Tag: focal distance

Tell Me More About Depth of Field

Get an overview of depth of field.

What Is Depth of Field

Depth of field is a range in front of your camera in which everything within that range is in focus and elements that are either in front of the range or behind it are out of focus. Here’s an example.

Suppose you have the camera set up to give you a depth of field of 100 feet. The depth of field range starts at 50 feet and will extend to 150 feet. All of the elements between 50 feet and 150 feet will be in focus. Elements closer than 50 feet will be out of focus as will elements farther away than 150 feet.

Depths of field can be shallow or deep. A shallow depth of field could be as small as a few inches. A deep depth of field could extend from one foot to infinity.

What Determines Depth of Field?

Depth of field is determined by three factors – the focal length of the lens, the distance of the object you are focusing on from the lens (the focal distance) and the aperture or f/stop.

Lens Focal Length

Lens focal lengths range from wide angle to telephoto. Wide angle lenses are praised for their deep depths of field. A lens with an effective[1] focal length of 16 mm can have a depth of field of 18 inches to infinity with ease.

In contrast, a 400 mm lens could have a depth of field of as little as 3.5 feet or less when focused on an object 100 feet away.

Portrait lenses are often in the range of 80 to 100 mm focal length. This is enough to have the subject in focus while the background is blurred. This is a much sought after effect for outdoor portraits.

Focal Distance

The distance of the object that is focused on from the lens also affects depth of field. If the object is close than, say 5 feet, the depth of field will be shallow. If it is farther from the lens, the depth of field will be deeper.

In macro photography, the object being focused on is sometimes mere inches from the lens. This can contribute to a very shallow depth of field, an affect that is often desirable in macro photography.

However, with such a shallow depth of field it is critical that the camera focuses on the intended object. With autofocus, you take your chances and will often lose. Therefore, manual focus and a tripod is important.

Hyperfocal Distance

But near-far compositions pose a different challenge. In this situation an extremely deep depth of field is required. And the focal distance is of critical importance. You need to focus on an object that is at the hyperfocal distance. Fortunately, it is easy to accurately determine the hyperfocal distance. Here’s the process.

    • Set up your shot on a tripod and get it composed exactly the way you want it.
    • Now look through your viewfinder or live view screen and identify the object closest to your lens. This will usually be an object on the bottom edge of the frame.
    • Measure the distance from the lens to the nearest object as accurately as you can. For example, the nearest object is 3.5 feet from the lens.
    • Multiply that distance by 2. That is the hyperfocal distance. In our example, the hyperfocal distance is 7 feet.
    • Locate an object that is the hyperfocal distance from the lens.
    • Focus on that object. Be sure to use manual focus so the camera doesn’t change it. It is best to use live view and magnify the object you are focusing on to get a tack sharp focus.

The key to determining hyperfocal distance is in understanding that it is twice the distance to the nearest object in your composition. That’s all there is to it.

A rule of thumb for focusing at the hyperfocal distance is to focus on an object 1/3rd of the way up from the bottom of the frame.  This can be a close approximation except in extreme conditions.

F/stop

The third factor in determining depth of field is aperture or f/stop. Wide open apertures have a shallow depth of field. They are often used to get a sharp foreground and blurred backgrounds,

Small apertures have a deeper depth of field. Smaller apertures are used in most landscape photographs.

How Do You Get the Depth of Field You Want?

Shallow Depth of Field

Getting a shallow depth of field is pretty straightforward.

    • Use a moderately long lens; e.g., 80 to 100 mm
    • Get close, 10 to 20 feet or even closer if you can
    • Shoot with a wide-open aperture

Deep Depth of Field

This is more complicated.

If you’re effective focal length is 60 mm or less and your aperture is f/8 or smaller, then anything from 25 feet and beyond will be in focus. But think of this as a guideline, not a rule. There can very well be exceptions.

But getting depth of field when the nearest object is closer than 25 feet or the effective focal length is more than 60 mm, then depth of field becomes tricky.

The safest approach is to use one of the many depth of fields apps that are available on smart phones. In this situation you know two of the three things needed to create the needed depth of field – you know the focal length of the lens and you know the focal distance (the hyperfocal distance). Feed these values into your app and it can tell you the f/stop you need.

If an app is not available, you can always ‘bracket’ the depth of field by shooting the scene at different f/stops beginning at, say, f/8 and advancing stop-by-stop to f/22. Later in the digital darkroom, you can select the image that is the sharpest.

[1] An Effective focal length is the focal length for a full frame sensor. For crop sensors, you need to multiply the actual focal length of the lens by the crop factor to get the effective focal length. For example, a crop sensor camera with a crop factor of 1.5 and a 16 mm lens would have an effective focal length of 24 mm (16 * 1.5).

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Mastering Night Photography – Focusing

Solve your focusing challenges in nighttime photography.

A lot of people are doing nighttime photography these days including yours truly. There are many good sources of information on nighttime photography. I’ve written a few blog posts myself (Exciting Nighttime Photography in 10 Easy Steps). Nighttime photography falls into two categories – star trails and night sky. In this post I want to elaborate on something I’ve discovered recently with regards to night sky photography.

double-arch-joshua-tree-140628Nighttime photography is pretty much like daytime photography. The biggest difference is you can’t see what you’re doing. Let’s run through a quick comparison of camera settings in daytime and nighttime photography.

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Mastering Sharpness – Fuzzy Photos

How many things can go wrong that can render an image fuzzy.

How many times have you returned from a shoot with some photographs you are really excited about only to find out they are out of focus.  That’s always very disappointing and often frustrating.  And it happens all too often to me.  At the Joshua Tree Gathering this past March someone asked the question, ”How many ways can a photograph be out of focus,” and that got me thinking.  This would be a fun article to write.

But let’s get something straight from the start.  Not all ‘out of focus’ photographs are out of focus.  They may not be sharp but that can come from two causes.  They can actually be out of focus or they can be blurry.  This may seem like a subtle distinction but it’s an important one.  So let’s take them one by one and explore their causes and solutions.

But before we do, I want to make another very important point.  A photograph that is out of focus or blurry is not always a bad thing.  Often times the artist does it intentionally because that is his or her artistic vision.  When it’s done intentionally to create an expressive photograph then it’s not only OK, it’s necessary.  It’s when it’s unintentional that we get frustrated and loose great moments.

But now, let’s get into the details.  We’ll talk about blurs first.

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Mastering Sharpness – Depth of Field

One of the Four Pillars of a successful landscape photograph is Appropriate Sharpness. This article explains how to get sharp images and illustrates how a useful app – Lens*Lab – can help.

A topic that receives a lot of attention in our workshops is focus.  It’s incredibly important, so important that I consider Appropriate Sharpness to be one of the four pillars of a successful landscape photograph.  (For more, read Making a Photograph – The Four Pillars.)  Most of the questions center around depth of field and hyperfocal distance.  In fact, this is so important that I give a class on Appropriate Sharpness during just about every workshop.  Let’s start the discussion with Depth of Field

Depth of Field

This is the range, if you will, of objects in the view of your camera that are in focus.  Objects in front of this range are out of focus as well as objects behind the range.  A deep depth of field would have the flowers just a few feet from you camera and the distant mounts miles away all in focus.  The depth of field would then extend from a couple of feet to infinity and for all practical purposes would be infinitely deep.  This is often referred to as a ‘near-far composition.’

death_valley_sunrise_2012_rrpm_rc0A shallow depth of field may be just a couple of inches deep with nearer and more distant objects out of focus.  This is referred to as ‘Selective Focus.’

sego_palm_130629__SM36636

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Making a Photograph – The Four Pillars

Explore the four things that make a great landscape photograph – Fantastic Light, Strong Composition, Appropriate Sharpness and Optimum Exposure.

I’ve been giving a lot of thought recently to what goes in to making a great landscape photograph. It turns out there are four things, four pillars if you will.  Four, that’s a good number.  There are the four legs of a table or the four wheels of a car.  And not to forget the four sacred directions of the Native Americans.

In landscape photography the four pillars are evenly divided between the aesthetics and the technical.  So what are they?  The two aesthetic pillars are Fantastic Light and Strong Composition.  No surprise there.  The two technical pillars are Appropriate Sharpness and Optimum Exposure.  No surprise there either.  If just one of those pillars is missing, well, the table collapses, the image suffers.

Let’s look at them one by one….

joshua_tree_spring_sunrise_2011
Joshua Tree Spring Sunrise (2011)
(click on the images to enlarge them)

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