Aspherical or not aspherical?

[MacGee]

I'm thinking of buying the Opticron Verano 8x32, though I haven't managed to find a pair to try. But when I was trying out high-end binoculars recently (well, when they don't have the ones you're after, you don't want to just go away without trying any) and was really impressed by the Zeiss T*FLs, the man in the shop said their brilliant performance was due to their aspherical lenses. And since I noticed that the next model up from the Verano, the Imagic Oasis has "Aspheric eyepiece lens design," I wondered if they would be worth the extra weight and money. I expect they're better, of course, but is there a difference in class?

Michael.

[imac]

I'm thinking of buying the Opticron Verano 8x32, though I haven't managed to find a pair to try. But when I was trying out high-end binoculars recently (well, when they don't have the ones you're after, you don't want to just go away without trying any) and was really impressed by the Zeiss T*FLs, the man in the shop said their brilliant performance was due to their aspherical lenses. And since I noticed that the next model up from the Verano, the Imagic Oasis has "Aspheric eyepiece lens design," I wondered if they would be worth the extra weight and money. I expect they're better, of course, but is there a difference in class?

Michael.
Have a look thru them if you can't tell the difference then they are no better ! The man in the shop might or might not be helpful, depends on the man but you will be using the binoculars not him . I have never heard that FL's are so good "because they have aspherical lenses" and think he is talking thru his hat.

[matt green]

try out the opticron HR WP 8X42 model..£199

Its a truly waterproof porro prism with internal focusing,I recently owned these but sold them because they have a relatively slow focus,everything else about them however was spot on,beautiful image.

i've always been impressed with the veranos when ever i've tried a pair,however competition is fierce at this price level and there are many
options to choose from,nikon..bushnell..minox..swift etc.

best of luck which ever you choose

matt

[kabsetz]

Michael,

As far as I know & remember, the Zeiss range does not feature aspherical lenses. What they do have is an objective lens system utilizing a special glass which helps bring different wawelengths (read: colours) of light closer to the same focus.

Thus far, I have never yet been able to see any real benefits from the use of aspherical lenses. They are frequently claimed to provide a field which is sharp to the edge, but that claim is unsubstantiated in all but a handfull of special designs using field-flattener elements rather than aspherical elements in an otherwise rather simple eyepiece.

This is not to say that a binocular with aspherical lenses might not be very good, but I would certainly not choose a model on that ground.

Kimmo

[Tero]

Why did you want the 8x32, just for the aspherical lens? If you like that format, there are some affordable products, under 500 dollars here in US. I think a Pentax is one many have liked. The 8x32s are very similar to 8x42s in use but FOV may be better.

Or was it the 8x32 porro Opticron sells? That looks pretty good too, as eg Nikon sells no new 8x32 porro anymore.

[Pileatus]

Some interesting reading on the subject...
http://www.nikon.co.jp/main/eng/portfolio/about/technology/nikon_technology/aspherical_lenses_e/index.htm
http://www.us.schott.com/optics_devices/english/products/lenses/aspherical.html

[ksbird/foxranch]

Asphericaql eye lens designs do make a big difference in a super or ultra wide field design binocular/telescope system. Beyond about 55 degrees AFOV it is very difficult to retain sharpness in a tele/bin system without either a field flattener or an aspherical eye lens design. The early Zeiss Deltrintem and Deltrentis used an aspherical design and it is still one of the best desgns for a wide field bin that is reasonably sharp to the edge. The Delactis used an aspherical Abbe Orthoscopic eye lens design and it's only purpose was to increase the reasonably sharp field from 70 degrees to an astounding 89 degree AFOV. This was all pre-coatings. The Delactis proved too difficult to make for a price that consumers were willing to pay.

The Deltrentim eye lens design continued to be made for the Deltrintim or the Deltrentis or the less expensive Jenoptem during the years when CZY perfected the T3M multicoatings and some of the best views I've ever seen have been through binoculars like this. The Japanese began copying this type of eye lens in the 60s and produced some binoculars that were good values up til the early 80s, with wide reasonably sharp fields (although not nearly as good as the CZJ products). The Asian companies stopped making binoculars with aspherical eyepieces in the early 80s because these binoc designs became too expensive and "wide field" wasn't a big selling feature because there were low quality wide field designs that could be marketed for much lower prices than an aspherical eye lens design. CZJ, Docter and Jenoptic kept making/selling aspherical eye lens design bins sporadically after that, and may even make one or two models of this type now.

But when the Chinese entered the market in a serious way, they were asked to make labor intensive asphericaL eye lens systems again. Now companies like Nikon, Olympus and others sell wide fleld binoculars (made in China) using aspherical eye lens designs because they are affordable again. The aspherical eye lens design may only cost a few pennies more to produce so the large companies think "Why not", because the improvement is quite obvious. The aspherical eye lens design doesn't adapt itself as well to roof prisms because of various other considerations and so there aren't any 9.5+ degree field of view roofers that I know of (and that's where the aspherical design shows itself to be better and better compared to any other standard eye lens design.

So if you are wondering whether a wide field design would benefit from an aspherical eye lens design then the answer is yes. A narrower field view bin might benefit slightly as well because the field might be sharper towards the edge. But a field flattening lens works much better keeping the focus sharp on a standard field of view, so unless the binocular is trying to produce a wide field view, there isn't much point in making an aspherical eye lens design. Other aspherical designs improve the sharpness of zoom lens systems but that isn't a huge consideration for serious bird watchers, because we don't use zoom bins much.

I'm not at all familiar with the bins referenced in this thread, but if they are wide field (or super or ultra wide field) view bins then an aspherical eye lens design would help with edge sharpness. If the Japanese example is comparable, get these binoculars now because after about 5-10 years, labor in China will become more expensive the way it did in other Asian countries and then that will be the end of low priced wide field bins. By the way, an aspherical eye lens designs has nothing to do with brilliance, brilliance has to do with the multi-coatings, the type of glass(es) used to make lenses and prisms, the design of the prism and the size of the exit pupil.

I'm thinking of buying the Opticron Verano 8x32, though I haven't managed to find a pair to try. But when I was trying out high-end binoculars recently (well, when they don't have the ones you're after, you don't want to just go away without trying any) and was really impressed by the Zeiss T*FLs, the man in the shop said their brilliant performance was due to their aspherical lenses. And since I noticed that the next model up from the Verano, the Imagic Oasis has "Aspheric eyepiece lens design," I wondered if they would be worth the extra weight and money. I expect they're better, of course, but is there a difference in class?

Michael.

[MacGee]

I've checked on the Zeiss websight and it seems that Kimmo is right; Zeiss don't use aspherical lenses, or if they do, they're keeping very quiet about it. So the premise of my question was false, for which I apologise. Still, the answers I've received have been interesting and informative. Thank you one and all.

Michael.