Binoculars review

Delta Optical Chase 10x42 ED

Delta Optical Chase 10x42 ED
20 June 2017
In March 2017 the Polish Delta Optical company announced a launch of a new series of binoculars called Chase ED. The series was supposed to consist of four models with the following parameters: 8×42, 10×42, 10×50 and 12×50.

All binoculars are roof prisms Schmidt-Pechan instruments with silver-coated reflective layers. The producer doesn’t mention anything about phase correction coating but all air-to-glass surfaces are supposed to be covered by multilayer antireflection coatings. In objective lenses low-dispersion ED glass was used.

The bodies of the binoculars are compact, with an inner focusing mechanism and dioptre correction so these instruments are completely waterproof and nitrogen-filled.

Buyers get a case, a clearing cloth plus caps for eyepieces and objective lenses in the box. The product comes with a 10-year warranty period.

  • Lornetka Delta Optical Chase 10x42 ED
  • Lornetka Delta Optical Chase 10x42 ED
  • Lornetka Delta Optical Chase 10x42 ED
  • Lornetka Delta Optical Chase 10x42 ED
Manufacturer data


Delta Optical
web site

Distribution / Sales:

Delta Optical
web site

Magnification Lens diameter Angular field of view Prisms Eye relief Weight Price
10 42 112/1000(6.4o) BaK-4/roof 17 mm 730 g 1190 PLN
Results of the review
Real front lens diameter Left:   42.2+/- 0.05 mm
Right:  42.2+/- 0.05 mm
8 / 8.0 pkt
Real magnification 10.01+/- 0.1x 3/3.0
Transmission 83.3+/- 1% 11/25.0
Chromatic aberration Slight in the centre, a bit higher than medium on the edge. 6.3/10.0
Astigmatism Moderate. 6.4/10.0
Distortion Distance between the first curved line and the field centre compared to the field of view radius: 49% ±5% 5/10.0
Coma Appears far from the centre, in a distance of about 75% of the field of view radius and is a bit higher than medium on the edge. 7.4/10.0
Blurring at the edge of the FOV Blur occurs in a distance of 85% ± 3% from the field of view centre. 7/10.0
Darkening at the edge the FOV Moderate. 3.8/5.0
Whiteness of the image A slight inclination of the transmission curve. About 5-6% of difference between red and blue light. A good result. 4.1/5.0
Collimation Perfect. 5/5.0
Internal reflections
Left: Right:
Delta Optical Chase 10x42 ED - Internal reflections - Left Delta Optical Chase 10x42 ED - Internal reflections - Right
A semblance of a false pupil.
Housing Very stylish and shapely. Rubber armour of good quality but a tad too slippery. Rubber sticks to the casing very well. Slight rubberized eyecups with three stops. Produced in China. 7.7/8.0
Focusing Huge, ribbed central wheel which works properly well and its full range amounts to as much as 900 degrees. You really have to do a lot of turning. A joystick next to the central wheel controls the dioptre values. Nothing moves outsider – a rare occurrence at this price point. 5/5.0
Tripod A comfy exit. 3/3.0
Interpupilary distance from 55.8 to 76mm 5/6.0
Closest focusing distance 2.05 meters. 2/2.0
Eyepieces FOV Apparent field of view of 62.9 deg (according to simple formula) and 57.5 deg (according to tangent formula). 12.5/20.0
Field of view Measured by us amounted to 6.28 ± 0.04 degrees and it was a bit narrower than stated in official specifications. A sensible field for this class of equipment. 6.5/8.0
Quality of the interior of the barrels Nicely blackened, matted and ribbed tubes. A wide bottom, black near the prisms, the smaller case is grey. Some specks of dust on the prisms. 4.1/5.0
Left: Right:
Delta Optical Chase 10x42 ED - Vignetting - Left Delta Optical Chase 10x42 ED - Vignetting - Right
OL: 2.91%, OR: 3.42%
Prisms quality Good quality BaK-4. 8/8.0
Antireflection coatings Pink-yellow-green on objective lenses, green-blue on prisms, green-purple-yellow on eyepieces. Intensity a bit higher than medium. 4.2/5.0
Warranty [years] 10 4.5/6.0
Final result
137.1 / 190 pkt
Econo result 0pkt.


  • shapely and very stylish casing,
  • lack of any serious problems with chromatic aberration,
  • moderate astigmatism,
  • slight coma,
  • sharp image in the majority of the field of view,
  • good colour rendering,
  • moderate brightness loss on the edge of the field of view,
  • proper blackening and cleanliness inside the tubes,
  • BaK-4 glass prisms,
  • inner focusing and dioptre correction.

  • runcated exit pupils.

Pentax ZD 8x43 ED, Delta Optical Chase 10x42 ED and Focus Nordic Handy 8x42.

We would like to start the summary of our test by describing the casing of the Chase 10×42 ED because, in my opinion, it is one of serious assets of this pair of binoculars. First of all you deal here with a small, handy instrument and the photo above is the proof. What’s more the casing’s design is really good – the binoculars look simply nice, there’s no doubt of it. The same should be said about accessories, properly fitting and appropriately selected. The rainguard might be an example. In many cases a rainguard consists of just a black cover which colour doesn’t match the rest of the instrument; often the whole series gets the same size of the rainguard, no matter how big particular sets of binoculars are. Here you deal with a small blind stopper which comes in different sizes so it fits particular models in a perfect way.

The casing itself features one more interesting thing, characteristic for models far pricier than this one. As the inner focusing is already a standard when it comes to roof prism instruments, the dioptre correcting system usually entails moving the whole right eyepiece. In the tested binoculars the dioptre values are set by the movement of inner optics elements, a solution typical for top-of-the-range devices. Such a system is especially important if you want your instrument to be completely sealed.

When it comes to optical properties you have one serious reason to complain and two less important ones. First of all small physical dimensions of the binoculars caused the truncation of exit pupils. Then, in order to make you completely happy, the instrument could have had a tad better distortion correction and coatings of higher quality.

The graph above shows that the transmission level can hardly be called impressive. Still you must also say that, at this price point, it is perhaps not very bad either and the graph remains quite flat so the colour rendering is good.

In the rest of optical categories of our test the results reached by the Delta Optical Chase 10×42 ED were good or very good; as a result the final score amounts to slightly more than 130 points. The tested pair of binoculars seems to be a worthy rival of many more expensive models and I don’t doubt it is going to become a market hit pretty soon.