Results 1 to 12 of 12

Thread: 1/3-2/3 and 50/50 bevels

  1. #1
    Bad address email on file
    Join Date
    Apr 2014
    Location
    South West U.S.
    Occupation
    Optical Retail
    Posts
    56

    1/3-2/3 and 50/50 bevels

    What are the differences or uses for the two? Do laboratories even pay attention to which one you choose, or do they usually just select the one they see best for that job?

  2. #2
    Master OptiBoarder
    Join Date
    Jun 2008
    Location
    Seattle WA
    Occupation
    Optical Wholesale Lab (other positions)
    Posts
    3,137
    Good question. Some lenses because of the differences in curves between frames cannot simply be fabricated well as the customer requested.

    Assuming you have a high minus lens (=flatter base curve), and a flatter frame curve, you have a higher chance of getting what you requested.

    a 1/3 2/3 will place one third of the lens in front of the eyewear, 2/3 behind it. A 50/50 will bevel the lens right in the middle, leaving half in front.

    There is also a "nudge" where you mount just bit of the lens in front, you can call it 10/90 if you want. The idea of all of these is to reduce the perceive thickness in high minus lenses. Since the price of high index has dropped the last few years, here at the lab I haven't seen a request in about 4 years for either of these.

    Its still a much better solution to choose a smaller frame, a thicker eyewear and use a high index lens. The 1/3 or 50/50 developed for older larger frames in CR-39 and Poly. We have better choices all around now. IF you have to choose one, do the 1/3 2/3 or 10/90, include polish, but don't roll until the patient requests it. You an always add a roll, but you can't take it away. Rolls can really make the view through the lens from the outside look freakish if done poorly.

  3. #3
    OptiBoard Professional Flux3r's Avatar
    Join Date
    Mar 2013
    Location
    Dallas
    Occupation
    Optical Laboratory Technician
    Posts
    145
    We make the determination based on the frame size/shape, and the RX, unless its requested. then we just follow the paperwork to the letter, let them worry about it later.

  4. #4
    Master OptiBoarder OptiBoard Silver Supporter Barry Santini's Avatar
    Join Date
    May 2000
    Location
    Seaford, NY USA
    Occupation
    Dispensing Optician
    Posts
    6,008
    We ALWAYS strive to match lens apex curve to frame curve...at least to within 1D of frame curve. But, we also do alot of FFSV, and we tweak the ordered base curve in advance...plus or minus 2D of "normal"... to arrive at target cosmetics.

  5. #5
    Master OptiBoarder TLG's Avatar
    Join Date
    Feb 2007
    Location
    S. California
    Occupation
    Dispensing Optician
    Posts
    814
    The chances you'll ever order a 50/50 are slim to none. Think about having just as much lens sticking out the front as the back. Ugh.

  6. #6
    Master OptiBoarder
    Join Date
    Mar 2008
    Location
    Oakland, California
    Occupation
    Dispensing Optician
    Posts
    1,573
    Quote Originally Posted by Barry Santini View Post
    ...match lens...curve to frame curve...
    I would (nearly) always match the curve of the bevel to the curve of the lens, and place the bevel 90/10 or 95/5; I hate to see lenses jutting out in front of the frame. And don't change to lens to match the frame, recurve the eyewire to match the lenses. You'll have to reconfigure the endpieces to suit the patient, but that's not hard to do.

  7. #7
    OptiWizard
    Join Date
    Apr 2014
    Location
    California
    Occupation
    Other Optical Manufacturer or Vendor
    Posts
    382
    Quote Originally Posted by TLG View Post
    The chances you'll ever order a 50/50 are slim to none. Think about having just as much lens sticking out the front as the back. Ugh.
    The only time I've run a thicker lens on a 50/50(50%) bevel in the past 3 years is for a -20.00 biconcave, and recently for a customer that was a -7.50 total power in the 180 that did not want any lens sticking out of the back.

  8. #8
    OptiBoard Apprentice
    Join Date
    Oct 2002
    Location
    Austin
    Occupation
    Optical Retail
    Posts
    12
    Thanks for asking this question.

    When filling rx's for those patients who are high minus, I try and choose the 1/3 2/3 bevel to help eliminate some of the thickness. Sometimes it looks good, sometimes it looks as if nothing was done.
    "Turns out not where, but who you're with that really matters!"

  9. #9
    Master OptiBoarder
    Join Date
    Dec 2013
    Location
    here
    Occupation
    Dispensing Optician
    Posts
    507
    A 2/3 bevel on a polarized lens will assist with lens placement in the frame. Its mainly for ascetics so the front of the lens is flush with the frame front. This also has an additional benefit. It prevents light or reflection from seeping in though the part of the lens that's sticking out of the front if it's not flush.

  10. #10
    OptiBoard Apprentice
    Join Date
    Oct 2002
    Location
    Austin
    Occupation
    Optical Retail
    Posts
    12
    Quote Originally Posted by chaoticneutral View Post
    A 2/3 bevel on a polarized lens will assist with lens placement in the frame. Its mainly for ascetics so the front of the lens is flush with the frame front. This also has an additional benefit. It prevents light or reflection from seeping in though the part of the lens that's sticking out of the front if it's not flush.
    Thanks for the info! I have been doing this for 16 years and still learn something new every day!

    On a side note- what spex911 was trying to ask if they labs did the 1/3 2/3 or 50/50 lay over when it is chosen. I have seen it done, but have also received jobs back that it wasn't done... when it was in fact chosen.
    I like to use it for those patients that won't pay for much of an upgrade for lenses, but still want them to look at appealing as possible. It helps, for the most part.
    "Turns out not where, but who you're with that really matters!"

  11. #11
    ATO Member HarryChiling's Avatar
    Join Date
    Apr 2005
    Location
    Nowhereville
    Occupation
    Other Eyecare-Related Field
    Posts
    7,765
    As far as I know, currently no standard exists for bevel placement. So asking and receiving a specific bevel are at the labs discretion, as it should be.

    Rimless = no beveling, flat surface.

    1/3 - 2/3 = is the average setting for most older machines. Looks nice on most jobs.

    50/50 = is best used for groove mount frames and high Rx's to avoid the temples not closing properly.

    Follow Front = is best used for polarized lenses where the dreaded ring around the front is to be avoided, set the bevel within 0.8mm of the front and you should create a nice looking job.

    Follow Back = when a high power Rx goes into a wrap frame when it shouldn't. Flatter front with steeper back means that this bevel setting can allow the operator to order a more conventional base curve and reduce the face form tilt by setting the lens to follow the steeper back curve and pushing the bevel as far forward to the front as possible. The lens will stick out of the front unfortunately but the optics won't be as compromised. (I reserve this for the hard headed clients that absolutely must have a wrap.)

    Frame Bevel Match = some newer equipment will follow the frame traces Z record set in a trace file allowing very little pressure/distortion to the frame. This tends to work nicely for frames that have a high plus in a shallow B, especially those plastic frames.

    Sports Bevel = for wrap frames the back profile circumference is cut smaller to alleviate pressure that causes splay, many different versions of this setting out there, depends on machine.

    Hybrid = a mix of groove and standard bevel mounting. Newer equipment allows for these bevel setting where multiple bevel types can exists on the same lens trace.

    Some other terms you may hear:

    Hide-a-bevel = low profile bevel.

    Float Bevel = often 50/50 or 40/60, the bevel wheel slanted towards the groove allowing the lens to float or center itself on older equipment, if the shape was too angular sometimes this bevel would have jitter errors present.

    I particularly pay attention to bevel placement with my aniso clients, sometimes just moving the bevel to the back on one lens and to the front on the other is enough vertex disparity to eliminate issues on a class I or class II aniso.

  12. #12
    OptiBoard Apprentice
    Join Date
    Oct 2002
    Location
    Austin
    Occupation
    Optical Retail
    Posts
    12
    Thank you, HarryChiling!
    Like I said.. I learn something new every day :)
    "Turns out not where, but who you're with that really matters!"

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. Bevels.....
    By autumneyes in forum General Optics and Eyecare Discussion Forum
    Replies: 20
    Last Post: 05-19-2017, 12:23 PM
  2. 37 bevels
    By harry a saake in forum General Optics and Eyecare Discussion Forum
    Replies: 13
    Last Post: 05-01-2009, 09:33 AM
  3. Bevels w/ my Gamma
    By MarcE in forum General Optics and Eyecare Discussion Forum
    Replies: 3
    Last Post: 08-04-2007, 10:01 AM
  4. Bevels are not boring
    By drk in forum General Optics and Eyecare Discussion Forum
    Replies: 15
    Last Post: 06-10-2007, 11:48 AM
  5. European Safety Bevels
    By skirk1975 in forum General Optics and Eyecare Discussion Forum
    Replies: 3
    Last Post: 11-25-2002, 09:02 PM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •