Formula for changing eye size and seg hgt?

[jeffsoptical]

I remember seeing a formula that would allow you to calculate a different seg. height for changing eye sizes. I have a customer that I'm having to do a Dr. Redo, Rx changed. He is in a Jaguar mod. 33003 drill mount frame. The measurements are A54 DBL 18 B34 ED56. His current seg. hgt. is 21 (Hoya summit ECP). I want to change the eye size to a 52mm. I know that I will need to lower seg. hgt. Harry do you have the answer?

Thanks

Jeff:cheers:

[RA]

You cut the original B in half. = 17 , so yuor seg is 4 up

use the same for the new frame. you didn't give the b for the 52 eye, but let's say it's 32.

this gives you 4 up from center = 16 +4

new seg would be 20 hi

or just order it 4up

haven't done it for a long time but it always worked for me.
:)

[Fezz]

RA is right on. You can also use the 1/2 the difference formula. If you drop the size by 2, seg changes by one.

Good luck.

[jeffsoptical]

RA is right. You could get it more precise by using proportions (fractions).

B1/A1 = B2/A2

34/54 = B2/52

cross multiply

1768 = 54B2

B2 = 32.7

1/2 B2 = 16.4

new seg. height 20.4

Thanks again,

Jeff:cheers:

[obxeyeguy]

RA is right. You could get it more precise by using proportions (fractions).

B1/A1 = B2/A2

34/54 = B2/52

cross multiply

1768 = 54B2

B2 = 32.7

1/2 B2 = 16.4

new seg. height 20.4

Thanks again,

Jeff:cheers:

Or just subtract 1 for each size down.:cheers:

[LENNY]

And when you drop the bridge?
Or temples?

[obxeyeguy]

Lenny, how many frames today come with more than one bridge size?? And when you change the temple length, subtract 3mm for each decrease, add 4 for each increase. Works every time.:D