Bokeh, it’s something that we all love, whether we like to admit it or not. It seems like every other client I work with asks me to "make the background blurry" or tells me "I want everything behind me to be out of focus." The obvious solution would be to shoot wide open, but the truth is, having your aperture wide open can actually have a negative impact on the quality of your image.
The most obvious problem you run into when shooting with a wide open aperture is focus. When your aperture is open really wide, the focal plane is near razor thin which makes properly focusing next to impossible. I shoot most of my portraits at either 50mm or 85mm and if I shoot at f/1.4, getting the correct focus is almost impossible because everything has to fall perfectly into place in order for my image to have the proper focus.
Not only does my model need to stay still, but I can't be moving either. Of course, shooting with a tripod will alleviate any movement on my end, but it is still remarkably hard to achieve proper focus with your lens at its widest aperture. What I have started doing is shooting with my aperture around f/2.8 to make focusing easier while still allowing for a good amount of bokeh in the background. Granted, the background may not be as blown out of focus as you may want, but I like having the piece of mind knowing that my images will be in focus.
Chromatic aberration, sometimes referred to as “color fringing,” is defined as: "The material effect produced by the refraction of different wavelengths of electromagnetic radiation through slightly different angles, resulting in a failure to focus. It causes colored fringes in the images produced by uncorrected lenses."
Since I’m no scientist, and that definition sounds pretty darn scientific, let's break chromatic aberration down with picture examples instead.
In this first example, there is a really strong purple fringing which is the most common form of chromatic aberration. I shot this image with an 85mm f/1.4 lens and had the aperture wide open at f/1.4. The place to keep an eye out when looking for chromatic aberration is anywhere in your image where there is a lot of contrast. In this example, the crown my model is holding is silver with jewels that are a very dark color. Since the silver is a very light color and the jewels are dark, there is some really noticeable chromatic aberration that shows up right on the edge where the light meets the dark. Here's a closer look.
Another common form of chromatic aberration is called "green fringing." Similar to purple fringing, this creates a green edge across an area of a high contrast in your image. In this example, the fringing isn't quite as noticeable as the purple fringing in the last image, but if you look closely you can see it on the edge of the stripes on her shirt, and along her jaw line.
There are ways to fix chromatic aberration in postproduction, but the easiest way to make sure your image doesn’t have it is to stop your aperture down. By shooting at a higher aperture you are increasing the focal plane which decreases the chance of chromatic aberration.
Lenses are expensive enough as it is, so adding another zero onto the already sky-high price tag doesn't seem worth it in my opinion. Sure, I have some lenses that are pretty fast, but they’re also third-party lenses that come with a significantly cheaper price tag than the Canon and Nikon lenses of the world. If you are in the market for a cheap, fast lens, I would highly recommend Rokinon or Samyang. The only caveat of shooting with Rokinon glass is that most of their lenses are manual focus except for a 14mm and a 50mm lens for Sony E-mount. Like I said before, I don't mind manually focusing in a lot of situations, but there are other times when that is simply not an option. I get by just fine with a Nikon 85mm f/1.8 D lens that I picked up off craigslist for $200. It does get a little funky when I shoot at f/1.8 but when I’m at f/2.8 and higher I couldn't ask for a sharper lens.
Does the Background Add to the Image?
If you answered yes then that’s a great reason not to shoot wide open. There are plenty of times that I want the environment I am in to be a part of the image. If I completely blow out the background then there’s no point in shooting in that location. On the other hand, sometimes you can use an open aperture to your advantage and hide any undesirable distractions from your image like in the example below where there was a gas station directly behind my model and I obviously didn't want that to be a part of my image.
By shooting with a close crop and a pretty wide open aperture I was able to make the ugly, distracting background unrecognizable. As I’ve mentioned in previous articles, a lot of clients I work with rely on me to have all of the artistic input. They may not see or be able to comprehend how a background can add to an image, so that is when I tend to shoot a little more open. I just make sure to be a little more careful not to shoot completely wide open to secure proper focus.
Exception to the Rules
Like all things in life, there are exceptions to the rules, and to be honest, they’re really more guidelines than rules. Sometimes an image can be a little out of focus and still be good. For instance, a little while back I purchased the Rokinon AF 50mm f/1.4 FE for my Sony a7 II. It was actually delivered in the middle of a shoot, so when it arrived I threw it on my camera, opened the aperture to f/1.4 (because why not), and went to town.
It’s a little soft at f/1.4, but the image I came up with was one that both my model and l were really happy with, even though the focus isn’t technically correct, and the image itself isn’t really all that sharp.
I can’t tell you how you should or shouldn't use the tools you have in your kit, but I can hopefully help you use them to their fullest potential. Do I shoot wide open from time to time? Sure I do, but it's a rare occasion because I would rather have an image that is in focus than one that has beautiful bokeh and a soft subject.
What do you think? Should you push your lenses to the limit and shoot wide open, or should you take advantage a sharper image and stop down a little? The bottom line is that your style is your style, and I am in no way trying to get you to change that. All I want you to do is understand that there are ways to achieve a similar style without compromising image quality in the process.