how to assess optical quality of binoculars (1 Viewer)

[pat mitchel]

OK, A new poster on the cloudy nights binoculars forum posted a question as to how people assess the optical quality of a binoculars and that got me to thinking - what are the common methods that people have made a habit of employing as to assess the various attributes or failure of the myriad of binoculars out there. The kind you employ in the field quickly to determine whether a pair might be keepers or weepers. This might be worth writing down if I find methods that I simply hadn't thought of. I've stapled newspaper (remember those?) to a fence 20 feet away on lower mag binocs, checked the sides of high rise and looked at a string of telephone poles that happens to point straight east of me to check early (low sun angle) for glare. . What do you use... Regards, Pat

 

[eitanaltman]

There is no substitute for using them in the field. If you spend any time reading this forum you’ll see the consensus that ergonomics, individual variation and personal preference vary to a much larger extent than “raw” optical quality within a given price bracket.

Back to back comparisons can be useful for checking specific parameters like color balance or chromatic aberration, but it doesn’t tell you much about which one will actually be more pleasing to use in the field. If you’re constantly getting blackouts, or have difficulty acquiring precise focus, or you get fatigued from poor balance and hand position.... that will matter a lot.

Unless something is obviously defective, I try not to pass judgement on a binocular until I’ve had a few days to use them and let myself adapt to their quirks.

 

[Maljunulo]

Um ......... how about "look through them"?

Not trying to be a smarty-ass here, but one would think that after using vision for whatever one's lifetime is, that defects might just be obvious.

And if there are no defects, the glass might be acceptable.

What am I missing?

 

[pat mitchel]

The gent that posted the original question was looking for a 10x50 that primarily would be used for astronomical purposes with perhaps 20% use in birding activities and under $200 US.. I was thinking attending a star party (if that is currently possible). There seems to be a consensus that the oberwerk optics would likely be a probable source , in addition a couple responders mentioned the Nikon AE 10x50. Another thought was a Vortex 10x50 diamondback (as it has a reasonable return policy/guaranty) . If he is going to order and evaluate at home, he might get know what to look for in addition to knowing how to evaluate. Pat

 

[etudiant]

You pose an interesting question to which there is no simple answer afaik.
You can check the mechanicals, whether the glass is reasonably collimated, the focuser smooth and without slop, the hinges tight, but optical quality is harder.
If there is a quick 'keepers or weepers' test available, I too would love to learn about it.

 

[Brink]

You should be able to make a rough assessment just looking around the house or a store. Pan across straight lines (windows, picture frames, blinds, etc) to get a feel for the distortion profile. Of course, different people prefer a different look, so perfectly straight lines throughout the FOV might be desirable to some or might cause too much rolling ball for others. Look past a light source (like across a room with a lamp just outside your FOV) and pan around to see if you get a lot of glare. It is really easy to see glare this way in a dimly lit room. Look directly at a light source (preferably a distant point source) to see if there are spikes. Pan around a high contrast object to look for CA (very easy to see on dark objects against a daytime sky). Contrast and brightness may be really hard to assess without either direct comparison or prolonged field use - and these are two of the characteristics that really separate the high end products from the rest of the pack. Just my two cents and I am certainly no expert.

 

[Sebzwo]

If you have a chance, look at stars on a clear night. Maybe comparing your binocular to another binocular you might have. You will see how bright it is and how wide around you you can see by angle and field of view and if the stars -especially the ones at the edges of your field of view- are still razor sharp or maybe more like lines or foggy dots. And then there might be all those much tinier smaller stars between and far behind the stars only better binoculars show. My Zeiss 7x50 does really well at night. I have to admit I am not measuring this in a proper way but I can tell the difference by looking at it.

 

[ZDHart]

It helps very much to have a pair of "reference" binoculars to compare to, back-to-back, OUTDOORS - preferably in sunlight.

If you have, or can borrow, a pair of high quality $2000+ alphas (or $1000 near-alphas, if you are evaluating sub-$1000 bins), closely and carefully comparing the view to the reference bins, back-to-back, can really help you determine how good another pair of bins may be.

Of course, don't expect a pair of $950 binoculars to match a pair of $2300 binoculars, nor a pair of $450 binoculars to match a pair of $1000 binoculars. But, what if you can come acceptably close to your reference, within your price range? That's your call, according to your expectations and your budget.

Comparative analysis is typically more useful than stand-alone evaluation of a single pair of binoculars.

Compare image clarity and sharpness, within the most-used central 70% of field, to your reference.
Field-of-view - at your most frequent viewing distances, does the field of view suit your preferences?
Color quality, contrast, brightness - do these aspects please you?

Important attributes to evaluate, aside from what you see through the looking glass:
• Feel-in-the-hands / handling - does this feel natural, and immediately very comfortable?
• Focuser smoothness/lack of a null spot or backlash - does the focuser move smoothly without any gritty feel or null spots?
• Focuser even-ness - does this feel even throughout the range from close-up to distant views
• Focuser ease of turning - can you move the focuser very easily, in tiny increments, to obtain very precise focus?
• Focuser speed, changing from focus at, say, 10' to perhaps 75' - can you change range distances quickly and easily enough?
• Focuser positioning on the barrels - is focuser ideally placed for your fingers, when holding the binoculars?
• Eye cup options for distancing - can you find a sweet-spot for eye cup positioning for your anatomy/glasses?
• Interpupillary distance - can this be adjusted sufficiently to suit your personal IP distance?
• View - are you able to find adjustments in IP distance and eyecup positioning to minimize blackouts?
• Weight - is the weight suitable for your intended use?
• Size - is the size suitable for your intended use?
• Diopter - though once set, you may only rarely ever change it - how does the adjustment suit you?

I have emphasized focuser quality because the focuser IS the primary user interface, the mechanical control of your binoculars that you will forever, always, and continuously operate! Just like the steering wheel of your vehicle. Yes, I'd say that's important.

If you're happy with the aforementioned, then any further aspects such as accessories, etc. are virtually irrelevant.