Lens Buying Guide - Introduction - So You Want to Buy a Lens...

Introduction&#; So you want to buy a lens?

Stepping into the world of lenses can be a daunting task, but we have written this guide in hopes of making your buying decision relatively easy. The first thing to remember is: Making a lens selection is as personal as the style of the photographer. In other words, what you buy must first of all satisfy you. Second, you&#;ll get a chance to select from the wide variety of lenses available today &#; everything from fixed to zoom lenses, large telephotos, and even specialty lenses like fish-eye.

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The vast array of lenses in today&#;s market offers new opportunities for photographers to expand their capabilities and make the most use of their cameras. Understanding the terminology and engineering of the lenses in today&#;s market will help you make a better decision in your camera and lens purchasing.

&#;which lens is your perfect mate?

There is not a single lens that is absolutely perfect for every lighting and photographic situation, which is why you shouldn&#;t limit yourself to just one. Standard lenses have a focal range of 35mm to 80mm, with the 50mm (standard on 35mm cameras) being the most common. These lenses are fairly adequate in most lighting situations and good for general purpose photography. The added benefit of this range is its portability; because they&#;re not big or heavy, standard lenses allow you to travel lighter.

Photography Style&#; What is your shooting style?

You may not be able to define your shooting style just yet. No problem. But you can start to do so by asking yourself what kind of subjects you shoot the most.

• Do you shoot indoors or outdoors? What are the lighting conditions you are normally shooting in?
• Do you take close-ups and really pay attention to detail and texture? Are these subjects insects, flowers, and collectibles? Are they product shots?
• Do you take photographs of vast landscapes and subjects that are far off in the distance?
• Are you an action photographer who takes photographs of fast-moving objects and subjects like sports?
• Are you a wedding, event, or portrait photographer?
• Do you take pictures of interiors and architecture?
• Is the weight of a lens a consideration if you travel frequently or need to be on the move?
• Do you prefer compact, convenient lenses; or those that are bulkier and offer better quality?

Thankfully, lenses are manufactured to meet the need of all these different types of shooting styles. Many accessories, like filters, step up/down rings and extension tubes, are available to enhance these lenses so you can take advantage of the full potential of your equipment.

&#;what is your budget?

Lenses cost money, and the more engineered and specialized they are, the more they cost. Determine which style of photography is your priority and how many lenses you will require. Knowing your photographic needs is the first step in choosing the right lens.

Under $500

Lenses in this range are usually labeled as multi-purpose lenses. They will probably have a focal length between 28mm to 200mm , with their largest f-stop being f/2.8 to f/5.6. You may find some Tele Converter lenses in this category as well, but predominately it will be fixed lenses at 50mm and standard zoom lenses. A solid third party lens manufacturer like Tamron offers great all-purpose lenses in this price range and will provide you with good lens choices for adequate lighting conditions. However, these lenses may not serve you well under low lighting situations where using a flash unit is prohibited. Nikon, Canon, and Pentax all make lenses in this range as well. 
Lenses under $500 »

$500-$

This range will encompass a large selection of lenses that begin to be more specific in application and include additional engineering features that offer better quality images. You will notice that the zoom lenses will have a smaller range and the introduction of wide angle, and macro lenses fall into this group. The fixed focal length lenses in this group are further away from the 50mm size, allowing for wide angle and telephoto views. These lenses may have special coatings to minimize internal reflections, aspherical lens elements, internal focusing, or other elements offering a superior product.
Lenses $500-$ »

$+

The sky is the limit! Entering the professional photographer&#;s price range will give you the option of purchasing specialized lenses for specific lighting conditions and photographic situations. Premium lenses with large apertures of at least f/2.8 allow for indoor, low light photography; while telephoto lenses of 300mm or more offer you the ability to bring subjects in closer with optimum clarity and focus. Specialty lenses such as shift/perspective lenses are available that enable you to shoot architecture without distortion.
Lenses $ and over »

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High-index eyeglass lenses are the right choice if you want thinner, lighter lenses and eyeglasses that are as attractive and comfortable as possible.

Thinner, lighter high-index lenses are especially recommended if you have a strong eyeglass prescription for nearsightedness, farsightedness or astigmatism.

Most eyeglass wearers are nearsighted, which requires corrective lenses that are thin in the center but thicker at the edge of the lens. The stronger the prescription, the thicker the edges (see lens drawings below).

Most of today's fashionable frames are made of plastic or metal with rims thinner than the lens itself. Also, popular rimless mountings mean that the edges of the lenses are completely exposed. In either case, the lens edges are highly visible, and thicker edges can detract from the appearance of your eyewear.

How High-Index Lenses Differ From Regular Lenses

Eyeglass lenses correct refractive errors by bending (refracting) light as it passes through the lens. The amount of light-bending ability (lens power) that's needed to provide good vision is indicated on the eyeglass prescription provided by your optician or optometrist.

Refractive errors and lens powers required to correct them are measured in units called diopters (D). If you are mildly nearsighted, your lens prescription might say -2.00 D. If you are highly myopic, it might say -8.00 D.

If you are farsighted, you need "plus" (+) lenses, which are thicker in the center and thinner at the edge.

Regular glass or plastic lenses for high amounts of nearsightedness or farsightedness can be quite thick and heavy. Fortunately, chemists have created a variety of new "high-index" plastic lens materials that bend light more efficiently.

This means less material can be used in high-index lenses to correct the same amount of refractive error, which makes high-index plastic lenses both thinner and lighter than conventional glass or plastic lenses.

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Advantages of High-Index Lenses

Thinner. Because of their ability to bend light more efficiently, high-index lenses for nearsightedness have thinner edges than lenses with the same prescription power that are made of conventional plastic material.

Lighter. Thinner edges require less lens material, which reduces the overall weight of the lenses. Lenses made of high-index plastic are lighter than the same lenses made in conventional plastic, so they're more comfortable to wear.

High-index glass lenses also have thinner edges, but high-index glass is heavier than conventional glass, so there is not as much weight savings with glass as there is with plastic lenses.

Lightweight lenses are even more of a benefit for farsighted prescriptions, which can make conventional lenses very heavy. And most high-index lenses also have an aspheric design, which gives them a slimmer, more attractive profile and reduces the magnified "bug-eye" look that conventional lenses cause in strong farsighted prescriptions.

Many High-Index Lens Choices

There is a wide variety of thin, lightweight high-index eyeglass lenses, based on how efficiently they bend light.

The light-bending ability of eyeglass lenses is determined by the "index of refraction" of the lens material. This refractive index is the ratio of the speed of light when it travels through air to the speed of light when it passes through the lens material.

The speed of light is reduced the more it is refracted as it passes through a lens material. Therefore, lenses that bend light more efficiently have a higher index of refraction than those that bend light less efficiently, and lenses with a higher refractive index are thinner than lenses of the same power made of materials of a lower refractive index.

In short: the higher the refractive index, the thinner the lens.

Conventional plastic lenses have a refractive index of approximately 1.50. For glass, it's 1.52. Any lens material with a refractive index that's higher than that of glass or plastic is considered to be high-index.

High-index plastic lenses are now available in a wide variety of refractive indices, typically ranging from 1.53 to 1.74. Lenses with an index of refraction of 1.70 or higher typically are at least 50 percent thinner than conventional plastic lenses.

Also, generally speaking, the higher the index, the higher the cost of the lenses.

Your eyeglass prescription also determines what kind of high-index material you might want for your lens. The highest index materials are used primarily for the strongest prescriptions.

If you want high-index lenses, be sure to ask for them. But rely on your eye doctor's, optometrist's or optician's advice regarding which index to use. Your eye care practitioner can explain which high-index lenses are the best choice for your needs and budget.

Most of today's popular lens designs and features (single vision, bifocals, progressive, photochromic, etc.) are available in high-index materials. But there are exceptions, so ask your optometrist or optician for details.

AR Coating: A Perfect Companion for High-Index Lenses

All lens materials block some light from passing through the lens. This light reflects back from the lens surface, causing distractions and reducing the clarity of night vision.

Conventional glass or plastic lenses reflect about 8 percent of light that otherwise would reach the eye. High-index lenses reflect up to 50 percent more light than conventional glass or plastic lenses.

For the best vision and appearance, it's a good idea to have an anti-reflective lens coating (AR coating) applied to high-index lenses. AR-coated high-index lenses transmit up to 99.5 percent of light to the eye for optimum vision.

And because AR coating virtually eliminates lens reflections, it makes high-index lenses appear nearly invisible, so others see your eyes, not your lenses.

Also, studies have shown that eyeglass lenses with anti-reflective coatings provide sharper night vision with less glare &#; a real advantage for night drivers.

Contact us to discuss your requirements of Aspheric Lens. Our experienced sales team can help you identify the options that best suit your needs.