Search for This Information Before You Buy a New Lens

More and more people get infected every day, and I’m a victim of it, too. Yes, I’m talking about GAS, which usually hits me when spring is coming. For this reason, I am focusing a little on purchase decisions lately.

When the weather in my region slowly becomes endurable and new photography projects are rushing through my head on a daily basis, I like to spend hours checking the variety of great gear that’s out there. At the moment, I’m dallying with the different 35mm prime lenses, which are mostly of highest quality. While I was checking the lenses on the web, I read many reviews from many sources. Some were better, some were the worst.

Test Images Need a Minimum of Information

Many of the test images that you will find online lack one very important feature: text. When you only see an image shot with a certain lens, it doesn’t give you a lot of information about its overall performance.

But not only the EXIF data (i.e. under which settings the photo was shot and which gear was used) will help you evaluate the image. A small text about what should be proven by an image is also useful. There are many great reviews out there, which only use photographs to underline their profound description of the lenses’ strengths and weaknesses. Watch for these reviews, but forget about those that only claim “not worth the money. Some images are unsharp, so I sent it back” and provide second-class images of proof.

Also, when you have a written text in front of you, you’re able to evaluate the test person him- or herself. Does the person focus on the right things? Can you find some proof of expertise in the text? Of course, it makes you feel a bit ungrateful to be picky when someone gives you information for free. But you don’t want to spend hundreds of dollars on the wrong product, do you?

Good Visualization of Bokeh

In the last article, I mentioned that images of flowers at f/2.8 aren’t proper test images. Well, of course you could read the quality of the bokeh (quality of blur outside the focus plane) from some of them. Only providing an image of a flower with a shallow depth of field doesn’t make the best example for bokeh, though.

To make an image of a flower become a proof of bokeh, make sure that you have some areas in the image where bright light shines through a darker area. Here, you can see the bokeh bubbles pop. And after all, the distance of the background plays a crucial part for evaluating bokeh, too. To really demonstrate the shape of the bokeh bubbles, shoot single light sources in a dark environment. Make sure they’re out of focus. You don’t need flowers for that, not even a foreground.

Vignetting, Distortion, and Chromatic Aberration

Vignetting, distortion, and chromatic aberration are correctable in the post-processing. Adobe Lightroom, for example, offers automatic lens corrections for most lenses. But of course, you want to get the best possible quality already in camera.

Vignetting is something that can be evaluated in almost every full-size image. It’s helpful, though, to find some photographs of a pure white (or gray), evenly lit surface. Here, you can easily see the difference between the brightness of the center of the image and the gradient towards the periphery.

Distortion can be evaluated on every image that has a subject with straight and even lines. The brick wall is a frequently used subject, as well as bookshelves. Ideally, you even find a grid laid over the lines of the wall to emphasize the deviation.

Chromatic aberration is one of my personal nemeses. I simply hate it. It creates green or purple lines around high-contrast areas, which can to some extent be removed by software, but often, it still leaves a gray, blurry line. The color fringing appears in wider apertures and can range from giant lines to small spots. If you want to find proof of chromatic aberration, look for images of trees shot against a bright sky. You won’t see them in a thumbnail, though. It should be a 100-percent crop.

Proof of Sharpness Needs a Lot of Effort

Proving lens sharpness is a tough task. Because sharpness is also dependent on the focal length and aperture of lens, you need many shots to get an impression of the quality of the lens under different settings. Apart from that, the image needs to be flawless, which means no camera shake that could blur the image.

You also need to get an impression about different parts of the image, namely the center and the periphery. While the center is usually the sharpest area of the image, the quality of a photograph can significantly decrease towards the edges. 

If you’re into this form of pixel-peeping, you might also become acquainted with MTF (Modulation Transfer Function) charts. These graphics let you read the performance of a lens in a laboratory test, only regarding their sharpness at different levels under the same aperture, though. They don’t measure overall performance.

Practical Tips Are Often More Helpful Than Pixel-Peeping

The best way to find information about a lens is finding reviews that took it out to test under extreme conditions in the field. For fast telephoto glass, photographs of sport events are quite helpful to see what you can reach with a certain lens.

Keep your eyes open for other photographers who shot photographs similar to what you do. You will find many on the web. Flickr, for example, offers groups for most lenses, where you can see what others have achieved. Always be aware that the quality of the photographer matters, too. While bad images don’t prove a bad lens, great photographs don’t mean that every of your pictures will look like that. They only show the maximum capability of the gear.

Beyond photographs under real-life shooting conditions, stories from photographers who took the gear out are the best way to evaluate a lens that you didn’t hold in your hands. At Fstoppers, for example, reviews are focused on real-world application. This makes it possible to not only understand what the final result of your photography will look like, but how it feels to work with the product.

After all, you shouldn’t only focus on good results, but also on how hard it is to achieve them with a certain lens.

Do You Need to Test a Lens in Person?

Of course, not everyone has a lens rental store around the corner. Some of us don’t even have an affordable camera shop in our area and rely on the internet to get our gear. That being said, the best way to check a lens is still by using it. If your fellow photography friend is in love with her 70-200mm and you like her images, ask her if you could play around a bit before you blindly purchase the lens. I have bought and sold far too many lenses (like the 70-200mm) already only because of greed.

On the other hand, a test for a few hours can make you feel even more greedy, because you become fascinated by the new capabilities. Honestly, do you really need them? Make sure that photographers who shoot a similar style approve of the lens. The internet is still a great source for that, just like local fellow photographers are. The more opinions you get, the more angles you have to look at the practicality of a lens. You need to know what you need, though. This should be your main focus for a purchase decision.