Where can I get spherical clear 1.67 Crizal or something decent lenses.
Everyone seems to have Aspheric only.
I know they exist but....
Where can I get spherical clear 1.67 Crizal or something decent lenses.
Everyone seems to have Aspheric only.
I know they exist but....
Yeah in the UK Essilor do stock spherical 1.67 crizal which i use if prism is needed
Al
Surface and have them coated.
No way!Originally Posted by Jacqui
THe worst part Essilor does make them!
You may have to, unfortunately, get them there. I checked and the only place I found was in Korea, but they have a 5000 pair minimum.
500 is just a bit too much for me!
Its strange, but there are quite a few chaises theoretically available, but....
Essilor Stock Club has it in Crizal and Crizal EC.
May I ask, why do you want Spherical versus Aspheric?
Prism!
LEN, Vision-Ease has 1.70 spherical semi-finished lenses in LOTS of base curves. You'd have to have them surfaced, but then you could have whatever AR applied that you'd like. I think in an earlier post you were opposed to surfacing, but thought I'd throw this out there.
Just got this today.....................................
CR39 uncoated white lenses 65mm: CR39 AR coated white lenses 65mm:
1.56 AR coated white lenses 70mm: 1.61 AR coated white lenses 75mm: 1.67 AR coated white lenses 75mm:
PC AR coated white lenses 70mm: 1.523
PGX uncoated lenses 65mm: 1.56 photochromc (grey/brown)
SV HMC lenses 70mm: 1.56 photochromc (grey/brown)
FT Bifocal HMC lenses 70/28mm: 1.56 photochromc (grey/brown)
Progressive HMC lenses 70/14mm:
Please check the prices above, if you have any interests, please contact us freely.
Best Regards!
Hong
I removed pricing as per OptiBoard rules but will post the whole e-mail including prices on the "For Professionals Only" Forum, so you can see it there.
We argue about the same thing at our office..from time to time. I may be wrong, but I understand why you should not decenter an aspheric to create a prescribed prism, but why can't you grind prism into an aspheric, and keep the front OC in front of the pupil?
And while we are on the topic, why don't SF aspherics come with a dot marking the exact front OC?
They should, it would be easy for the factories to do this.
Hoya make that lens in two forms. Nikon also has a spherical 1.67. You can get it from Kodak, and Essilor UK (as stated previously)
Isn't it silly. All that computer generated advanced optics and then you have to "eyeball" where the center is.
Trying to understand here - what do you mean "eyeball" where the centre is? Is this referring to the measurements for aspheric lenses or the wearer's view in a spherical lens? Sorry for being thick.
They do. Or at least the ones we use do. It does depend on material and vendor. For example, Seiko's 1.67 aspheric lenses have a 10mm spherical fitting "button" which gives you a 10mm circle to play with when grinding decentration/prism into them, so they usually won't have one.
Most of the aspheric Trivex and Poly that we use has a cross, either stamped on the front or engraved in the back for surface blocking. Sola's Specralite used to have a cross, but I haven't run one in so long I don't know if they still do.
There are rules. Knowing those are easy. There are exceptions to the rules. Knowing those are easy. Knowing when to use them is slightly less easy. There are exceptions to the exceptions. Knowing those is a little more tricky, and know when to use those is even more so. Our industry is FULL of all of the above.
As the previous post indicates, some SF SV aspherics come with a center mark stamped on the lens and some don't. Since the radius of curvature on an aspheric is not constant, it is theoretically (and practically) important to keep the front OC in front of the pupil... If the lens is not stamped then the actual OC has to be approximated by centering the diameter of the lens on a layout marker. A fairly accurate procedure, but still, the centers should be stamped from the factory.
I use aspherics for prism, as long as its under 4 D in each eye. You may need to decenter the lens a hair. We do Prism all the time in Progressives, and yet EVERY progressive is Aspheric.
The 1.66 Semi-finished non-aspheric was discontinued last year.
I'm not sure that Seiko is doing anything different with their spherical button- there's very little power error and marginal astigmatism 5mm off-axis, requiring very little if any asphericity at this area of the lens.
I am sure that the 'design center' or the 'asphericity pole' needs to be aligned with the distance PD, and that prescribed prism must be surfaced, not decentered.
Science is a way of trying not to fool yourself. - Richard P. Feynman
Experience is the hardest teacher. She gives the test before the lesson.
Yes, PAL are aspheric, but you grind Rx'ed prism on every single one. I'm with Robert on this one, prescribed prism should be ground on all aspherics.
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