OK, I bought a Varga frame and thought I could get lenses easily. While I can find +.25D, +.5D, etc. lenses, I cannot find the cylindrical (astigmatism) lenses I swear I once saw. Does one simply (?) go to the optometrist and ask for a 23mm lens? I was thinking of using a pair of lenses -- one with the cylindrical correction and one with the spherical -- so that I could vary the spherical as needed.
What are the sources for lenses? Do any offer cylindrical lenses?
Best,
Joe
Shooting Glasses Lenses?
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jrmcdaniel
- Posts: 240
- Joined: Wed Feb 09, 2005 1:01 pm
- Location: Grantsville, MD
My optometrist can make lenses for my glasses. Neil Stepp at I.S.S can get them for you as well. http://www.iss-internationalshootersservice.com/.
Opticians have machines that use a plastic template to cut the lenses to fit specific frames. Although cutting a round lens is fairly easy, they may want a template. I know I've seen one for sale by one of the glasses manufacturers (Champion?, Knobloch?). I've just left a lens mount with them, and they can cut to fit.
You should know that once you get down to specify a lens to the 0.25 diopter level, the accuracy can be poor. You can buy lenses in 1/8th diopter increments, but unless you measure them yourself, it's hard to say what you will get. I've seen errors as high as 0.25 diopter.
I had an array of lenses, and swapping them in & out gave me odd results. I took them to my optometrist, and tested them on one of his machines & they were all over the place.
I also set up my own optical range in my basement. I had a small Maglite flashlight as a source, and I made a tripod mounted lens holder. Park the lens as far from the light as possible (to get ~ parallel light rays), and then hold a white piece of paper up and find the distance from the lens where you get a focused image of the light. If you have a perfect parallel light source, the diopter rating is one over the focal distance (in meters). 1 Diopter focuses at one meter, two diopters at 1/2 meter, etc. You need some serious darkness to get this to work well, or a really bright light source.
This gets tricky with low diopter lenses, but at 1 or higher, it works pretty well. The other thing it shows you is if the lens is of good quality. If you get a nice image of the light, you have a good lens. If the focus is good in one direction & poor in another, you've got astigmatism in the lens. If the image is distorted, so is the lens. This is a bit of a cheat, because this test uses the entire lens. In theory, you will never be using more than about the center third of the lens because it is so close to your eye. If you have a lens that is suspect, you can cut a hole in a piece of paper to block the outer edge of the lens & see if it's OK that way. If you use an aperture, the region of the lens that has to be good is quite small, but testing like that is difficult because you have so little light to work with.
One other issue with custom lenses: The ones the optical shops make can be thicker than the ones from the shooting glasses vendors, and this can interfere with stacking accessories (like filters & an aperture). My wife has a fairly strong correction, and the edge of a lens I had made for her is thick enough to be an issue. I wear contact lenses, so my glasses only have to bring my focus where I need it, as opposed to also correcting for nearsightedness, so I don't have a problem. If you have lenses made, make sure you get them as thin as possible.
Opticians have machines that use a plastic template to cut the lenses to fit specific frames. Although cutting a round lens is fairly easy, they may want a template. I know I've seen one for sale by one of the glasses manufacturers (Champion?, Knobloch?). I've just left a lens mount with them, and they can cut to fit.
You should know that once you get down to specify a lens to the 0.25 diopter level, the accuracy can be poor. You can buy lenses in 1/8th diopter increments, but unless you measure them yourself, it's hard to say what you will get. I've seen errors as high as 0.25 diopter.
I had an array of lenses, and swapping them in & out gave me odd results. I took them to my optometrist, and tested them on one of his machines & they were all over the place.
I also set up my own optical range in my basement. I had a small Maglite flashlight as a source, and I made a tripod mounted lens holder. Park the lens as far from the light as possible (to get ~ parallel light rays), and then hold a white piece of paper up and find the distance from the lens where you get a focused image of the light. If you have a perfect parallel light source, the diopter rating is one over the focal distance (in meters). 1 Diopter focuses at one meter, two diopters at 1/2 meter, etc. You need some serious darkness to get this to work well, or a really bright light source.
This gets tricky with low diopter lenses, but at 1 or higher, it works pretty well. The other thing it shows you is if the lens is of good quality. If you get a nice image of the light, you have a good lens. If the focus is good in one direction & poor in another, you've got astigmatism in the lens. If the image is distorted, so is the lens. This is a bit of a cheat, because this test uses the entire lens. In theory, you will never be using more than about the center third of the lens because it is so close to your eye. If you have a lens that is suspect, you can cut a hole in a piece of paper to block the outer edge of the lens & see if it's OK that way. If you use an aperture, the region of the lens that has to be good is quite small, but testing like that is difficult because you have so little light to work with.
One other issue with custom lenses: The ones the optical shops make can be thicker than the ones from the shooting glasses vendors, and this can interfere with stacking accessories (like filters & an aperture). My wife has a fairly strong correction, and the edge of a lens I had made for her is thick enough to be an issue. I wear contact lenses, so my glasses only have to bring my focus where I need it, as opposed to also correcting for nearsightedness, so I don't have a problem. If you have lenses made, make sure you get them as thin as possible.
Shooting lenses.
I get my glases from the £1 shop, take out the lenses grind to shape on a sander to fit your holder, I bought +1, +1.25, +1.50, +1.75 and +2.0 for a fiver and tried them to find the best. Mind you at 85 I cant shoot for toffie-nuts now, so why waste money :-))
Bob.
85yr WW2 Veteran,
http://www.btinternet.com/~oneofmany/ht ... story.html
Bob.
85yr WW2 Veteran,
http://www.btinternet.com/~oneofmany/ht ... story.html
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deadeyedick
- Posts: 1186
- Joined: Thu Jan 24, 2008 5:55 pm
- Location: Australia
[
I've been doing this for years Bob, except I have the optometry lab do the cutting for me [$10]. The results and price are great. I have found a $2 store that stocks these glasses in .25 diopter variations as well.quote]millsbomb
Joined: 08 Jan 2007
Posts: 14
Location: West London, England.
Posted: Sun Jan 24, 2010 5:50 am Post subject: Shooting lenses.
--------------------------------------------------------------------------------
I get my glases from the £1 shop, take out the lenses grind to shape on a sander to fit your holder, I bought +1, +1.25, +1.50, +1.75 and +2.0 for a fiver and tried them to find the best. Mind you at 85 I cant shoot for toffie-nuts now, so why waste money :-))
Bob.
85yr WW2 Veteran,
http://www.btinternet.com/~oneofmany/ht ... story.html