Your The Camera’s Aperture Affects your Focus

Single Exposure using my focus technique

We’re focusing on focusing this month. How do I focus my photos is one of the most asked questions of me by other photographers. It’s a great question, and one that one would think would be pretty basic and simple. It’s usually the last skill that a beginning photographer considers when starting out but seems to be the toughest to master. I mean it seems that it would be pretty basic, what with the sophistication of the Auto Focus features in modern digital cameras, but once one takes a few photos and is let down by the Auto Focus Mode it’s easy to see why in many cases, especially landscape and portraiture, you will want to manually focus your photo.

There are several things that will affect the focus or clarity of our photos including a completely out of focus image, one where the focus is so far off that nothing is clear or in focus. That issue is obvious, of course, so we won’t discuss this in depth. We will assume that we are focusing but want to refine the clarity and focus of the shot. I’m going to try to proceed without citing mathematics or terms and theories such as Hyperfocal Distance, Circle of Confusion etc. The purpose of this article is to just understand the basics enough to understand how to overcome a common problem with focusing. Trust that this could become so lengthy that it would require another ten pages of the Mountain Times to cover it. Sometimes when someone is learning something new more information beyond what it takes to understand the concept causes confusion and discouragement. Once the basics are learned the understanding can be broadened in the future. I always tell people that if it requires mathematics to take photos I’d be a C-Minus photographer.

First let’s consider blurring caused by the camera moving or objects in the scene moving. This is not a focus issue but it can affect the clarity and areas of focus in the photo as you affect it. If movement is causing problems then your shutter speed is too slow. You’ll need to make sure that your shutter speed is sufficiently fast to freeze the movement. There are times where a slow shutter blur effect is desirable such as in creeks or waterfalls. This typically requires one to make an aperture adjustment to vary the shutter speed. Opened more to make it quicker and closed more to make it slower, but the depth of field will change with each aperture change.

So what’s this depth of field of which you speak you ask? The depth of field is how deep the area that will be in focus is from front to back. The wider your aperture the shallower or narrower your depth of field will be and then when you stop down, or close the aperture down, the depth of field becomes deeper. Remember that the larger the aperture opening the smaller the f/stop number and the smaller the aperture opening is the larger the f/stop number. Something to consider when you’re trying to maximize your focus is that the closer you are to the subject or foreground narrower your depth of field will be as well. If you’re having trouble getting everything in the scene within acceptable focus stand back a little. The same with portraiture. If you’re shooting with a wide aperture to blur the background intentionally you may have trouble getting the person’s whole face in focus. There’s not a lot worse in portrait photography than having the eyes in focus but the nose out of focus or vice-versa. Either stop down (close down the aperture) or stand back a little further or both. This works best with a zoom lens so you can recompose as you move away.

Hyperfocal Distance - I know. I said that I was going to try not to mention this but I think that curiosity will eventually lead a photographer to wonder. Simply and basically, the hyperfocal distance is the point where you will focus to allow everything from the foreground to the background to be in “acceptable focus”.

There’s a mystical mathematical formula to determine what that the hyperfocal distance is, but if you remember this advice you will get by like I have been for a long time without taking a calculator into the field with me. Here goes - I remember that I want to be in my lens’s sweet spot, which is the upper and lower limit of the aperture’s clearest settings. Each lens is different but the average lens is approximately f/8 to f/14. Compose your shot but try not to get too close to the foreground unless you don’t mind the background to be soft - Remember the closer to your foreground the less likely the object in the background will be in focus - And then focus to infinity on your lens focus ring and then focus back until the foreground just comes into focus. Then you will usually have the depth of field maximised and pushed out as far as possible while still maintaining a focused foreground. It’s easy to understand once you try it.

That may have been a long road to a short conclusion but just a basic understanding of how your aperture and depth of field affects focus allows you to take control of exactly how you will focus your photo. I hope that I made that as clear as possible.

Shallow Depth of Field Photo
Shallow Depth of Field Photo
Focus Stacked Photo
Focus Stacked Photo

Finding Fantastic Focus – Learning Hyperfocal Distance

Purple Mountain Lavender

Finding Fantastic Focus - Learning Hyperfocal Distance. It’s a beautiful morning as you gather your camera and gear to head out to take some beautiful landscape photos. You understand the settings that you’ll need to get the proper exposure, in this case with a fast enough shutter to overcome the blur caused by the breeze that’s tosses the flowers around in front of you. In the background is a view of Mount Hood on the horizon. You allow the camera to set the focus by using one of the automatic settings. Perhaps you focus on either the foreground or the background. Or, if you are using manual focus, you use the age old method learned from another photographer who learned it from his uncle who was a photographer who learned it from some guy named Ansel, you focus a third of the way into the scene and hope for the best.

Once you get home and download your photos you notice that in some of the photos the foreground is out of focus and the background is in perfect focus, while in others the foreground is sharp but the background is out of focus. Some may be fine from front to back but you don’t know why or how it happened.

In time, as you hone your photography skills, you will want to understand how to focus properly and consistently. It’s something that is hard to guess your way through or to accidentally discover. And once you figure out that there’s a method, understanding it seems daunting but it’s rather simple to understand if explained properly, so I’ll give it a try.

What you need to understand is something called hyperfocal distance. By focusing your camera at the hyperfocal distance your photo will be in acceptable focus from half that distance all the way to infinity. In other words if your hyperfocal distance is 20 feet everything will be in focus from 10 feet to infinity. In landscape photography especially it allows you to maximize your depth of field. Knowing this, in this example, we can then push our depth of field out by focusing to 30 feet, ten feet past your subject, maximizing the depth of field.

Determining the hyperfocal distance for a particular focal length and aperture combination can be tricky, but there are charts that you can put in your billfold or camera case. There are also apps for your smartphone that will help you calculate what it is for your particular camera, focal length and aperture setting. Because of this I won’t go into the complications of the mathematics involved in determining your hyperfocal distance. With one of the variables being “The Circle of Confusion”, it would be easier to explain a method that I use that you can start using right away to maximize your depth of field resulting in a more accurate and consistent focus in your photos.

Start by switching your lens to Manual. Turn off any kind of vibration reduction if you’re using a tripod, leave it active if you’re hand holding. Make sure to stop down, aiming for the lens “sweet spot”, an aperture setting of roughly f/8 - f/11. The sweet spot is the range of sharpest aperture settings of your lens. It’s typically two full stops from your widest aperture depending on the lens. Just make sure to stop down to increase your depth of field.

Turn on your Live View screen and increase its magnification and scroll the view to the closest spot that you want to be in focus in the scene. Observe that area as you turn your lens focus ring to infinity, which will slightly blur your foreground, and then focus back from infinity slowly until your foreground object just comes into sharp focus then stop. Once you do this you’ve moved your depth of field out as far as it can go while maintaining focus at your foreground object. Using this method you don’t need to know distances to set your focus.

I should mention that there are times when hyperfocal distance is not desired or necessary. Many forms of photography rely on a shallow depth of field such as portraiture or macro photography. In that case, none of this is necessary as having areas that lack focus is desired to direct the viewer's attention to the subject which is in focus.

Also modern digital photography and computerized post processing allows a photographer to take multiple shots of a scene, focusing from front to back, and then combine them to create a focus that is sharp throughout the image. This method is called Focus Stacking, but in most cases it’s unnecessary if you use the methods described in this article.

As in most cases when an instructor explains something, they will always seem to take the long way. I know that I gave you the shortcut at the end of a lengthy description, but in any skill it’s more than doing, it’s also about understanding. The more that we understand what we are doing, the more we’re able to perfect how we do it. I hope that this rudimentary explanation of hyperfocal distance helps you to take your photos one step closer to perfection.

s2Member®