A Work Commenced April 2 2022

 

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Product: Opticron Savanna 8 x 30

Country of Manufacture: China

Exit Pupil: 3.75mm

Eye Relief: 18mm

Close Focus: 3m advertised, 2.8m measured

Field of View: 131m@1000m(7.5 angular degrees)

Coatings: Fully Broadband Multi-Coated

Chassis Contruction: Rubber armoured aluminium alloy and polycarbonate

Prism Types: Porro BAK4

ED Glass: No

Tripod Mountable: No

Dioptre Compensation: +/- 3

Waterproof: Yes

Nitrogen Purged: Yes

Weight: 491g advertised, 458g measured

Dimensions: LxWxD (cm)/ 11.6×16.0x4.0

 

Porro prism binoculars have received quite a bit of bad press in recent years. In surveying some of the literature, I’ve read that they’re heavy and unwieldy, lack water-and fog-proofing, and are more prone to misalignment of the optical elements than their roof prism counterparts. Others seem to have dismissed them purely on aesthetic grounds, citing their ‘ugliness’ as a reason to reject them. How shallow is that? But after extensively testing a thoroughly modern porro prism binocular from Opticron – the Savanna 8 x 30 – I’ve discovered that many of these assumptions are either misleading or totally untrue.

Let’s begin by listing some of the key advantages of porro prism binoculars.

1. They are much more economical to manufacture to a high standard than roofs.
2. They have much more forgiving design tolerances than roof prism binoculars.
3. They offer naturally brighter images, owing to fewer reflections through porro prisms
4. They offer very wide fields of view with simpler eyepiece designs
5. They throw up much more pronounced 3D or stereoscopic images than their roof prism counterparts

Having said all that, this new model offered by Opticron promises to dispel many of the traditional reasons why porro prism binoculars have fallen out of favour with birders, hunters and outdoor enthusiasts. To see why, read on.

Ergonomic Features

The first thing that grabbed my attention was the feather light weight of the Opticron Savanna 8 x 30. Tipping the scales at just 458g(without the strap), this is actually one of the lighter models on the market. For example, the Nikon Monarch HG 8 x 30 comes in at only 8g less!

The chassis is covered in a nicely textured rubber armouring that feels quite spongy to the touch, protecting the instrument from accidental knocks and bumps.

The central hinge is nice and rigid, keeping my optimal IPD even after taking it out of its tightly fitting soft carry case many times during my tests.

The eyecups are strong and are of good quality, and twist up like most roof prism models. This is a departure from the fold-down rubber eyecups I’ve seen on a few other porro prism designs. They click rigidly into place, but there is no provision to set them at an intermediary position. I rather like two stage eyecups like this, as I’ve not found an intermediate detent in any binocular that conveys a more comfortable view. The eye relief is quite generous though. I was able to image the entire field comfortably using eye glasses.

The focuser is very large and easily accessed. Movement is smooth and firm with very little in the way of play. What’s more, the focuser only rotates through about three quarters of a full revolution in order to go from one end of its focus travel to the other. Close focus was measured to be 2.8m, significantly closer than the advertised 3m. It also focuses a wee bit beyond infinity, useful for snapping edge of field objects into tighter focus.

The ocular field lenses are large( 21mm in diameter), making eye placement easier to achieve and comfortable to place one’s eyes against.

 

The dioptre compensation ring is located under the right ocular lens. It moves with a nice amount of rigidity.

The external focuser is fashioned from aluminium which affords good tensile strength. Examining the progress of its motions, I was delighted to see there was zero wobble as it was racked in and out of focus. The binocular is advertised as waterproof and fog proof( nitrogen purged), so I assume it’s o ring sealed. This may come as a surprise to roof prism fans, but surveying the market, there are several other porro models that claim the same.

One very welcome feature is the minimum inter-pupillary distance of 50mm, making it eminently suitable for those of us who have smaller faces. These will work brilliantly with kids!

The small 30mm objective lenses are very deeply recessed. This is a very welcome feature, as it protects the objective lenses from rain, dust and stray light. My experiences over the last several years has taught me that models without very deeply recessed objectives display higher levels of glare during field use

In the hands, the Opticron Savanna 8 x 30 feels great. There are plenty of places on its nicely contoured body to wrap your fingers round. Indeed, I’ve not held a more comfortable binocular in quite some time! Overall, this appears to be a very nicely designed porro prism binocular, incorporating many of the great features found in roofs costing substantially more!

Now, let’s talk about optics.

Optical Assessment

The binocular arrived in good collimation, as judged in daylight testing and by examining the bright star Arcturus, defocusing it using the right eye dioptre. By directing a beam of intensely bright light into the binocular objectives, I was able to verify that there was no annoying internal reflections, diffraction spikes and only a very small amount of diffused light around the light source. The result was just as good, in fact, as a top-rated roof prism control binocular I used as a control – the GPO Passion ED 10 x 32. I measured the effective aperture as effectively 30mm by directing a beam of light through the ocular lens and measuring the diameter of the emerging disc of light. There was also no internal reflections when I tuned the binocular on a bright sodium street light after dark.

The Opticron Savanna 8 x 30 throws up a very impressive image. The sweet spot covers about 80 per cent of the field, with mild field curvature setting in as the target was moved to the edge of the field. Contrast is excellent too. Comparing it to the less expensive Adventurer T WP 8 x 32 porro prism binocular, the Savanna displayed far less glare. Veiling glare was also far less pronounced in the Savanna too but not quite as well controlled as in the GPO 10 x 32 binocular costing three times its modest price tag. Though the field of view is smaller than in the Adventurer T WP 8 x 32(8.1 degrees), it’s much cleaner, with nicer edges and a clearly defined field stop.

The Savanna 8 x 30 image is very bright and tack sharp within its generously large sweet spot. In careful side-by-side tests with my GPO 10 x 32 Passion ED, I judged the images as equally sharp(or maybe a tad sharper in the Savanna porro) in the middle of the field, but fell short of the roof prism bino from about 50 per cent of the way from the centre to the field stops. In addition, the colour tone of the Savanna 8 x 30 was very neutral in comparison to the warmer colours garnered with the GPO. Chromatic aberration was not seen on axis, and only a trace was detected off axis while looking at denuded branches of trees against a bright, overcast sky. This shows, once again, that a good binocular needn’t employ ED glass to deliver a really good image. Indeed, all of the top porro models now available don’t employ ED glass.

Go figure!

In yet another test, I ordered up a classic Opticron Dioptron 8 x 32, a vintage Japanese- made instrument dating to the late 1990s. I was amazed to discover how much brighter the Chinese-made Savanna 8 x 30 was in comparison. Sporting a field of view of 8.25 angular degrees, the Dioptron also enjoys a large sweet spot but once outside it, the images of stars rapidly deteriorated as they were moved towards the field stops. In comparison, the 7.5 degree field of the Savanna 8 x 30 kept those same stars under much better control even near the edge of the field. Though the Dioptron is also fully multi-coated, it showed some prominent internal reflections, unlike the Savanna, and daylight images were noticeably yellowed(warm) in comparison to the much more natural colour tones served up by the modern Savanna binocular. Glare was also much better controlled in the Savanna in comparison to the classic Dioptron  8 x 32. Indeed, I judged the less expensive Adventurer T WP 8 x 32 to have similar levels of glare to the Dioptron. What was also surprising to me however, was the finding that the Adventurer T WP delivered a brighter image than the Dioptron in daylight tests.

Collectively, these tests convinced me that great advances in coating technology have occurred in the last two decades, with even low cost ‘econo’ binos serving up noticeably brighter and more contrasted images than some of the best porro prism binoculars available from the late 20th century.

The Remarkable Phenomenon of Stereopsis

One of the things that struck me as being very obvious and visually striking in the Opticron Savanna 8 x 30, was its ability to generate wonderful depth perception, or stereopsis, as it’s referred to in the technical literature. Focus the binocular in the middle distance and objects remain razor sharp all the way to infinity. What does that translate to in field use? Less frequent focusing. Looking at some conifer tree trunks lying beyond my back garden, and comparing the view in a few roof prism models, revealed the total superiority of the Savanna porro in conveying three-dimensional, spatial information or contouring of the tree trunks in relation to each other. Simply put; more details remain in sharp focus compared to a good roof prism binocular imaging the same field. In another test, I used a very nice 8 x 42 ED roof prism binocular to focus in on a chimney some 40 yards in the distance, but background trees at about 65 yards distant were a little blurred, lacking information:- a wee bit out of focus. Not so with the little 8 x 30 porro prism binocular from Opticron! Both targets remained sharp! The effect becomes less pronounced at distance though. But for walks in the woods, where trees litter the landscape both near and far away, I can’t think of a better instrument than a small high-quality porro like this to enjoy those views!

Indeed, I’ve now come to see this effect as adding valuable information to the binocular image – just as our eyes were created to do.

Let’s just say roofs lack dimensionality in side by side comparisons.

 

Conclusions & Recommendations

The old adage is certainly true; you have to go to great lengths to make a roof prism binocular as good as porro prism designs. The quirky little Savanna 8 x 30 takes a tried and trusted optical design and puts a thoroughly modern accent on it. For the modest price of just over £100, you get an instrument that has excellent optics and ergonomics. It totally smashes the stereotype of porro prism binoculars being big and clunky. And it’s quite a good looking binocular too, don’t you think?

My experiences with this lovely little instrument has consolidated my conviction that porro prism binoculars will be my instruments of choice in the compact-size format, with their unparalleled 3D-enhanced images and brilliant, sharp, high contrast optics. I would highly recommend this instrument to savvy binocular enthusiasts wanting to get the absolute maximum bang for buck. I would also recommend the instrument or its lower power sibling – the Savanna 6 x 30 –  for younger individuals or adults with smaller faces. Rest assured, it will embarrass roof prism designs costing a few hundred pounds and the solid 10-year warranty from Opticron will put your mind at ease that it will stand the test of time.

Thanks for reading!

 

Dr Neil English is the author of a highly lauded 650+ page history of visual telescopic observing; Chronicling the Golden Age of Astronomy.

 

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De Fideli.