Hello all,
In subjecting my new 10x32 Ultravid HD binoculars to comparative tests against a few of my other high end binoculars, I've noticed for the first time that in some of them, the left and right scopes of a given unit do not neccesarilly offer the same optical performance. This new pair is absolutely fine, but I returned a previous purchase because the left scope did not achieve absolute focus, as determined when compared to the right scope. And in rigorous cross testing with other units offered by Leica, Swarovski and Zeiss I've noticed that some of them are inconsistent, left to right, with respect to brightness, contrast or resolving capability. All comparisons were done with tripod mounted units, using each eye on each scope respectively, and after diopter compensations were fully accommodated.
Has anyone else noticed this occurrence, and if so, what are your thoughts on the matter?
I've seen this many times. In fact, most binoculars I've tested show some quality differences between the barrels in a star test or resolution test with the magnification boosted to 40-80x. The usual defects revealed by a star test are astigmatism, pinched optics, coma (at the center of the field) and poorly made roof prisms. It's not uncommon to find one or more of those, at least to some degree, in even the most expensive binoculars. Most of the time the defects are minor enough so that there is no obvious problem at the intended low magnification, but as you see, sometimes the image is compromised.
Robert
As Henry says, of the binoculars that I have done more than a cursory examination, many, if not most, of them show some measurable difference between the barrels. It is not unusual to see one or two elements difference on a USAF resolution chart, a percent or two difference in magnification or a difference of collimation vector from either the other barrel or the axle. From observation, not measurements, I think there is even several percentage points difference in light transmission at times.
The current ISO 14133-1 standards call for metrics like power, entrance pupil and FOV etc. to be +/-5%. I may be wrong but I assume that means up to a 10% spread. They only two inter-barrel standards I am aware of are relative power, 2% and focus by central drive, 1D, which seems too large to me.
Although in normal use, I very seldom am able to see the differences.
Ron