If you haven’t noticed, I love writing posts that explain things. Really, the more intricate, the better. I enjoy analyzing the details of something and translating those details into what I think someone might understand. I don’t always meet the mark though because I have a tendency to get excited and rush, but I do try my best.
Through the years, I’ve come to realize that many folks out there aren’t all that interested in the details and that they simply want the result of whatever it is they’re engaged in. They aren’t interested in the understanding behind things. I get this. I used to be like this and I still am with some things. I guess it depends on the interest level. We all can’t walk around all day understanding every minute detail of everything. None of us would get anything done.
If you’re a photographer though, and one who is determined to become great, you need to learn a few basics. One of these basics has to do with focus. I’m not talking about how to focus or the mechanics behind what your lens or camera does to make something look sharp. What I mean is what focus itself is. This is the very most basic of basic knowledge when it comes to photography. If the concept of focus is understood early on, so much more will be clear later in life.
In today’s post, I’d like to briefly discuss the concept of focus. What it means to see something clearly through a lens versus what it means for that object to be seen with a blur. This is actually a very straightforward idea, so it shouldn’t take long. There are some key points though and I’ll try to explain them below.
What is Focus?
For this section, I’m going to try my hardest to give you a definition of focus that isn’t technical. I get tired of definitions no one can understand sometimes.
For a moment, let’s pretend you have poor eyesight and that you can’t see the letters in books clearly. If your eyesight is poor and you’ve never been able to see what those letter really look like, you don’t know what you’re missing. It’s only when you put corrective glasses on that you understand what’s going on. So what is going on?
When something is blurry, or out of focus, there’s a transition between the edge of an object and a place where the object doesn’t exist. And that transition is smooth when it’s not supposed to be. The more something is out of focus, the greater the area of transition. Let’s pretend to expand the letters I’m talking about here so they appear really big, so we can take a close look at the edges in question. If a letter is in focus, the transition between the letter and the page it’s written on is sharp. It’s abrupt and it has lots of contrast. It’s like a cliff. One moment you’re standing on it and then, with just one step, you’ve fallen off.
Blur is like a hill. One moment you’re standing on it and you are still standing on it if you take one step. That step just brought you down in height a bit. And if you keep on walking, you’ll eventually make it to the bottom, but the transition was smooth. It’s like a gradient.
So that explains focus. In my own words, “clear focus is the amount of distinction that’s supposed to exist between the edge of an object with its background.”
Focus is a relative idea. It’s compared to other things in a scene. It represents the sharpness, contrast, detail and texture you might expect to see. But really, it’s the contrast that exists around the edge of an object or part of an object the most. And it’s the contrast that is supposed to exist if certain things are in alignment.
Focus, More Specifically…
There’s a big technical world out there that deals with focus. These are folks who are engineers, scientists, mathematicians, and others who live their lives to study and created all types of things that have to do with optics and various machinery that use optics. It’s these people who have come up with a few definitions we can use to understand this area just a bit more.
“Focus” can also be referred to an image point. This is the point on an object where light converges. It’s the smallest point of clarity and really, if you were to try to look for this area, you wouldn’t be able to see it. It’s too small. Because it’s so small, people came up with another term called a blur circle. The reason an area can be referred to as a blur circle is because an image point by itself is virtually invisible. You would need multiple image points to see anything and anything in multiples has what’s referred to as spacial context. Think about it like this; an image point is one dimensional and a blur circle is two dimensional. So basically, it’s a single point compared to a flat plane. Sort of like a dot from a pencil drawn on a piece of paper compared to the entire piece of paper itself.
In order to see something, whether it be through our own eyes (lenses) or through a camera lens, we’ll need to view all the image points as they were meant to be viewed. Now, if our lenses are perfect and there are no aberrations in them, we will see those image points clearly. But if they’re not; if there are some waves or bends in the lenses that aren’t supposed to be there, some points will overlap with others, causing confusion and, yes, you guessed it, blur. Or, non-ideal focusing, as they say in the trade. This is why it’s so important to wear high quality glasses if you can’t see well and purchase high quality camera lenses if you’re planning on taking great photographs. It’s those lenses that matter most and the precision that goes into them during production.
In Closing
I don’t want to go nuts here trying to explain something that will have little impact on you while your out in the field with your camera, but I do want to impress upon you how important focus is and how it can affect your pictures. When you look through the viewfinder on your camera or at the LCD screen in the back of it, at first glance, your scene may appear to be in focus. It’s important that you confirm that it truly is though. Your eyesight needs to be clear and the scene must be viewed as closely as possible. You can use the magnification feature on your camera while using the LCD screen and you can also make adjustments to the diopter in the viewfinder if you wear glasses. The goal here to is achieve as much clarity in your scene as possible. All of what I wrote above should come into play. You won’t need to think about any of this because from the day we were all born, we’ve either seen the world as something that’s in focus or we’ve worn eyeglasses to help us see clearly. So special care needs to be taken to assist our cameras and lenses to see clearly as well. Because really, clear, in focus photographs and blurry ones are a world apart. Anyone can tell the difference very quickly.
What are the Limits When it Comes to Focusing My Lens?
This is a great question. I love getting into the nitty-gritty of camera lenses and I enjoy looking at the specs of each lens I come across. A long time ago, I taught myself what those specs actually mean and I’ve been rewarded with knowing what I’m talking about and looking at ever since. For a lot of people, I know it can be a challenge when attempting to figure out what a lens does. Today, I’d like to demystify a few small areas.
I’m going to try to make this as clear as possible. We already know that two factors primarily determine the focus of a camera lens. Those two things are the size of the aperture that’s inside the lens as well as the distance the camera is away from whatever it’s trying to focus on. As a matter of fact, it’s fairly easy to calculate the depth of field that a camera lens can create by simply punching a few numbers into a calculator. But realistically speaking, we all need a more personal feel when we’re dealing with our cameras and lenses when we’re on the job or in the field.
I’d like to discuss the two limitations we face while focusing our camera lenses here. I don’t know if there are more limitations, but these are the two that come to mind that we all deal with every time we shoot.
Depth-of-Field
The first limitation we deal with is called depth of field. All depth of field is is the area of a scene that’s considered sharp as you’re looking through your camera lens. Again, the two primary factors that contribute to the depth of field you’ll experience are the aperture size inside the lens as well as the distance you have your camera from the subject you’re photographing. If you’re like me, you notice a stark difference between the depth of fields when having your camera as close as possible to your subject and having it further away. If you need a deeper depth of field, you can either close down (shrink) your lens’s aperture or you can move your camera away from the subject. So this is definitely something you need to consider when photographing. The reason I call it a “limitation” is because each lens handles these things in its own way. One lens might give you a sharp area that’s much deeper than another, or vice-versa. You need to know what each lens you use is capable of before using it. If you need a deep depth of field and your current lens isn’t able to give you that, you’ll need to change lenses.
Minimum Focus Distance
The second limitation we need to concern ourselves with is called minimum focus distance. Focus distance is the distance between the lens and the subject you’re shooting. I’m sure you’ve, at one time or another, tried to focus on something that was simply too close to your camera. No matter what you did, your camera couldn’t and wouldn’t focus on the subject. As you were trying to focus, you probably didn’t realize that you were up against one of your lens’s limitations, but you were. Certain lenses can only focus on something when they are at least a specific distance away from it. Beyond that distance is fine (within reason), but any closer to it, you’ll need to switch out your lens again.
If you’re into macro photography, you have most likely already discovered this limitation of your lenses. That’s usually what brings people to macro lenses; lenses that can be physically moved a much closer distance to a subject than their non-macro counterparts can. Another remedy to a focus distance that’s not close enough is to add a magnifying filter to the end of the lens in question. Magnifying filters have the capability of bringing the end of a lens mere inches from a subject while still maintaining focus. They’re incredible and very inexpensive little devices.
How can you test out what your lens is capable of? Well that’s easy. To start off, attach your camera to a tripod that’s next to a table. Place a small object on the table and then focus on the object, setting your camera to the closest possible focusing distance and making sure your lens is all the way zoomed out. Then, bring the object as close as you can to your camera, until it’s just out of focus. This is the minimum focus distance that you’re up against. If it’s too far away, you’ll need to look into other lenses that can bring you closer.
To test out depth of field, keep your camera set up the same as I just described above. Then, set your aperture to the largest and the smallest sizes. Twist and turn the object so you can get an idea of how deep or shallow the depth of field is at a certain distance. Then, change the distance and repeat. This will give you a feel of what your camera lens can do.
I know none of what I just wrote is hard data that you can run with, but more soft ideas that I’m hopeful will give you a better feel for the photography equipment you choose to use out there in the world. If you have any questions or would like to add anything to this conversation, please do so below. Thanks!
Leave a Reply