Swift Optics 820 ED Audubon 8.5x44
The porro prismatic Swift Audubon ED 8.5x44 model includes low dispersion ED glass in the objective lens which task is to fight against the chromatic and spherical aberration and raising the contrast level by 5-10% compared to normal binoculars.
Apart from the objective lens we deal here with Porro system prisms and five-lens eyepieces, which ensure one of the widest field of view in this class.
Everything is closed in a waterproof and nitrogen-filled magnesium barrel padded with high quality rubber. All air-to-glass surfaces were covered by antireflection coatings.
| Magnification | Lens diameter | Angular field of view | Prisms | Eye relief | Weight | Price |
|---|---|---|---|---|---|---|
| 8.5 | 44 | 144/1000(8.2o) | BaK-4/Porro | 17 mm | 730 g | 1719 PLN |
| Real front lens diameter |
Left: 43.83+/-
0.05 mm Right: 43.8+/- 0.05 mm |
7 / 8.0 pkt | ||||
|---|---|---|---|---|---|---|
| Real magnification | 8.8+/- 0.15x | 3/3.0 | ||||
| Transmission | 90+/- 3% | 17.5/25.0 | ||||
| Chromatic aberration | Very low in the centre, low at the edge. | 8.3/10.0 | ||||
| Astigmatism | Between low and medium. | 6.8/10.0 | ||||
| Distortion | The distance of the first curved line from the filed centre compared to the field of view radius: 38% +\- 4% | 4/10.0 | ||||
| Coma | Between low and medium. | 6.5/10.0 | ||||
| Blurring at the edge of the FOV | The blur occurs in the distance of 70% +\- 5% from the field of view centre. | 3/10.0 | ||||
| Darkening at the edge the FOV | Visible but at a medium level. | 3/5.0 | ||||
| Whiteness of the image | Slightly yellow. | 3.9/5.0 | ||||
| Collimation | Perfect. | 5/5.0 | ||||
| Internal reflections |
|
1.2/5.0 | ||||
| Housing | Solid barrel, comfortable to hold. Uninterested eyecups – made of plastic and loose-fitting. | 7/8.0 | ||||
| Focusing | Central screw moves conveniently and smoothly (700 degrees). The bridge’s movements minimally uneven. Putting pressure on it doesn’t cause defocusing. Slight lateral “play” of the eyepieces. Individual focusing is comfortable but it moves the lens. | 3.6/5.0 | ||||
| Tripod | There is a comfortable exit. | 3/3.0 | ||||
| Interpupilary distance | from 55.2 to 71.1mm | 2/6.0 | ||||
| Closest focusing distance | 2.60 m | 1/2.0 | ||||
| Eyepieces FOV | Apparent field of view of 68.9 deg (according to simple formula) and 62.1 deg (according to tangent formula). | 15.5/20.0 | ||||
| Field of view | Measured by us amounted to 7.83 +\- 0.03 degrees and it was by as much as 0.37 degrees narrower than in the specifications. Even so, the field is still very wide for this equipment class. | 5/8.0 | ||||
| Quality of the interior of the barrels | Tubes are black and matt; the bottom - bright and gray. Two big points on the left prism. White glue. | 3/5.0 | ||||
| Vignetting |
|
7/8.0 | ||||
| Prisms quality | Good quality BaK-4. | 8/8.0 | ||||
| Antireflection coatings | Blue-green on the objective lenses. Purple on the prisms. Green-purple on the eyepieces. Low intensity. | 5/5.0 | ||||
| Warranty [years] | 25 | 5/6.0 | ||||
| Final result | 70.7% | 134.3 / 190 pkt | ||||
| Econo result | 0pkt. |
Summary
Pros:
- solid barrel,
- very wide field of view,
- good transmission,
- slight chromatic aberration,
- good whiteness rendition,
- good quality prisms and coatings.
Cons:
- visible flares,
- not comfortable eyecups,
- blurred edges of the field of view,
- dirt on one of the prisms,
- the maximum IPD too narrow.
A handy set of porro binoculars with a wide field of view and equipped with low dispersion glass should be on every producer’s offer. Such an instrument is easy to manufacture so it doesn’t have to be very expensive and if you take care of the build quality and other details it might be even a best-seller. Will the Swift 8.5x44 ED be such a product? It’s difficult to say; it seems that the producer didn’t exactly see to the details in this case. On the one hand we have ED glass, which corrects the aberration efficiently, and good coatings which assure good transmission and whiteness rendition; apart from that the binoculars do have a wide field of view and good quality prisms. On the other hand, though, you can get annoyed by trivial flaws, such as insufficient blackening and cleanliness inside, low quality of eyecups which are ergonomically badly designed, the average quality of the edge of the field of view (significantly smaller, by the way, than in the specifications).
Does this balance of profits and losses is favourable for the Swift, taking into account its price? Customers will have to determine it for themselves.
