it to be used together with the sight attached to your camera on the flash hot shoe plate, this helps to quickly line up the subject and get it into the field of view when using the lens for super-telephoto photography.

Lens Covers
All lens covers, including the main objective lens cover are of good quality and fit well and so should not fall off accidentally.

Conclusion

Strong Points: It is difficult to know where to start! Overall the build quality of the master lens is excellent and the optics used are as good as it gets. As a scope it is compact and light, as a super telephoto lens, it is extremely compact and light. The fact that the lens can be broken down into smaller parts also really helps if you want to take it with you on an aircraft for example and so is an ideal travel telephoto lens. The glass and coatings quality are excellent, which in turn produce extremely high quality images.

But for me the biggest selling point is the price. Whilst the Kowa TP556 Telephoto Master Lens that comes with a TX10-C 500mm f5.6 Mount Adapter currently costs more than many other top of the range spotting scopes, you must remember that this is essentially a high quality super telephoto lens that costs way less than what many other SLR telephoto lenses do and you can also use it as a spotting scope for pure observation. For this reason I think it will appeal more to the person looking for a large telephoto lens for photography, rather than someone looking for a scope to do the occasional "digiscoping" with.

To try and put this into some sort of context I have listed what you can expect to pay for some similar bits of kit:

Approx cost of some Telephoto Lenses:

• Sigma 800mm f5.6 EX DG - $6500 / �4300
• Nikon 600mm f4.0G ED AF-S VR - $9000 / �7000
• Nikon 500mm f/4.0G ED VR AF-S SWM Super Telephoto Lens - $8400 / �6000
• Sigma 500mm f4.5 EX DG APO HSM - $5000 / �3700
• Nikon 300mm f2.8G AF-S ED VR II - $6000 / �4000
• Canon EF 70-300mm f4.0-5.6 IS USM - $500 / �500

Approx cost of some High End Spotting Scopes:

• Nikon 85mm EDG Fieldscope - $3500 / �1700
• Zeiss 85mm Diascope - $3000 / �1700
• Kowa TSN-883 - $2000 / �2000
• Swarovski STM 80HD - $2500 / �1800

Weak points? Looking at it from a photographers perspective, I guess the biggest drawback would be that it does not have auto focus, but for those who already digiscope, this will be no different from what they are used to.

If you are used to using an angled spotting scope, a straight scope like this one does take a little to get used to, but remember they have their advantages too like being much simpler to line up your subject.

Acknowledgements

I would like to thank Alpha Digital Services Ltd. the UK distributor of Kowa Spotting scopes and binoculars for sending the Lens /Scope over to me to review. At this time, I would also like to make it clear that this and all the other reviews on this site are my opinion and are not influenced in any way by manufacturers, distributors or suppliers.