It’s shopping season again, and I want to talk a little about that obsession we have with camera lenses. Often times, you’ll hear, “get the best glass, you won’t regret it.” This is certainly the case in terms of total image quality, but is it practical advice? I mean, there are entire websites devoted to the minutia of MTF charts and brick-wall photos trying to convince us which lenses are the best, and which are marginal. I’ve been thinking about this topic a lot lately, especially when going through my images and examining my gear needs as they have evolved.
What makes good glass good?
There are many factors that go into choosing a lens, and optical quality is simply one of them. Here is a short list of the things one might consider when purchasing a new lens (or dreaming of purchasing one).
- Sharpness (center to corner)
- Chromatic Aberration (CA)
- Light fall-off (vignetting)
- Focal length or zoom range
- Maximum aperture (f/stop)
- Constant aperture zoom vs. variable aperture zoom
- Form factor (size, weight, filter thread size)
- Image stabilization (i.e., VR/IS/OIS)
No single lens will deliver the “best” solution across all of these criteria. There is no 10-1000mm f/1.4 zoom lens with perfect optics that weighs under a pound. In other words, every lens design represents a trade-off between some of these components. It’s up to you to determine what fits your needs. You want a fast telephoto lens? It’s going to be big and heavy. A wide-range zoom lens like the 28-300mm zoom won’t deliver the optical quality that a 300mm prime will, nor will it be as fast to focus, but it will be an all-purpose lens that you don’t need to change while traveling. While the 600mm f/4 is a beautiful lens for birding, not everyone has a spare $9000 lying around to buy one. Here in the real world we need to make purchasing decisions based on our needs and budget, not just an MTF chart.
While the optical benchmarks are one measure of performance, one thing we need to consider today is that we have a lot of technology working in our favor to improve our images. Not the least of which is that most modern lens designs are actually quite good. The newest lenses from both the camera manufacturers and the third parties like Sigma and Tamron all offer good optical quality. In fact, the differences in optical quality tend to be quite small in most cases.
Modern problems resolved
Let’s start off by looking at some optical parameters that might not be as problematic as they seem in the tech reviews. Distortion, light fall-off, and CA can all be fairly well corrected in post, especially if you capture your images in RAW. This was not the case with film photography, because you didn’t have the latitude to correct images after the fact like you can now. Only serious offenders in these categories will really impact your images, and even then you’d probably only notice it in larger prints. So while it’s nice to have a lens with no vignetting wide-open and no CA, we need to down-weight these parameters somewhat in the real world.
Sharpness, on the other hand, is indeed important, and if a lens isn’t very sharp, you probably won’t want to use it. The best lenses will typically be sharper in the corners and at a wider range of focal lengths than inferior ones. Keep in mind that MTF tests, which measure lens resolution and contrast (measures of sharpness) are performed with the lens at its widest aperture. This can be important if you like to shoot wide-open frequently. On the other hand, even the best lenses still have better corner sharpness and less vignetting when you stop them down a bit. If you’re a landscape shooter, do you care if the corners are somewhat soft at f/2.8 if you are usually shooting at f/11? This takes us to the next question, which is maximum aperture.
Do you really need fast glass?
“Fast” glass is a term used to describe lenses with a maximum aperture of f/2.8 or wider. Typically, these are usually the manufacturer’s best lens designs. Fast lenses offer several advantages over their “slow” counterparts. These advantages are shutter speed, depth of field, and focus performance. A fast lens allows you to let more light into the camera, giving you a fast shutter speed to freeze action. You can also get shallow DOF with a wider aperture. Lastly, because your camera opens the lens aperture completely when focusing, a fast lens will usually offer better autofocus performance.
There is no question that fast lenses deliver excellent performance. But you can’t make this decision in a vacuum. Today’s cameras have ISO ratings well beyond what film cameras had. I can shoot my D4 at ISO 5000 with abandon without worrying about noise. Getting a fast shutter speed does not require the fastest lens anymore. Moreover, fast lenses are big and heavy. My 70-200mm f/2.8 lens is more than twice the weight of the 70-200 f/4. And because both lenses offer image stabilization, the performance drop for the f/4 lens isn’t as much as you might think.
Form factor and price
You won’t buy a lens that you can’t afford, and you won’t use a lens that you don’t carry with you. Big, fast lenses have their place. If you shoot action, dark theaters, or serious portraits, you’ll probably want one. On the other hand, you probably don’t want to walk the streets of Paris carrying a 25-lb camera bag, either (unless you have an able-bodied assistant). You might also want to use lenses that share a similar filter thread diameter to reduce the number of filters or adapters you need to carry in the field.
Some quick kit comparisons
Ok, now that I’ve convinced you (hopefully) that there’s more to a lens than just sheer optical performance, let me take inventory of some of the glass I have and make some observations. Lately, I’ve been doing more travel/urban photography and less action/wildlife photography. As I’m primarily a Nikon shooter, I’ll discuss my current situation as it pertains to Nikon lenses.
The holy trinity of Nikon glass
Conventional wisdom says that if you shoot Nikon FX (full-frame), then these are the must-have lenses:
If you own these lenses, you’ll be very happy with the image quality. You’ll also have to spend about $6300 (based on prices at B&H Photo) to get these three lenses, and your kit will weigh 7.5 lbs.
Alternatively, you could opt for the f/4 versions of these lenses:
This kit would cost you $3948 and would weigh 4.84 lbs. That’s a savings of $2331 and 2.66 lbs.
The lens you want versus the lens you’ll use
I personally own all the lenses listed above. Since I moved to Lightroom, I can easily see which lenses I use the most. I also know what I tend to pack for different types of trips. So let me run down my thoughts comparing these lenses.
14-24mm f/2.8 AFS G Nikkor vs. 16-35mm f/4 AFS G VRII
The Nikon 14-24mm is as good as everyone says it is, optically speaking. It’s really killer. I almost never use it. In 2014, I captured 1479 images with these focal lengths. I used the 14-24mm for only 280 (19%) of them. Why? The 16-35mm f/4 offers VR, is lighter weight, and accepts front filters (something very important for my long-exposure work). It’s not as sharp in the corners as the 14-24mm, but I don’t care. It’s a workhorse for me. I also like the fact that at the long end, having 35mm means I change lenses less frequently. Moreover, the 14-24mm is very prone to flare when used outdoors. I like to use it for indoor shots and also for night shots, like stars. That’s where the f/2.8 aperture really helps.
24-70mm f/2.8 AFSG vs. 24-120mm f/4 AFS G VRII
The differences between these two lenses are quite numerous. For landscape photography, the 24-70mm Nikkor has been my go-to lens. It’s absolutely deadly-sharp and delivers wonderful starburst patterns in night photography. I love it. The 24-120mm f/4 lens, on the other hand, would be one I put into the “very good” category. It’s not as well-corrected as the 24-70mm, but it has a couple of features that make it compelling for travel photography. First and foremost, it has a wider zoom range. While we might consider 70mm to be a “telephoto” focal length, it really isn’t. I find myself having to change lenses often because a lot of times, 70mm just isn’t enough reach. The 120mm range of this lens is extremely useful in urban photography, and in fact it offers enough reach for the majority of shots in that setting. You can use the 24-120mm f/4 as a single lens solution when traveling. The 24-70mm would be somewhat constraining. However, for my landscape workshops, I will probably pack the 24-70mm lens as it is in a class by itself.
70-200mm f/2.8AFS G VRII vs. 70-200mm f/4 AFS G VRII
Here’s a case where a new design (70-200mm f/4) is really amazing. I’ve owned both Nikon 70-200mm f/2.8 lenses, and they are really good, with the VRII model being downright awesome. I was pleasantly surprised to find that the 70-200mm f/4 is just as sharp and works well even with a teleconverter. The f/2.8 model of this lens is ideal for people who really need that extra stop of light when photographing action or theater. Otherwise, I’d strongly consider the f/4 version. The slight difference in depth of field is somewhat offset by the fact that the f/4 version of this lens focuses closer than the f/2.8 version. The f/4 has a magnification of 0.274x while the f/2.8 only gets you 0.12x. Both are awesome lenses, but lately I’ve gone with the f/4 version almost exclusively because of its smaller size and weight.
Other lenses to consider
If you travel a lot and don’t use long focal lengths frequently, then the 70-300mm f/4.5-5.6 AFS G VRII lens is a nice choice. It’s not an action lens, but it delivers well enough for those times when you want to go long without weighing down your bag, or your wallet.
If you shoot the occasional portrait or like having a fast prime for creative depth of field, consider the f/1.8 versions of prime lenses instead of the f/1.4 versions. They are less expensive, and nearly as good (especially when corrected in post). The Nikon 35mm, 50mm, and 85mm lenses are all offered in f/1.8 versions now and they are significantly less expensive, and somewhat smaller to pack.
At the end of the day, you as a photographer have to decide just how you intend to use your gear. Size, weight and versatility can be just as important or even more important than just pure optical quality. Know your subject and get the lenses that deliver the results you need. The needs of a sports photographer can be quite different than the needs of a landscape photographer. As my photographic journey continues, I will continue to evaluate my gear based on how I use it, not just how it rates in optical benchmarks.
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