Ceenda Monocular Telescope,12x50 HD BAK4 Prism Waterproof High Power Monocular with Phone Photography Adapter and Wireless Remote Control，Perfect for Bird watching Hiking Concerts

This is a generic 12x50 monocular from China offered in Amazon by several sellers under various brand names that simply differ by the decorative design of the plastic body, location of the brand name on the body, and type of accessories included with the unit. Most of such devices have a comparatively narrow price range, and this one is at the range's low end.SPECS & OPTICSThe field of view seems ~210 ft at 1000 yd, or 4 degrees. The eye relief (the distance from the eye at which to hold the device and still see the field of view) is ca. 1 cm. Those wearing thick eyeglasses may need to remove the eyepiece's protecting sleeve. The long focusing knob stops cleanly at the end of turning it clockwise, but jumps back on its thread (with a noise) at the end of the other direction indicating a faulty assembly.Several specs and performance claims are just hype or false. This is not a "low night vision" that works with a trivial amount of illumination or is sensitive to IR lights. Also, is not waterproof: the O-ring mounting of lenses provides a degree of water-resistance, but the degree is undisclosed as no IP rating is provided. This page claims that the device's nominal 12x50 specs, BAK4 prism, and multi-coated lens coating provide a "superior light transmission and brightness ... and delivers [sic] crisp images." As described below, however, its optics have several obvious defects, and there are issues that limit light transmission as compared to that of higher-quality devices.One issue is the size of the exit pupil, a virtual aperture between the eyepiece and the eye that should equal the quotient between the physical aperture and the magnification. In this device it should be 4.2 mm (50/12), but the measured size is ca. 3.5 mm (equivalent to having a physical aperture of 42 mm), which yields 1½ times less transmission than expected from the nominal specs.Another issue involves the BAK4 name. The German manufacturer Schott's glass BaK4 (barium crown) has a higher refractive index than another type of glass commonly used in prisms, BK7 (borosilicate crown), so BaK4 prisms have the fame of gathering more light. But there are no international standards for optical glass *names* --a glass is identified by three digits for its refractive index plus three other digits for its Abbé number-- and what Chinese manufacturers call BAK4 is phosphate crown glass [552634], whose index of refraction is less than the Schott BaK4 [569561] and thus gathers less light.A third issue is the term "Multi-coated Lens Coating," which can mean whatever the seller wants as there are no standards for coating labels. Coatings in this unit show weak greenish reflections. It is not disclosed if the coating was applied to all glass-to-air surfaces of all the lenses and prism faces, or just some, and how many layers were used. Given the product's low price, the reflection color suggests that MgF2, the least expensive coating (having a higher than desirable index of refraction), was applied as one or perhaps two layers.PERFORMANCEA 7x focusing loupe placed on the eyepiece showed vignetting all around the periphery of light field. To evaluate defects I used a lens test chart (see left panel of my figure) of 4.5" W by 7.75" H, placed at 12 ft. The device produced a moderate but noticeable *pincushion distortion* of the rectangular black frame of the chart, with slight *lateral chromatic aberration* fringes more noticeable on the horizontal sides of the frame (which were closer to the periphery of the circular view field than the vertical sides).The optical defects became much more obvious when the device was attached to, and carefully aligned with, the camera of a Sony Xperia XZ2 mobile phone. This right panel of the figure is a photograph of the test chart at 12 ft. Pincushion distortion is quite marked and so is the lateral chromatic aberration ("purple fringing") along the horizontal sides of the rectangular frame, with reddish fringes on the outer frame edges, and bluish on the inner ones.The camera mounting uses a pressure collar around the device's eyepiece, which screws to a slotted extension arm that attaches to a tensioned two-lip clamp holding the borders of the camera body. The clamp has maximum opening of 3.19" [81 mm] and each lip clamps a length of 1.25" [32 mm] of the camera's border; the depth of the clamp, 0.55" [14 mm], makes it difficult to hold the camera securely when using a phone case. Aligning the eyepiece with the lens of the camera It is not an easy or quick procedure,and is rarely satisfying, as shown by the exaggeration of the optical defects seen without a camera.MANUAL & WARRANTYThere are brief instructions written in Chinese and an abhorrent English translation on the use and cleaning of the monocular. They are of little help. For example, one refers to a mysterious "scale location under the manual wheel of the Ocular lens," followed by the nonsensical advice "under the common station, in the following usage only need to turn to the scale location same as the first time." (Using a dictionary and a translation Web engine, the Chinese text for that reads: "position of the mark under the hand wheel of the eyepiece" and "to reuse it, you can go later to the same position as before.") There are no instructions on how to attach the device to a phone camera or on how to align them properly.The English translation skips the Chinese text describing a "ONE year free warranty service since the date of purchase," the conditions that void that, and the fact that return shipping costs "are borne by the user." In contrast, the FBA seller LAPSO claims at the top of this webpage a TWO year warranty of free replacement. This contradiction is deepened by LAPSO itself in the Q&A section, when it says it "offers a 12-month repair service" in response to a query.

When the supplier found out the item was shipped with a broken tripod, they replaced the entire order. Great support without having to ask for it.Monocular seems pretty good. My LG G5 attached nicely to it. Blue tooth shutter remote is a nice touch to not shake the camera while in a zoomed shot.The optics look good to me and pleased with the product and the support. Highly recommended this.

Gave this as gift. He loves them. Absolutely perfect for what he wanted them for. He always has them close by...

Purchased specifically for bird watching. I haven't had much of a chance due to the weather.Otherwise it is a quality product.

The design for attaching to the phone takes some effort to figure out and you need to play around to get to the correct spot. Wish this is easier to set up. Other than that it is ok. Not the best out there but the hence the price.

I think this is good product because i like to tak pictures, but i don’t like to bring a big camera. This product is very good for my needs, easy to carry, photos are very good. I can’t wait to use it more during my Yosemite trip!

Good

Great Monoscope.