I read on another site that: 1/2 the cylinder measurement + the sphere measurement = diopter strength. Because I have a lot of astigmatism this changes the measurements quite a bit (-3.25 cylinder, -3 sphere). Has anybody else used this equation to determine the strength in buying goggles? I read on another site that: 1/2 the cylinder measurement + the sphere measurement = diopter strength. Because I have a lot of astigmatism this changes the measurements quite a bit (-3.25... » Read More I read on another site that: 1/2 the cylinder measurement + the sphere measurement = diopter strength. Because I have a lot of astigmatism this changes the measurements quite a bit (-3.25 cylinder, -3 sphere). Has anybody else used this equation to determine the strength in buying goggles? « Show Less
107802
That equation is correct... it is called spherical equivalent. With a -3.00 sphere and -3.25 cylinder, your spherical equivalent is -4.50. Keep in mind this will give you pretty decent vision - good enough to see at a reasonable distance, but this will not be equal to a full spectacle prescription. I am an optometrist.
40139
That's the method we used when buying my daughter's goggles. She ended up with -3.625 (R) and -4.25 (L) so we split the difference with a -4 prescription. She says they work well enough for her, and she has to be read a white board to get her workout during swim practice.
107803
hi, none of us are opticians. I'd give them a call and ask. That way you'll get a pair of goggles that you can use to read underwater - haha - but seriously, I was thrilled when I could see clearly underwater. It's worth the effort!
2263148
with out the 3x magnifier I wanted the two dot easy to see . with out the 3x magnifier over two dots hard to see them . yeah with 4 dots and no &#9726;3x magnifier looks like a straight line. I dint want the weight and pay the extra cash. my friend has the 4 dot and 3x magnifier really nice set up. hope this helped you :)
2230132
All I know is that it refers to the unit of measurement of the optical power of the lens. I can't quantify the numbers, but this lamp magnifies very well.
1190630
More strength? If you could explain I might be able to answer. This is a standard adapter for your camera-specific T-ring. You need both to mount/use a camera with a telescope (unless you get real lucky shooting through an eyepiece) - I've used them with heavy film cameras with no problem - on a decent telescope. If the 'scope is lightweight it's probably not good for astrophotography anyway. But the "strength" issue is unclear - are you planning on some other kind of use?
897742
I have been satisfied with my refractometer so far. I previously had one that came in a gem lab I purchased 25 years ago and it wasnt nearly as easy to read as this one. No complaints to this point.
1743
The 1.25, 1.50, 2.0, etc refers to the strength of the glasses----the "prescription strength". The higher the number, the stronger the prescription. Someone who only needs reading glasses might only require a 1.50. Someone who can't see well without glasses would require a higher number. I would suggest you go some where like a Dollar General store and try on several different strengths of their over the counter glasses so you will know what works best for you. As for the "size" of the glasses....they kind of telescope in and out in such a way that you can adjust their size by about 4" total. Doesn't sound like much, but that's enough to accommodate most people's head size. Hope this helps! The 1.25, 1.50, 2.0, etc refers to the strength of the glasses----the "prescription strength". The higher the number, the stronger the prescription. Someone who only needs reading glasses might only require a 1.50. Someone who can't see well without glasses would require a higher number. I would suggest you go some where like a Dollar General store and try on several different strengths of their over the counter glasses so you will know what works best for you. As for the "size" of the glasses....they kind of telescope in and out in such a way that you can adjust... » Read More The 1.25, 1.50, 2.0, etc refers to the strength of the glasses----the "prescription strength". The higher the number, the stronger the prescription. Someone who only needs reading glasses might only require a 1.50. Someone who can't see well without glasses would require a higher number. I would suggest you go some where like a Dollar General store and try on several different strengths of their over the counter glasses so you will know what works best for you. As for the "size" of the glasses....they kind of telescope in and out in such a way that you can adjust their size by about 4" total. Doesn't sound like much, but that's enough to accommodate most people's head size. Hope this helps! « Show Less
2127892
Mika said yes. Mika has done this. I have not tried but the red hole is about 2.5mm and the white hole is about 1.5mm (This was an eyeball measurement without a micrometer.)
1660679
As others have stated there is no magnification. The 1-4 I believe refers to the MOA size of the dot. 1 MOA for more precise aiming 4 MOA for faster sight aquisition. You probably already know this but 1 MOA is roughly equal to 1 inch at 100 yards, 4 MOA roughly 4 inches so the bigger the dot the more of your target is covered and the less precise your aiming. This is a very generalized explanation. Hope it is helpful.
834168
The first number is the magnification and the second number is the lens diameter. The larger the numbers the more magnification and light gathering potential.
377710
I not sure what you mean by 'strength'. I certainly do not have a spectrum analyzer or light meter to measure intensity and wave lengths from a specification perspective. What I can tell you is that I have prior experience with UV light in water supply systems and air vent systems and the results I have achieved with this device are consistent with these other better known systems/applications. Furthermore, like I posted, this is not a toy and should be handled as a tool. I also bought the UV glasses for eye protection, keep my skin out of the light ray, and keep me kids away when in use. One really good indication of it working is the 'ozone' smell associated with disinfected area. It is the same smell you get after a lightning strike. To find out how it works, I would suggest looking into water supply UV light systems. It takes very little exposure to UV light to kill bacteria that can be found in well water. I would be happy to share specific details if know the application for which you are considering this purchase.
315445
I have held a ring with the stone facing down against the measuring opening. I get a reading but it fluctuates if I move the stone. With a faceted surface it's easier but I have gotten readings for cabochons. It's a good tool but of course not definitive. There are different stones that have the same refractive range...for example...quartz, amethyst, onyx, aventurine, citrine...so I think you have to make a judgment on the stone using other info too. I am not a professional gemologist. I use this tool as additional confirmation of what I think the stone is. I also like the presidium Gem tester. There's a lot of glass on the market...even set in gold! I have held a ring with the stone facing down against the measuring opening. I get a reading but it fluctuates if I move the stone. With a faceted surface it's easier but I have gotten readings for cabochons. It's a good tool but of course not definitive. There are different stones that have the same refractive range...for example...quartz, amethyst, onyx, aventurine, citrine...so I think you have to make a judgment on the stone using other info too. I am not a professional gemologist. I use this tool as additional confirmation of what I think the stone is. I also like the presidium Gem... » Read More I have held a ring with the stone facing down against the measuring opening. I get a reading but it fluctuates if I move the stone. With a faceted surface it's easier but I have gotten readings for cabochons. It's a good tool but of course not definitive. There are different stones that have the same refractive range...for example...quartz, amethyst, onyx, aventurine, citrine...so I think you have to make a judgment on the stone using other info too. I am not a professional gemologist. I use this tool as additional confirmation of what I think the stone is. I also like the presidium Gem tester. There's a lot of glass on the market...even set in gold! « Show Less
581157
As effective? That depends on what you mean... As effective against eye strain.. No. Period.This is readily confirmed at Gunnar's website:http://www.gunnars.com/view_crystal_lenses.php"The CRySTALLINE lens tint and coating formula is designed specifically for the graphic designer, video/film editor, or creative visual artist that requires an equally balanced color spectrum. If your profession does not allow for a shift towards the warmer part of the color spectrum, with enhanced contrast ie. your tasks require you to design or work in true color, then this lens option is for you. However, if your profession does not require you to perform many daily tasks in true color, then AMBeR is the most effective lens choice." As effective? That depends on what you mean... As effective against eye strain.. No. Period.This is readily confirmed at Gunnar's website:http://www.gunnars.com/view_crystal_lenses.php"The CRySTALLINE lens tint and coating formula is designed specifically for the graphic designer, video/film editor, or creative visual artist that requires an equally balanced color spectrum. If your profession does not allow for a shift towards the warmer part of the color spectrum, with enhanced contrast ie. your tasks require you to design or work in true... » Read More As effective? That depends on what you mean... As effective against eye strain.. No. Period.This is readily confirmed at Gunnar's website:http://www.gunnars.com/view_crystal_lenses.php"The CRySTALLINE lens tint and coating formula is designed specifically for the graphic designer, video/film editor, or creative visual artist that requires an equally balanced color spectrum. If your profession does not allow for a shift towards the warmer part of the color spectrum, with enhanced contrast ie. your tasks require you to design or work in true color, then this lens option is for you. However, if your profession does not require you to perform many daily tasks in true color, then AMBeR is the most effective lens choice." « Show Less
614136
Some people with an astigmatism will see more than one dot or the dot will seem out of round. I am one of those people and you just get use to it over time. My aimpont and delta point do the same thing.
282298
I do not know what 'cyl' and 'axis' measurements are, but, here is what we did:1. when ordering Speedo goggles, we got the +/- number, from our opthomologist.2. when ordering the ProMate snorkeling mask, we selected the the color and then selected the appropriate eye-adjustment (my son is nearsighted) from the "size" pull-down menu on the ProMate scuba options.3. My 13 year-old son loves the mask and was our family underwater photographer in Cozumel.
1951961
There are three lenses which can be stacked for greater magnification. Using the first lens only it's about 8-8.5 inches. Add the second lens and that drops to about 4 - 4.5 inches. Add the circular lens (for the right eye only) and it drops to about 3/4 - 1 inch. Hope this helps.
847841
Sorry, Heather, I don't know the answer to that question. I was recently using my table saw when a piece of Cedar, about 1"x4" flew off the blade and hit my chest. It hurt like crazy. I was wearing eye-glasses but no goggles - lesson learned. I turned the saw off, vacuumed all the sawdust and didn't use it again until a few days ago when I received the goggles. My ... guess ... is they are osha approved. Hope that helps, and good luck.
57695
The goggles only come with a negative value which is for near-sighted. Mine were totally useless, terrible distortion, I could not use them and was given bad information by customer service. When I complained, iI was treated rudely. They offered no positive numbers for far-sighted