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Let’s talk about how to choose lenses first. We will discuss from the aspects of refractive index, wear resistance, spherical surface selection, Abbe number, antifouling ability, brand selection, and functional selection.
1. Refractive index
The refractive index of the lens depends on the material used in the lens.
In the case of the same center thickness, the higher the refractive index of the lenses of the same material and the same degree, the thinner the edge of the lens; when the brand is the same, the level of the refractive index means the difference in the material used, and the price of the lens can also be judged. , the higher the refractive index, the higher the price, and vice versa.
Refractive index selection reference:
(for reference only, no mechanical comparison)
1.56: 0—400° (-4.00D)
1.60: 300° (-3.00D)—600° (-6.00D)
1.67: 400° (-4.00D)—800° (-8.00D)
1.74: Above 800° (-8.00D)
2. Wear coefficient
The reason why we want to mention the wear resistance factor is that when resin lenses first entered the market, they were not wear-resistant, and they were basically worn out after wearing them for half a year. However, with the continuous iterative update of technology, the surface hardness of ordinary resin lenses is 2-3H. After hardening treatment, the hardness reaches 4-5H, while the hardness of current resin lenses has exceeded 6-7H. Adding a hard coating solves the disadvantage that the lens is not wear-resistant.
Although the hardness is still incomparable with the glass sheet, most of the glass sheet has been withdrawn from the market at present, and the only remaining ones are mainly high refractive index, such as: 1.8, 1.9, refractive index.
By the way, let’s talk about PC tablets.
Light weight, high toughness and not easy to break are the significant advantages of PC sheets. However, the maturity of domestic PC film brands has yet to be confirmed, and it is recommended to choose the products of major brand lens manufacturers.
By the way, I will teach you a little trick – to identify the hardness of the lens, you can use items of the same material to circle back and forth on the sample. According to the depth and thickness of the scratch, the surface hardness of the lens can be roughly detected.
3. Spherical and aspherical
A lens with a convex or concave shape cut from a sphere is called a spherical lens.
Since spherical lenses inevitably have aberrations (especially astigmatic aberration, flexural aberration) and so on, there are lenses that correct the shortcomings of spherical lenses, that is, aspherical lenses (usually single-sided aspherical lenses).
Aspherical lens: Refers to a surface of revolution (such as a parabola) with the same non-circular cross-section on all meridians.
Its biggest advantage is that there is no image distortion in the marginal field of view, and the edge of the lens is about 1/3 thinner than the ordinary spherical lens. Therefore, the price will be relatively higher. In addition, there are also double-sided aspherical lenses on the market. The wearing field of view is clearer and the imaging effect is better. Of course, the price is also very expensive.
4. Abbe number
Abbe’s number is the dispersion coefficient, which is an important indicator to measure the imaging clarity of the lens. It is usually expressed by the reciprocal of the dispersion coefficient, also known as the Abbe number.
The larger the Abbe number, the smaller the chromatic dispersion. On the contrary, the smaller the Abbe number, the larger the chromatic dispersion, and the worse the imaging definition. The Abbe number of the lens has a certain relationship with the refractive index. The greater the refractive index of the material, the more severe the dispersion, that is, the lower the Abbe number.
Therefore, as far as this single index is concerned, the lower the refractive index, the better, but the glasses need to be judged according to their own comprehensive vision. The fit is the most important, and it cannot be mechanically limited to the Abbe number.
5. Antifouling ability
In recent years, the research and development direction of many brand lenses has shifted from increasing the hardness and light transmittance to increasing the smoothness of the lens to improve its waterproof and oil-proof ability.
One of the most representative lenses is the Zeiss Lotus Film series.
Test method – we can wipe the lens clean and drop a drop of water and move it back and forth on the lens. If the lens is always a drop of water, it proves that its waterproof function is good. If all the water droplets are scattered and stained on the surface of the lens, the function is relatively poor.
6. Anti-UV ability, anti-radiation ability, anti-blue light ability
Let’s talk about UV resistance first.
Anti-UV lenses are anti-UV lenses. It can completely absorb or reflect the most harmful ultraviolet rays to the human eyes to protect the eyes. The UV protection coefficient is expressed by UV value: the best is UV400, generally UV375. Optical shops generally have equipment testing.
However, it should be noted that the optical lenses of regular lens manufacturers all contain UV protection (greater than or equal to UV375), so don’t be blinded by many market gimmicks.
Look at radiation resistance.
Now, almost all lenses on the market have anti-radiation coatings. However, the radiation protection effect of the lens is only the scope of the lens, and the electromagnetic wave is not completely straight. Therefore, lenses that use this as a gimmick need to be treated with caution.
Finally, let’s talk about anti-blue light.
Anti-blue light is the hottest lens feature in recent years.
For people who use computers or electronic display devices for a long time, the role of anti-blue light lenses can currently block some harmful blue light damage to the eyes, making the eyes more comfortable when working in front of the computer screen. However, there is no further evidence to prove that anti-blue light lenses can effectively improve eye soreness, dry eyes, decreased vision, and fundus lesions.
At present, many businesses have regarded this as a major business opportunity, consecrating anti-blue light lenses, which can treat various eye diseases. So, be wary of those exaggerated marketing ads in the market.
In addition to the above functions, there are many functional lenses on the market. Because of their different processing techniques and materials, the prices are also very different. But when we choose, we must remember that it is not expensive. It has many functions. It must be good. It may be just a gimmick, or it may not be suitable for the eyes. is the best.
7. Brand selection
German Zeiss lens – the most outstanding feature is the good image quality, so it also occupies a high market rate in the field of camera lenses, with impeccable technical aspects, but the price is very expensive.
Essilor, France – a time-honored brand with stable quality, wear-resistant and easy-to-clean, and strong anti-fouling ability, it is currently the brand with the highest market share in the lens field.
Nikon, Japan – Focus on imaging quality, technology is guaranteed, but its lenses do not have a high market share in the domestic market, especially color-changing films and customized films need to be processed in foreign original factories, and the customization cycle is very long.
Japan Tag Heuer—both a Japanese brand, Tag Heuer has a relatively high market share in the domestic market, especially in the field of anti-blue light lenses.
Rodenstock, Germany – Military quality, precise grinding, high film strength, and very high price. It has been focusing on the eyewear industry, so its popularity is limited to the professional field, and not many people know the brand.
South Korea’s Kemi – a rising star that has grown up in recent years, compared with the previous big brands, Kemi’s price is more affordable and cost-effective. If the economic conditions are limited, Kemi is a good choice.
The technical requirements for lens production are very high. In comparison, the technical force and R&D accumulation of big brand lens companies are much stronger. Companies such as Zeiss and Essilor have been established for many years, but in China, most of the lens processing companies have insufficient technical precipitation, and quality control still needs to be improved.
Of course, there are also some good brands worth mentioning, such as Wanxin, Mingyue and other brands.
There are many people who are concerned about how to identify lenses?
The lens manufacturing and processing technology is extremely precise, and it is impossible to determine the authenticity of the lens without the professional testing equipment provided by the lens manufacturer. As a consumer, it can only be identified by the lens anti-counterfeiting logo, the original packaging bag, and the verification code. Some big brand lenses (such as Essilor) also have a brand-specific fog display logo, which can be seen by blowing on the lens.
However, it should be noted that the above anti-counterfeiting measures can theoretically be faked.
Therefore, the identification threshold of the lens itself is very high, which has caused many optical shops to be confused. In this case, the best way to avoid encountering fakes is to introduce friends or read online word-of-mouth recommendations, and find reliable and trustworthy merchants. Be realistic.
After talking about the lenses, let’s take a look at how to choose the frame?
First statement: I have only one answer for you about what kind of frame matches what kind of face.
Look in the mirror, look in the mirror, look in the mirror.
Really, all reference manuals are LESE, just refer to it, don’t take it too seriously.
So, let’s talk about wearing comfort and frame quality appraisal.
A good pair of frames should be constructed of materials that are safe, reliable, and harmless to the skin, and should be lightweight, strong, and non-distorting when worn on the face. Secondly, for the wearer, it is also necessary to purchase from the perspective of the practicality of the frame.
When choosing a frame to wear according to the vision condition and purpose, the glasses are for long-term wear, and other conditions can be appropriately relaxed to choose a light frame to reduce the fatigue of wearing.
If the glasses are only worn under the condition of concentrated eye use such as reading and watching computers, the frames can be selected completely according to individual needs.
Those with high myopia should not choose half-frame and rimless frames, because the thicker lenses and rimless frames are not only unsightly but also easily damaged.
Those with higher astigmatism should not choose rimless frames, because the lenses with rimless frames will have the problem of displacement of the astigmatism axis after long-term use, which will lead to the deformation of the viewed objects.
Specific needs: If the purpose of glasses is largely to match the image and the occasion. At the same time, in the case where the vision condition does not limit the frame, you can choose according to your specific needs.
What kind of frame is a good frame, the quality of a pair of frames can be basically judged from three details.
1. On the color and luster – see the depth.
Lay the glasses flat in front of your eyes, and observe whether there is a difference in the color of the temples under the same light intensity. Sometimes due to processing errors, the color of the left and right temples will be asymmetrical.
2. In terms of craftsmanship – look at the details.
Craftsmanship is the quality assurance of the frame, and the quality of a pair of frames is often reflected in the details.
(1) Whether the two temples are flat.
Place the frame flat on the table to see if the contact point is free. If there is a situation where one side is high and the other is low, it is necessary to ask professionals to adjust the temples to achieve the effect of left and right balance and up and down symmetry.
(2) Pay more attention near the welding point of the metal frame to see if there are any cracks.
Due to the thermal effect during welding, the stress structure of the material is changed, or it is prone to fracture when subjected to force due to virtual welding, material fatigue, etc.
(3) Pay attention to whether the stipules of the frame are symmetrical on both sides and whether the fixation is safe.
(4) Open and close the temples and feel the elasticity.
It is generally wrong to think that the tighter the better, which means that the lubricating degree of the screw is not enough, and it is easy to cause damage to the temple. Too loose is not good, and the screw may not be tightened. Moderate tightness is best.
3. On the logo – look at the material.
Many frames will have the frame material marked on the temples, especially the precious metal frames of gold and titanium. Let’s take a brief look at their logos.
(1) GF/GP: GF is a gold-clad frame, that is, a frame made of thin gold sheets welded on other metal substrates and rolled; GP is a gold-plated frame, that is, a frame made of gold plated on other metals by electroplating Frame surface.
(2) Ti-P/Ti-C: Ti is a logo containing titanium materials, Ti-P stands for pure titanium, Ti-C stands for titanium alloy and so on.
By the way, what is the difference between titanium, titanium alloy, beta titanium, memory alloy?
A. Pure titanium.
When the titanium purity reaches more than 99%, the titanium metal material can be called pure titanium glasses. The frame made of pure titanium material has excellent characteristics such as high melting point, light material, strong corrosion resistance and firm electroplating layer, which can ensure the two important properties of the beautiful and durable glasses frame.
B. Beta Titanium.
It can be understood as another molecular state of titanium material. Although the purity of beta titanium cannot be compared with pure titanium, its strength, fatigue resistance and environmental corrosion resistance are better than pure titanium.
C. Titanium alloy.
The definition of titanium alloy is relatively broad, as long as it contains titanium material, it can be called titanium alloy. Therefore, the quality and grade of titanium alloy glasses frames are uneven, and the composition of titanium alloy has a direct impact on the price of titanium alloy glasses. The use of titanium alloys to make glasses is not to reduce costs, but to improve the application performance of materials.
D. Shape memory alloys.
It is composed of nickel, titanium, vanadium and other metals, and has excellent elasticity. If the temples encounter external force, the bending degree can exceed BETA-titanium alloy, and can return to the original state. Hence the name shape memory alloy.
The difference in titanium prices is not just the price, but more importantly, they each have unique craftsmanship and product performance. Therefore, the price of frames that are not of that kind of material is definitely higher.
In recent years, there is also a TR material that is particularly popular.
TR90 is a kind of memory polymer material, which is light in weight, less than half of the weight of the plate frame. It can reduce the burden on the bridge of the nose and ears, and is more light and comfortable to wear. Vibrant colors, more vivid and excellent than ordinary plastic frames.
Impact resistance: It can effectively prevent eye damage caused by impact during sports.
High temperature resistance: It can withstand high temperatures of more than 300 degrees in a short time, and it is not easy to melt and burn. The frames are not easily deformed and discolored, and the frames can be worn longer.
TR100 is an upgrade board for TR90. With memory function.
The material is light and can float on the water surface, which can reduce the bridge of the nose and the load on the ears. It is elastic, and can be loosened after being bent or tensioned hard, and it will quickly return to its original state, not easily deformed or broken, and the frame is colorful. The appearance is fashionable and easier to match with clothes, combining the thickness of the plate and the metal texture.
