Eyeskey 10x25ED – small compact binoculars with a declared magnification of 10x and a lens diameter of 25 mm. Thanks to the folding and compact design, the Eyeskey 10x25ED binoculars do not take up much space during transportation, and the small weight of the binoculars allows you to wear them on your neck for a long time. The use of ED glass is declared, which should reduce chromatic aberration on the axis compared to binoculars on ordinary glass. Schmidt-Pechan prisms are used to invert the image.
Specs:
EQUIPMENT
I only got the binoculars with covers for review. The covers are the same size, 4 pieces, rubber. The binoculars should also come with a case for storage and transportation, a neck strap, instructions, and a cloth for wiping the lenses.
HOUSING, MECHANICS
The body is metal with rubber pads. There is an inscription “Eyeskey” on the top, and an inscription “ED” on the left rubber pad. In the lower right part under the bridge there is a serial number of the binoculars. The weight with caps is only 260 grams. When folded, the length with caps is 111 mm, without caps 105 mm, width 65 mm, height 43 mm. The diameter of the tubes is 29.5 mm. At the bottom of the binoculars there are two “ears” for a neck strap. There is no socket for a tripod adapter.
The hinge is tight enough and holds the set interpupillary distance well. The range of interpupillary distances due to the use of a folding design is very large – from 36 to 74 mm.
In the front part of the binoculars there is a ribbed metal drum for focusing with a diameter of 16 mm. It is more convenient to focus it not with the index finger, but with the ring finger. In the back part (closer to the eyepieces) there is a ribbed metal drum for diopter correction with a diameter of 11 mm with the inscription “10×25”, it is convenient to focus it with the thumb. The minimum focusing distance according to the measurement is about 2 meters.
The ergonomics of compact binoculars of this type are unique and you need to get used to them.
The eyecups are retractable, 29.6 mm in diameter, metal + rubber, they are unscrewed and screwed in very easily, the stroke is 11.5 mm without intermediate positions and fixation. There is an inscription “FLAT FIELD” on the eyecups.
OPTICS
Objectives are 25 mm in diameter, green and lilac coating. Prisms are coated.
The eye lenses are 19.3 mm in diameter, convex, and recessed relative to the eyecup by 4.5 mm. The measured field of view is approximately 54 degrees. The pupil removal is the maximum for observation in glasses with the eyecups screwed in.
TEST
The light test showed that the binoculars introduce yellowness into the image. Moreover, the red and green channels are practically the same in brightness, but in the blue channel there is a noticeable decrease in brightness.
Testing the phase coating with a polarizing filter showed that the halves did not darken quite simultaneously.
The measured magnification was approximately 10x.
The binoculars have excellent collimation, and the eyes do not get tired during observations.
No channel desynchronization was detected, there are no delays when refocusing in either direction, and constant adjustment of the diopters in the right eyepiece is not required.
The image on the axis is sharp and contrasty. Longitudinal chromatic aberration on the axis is not noticeable. Lateral chromatic aberration is noticeable and quickly increases to the edge of the field of view. Despite the inscription “Flat Field”, there is a curvature of the field, the sharpness of the image decreases to the edge. After a small refocusing, the image on the edge improves. There is a small pincushion distortion (straight lines on the edge bend slightly inward).
When testing with stars, chromatic aberration of magnification remains noticeable; at the edge of the field of view, the star turns into a “stick”.
SUMMARY
+ compact
+ lightweight
+ fully coated
+ very sharp in the central area of the field of view
+ slight distortion
— there is a curvature of the field
— color rendition distortion
— significant chromatic aberration of magnification
— ergonomics require getting used to
— caps do not hold well, easy to lose
— eyecups rotate too freely.
Eyeskey 10x25ED – small binoculars for traveling and daylight observing. They will not pull your neck when worn for a long time, while having excellent sharpness in the center. For quick observations in the format “saw something interesting > looked > went on” more than suitable. However, a fairly high magnification requires some training of the grip to hold the binoculars stably. Due to the small exit pupil (2.5 mm), these are binoculars for observing in daylight, but it is quite possible to admire the Moon or examine areas of bright constellations.