Using Opticron bins with progressive glasses. (1 Viewer)

I wear progressive glasses which I normally keep on all the time although my sight is not too bad without them. For the last 10+ years I have been using an Imagic 8x32 BGA and in almost all cases with my glasses. I never noticed any significant differences in the quality of the image with or without my glasses once I had adjusted to bins accordingly. Last year I bought a 8x42 DBA S-coat for better brightness and without my glasses they are fine with a good clean image with minor chromatic aberration. However with my glasses the chromatic aberration becomes almost intolerable. Anybody have an idea why the DBA would be so much worse than the Imagic when used with my glasses?
It's almost got to the point where I have gone back to the 10 year old Imagics with the DBA reduced to garden duty.

Mike

Mike

If by progressive you mean varifocal, I have the DBA S coat and have not experienced any problems, on the other hand if by progressive you mean glasses that respond to sunlight I do not use them but still find that the DBAs work well just as well with conventional (and in my case prescription) sunglasses
I would add that in both cases I have glasses that were designed to fit very closely so as to reduce any potential problems of eye relief. For the record I really rate the DBAs and although tempted from time to time can see no real justification in trading up to a so called alpha

Barrie

Barrie,

Yes I meant varifocal, (not light sensitive), without thinking I used the French terminology... Actually even without glasses I notice that the 8x42 DBAs are slightly less sharp than the ten year old Imagic 8x32. I have been comparing by looking at twigs on tree branches and things like that and there is no doubt that the old Imagics are slightly better. I would be interested if anyone else has found this difference. In particular using my glasses the chromatic effects are much more noticeable on the DBA. I wonder if I got a lemon but it is so difficult comparing bins in a shop environment. I hadn't used the DBAs very much until early this year as I had not done very much winter birding before I went to West Africa in January/February. Since then I have been persevering with the DBAs but I am coming back to using the Imagics as my main birding bins. Maybe my Imagics were particularly good ones and the DBAs are a little off peak performance?

Mike

Mike,

I confess I find your observations quite puzzling. I use varifocals too and have very good corrected vision. I never found the Imagic particularly sharp. I first checked them out around 6 years ago so yours may have come from an different production batch. I found the DBA S-coat, on the other hand, to have a better effective resolution and better, if not perfect, CA control.

I don't recall if I've used either without glasses but I've never noticed a difference in CA with and without glasses with the binoculars I own or the CA levels change over the course of time. I apologise if they seem obvious questions, but have you had your eyes checked recently or changed your frames or prescription, needing a different ER?

David

David,

Yes I have been puzzled too as I quite expected the DBA S-Coat to be better in real use than the Imagic. I do get my eyes checked quite frequently and my current varifocals are just about a year old. Apart from the CA I do find the Imagics slightly sharper with or without my glasses. I know that batches can vary and perhaps I have an extremely good Imagic and a somewhat below standard DBA S-Coat. Nevertheless the differences really do show up when wearing my glasses which is a bit annoying as the CA becomes much more apparent. Obviously the DBA S-coats are perfectly usable but I always get the impression when using them with my glasses that I should be seeing somewhat better. I didn't realize immediately until one day when I was forced to use the Imagics again and everything seemed so much sharper which got me doing some serious side by side testing which showed up the differences. I tried to did blank off alternatively the RH and the LH barrel to see whether just one side of the DBA was bad or out of alignment but both sides seemed to be near enough the same. The Imagics are about 10 years old and the model is 8x32 BGA WP.PC.ASF T the only problem is that they are not quite as bright as the DBA S-Coat which is normal as they are 8x32 compared with 8x42 for the DBA. In any case I guess I will go back to the Imagics as my every day birding bins.

Mike

Mike,

I've thought of a couple of possibles.

I don't know if it's an explaination, or any comfort if it is, but the improved transmission profiles of the newer S-coat might actually be part of the story. There is simply more blue, yellow and red getting through to the eye making the CA brighter?

The second notion is that pretty much all binoculars show more CA if your eye isn't perfectly on axis. Sometimes facial features or a the raised rim of a spectacle frame make alignment difficult with eyecups of certain dimensions. I use close fitting rimless glasses myself so if I see CA it's easy to make a small adjustment and make, at least most of it, go away.

People mean different things when they say one binocular is sharper than the other. Although I believe the S-coat has a higher effective resolution than the Imagics I've seen, for the majority of users the limit of the detail you see will be due to the acuity of the eye. That's something quite easily checked by putting the binoculars on a tripod or stand and viewing a test chart or even just printed text at sufficient difference. Sometimes sharpness just means that the contrast is better. The shadows will look deeper with the older coatings in general. It's also a fact of life that that opacity of parts of the eye increase with age and we become more susceptible to glare. Better blue transmission could look less sharp. There is also perceptual sharpness which is much more difficult to pin down. Just as the contrast settings on a camera trade resolution for contrast there are perceptible differences between different binocular models on the slightly coarser detail as well. However, in my experience it is very dependant on the light conditions and the effect can appear and disappear. Sorting out which sharpness probably won't help you solve this issue but may help with choosing another binocular should you need to.

David

Thanks for those thoughts David,

I have certainly tried checking very carefully whether I might be looking through them slightly off-axis and I believe that is not the problem. In particular because I have some problems both with and without eye glasses which ought to eliminate being off-axis.

You might well be correct in saying that increased blue transmission might be causing some problems however I will do some more testing with a test chart or printed text but that corresponds with my twigs on the top of a tree outside my study, but so far I have not repeated this using a tripod, a job for this afternoon.

Thanks for your inputs and I will let you know the outcome of some more testing. My eyes are still pretty good provided I wear glasses to correct my distance vision. I was watching a group of Griffon Vultures high above the Alps a couple of days ago and at the height they were flying they were invisible without my glasses but were quite obvious with my specs. The nice thing was later when I looked though the bins at a Lammergeier a couple of Snowfinches flew across my field of view at a height of about 2400 metres. (I was at about 1700 metres).

Mike

David,

I did some reasonably serious side by side testing this afternoon looking at some black on white typescript the other end of the garden. It was just at the limit of what I could read through the bins at that distance. There was still a difference in favour of the Imagics but not huge under those conditions, both with and without glasses. I went back and forth many times to try and get a reasonable understanding but I always found that the old ones were marginally better under those conditions.
I guess that perhaps the S-Coat is towards the low end of its spec and the Imagic is on the high end. I'll just have to live with it I guess.

Cheers,
Mike

Mike,

I'm surprised. I've measured the resolution and effective resolution on quite a number of binoculars now and have become pretty good at judging the performance by eye. The S-coats I've tried have been really very good and really shouldn't have come second best in that test. Apart from the recently discontinued Aurora, there are no listed specifications for the other Opticron models. However all "high quality" binoculars should comply with ISO14133-2:2006 standard. It doesn't guarantee that all the binoculars meeting the standard will out-resolve the eye, but a large majority do. I suggest you have a word with Opticron about your comparison.

It's quite possible to do a resolution check for yourself to see if it's non-compliant. PM me if you want to know how.

David

Mike,

I've been wondering about the additional CAyou see when you are using glasses. From what I've been able to figure out if your prescription is reasonably weak and you are viewing through the centre of the lens the glasses should make negligible difference to levels of CA. At high dioptre correction or prism correction then CA may be noticable outside the centre. In such cases the lens material might might affect CA levels. The different plastics do have different light dispersion properties or Abbe values. Low Abbe number potentially produce more CA than high values. Polycarbonate has a value of 30 and is potentially the most problematic followed by some high index plastics. CR-39 and crown glass have values in the high 50s and should causes fewest problems.

My own lenses are Zeiss 1.67 index which probably have an Abbe value of 32 but with a fairly small distance correction I honestly can't spot any difference in CA with or without glasses using the binoculars I own. Another puzzle.

David

David,

By the way my glasses are, I guess, polycarbonate light weight ones. THey are certainly not glass and are what are called organic locally. Made in Switzerland but I don't recall the maker's name. Nevertheless I don't see significant CA with the Imagics so the problem remains! Obviously I can look for CA around the edges if I want to but it is never tiresome.

Mike

bittern said:

David,

By the way my glasses are, I guess, polycarbonate light weight ones. THey are certainly not glass and are what are called organic locally. Made in Switzerland but I don't recall the maker's name. Nevertheless I don't see significant CA with the Imagics so the problem remains! Obviously I can look for CA around the edges if I want to but it is never tiresome.

Mike

Click to expand...

Mike,

I believe all types of plastic lenses are called organic in some countries. I don't know if changing your glasses to a high Abbe number alternative would make a difference, but in would probably be cheaper to buy new binoculars.... if my last trip to the optician is anything to go by. :-C

David

You're quite right and this is Switzerland! I certainly won't be changing my glasses for another year or so as at the moment they are scratch free and suit my eyes perfectly. I've also reached an age where there is really no change in my eyes from year to year.
Mike