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!
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
2089240
My belief is that the True Depth $53.00 glasses actually do give better depth results. This in not scientific but my opinion. I would stick to the True Depth model.
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
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 :)
2071543
I physically measured mine using a digital caliper, it can only hold lenses with diameter 65mm safely.
1591412
This is a very complicated answer. I defer to this link.http://www.astroadventures.net/cohen/articles/Wear%20or%20Not%20to%20Wear%20Glasses.pdfWhether you wear glasses or not, each lens that you use requires that your eye be placed at an optimum distance from the lens. Wearing glasses prohibits one from getting one's eye close enough to enjoy the full field of view with some lenses but not others. The preferred method is to NOT wear glasses and each person must adjust the focus for the best clarity. If your wife has an astigmatism, you can switch to higher eye relief lens while wearing glasses or purchase Televue Dioptrx Astigmatism-Correcting Lenses while not wearing glasses. Have her optometrist make her a monocle. This is a very complicated answer. I defer to this link.http://www.astroadventures.net/cohen/articles/Wear%20or%20Not%20to%20Wear%20Glasses.pdfWhether you wear glasses or not, each lens that you use requires that your eye be placed at an optimum distance from the lens. Wearing glasses prohibits one from getting one's eye close enough to enjoy the full field of view with some lenses but not others. The preferred method is to NOT wear glasses and each person must adjust the focus for the best clarity. If your wife has an astigmatism, you can switch to higher... » Read More This is a very complicated answer. I defer to this link.http://www.astroadventures.net/cohen/articles/Wear%20or%20Not%20to%20Wear%20Glasses.pdfWhether you wear glasses or not, each lens that you use requires that your eye be placed at an optimum distance from the lens. Wearing glasses prohibits one from getting one's eye close enough to enjoy the full field of view with some lenses but not others. The preferred method is to NOT wear glasses and each person must adjust the focus for the best clarity. If your wife has an astigmatism, you can switch to higher eye relief lens while wearing glasses or purchase Televue Dioptrx Astigmatism-Correcting Lenses while not wearing glasses. Have her optometrist make her a monocle. « Show Less
998685
It says"Magnifier 2 5x ...". I believe the 2 is just part of the product name, there is no decimal point. A 4" lens diameter can't be 5x, they just can't make them. I even asked my eye doctor about ordering one from him. So I think the lens is a 1.5x with a 3x inset as the lower information on the page description says,. I sent mine back as the one I bought at a fabric store was better. I think you could find a 2x or 2.5x in a large lens with a 6x inset somewhere else. The around the neck batteries wear out very fast so you need rechargeable batteries for cost reasons.
1074584
Refractometer is really easy to use. If you have DI water source u can use it to calibrate. If not the calibration solutions are inexpensive.
571851
no, it measures the light reaching the subject which is independent of the lens used. It gives you accurate light measurements either in e.v. units, or in f stops. f stops as a measurement of light are equivalent. Differing lenses will affect the depth of field, but the amount of light will be constant and not vary with the lens. Thus, f/1.4 on a 50mm lens will give you the same exposure as it would on a 100mm lens.
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.
1683132
It depends on what you'd eyeglass prescription is. You should check with you Optomotridt and find out what your prescription is and then get the diopter closest to that.Rich Signorelli
1990075
you will notice the top of the clear ring starts lined up with zero at the top of the scale. You want to use the top of the ring to get your measurement from. You have to slide the ring back up for each measure. You should measure 3 times or more and average the reads. For a pistol hold the gun down on a table or sturdy surface as just holding it in your hand introduces errors. I found doing that usually caused it to read as much as a pound more than when the guns held butt down on my bench.
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.)
1632329
Hi, The focusing distance is always measured from the sensor. Therefore, subtract the distance from the sensor to the front of the lens barrel (approximately 3 inches), and you are left with actual "working distance" of about an inch. Hope that helps.
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.
21264
Honestly there isn't a big deal between -3.50 and -3.00 and you can get either one and you will see grate. But if you are still not satisfied go for 2 pairs of one -3.00 and -3.50 and just switch lenses and this way you have to pairs with perfect match