Would love to see someone do a piece on weight management for glasses. A few old school books delve into it talking about weight distribution. It frustrates me see patients come in for adjustments because they were told extremely light weight frames would reduce the overall weight and increase comfort especially with higher prescriptions. Seems logical initially but the problem is the center of gravity shifts to the frame front. The frame becomes unbalanced and more prone to slippage as the nose pads must support nearly all the weight and the ability of the lens to support the weight sufficiently is dependent on angles of the bridge and inclination of the head. It may seem counterintuitive to recommend a “heavier” frame but it pushes the center of gravity back creating a more balanced fit and creates greater stability and comfort with dynamic head movements
I think you got something there! It's not quite enough for a video, but I will certainly add it to the online content on advanced frame fit. Wicked Good. THANKS! John
Hi I don't know if you can help but I'm doing a course in optics and I'm struggling with wording a question - What effect would increasing the refractive index have on the density and v-value of the lens material? I understand the concept I just don't know how to word it
Liz, That is in the video next to this one on Abbe. There is NO direct affect/effect relationship between the three. We think there is (we are often taught there is) but there isn't. An increase in density does not mean an increase in index. See index, Abbe and specific gravity and watch them in that order again. John
_@Laramy-K Optical_ -- Most of these videos are great and I usually enjoy them very much. However, respectfully, your attempts to explain the physics of lenses is often flawed. In the case of the Abbe specification in your previous video, your explanation used a convex lens of a hyperopic customer in your illustration when you should have used the concave lens of a myopic customer. The reason a myopic customer observes an increase in red and blue fringing (chromatic aberration or dispersion) toward the periphery of the lens is because the lens gets thicker there. This is unique to near-sighted customers. The convex lens in your illustration does not exhibit this because it gets thinner at the periphery. *In this video about specific gravity,* the explanation of specific gravity was muddled with regard to lens weight because you fail to explain the contradictory relationship between refractive index and specific gravity. For a given lens power, the higher the index, the thinner the lens will be. Therefore, *the higher the index, the less lens material is used.* On the other hand, *plastic* lenses with a higher index usually have a higher density and therefore a higher specific gravity. If two lenses have an identical shape and thickness, the one with the higher specific gravity will always weigh more since both lenses use the same volume of plastic. So, why does a dense 1.74-index lens sometimes have a similar (or less) weight than a less-dense 1.60-index lens *for the same power?* _Answer:_ Because the 1.74 lens is so much thinner that, even with its higher density, it's weight does not increase much compared to the 1.60 lens. Because the amount of plastic used by the 1.74 lens is less, it offsets its higher density. This can make decisions of weight vs thickness tricky when only plastic lenses are considered. The issue of weight mostly goes back to glass vs plastic and a fashion-conscious move toward larger lens sizes. With the rarity of glass today, lens weight has largely gone away (except for very large lenses).
I ignored your first lengthy diatribe. But you persist. I really don't care what you think. This is optician stuff not physics stuff. Please go troll a site where your being smarter means something. Being smarter than me isn't really very hard. John
@@D.Eldon_ The "lens" I chose was completely random and is simply a recognizable or generic lens shape. It has nothing to do with the concept being presented. As to your other points and conclusions they are exactly the same as those I mention in the video and those I mention as being "good optician" stuff that we cover over and over in others. I'm old, I'm cranky and I'm sorry but I struggle to find how your comments help others. Truly from my heart - as I always say, "If you can do better then make a video and if it is actually better I'll gladly include a link out to it." Heck, I'll even promote it! I've done it before, I'll pin comments from others and I often pay people who are true experts at what they do to drive content for the website. I'm not shy of genuine criticism. I am shy of nit-picking on a video which I think/feel is among the best I ever did. Of course you may have noticed that it is among the least watched of all time. If you had approached me through email with a genuine error in the lesson I would, as I have done before, corrected it. In fact you can find a few videos where mid-video I wear my RED shirt to match my RED face. Since we started on RUclips we have had a 100% no delete policy on comments. Your comment is/was there for people to read if they choose to. I chose not to react to your first posting - you insisted on pushing so like they say - you were asking for it. Peace John
It all goes back to the perfect measurements. Love you man!!
Would love to see someone do a piece on weight management for glasses. A few old school books delve into it talking about weight distribution. It frustrates me see patients come in for adjustments because they were told extremely light weight frames would reduce the overall weight and increase comfort especially with higher prescriptions. Seems logical initially but the problem is the center of gravity shifts to the frame front. The frame becomes unbalanced and more prone to slippage as the nose pads must support nearly all the weight and the ability of the lens to support the weight sufficiently is dependent on angles of the bridge and inclination of the head. It may seem counterintuitive to recommend a “heavier” frame but it pushes the center of gravity back creating a more balanced fit and creates greater stability and comfort with dynamic head movements
I think you got something there! It's not quite enough for a video, but I will certainly add it to the online content on advanced frame fit. Wicked Good. THANKS! John
Awesome lyrics John👏👏👏👏
THANKS FOR YOUR VALUED EXPLANING BUT I HAVE A COMMENT THAT YOU DIDNOT PUT THE 1.56 INDEX IN THE CHART THOUGH ITS MOST POPULAR ECONOMIC MATERIAL
1.56? Not familiar with that index. Mid-index materials like Spectralite left the market years ago. At least here in the US.
too much thanks really good
Il love your videos
Hi I don't know if you can help but I'm doing a course in optics and I'm struggling with wording a question -
What effect would increasing the refractive index have on the density and v-value of the lens material? I understand the concept I just don't know how to word it
Liz, That is in the video next to this one on Abbe. There is NO direct affect/effect relationship between the three. We think there is (we are often taught there is) but there isn't. An increase in density does not mean an increase in index. See index, Abbe and specific gravity and watch them in that order again. John
Do you guys have any videos on passing the NCLE? There does not seem to be much anywhere on you tube?
Nope. Can't find anyone to drive even the written content let alone videos. We have been trying for years now.
Hi, please i need traduction by french, im francofonne
_@Laramy-K Optical_ -- Most of these videos are great and I usually enjoy them very much. However, respectfully, your attempts to explain the physics of lenses is often flawed. In the case of the Abbe specification in your previous video, your explanation used a convex lens of a hyperopic customer in your illustration when you should have used the concave lens of a myopic customer. The reason a myopic customer observes an increase in red and blue fringing (chromatic aberration or dispersion) toward the periphery of the lens is because the lens gets thicker there. This is unique to near-sighted customers. The convex lens in your illustration does not exhibit this because it gets thinner at the periphery. *In this video about specific gravity,* the explanation of specific gravity was muddled with regard to lens weight because you fail to explain the contradictory relationship between refractive index and specific gravity. For a given lens power, the higher the index, the thinner the lens will be. Therefore, *the higher the index, the less lens material is used.* On the other hand, *plastic* lenses with a higher index usually have a higher density and therefore a higher specific gravity. If two lenses have an identical shape and thickness, the one with the higher specific gravity will always weigh more since both lenses use the same volume of plastic. So, why does a dense 1.74-index lens sometimes have a similar (or less) weight than a less-dense 1.60-index lens *for the same power?* _Answer:_ Because the 1.74 lens is so much thinner that, even with its higher density, it's weight does not increase much compared to the 1.60 lens. Because the amount of plastic used by the 1.74 lens is less, it offsets its higher density. This can make decisions of weight vs thickness tricky when only plastic lenses are considered. The issue of weight mostly goes back to glass vs plastic and a fashion-conscious move toward larger lens sizes. With the rarity of glass today, lens weight has largely gone away (except for very large lenses).
I ignored your first lengthy diatribe. But you persist. I really don't care what you think. This is optician stuff not physics stuff. Please go troll a site where your being smarter means something. Being smarter than me isn't really very hard. John
@@LaramyKOptical Wow! I didn't expect a response like that. My goal was never to "troll" but just to help you be more accurate. My sincere apologies.
@@D.Eldon_ The "lens" I chose was completely random and is simply a recognizable or generic lens shape. It has nothing to do with the concept being presented. As to your other points and conclusions they are exactly the same as those I mention in the video and those I mention as being "good optician" stuff that we cover over and over in others. I'm old, I'm cranky and I'm sorry but I struggle to find how your comments help others. Truly from my heart - as I always say, "If you can do better then make a video and if it is actually better I'll gladly include a link out to it." Heck, I'll even promote it! I've done it before, I'll pin comments from others and I often pay people who are true experts at what they do to drive content for the website. I'm not shy of genuine criticism. I am shy of nit-picking on a video which I think/feel is among the best I ever did. Of course you may have noticed that it is among the least watched of all time. If you had approached me through email with a genuine error in the lesson I would, as I have done before, corrected it. In fact you can find a few videos where mid-video I wear my RED shirt to match my RED face. Since we started on RUclips we have had a 100% no delete policy on comments. Your comment is/was there for people to read if they choose to. I chose not to react to your first posting - you insisted on pushing so like they say - you were asking for it. Peace John