Hi Dave. I've seen something similar to what you describe about the sharpness of this Maven B2 before, several times with Russian, Japanese and Chinese binoculars. I single this out as a separate type of defect... The last time I observed such a defect effect was with my new BOSMA APO 10x42, this is binoculars from Kunming United Optics (KUO), the same as the one that made a lot of noise on English-language forums - Sky Rover Banner Cloud APO 10x42. Even when the first reviews about Sky Rover appeared, BOSMA was already announced, it is the same model under two brands. By the fact that both of these brands apparently sell KUO products. So about the Maven B2 defect that you describe, or rather about its "ghostly sharpness", which I met earlier. As it was with my BOSMA APO, when looking at small details through binoculars, they become visible (unambiguously distinguishable) somehow gradually, at first I observe some blurring of the smallest details (for example, small letters in the inscription) - not clarity, then small details gradually appear and the inscription differs entirely, each letter. But if you take the binoculars away from your eyes for a while, and then look at the same objects again, then everything will repeat from the beginning, small details do not differ unambiguously (only some of them are the largest), it seems that small details float slightly and it remains so for a while, then it becomes clearer and more distinguishable. But the feeling that something is wrong remains all the time observing these details. Having watched so many times, I realized that my vision compensates for the lack of information from one eye with information from the other, and the brain puts it into a general image in which there is enough information, but gives a signal "something is wrong". At the same time, there is no pain in the eyes and head, this feeling is different. I checked my guess, looked with my left eye alternately through each half of the binoculars. All right. I asked my wife to look at it, she confirmed my observations. I mean, this is an optical flaw in one half of the binoculars, which causes the eye looking through it to see less detail, and the eye looking through the other half of the binoculars to see more. The brain gradually compensates for this disadvantage, gradually pulling up vision to normal, small details of objects are being drawn. I also noticed that in addition to the lack of sharpness in the right half, there is also less brightness, there is no explanation. The binoculars were sent back, and I am now in correspondence with the manufacturer. As I understand it, they have a different opinion, but I'm thinking of fighting. Regarding the model of the binoculars itself, I liked the very wide field (7.8°), excellent brightness and color reproduction. Excellent immersion in the image and the unexpected presence of a 3d effect, better than other Roof binoculars that I had. The sharpness that this model is capable of could not be estimated, for obvious reasons. Of the disadvantages, binoculars are heavy for 10*42 - 930 grams and Eye relief is not as big as we would like to see the whole field in sunglasses, the whole field is visible in corrective glasses. In general, provided that these defects are eliminated, I liked the binoculars, and so did my wife.
Thank you Alex for coming through with this evaluation. I now have a working theory to explain the ghostly resolution found in my two Mavens. Also, people have been asking for a review of the new Kunming offering and you have given us one. I found it most interesting and helpful. At least, your Bosma didn't cost you $1500.00. Would you be able to live with the anomaly in the Bosma/Sky Rover, considering how inexpensive it is? Anyway, thanks again for coming through with your review. I really do appreciate it.
@@davidlytle3974 Such a defect as "ghost sharpness" will remind me of itself every time I look through binoculars, and annoy me, I have already suffered enough of this, so I am no longer ready to tolerate it. The presence of such a defect in binoculars means to me that I do not need it (binoculars). In addition, unlike a violation of collimation, this defect cannot be corrected.
The same old 50% center sharpness criticism. I have 2 Mavens B series and a perfect 20/20 vision. There is no way the center axis sharpness goes out to only 50%. I do not notice any fall off, and i mean any, till just short of the field spot. The B2 9x45 also has a field flattener as far as I have read. This means the sharpness is all the way to the edge. Not for one second do I believe your 50% sharpness ( 50% seems to be your favorite number since most of your reviews are all 50% center sharpness result ) Dave, I enjoy your videos very much, but I think you need a trip to see an eye Dr and get new pair of glasses. Thanks. ( Maybe your eyeglasses are 50% sweet spot )
Well, when I started this little project, I judged sweet spots based on whether the general view appeared relatively in focus. Basically, as long as the focus fall-off appeared mild and didn't seriously irk me I judged that view to fall within the "Sweet spot". Later on, as my eyes became more trained to notice differences, I realized that, under this definition, what constituted a sweet spot was rather subjective as everybody may have a different perception of serious fall-off. In order to make this measurement less subjective (at least somewhat objective) I instituted the following standard. I have been using the smallest element of the 1951 USAF test target that can be easily judged to be fully resolved at the center of the field. As I pan away from that element, I check to see at what point that element can no longer be perceived as resolved. Naturally, as you pan away you can expect to gradually lose focus, at least in binoculars that don't employ special non-spherical lenses to counter for this. Anyway, once the test element can no longer be resolved at all, this is the point where I determine the outer edge of the sweet spot. This results in a much more precise measurement that is less subjective than that of personal satisfaction with the general view. At least, that is how I see it and I am better served by it. If I report that the Fujinon FMT-SX 10x50 has a sweet spot of nearly 90 percent, you can be assured that the test element is resolvable to that extent vs I think that the bark on the pines is pretty much in focus out to that point. The fact is that most binoculars that have spherical lenses tend to not pass this test much beyond 50 percent of FOV. Those with non spherical lenses do better. Binoculars that have field flattening elements, like the Fujinon, beat this limitation. That is why I was so disappointed in the performance of the B5. The B2 did better but not by much. I hope that this explanation will help you to get more specific information from my video reviews. It has not been my intention to lead anyone astray or piss anyone off by seemingly denigrating their favorite binos. I promise you that I don't have a fixation with the number 50. Thank you for watching, commenting and I look forward to hearing from you again.
Winnon992, The sweet spot isn't small, just not super generous. The degree of focus fall off isn't horrible but it's noticeable after 60 percent out from center.
