How to choose a lens
Every now and then, someone will ask me “what lens should I use?” or “do you think this lens would be good?”. The answer is nearly always “it depends”, and the first thing I ask is what the person intends to shoot. Let’s assume for the purposes of this post that the answer is “people.”
Focal length
The first question is focal length - and that just depends. :-) Personally, I use anywhere from about 30mm to 200mm for my fashion and glamour work, and that’s on a Nikon digital body with a 1.5x crop factor. The big thing to worry about is normally the perspective distortion you’ll run into if you use a short lens, and end up having to get very close to your subject. Longer lenses also have perspective issues of their own (in that they tend to “flatten” images), but it’s generally a pleasing perspective for photographing people.
The focal length question is also related to how much room you have to shoot. If your studio is 50 feet long, you will have no problem shooting full-length shots at 100mm if you wish. But if space is more cramped, or you want to be closer to your model, you may need to go with a wider lens.
Max aperture
The max aperture is a more touchy question, as the price of the lens is often directly related to how wide the max aperture is. Having a “fast” lens gives you two advantages: first, it lets you shoot at that max aperture (duh!), in the event you don’t have a lot of light or you want to limit your depth of field. And second, it lets more light into the autofocus mechanism in your camera, which will generally let it focus faster and more reliably. Let’s dive into each of these for a moment.
How often are you going to be actually shooting at f/2.8, or perhaps even faster? Good question. When I first got started, I thought I’d be shooting down there a lot in the studio…turns out I actually don’t all that much. You can take some cool shots with very wide apertures; it just depends on your style and what you’re trying to achieve. Note, however, that I do use f/2.8 or faster fairly often when shooting outdoors…just not often in the studio.
What about the autofocus advantage? This one is big. When you’re setting up a shot in the studio, often you’ll have all of the ambient lights off (or turned way down), and you’ll be setting up the shot with just the strobe modeling lights on. These modeling lights are sometimes nice and bright, but not always, especially with big softboxes or other modifiers. If you don’t turn up the ambient lighting before you start shooting, you’re just going to have the modeling lights - which means you won’t have a ton of light to focus. You’ll likely have enough - just not a lot…which means the more light your lens can pull into your camera’s AF mechanism, the better off you are.
Variable aperture
The last thing I’ll mention about lenses for studio work is this - be careful about variable-aperture lenses. Many “consumer-grade” lenses (meaning ones that are reasonably priced!) have a variable maximum aperture. So for example, Nikon makes a 55-200mm lens that has a maximum aperture of f/4 at 55mm, and f/5.6 at 200mm. The problem comes if you’re in the studio, using strobes, and shooting on manual…you may need an exposure of f/4, and when you set up the shot (at say 55mm), everything is great. Then during the set you zoom in for a close-up of your model’s face - and your camera is suddenly (and silently) shooting at f/5.6. You’re now a whole stop underexposed - and you might not realize it until you download your images later.
For that reason, all of the zoom lenses I use for studio work (or any other times where I’m shooting on manual) are constant-aperture across their zoom range.
Sharpness
This one never ceases to amuse me. On some of the internet forums, people obsess for days over whether a certain lens is sharper than another; and I’m not afraid to admit that I was one of them when I first got started. :-) But here’s the thing…
Most lenses are very sharp when stopped down a couple of stops.
Now, that’s a pretty big blanket statement to make…but if you buy a name-brand lens (Canon, Nikon, Sigma, etc), it’s generally going to be true. So if you can live with shooting at f/8 or f/11 (which is common in the studio), most lenses are going to be plenty sharp.
However, if you want to shoot with a lens wide open, or close to it, that’s what separates the wheat from the chaff, so to speak. If you need tack-sharp at f/2.8, or f/4, then do some research.
So for shooting people, do you need that sharpness? Interesting question. I about fell over when I read a forum post that said something to the effect of “for shooting people, you really don’t want a very sharp lens, because you’ll have to retouch more.” Not sure I would go that far. :-)
My take - yes, you want a lens that’s nice and sharp. And it’s not because you want to see every last pore on someone’s face - you usually don’t. But there are parts of an image you want nice and sharp. For example, fashion shooting isn’t only about skin, but it’s also about products - and there might be details in the product that you need absolutely tack-sharp, depending on what you’re shooting and how large it will be printed.
So anyway, lots of random thoughts in here…hope it’s helpful to someone!
