Because I have not found any review at english of this monocular I am happy to post my own impression of it. Since I regret I sold the Zeiss 6x20B monocular I have searched for a similar monocular.
Too bad that Zeiss discontinued the classic 6x20B. The newer design selection 6x18 has not as good eye relief as 6x20B. At least I tried the 4x12 and it didn't work good with eyeglasses, and I think these share the very same ocular. Then I found that Vixen offers a 6x21 monocular. That seemed good. Not only that it's an ED lens, the price tag seemed to show that this is a quality product.
While monoculars don't provide the same ease of view, neither as stable view as binoculars, they really have their use and advantages: much more compact size and no collimation issues like binoculars. And here I just want to say: 6x is perfect for a small monocular, in my opinion. The image will be stable enough, and the brightness and FOV will be better as well.
A 6x21 has almost twice as bright image at low light than an 8x20. That is according to my experience a valuable difference at these small exit pupil sizes. Also I remember that Zeiss 6x20B provided a pretty clear image at dusk and dawn.
So how does the Vixen HR 6x21 ED compare to Zeiss 6x20B? Well; I can't compare them side by side and it's several years ago I used the Zeiss. Still I can give some opinion. Vixen has significantly beefier body. Vixen has significantly wider FOV. Both have a long eye relief adequate for eyeglasses. Both provide a razor sharp image.
I am pretty sure the Vixen is optically at least on par to Zeiss 6x20B.
Vixen HR 6x21ED has a rubberised body cover with twist up eyecup. The focusing wheel is in patterned rubber. This makes the instrument very good in the hand and it will hardly slip out of the hand.
While the aperture is 21mm the body diameter is ~35mm. According to THIS SITE Zeiss 6x20B is 26mm thick and weights 53g. Vixen HR 6x21ED is stated to weigh 141g. With my digital kitchen scale I measure 147g. Whatever is correct the Vixen is more than twice as heavy than the Zeiss, and almost a cm thicker.
This indeed makes the Vixen more bulkier in a small pocket than the Zeiss. But with the advantage of a better hold comfort. Vixen fills upp the hand in a good way which contributes to the stability. And the Vixen has much wider FOV: 8,7/52deg compared to 6,8/41deg AFOV of the Zeiss.
When I have two 6x32 binoculars since earlier: Leupold Katmai 6x32 and Vortex Viper HD 6x32, I think it may be interesting to compare them to this Vixen monocular.
Field of view
Katmai and Vortex HD have the same stated FOV of 8deg. HR 6x21 ED has slightly wider with 8,7deg. My test confirms that Katmai and Vortex have very much the same FOV, while the 6x21 is slightly wider.
All these three have some amount of sharpness loss towards the edges. What I can perceive the image is sharp to 70-80% of the FOV and then it gradually worsens. No issue in any case if I don't really look for it and the difference between them is in my eyes very subtle.
Viper HD is clearly sharper than Katmai, and that's what I appreciate with the Vipers despite it's a bit bulkier to carry around. The 6x21 is in my eyes very in par to Viper HD. Yes; when I compare carefully I find the 6x21 to be even sharper than Viper HD. Not a big difference, but it's there. When panning I can sometimes see a field distorsion with Viper HD but have not yet seen it with HR 6x21 ED.
When I earlier compared Katmai to Viper HD I could not detect any brightness difference under low light conditions. The HR 6x21 ED will of course be dimmer due to the significantly smaller exit pupil. At daytime all of them look the same in my eyes.
All three have long eye relief fully adequate for my eyeglasses use.
Ease of view is very similar with all three models. All provide an open and relaxed view with eyeglasses on. When I compared them without eyeglasses I found that the eyecup of 6x21 can't be twisted out enough to avoid blackening, however. I need to hold the eye a bit from the eyecup rim to get it good.
I have no complaint about the focusing wheels of Katmai and Viper HD. Both have a certain resistance, maybe it could have been slightly lighter. But there is no play and the resistance is same at both directions.The focusing of the monocular is smooth and good as well.
It's very noticeable that focusing with a monocular is not as easy as with a binocular: with the binocular it's easy done with a finger while the monocular requires both a finger and the thumb.
All these models have a close focusing range, with the monocular as the clear winner. Measured distance for me with glasses on:
*HR6x21ED: ca 56cm
*Viper HD: ca 100cm
*Katmai: ca 130cm
Without eyeglasses the close distance is even shorter. At closest distance with the monocular the exit pupil is noticeably decreased, to 3mm, maybe a bit less. Which means the magnification becomes slightly higher, I guess 7-8x.
This is a matter often discussed among "binoholics". Personally I have never found it an important thing with binoculars. Maybe I am insensitive to that, but I usually never notice CA with binoculars at normal handhold magnifications. Also the CA increases with higher magnification. Consequently it should not be an issue with 6x instruments. And when it comes to this Vixen monocular it's an ED, so CA really should be a non-issue...
Both Katmai and Viper HD are claimed to be waterproof. But I find no information whether HR 6x21 ED is waterproof or if it's only water resistant.
In the comparison between Zeiss 6x20B and Vixen HR 6x21 ED both have their advantages. For the portability the Zeiss is the clear winner.
The vixen provides better FOV and better hold comfort. If I get the possibility I will get the Zeiss again, it will probably be available at the used market for long time. Still the Vixen HR 6x21 ED definitely is a keeper. If you want a high grade monocular Vixen HR 6x21 ED definitely is a good choice.
While Viper HD is optically superior to Katmai it's bulkier. As well a bit heavier, but not much: I measure~ 530g/560g. This is done when I holding the straps up, so it's difficult to get it perfect.
The hold comfort is better with Viper; it fills up the hand in a better way. But as soon I want to place it in the jacket pocket the Katmai is better.
There are of course more to tell about these three instruments, but I think it's enough for now. Hope this was of interest, and you are welcome with questions.
Edited by Swedpat, 16 May 2015 - 07:59 AM.