Various Lensometers

[Chabear703]

Not sure if this is the correct site for this question, but let's see. I am currently going to take the GA dispensing exam. My question to anyone who can answer is what does your lensometer look like when you peer thru the eyepiece. Example: I work on a Marco Lensometer and when I peer thru the eyepiece I see 3 thin lines (spheres) and then 3 fat lines (cyl). I would like to know what the B&L Vertometer looks like and a Lensometer looks like. Please don't ask which Lensometer cause I have been given only that by name.

Are you that perceptive to what you see? Please I wish to know. Thank you for your responses.

Chabear

[Fezz]

The B&L is basically the same reticle design. Most are the same as you mention. I have used an old Topcon that had 2 lines. I also have used a real old focimeter that had what could best be described as elliptical target "lines" and was the hardest thing to use next to a candle and trial lenses ;^)



Fezz
:cheers:

[Diane]

Did you specify which instrument you wished to use??? It stated on the application thay you could do this. The three instruments (focimeters) used are Marco, B&L and AO. I'm not sure if you can contact them at this point to request one specifically. You may have already received your confirmation on the exam.

Anyway, to answer your question, the Marco and the B&L have similar targets. To me the Marco is more defined. I like the B&L. The differences in the two, primarily include the location of the axis wheel/drum, and how you measure prism. The AO has a target that is different, but when you look in it, it will be easy to use.

The SouthEastern Opticians Conference in conjunction with the Opticians Association of America is sponsoring a lensometry workshop this Friday, August 4th in Atlanta that may benefit you. You may contact Cate Langley at OAA to register at 800-443-8997 or at this late date, just show up to register onsite. The meeting is at the Renaissance Waverly Hotel at the Cobb Galleria in Atlanta. Registration begins early at 7:00 Friday morning, and the classes begin at 10:00.

Call a couple of offices and/or labs around your area and just go look at them and try to neutralize some lenses through them.

Hope this helps.

Diane

[Jacqui]

AO's also look basicallyt like B&L

[Bezza]

There are typically 2 types, here in the UK we tend to name them "ring of dots" and "crossline" (named after the shapes of the targets), although some newer models like my lovely Magnon LM-350 are hybrid designs that combine both types ie; a ring of dots bisected by a crossline for ease and accuracy.
Both use exactly the same principles for measuring the power meridians of a lens but if you only learn to use one type it can be very confusing when sitting a practical exam if you end up being presented with the other type.
My advise is that you try and learn to use both if possible because learning how to use a focimeter with some alien target during an exam isnt fun.....HOWEVER.........
........if you can transpose from crossed cyl form to either the plus or minus cyl form you will never have a problem....read off the two powers and record their axes....and transpose....job done.