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...
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.
187867
I also noticed the "200" and assumed that it meant 2.00. Turns out that it did: the glasses are indeed a +2.0 correction. I'm not sure whether they just left out the decimal point after the 2, or maybe "200" is just what they call it.
1679463
Its infinitely variable as far as I can tell. Its like twisting a knob.I don't use this very often, only on one particular lens. I almost forgot about it. Thanks for reminding.No issues with this at all. Just guesstimate only for aperatures.
1198219
Your lens should say what distance it is accross the lens (diameter) or you can measure it.
2173896
Not at all. From the description, it is supposed to help people with imperfect vision. I found it pretty useless as I have 20/20. It further seemed like I was looking down a paper towel roll. I am very interested in their other magnifier which can work with a variety of others. Primary Arms makes one but I haven't seen any side by side comparisons.
743771
It's not a graduated cylinder that's for sure. Based on the overall diameter of the location you are taking a measurement I imagine it would be very hard to get consistent readings, just due to parallax. If you're looking for something super accurate, this isn't the right tool.
1120065
They adjust for interpupillary distance at the hinge. The adjustment is so wide, I can't imagine them not fitting everyone. Hold them up to your eyes and move them in and out until the two circular images merge into one. The interpupillary distance is set. Then focus them until the image in the left eye is sharp. If the right image is also sharp, the focus is done for that distance. If the right image is fuzzy, adjust the diopter ring on the right eyepiece until the right eye is also sharp. From then on, focus is done with the big wheel in the middle. Easy peasy.
1025376
Sorry, but I don't have an expert answer. Here's what I did. I simply measured, with a very accurate ruler the exact outside center cross distance on the lens. No matter if it measures in inches or metric, just Google the number for a conversion. Worked perfect for me on the first and subsequent orders.. The covers fit perfect, are very well made and I'm very happy to have this protection for all of my lenses. Hope this "grass-roots" method works for you. Bob D., Maine
882730
When I look through a eo tech with its red dot and circle they are very fuzzy to me. The triangle reticle is sharp with no blur and comes to a nice fine point which I use for aiming. I really don't know how a astigmatism would effect it but for my eyes it's great.
625014
Don't use it much anymore. When I did, I tested it and found it doesn't make much diff. The thing is, it's field of view widens as it gets further away. So if you measure something that is very small from a longer distance, you'll get a bad reading. When I used it, I was measuring small packages 5x8 inches from a very close distance like 1-2 ft. Sorry I can't be more help.
65715
I ordered the mask for my girlfriend who is near-sighted. She gave me a copy of her prescription. Under the "Dist" part of her prescription, sphere is -8.5 which is the number I used when I placed my mask order. I am assuming "DV" is distance, and "NV" is near. If so, I believe you would enter the "DV" number. The mask worked great for my girlfriend. She said she could see better out of the mask than her glasses. Hope that helps, Brian H.
21263
i would get the -3 that way you don't cause disorientation, because water as is does have refraction, so i would go with the lowest diopter.
1679461
Its infinitely variable as far as I can tell. Its like twisting a knob. I don't use this very often, only on one particular lens. I almost forgot about it. Thanks for reminding. No issues with this at all. Just guesstimate only for aperatures.
771645
The distance from the center of the 15mm rod to the center of the lens opening is adjustable between about 3.75 inches to 4.5 in. You just need to take a ruler to your rig and see if this your distance falls within that range. I got my matte box out and measured it. I just hell up a ruler so I could be off a little.
64369
Because of the difference I would suggest buying 1 pair in each of the diopters you need and swapping out the lenses. For me the difference was only 1 point so I went up a half. They've worked out great.
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?
1870387
Using another spyglass viewing a yardstick and doing a little math I came up with 145' at 1000 ft which would be 450' at 1000 yds. A quick test against my Mom's similar $135 device, including the 10" focus ability, showed no visible difference to me. I do wish it had a rubber eye cup, though.