How to Evaluate and Purchase Your Next New Lens

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It’s a day that comes for of us all at one time or another. You have to take the plunge…the big leap…go all in, take a chance. The decision can make or break you and your photography…or at least it can seem that way. It’s the day you invest in a brand new lens or one that’s new to you. Regardless, purchasing a fresh piece of glass can be confusing, frustrating, and painstaking. I’m here to tell you that we photographers who operate on limited funds (most of us) share in your anxiety when it comes to laying down what is usually a lot of money on something that we hope will improve our work and help us transcend to the next level.


How do you make the right choices? How do you choose the right lens to fit your particular needs? Well, there is both good and bad news for you. The bad news is that only you can finally determine the right lens to fit your own craft.

The good news, though, is that there are many ways you can lessen the anguish of lens buying and make sure that you find the right investment. In this article, you will learn how to look beyond just the obvious when shopping around for that new lens, so that you can ensure you make an informed and hopefully less painful decision. Lens reviews can become confusing in their own right. While there are infinite considerations, following these guidelines will help to make more sense of all those lens reviews.

Optical Performance

Sharpness

This is one of if not the most often encountered reasons for buying a new lens. We need better sharpness. But that sharpness, of course, comes at a price. So when evaluating the sharpness of a new lens it’s important to consider all the elements of the equation.

Are you looking for a lens that zooms or does not zoom? Prime lenses (non-zooming) are often cheaper and faster (have a larger maximum aperture) than zoom lenses of the same speed (more on this later). So, ask yourself if you need a lens that can change focal lengths quickly, such as for events or sports shooting? Or do you need a lens that can cope with more static scenes such as landscapes or posed portraits?


Sharpness is so subjective that it often takes looking at many sample images to see the actual results from real-world tests. Be sure to note the camera each image was made with and the source of the sample. Pay special attention to the entire frame especially at the corners to judge the overall sharpness. Speaking of corner sharpness….

Edge Softness

When we talk about edge softening the reference is to the deterioration of sharpness at the corners of an image. This is brought about by many variables but usually, it is due to the composition and quality of the glass elements within the lens. As you approach the wide or short end of the aperture range of your particular lens this softening almost always become more apparent.

Shot with the Rokinon 14mm at f/2.8. Note the more prominent loss of sharpness at the far edges and corners of the frame.

While shopping for a new lens, of course, you want the least amount of “softening” at the edges of the frame. Make a point to inspect the aperture at which each test photo was shot because different apertures carry with them inherent differences in edge sharpness. If you know you will be shooting wide apertures (low light, shallow depth of field) or small apertures (landscapes, large depth of field) pay special attention to test photos shot towards the wide or narrow f-stops.

Lens Distortion

Lens distortion is fairly self-explanatory. It is anything that alters the spatial appearance of lines within the frame. There are two main forms of distortion; “barrel” and “pincushion”. Barrel distortion is common with wide-angle lenses and appears as a bulged effect; with the straight lines within the images appearing to bend outwardly.

An example of “barrel” distortion often encountered with extremely short (wide) focal length lenses

Pincushion distortion is the exact opposite of barrel distortion. This type of image distortion occurs most often when telephoto lenses are zoomed to their maximum magnification. The appearance is a slight bending inwards of the photo towards the center. However, it’s not nearly as apparent (hardly perceivable at times) as barrel distortion.

A case of uncorrected pincushion distortion…

…and now corrected. As I said, almost in-perceivable….

If you’re in the market for a quality wide angle lens, make it a point to find one with little or relatively little barrel distortion. Keep in mind that the shorter the focal length the more prevalent barrel distortion becomes, even in high-grade lenses. The same is true for pincushion distortion. The higher the telephoto range the more often you will encounter pincushion distortion at long focal lengths.

Chromatic Aberration

Chromatic aberration is a technical term for the unsightly discoloration that sometimes occurs around high contrast areas in a photo.

It is evident to some extent in all lenses no matter the quality, but it is more perceivable at wide or small apertures. The key thing to look for is the least amount of chromatic aberration present at the extreme ends of the aperture range. Much like edge softening, aberrations can be controlled albeit not eliminated.

Autofocus and what is Image Stabilization anyway?

Autofocus

Ah yes, autofocus. Having the ability to focus on subjects by merely pressing a button is a gloriously underappreciated benefit modern photographers share. You probably owe your camera and lens a long overdue “thank you”. Go ahead and thank them…I’ll wait.


However, the question remains, how important should autofocus (AF) be to you? It all comes down to what type of photos you will likely be shooting. Back when I did location wedding and event photography, I could not have imagined operating without a fast and accurate AF lens. Now that I shoot primarily landscapes and nature photography, AF has become less of a priority for me.

That’s not to say that AF doesn’t have its uses even now for me and my work. The reason I share this is to demonstrate the priority that you should place on the quality of AF in whatever lens you might be looking at buying depends on your own needs.


If you shoot sporadic, fast-moving, or otherwise unpredictable subjects, place a fair amount of emphasis on AF performance in the lens you seek. However, if you’re a landscapist, shoot still lifes, or otherwise find yourself making photographs of static subjects, AF becomes less important.

That being said, if you find yourself requiring AF, look for a focusing system which consistently focuses accurately and is able to lock onto a subject. Granted, the type of camera you use plays a key role here as well.

Image Stabilization

There’s somewhat of a split in opinions when it comes to image stabilization. Some shooters swear by it, some say it isn’t worth the trouble. As for me, I’m a blend of the two factions.

For the majority of my work, which involves a tripod and slow moving/non-moving scenes, I seldom use a stabilizer even when it’s available. Still, there are times when I find myself saying, “Man, this stabilizer is awesome!” So as with many aspects of choosing a lens, it depends on you and your needs.


The truth is that the longer focal length lens you use, the more image stabilization will come in handy. It provides an exposure “cushion” when shooting handheld. I’m happy to say that the technology seems to be improving each year. If you shoot the majority of your photos without a tripod, for whatever reason, you will have the use of a stabilizer. The very bottom rung of modern image shake reduction systems can give you two to three stops of exposure latitude (to be able to use slower shutter speeds and maintain sharpness) which can go a long way depending on your camera.

Some final thoughts on lens evaluation

Hopefully, with any piece of gear you buy, you choose to analyze and find every scrap of information you can before taking the plunge. The tips here come from someone who has reviewed, tested, and used camera lenses from virtually every leading manufacturer on the market today. These lessons are simple, applicable, and most importantly, easy to understand so that you can make an informed choice.

Today we find ourselves fortunate to be able to select from a pool of increased quality when it comes to our camera lenses. Unfortunately, this means choices are nearly infinite. Be smart and be savvy. Don’t spend time and money on new glass that does more or less than what you need.

Read more from our Cameras & Equipment category

Adam Welch

is a full-time photomaker, author, adventurer, educator, and self-professed bacon addict. You can usually find him on some distant trail making photographs or at his computer writing about all the elegant madness that is photography. Follow his blog over at
aphotographist.com or pick up his new book Cameras in the Wild.

  • Peter Cleife

    Why do people especially americans refer to lenes as ‘glass’? They are lenses.

  • Pete

    Uh…because the lens has glass in it….

  • Peter Cleife

    My windows are made for glass, but I call them windows not glass.
    A lens is a lens, so why not call them that.

  • Mr. Fusion

    It’s slang. The same as we refer to American made autos as “Detroit Iron” or racing style bikes motorcycles as “Rice Rockets”. Electric guitars become an “Axe” and a drum set became a “Kit”.

    BTW, one is a “lens”. the plural of which is “lenses”. Besides referring to lenses as glass, we also refer to spectacles as “glasses”, “eye glasses,” or “reading glasses” and tumblers as “glasses” or “drinking glasses”. Some people refer to mirrors as “looking glass” although that term is archaic..

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