Understanding Depth of Field for Beginners

A Post By: Bruce Wunderlich

You may have heard the term depth of field (DoF), but if you are new to photography you may not yet be taking advantage of how DoF can enhance your photos. A basic definition of depth of field is: the zone of acceptable sharpness within a photo that will appear in focus. In every picture there is a certain area of your image in front of, and behind the subject that will appear in focus.

This zone will vary from photo to photo. Some images may have very small zones of focus which is called shallow depth of field. Others may have a very large zone of focus which is called deepdepth of field. Three main factors that will affect how you control thedepth of field of your images are: aperture (f-stop), distance from the subject to the camera, and focal length of the lens on your camera. Here are some explanations and answers to other common questions concerningdepth of field.

How does aperture control depth of field?

Aperture refers to the access given to light from the lens to the camera sensors. Thesize of your aperture (the diameter of the hole through which light enters the camera) controls the amount of light entering your lens. Using the aperture (f-stop) of your lens is the simplest way to control your depth of field as you set up your shot.

Large aperture = Small f-number = Shallow (small) depth of field
Small aperture = Larger f-number = Deeper (larger) depth of field

It may be easier to remember this simple concept: The lower your f-number, the smaller your depth of field. Likewise, the higher your f-number, the larger your depth of field. For example, using a setting of f/2.8 will produce a very shallow depth of field while f/11 will produce a deeper DoF.

The image on the left was captured at 250th of a second at f/5.0 which resulted in a very shallow depth of field.  Because of this the background is out of focus allowing the subject to stand out. The image on the right was captured at 1/5th of a second at f/32 which created a deep depth of field and a sharper background.

How does distance control depth of field?

The closer your subject is to the camera, the shallower your depth of field becomes. Therefore, moving further away from your subject will deepen your depth of field.

How does the focal length of a lens control depth of field?

Focal Length refers to the capability of a lens to magnify the image of a distant subject. This can get complicated, but the simple answer is that the longer you set your focal length the shallower the depth of field. Example: Your subject is 10 meters (33 feet) away, using a focal length of 50mm at f/4; your depth of field range would be from 7.5 -14.7 meters (24.6-48 feet) for a total DOF of 7.2 meters (23.6 feet). If you zoom into 100mm from the same spot, the depth of field changes to 9.2-10.9m (30.1-35.8′) for a total of 1.7m (5.7′) of depth of field. But if you move to 20m (66′) away from your subject using the 100mm lens, your depth of field is almost the same as it would be at 10 meters using a 50mm lens.

This image of a swan hiding in the tall foliage was captured from about 5m (16′)  with a 300mm focal length lens. This combination of focal length and distance created a depth of field of approximately 5cm (2″).

What if I just have a point and shoot camera, or don’t know how to change those settings?

Even with a point and shoot camera, there are ways to control your depth of field. In the Scene Modes menu, look for a symbol of a human head, which is the setting for portraits. This will give you a narrow depth of field. In the same menu there is also a mountain symbol, which is a setting for landscapes, which will give you a deeper depth of field.

If you are a beginner with a DSLR there are some simple ways you can control depth of field and still use and automatic shooting mode. By choosing Aperture Priority modeyou can set your aperture to get the depth of field that you want, and the camera will automatically set the shutter speed.

Can I set the depth of field exactly for each situation?

Yes, but because changing your aperture affects your shutter speed, the result may not meet the needs of your image. For instance, if you are trying to increase your depth of field by reducing aperture size you will also need to increase (slow down) your shutter speed which could make your image blurry. Understanding how all these settings work together can increase your control over depth of field.

Is depth of field equally distributed in front and back of my focus point?

No, it’s usually about one third in front and two thirds behind your focal point, but as your focal length increases it becomes more equal.

How will understanding depth of field improve my images?

Managing depth of field is one of the most important tools at your disposal, because having tack sharp images is one of the most important factors to getting that great shot. Knowing how to make the parts of your image you want sharp and the parts you want to be out of focus, is a great artistic tool to create great images.

Getting the right depth of field for your shot can make all the difference.

When should I use a shallow depth of field?

Using a shallow depth of field is a good way to make your subject stand out from its background and is great for portrait photography. Shallow DoF can also be useful inwildlife photography, where you want the subject to stand out from its surroundings. This is also useful because many wildlife photo opportunities are low light situations, and increasing your aperture size will give you more light. Shallow depth of field is also effective for sports photography where many times you want to separate the athlete from the background to bring attention to them. The result of this should also help give you a fast enough shutter speed to freeze the action.

This image captured at 300mm focal length and f/5.6 produced a very shallow depth of field. Because of this, it is important to set your focal point on the subject’s eye. Notice how the bird pops out from the background.

When should I use deeper depth of field?

In landscape photography it is important to get as much of your scene in focus as possible. By using a wide angle lens and a small aperture you will be able maximize your depth of field to get your scene in focus.

This landscape was captured with a 50mm focal length at f/16. The focus point was set at 8 meters, which made everything from 4 meters to infinity in focus.

How can you determine depth of field?

There are several on-line sites that will provide depth of field charts for your camera and lenses. Also, there are a number of apps available for smart phone users that can calculate it for you while you’re in the field. Most cameras have a DoF preview button which will give you a preview as you look through the eye piece. (This is probably the easiest and most under-utilized method.) Using this button may cause your image to appear darker as you view it through the eye piece, but not to worry. Your image will be properly exposed as long as you have the correct exposure settings.

Can depth of field be adjusted to get everything in focus?

Yes, using what is called the hyperfocal distance. When you are focused at the hyperfocal distance, your depth of field will extend from half the distance to your focal point to infinity. Use a DOF calculator to find your hyperfocal distance. If you don’t have a DoF calculator, a good rule of thumb is to focus a third of the way into the scene. Using an aperture of about f/11 or higher with a wide angle lens will maximize your depth of field.

What about depth of field in macro photography?

Because most macro images are produced in low light and with a longer focal length, the depth of field is often very shallow. Adjust your lens to the smallest aperture that the light will allow. It may also be necessary to increase your ISO to allow you to properly expose the image and to maximize your depth of field. Still, in many macro images your DoF may be very minute. With this very narrow focus it becomes necessary to use a tripod, because even the slightest movement of the camera will move your macro subject outside your depth of field.

This 120 mm macro even at f/8 still has a very shallow depth of field.

What is bokeh?

Bokeh (boh-ke) comes from the Japanese word meaning blur. This effect is produced by the out-of-focus areas in your image that are beyond the depth of field. Bokeh commonly refers to the pleasing circle shapes caused by the shape of the lens aperture. Usually created when shooting with your aperture wide open, such as f/2.8, bokeh can also be created with smaller apertures if the background is distant enough.

Bokeh in this image was created by the distance of the subject to the background, which fell well beyond the depth of field.

To summarize controlling depth of field:

Increase depth of field

• Narrow your aperture (larger f-number)
• Move farther from the subject
• Shorten focal length

Decrease depth of field

• Widen your aperture (smaller f-number)
• Move closer to the subject
• Lengthen your focal length

Take control of your depth of field. Understanding how these adjustments control your it will greatly improve your photography. What questions do you have about depth of field? Please share your photos and comments.

Flash photography basics: every common question answered

jmeyer | Photography Tips | 05/02/2013 16:00pm

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TTL? Rear Curtain Sync? Guide Number? All the flash photography basics you need to know are right here, as we answer all the common questions to all the common problems photographers have about using flash, as well as share some of our best flash photography tips.

Image by Rolfo Rolf Brenner

Sometimes my SLR’s flash pops up and sometimes it doesn’t. Why?
When you’re in fully automatic ‘green square’ mode, the small flash built into the majority of DSLRs will activate automatically when light levels are low.

However, in the advanced P, A, S, M modes you can pop the flash up manually whenever you like by pressing the button marked with a flash symbol.

This is useful for adding a little extra illumination, such as a brightening up an outdoor portrait. Bear in mind that you’ll have to stick with a shutter speed that isn’t faster than the maximum flash sync speed.

Maximum flash sync speed?
Despite the light from a flash being emitted very rapidly, you can’t freely choose the fastest shutter speeds your camera offers when you’re using a flash.

This is due to the way in which the two shutter ‘curtains’ inside a typical SLR work. These open and close to allow the imaging sensor to be exposed to light.

When you press the shutter-release button, the mirror flips out of the way and the first curtain opens to allow light to hit the sensor. This is followed by the second curtain, which closes across the sensor to end the exposure.

At very fast shutter speeds, the second curtain starts closing before the first curtain has finished opening – so the image is recorded through a rapidly moving gap rather than all in one go.

Because the burst of light from a flash is so brief, it would only be recorded on the narrow part of the sensor that’s clear of the curtains when the flash fires, and the exposure would be uneven across the picture.

The flash sync speed is the fastest shutter speed at which the shutter is fully open, ensuring that the exposure is even across the frame.

Historically, this has been 1/60 sec, but many current DSLRs take advantage of the fact that flash duration is extremely short and offer high sync speeds of 1/250 or 1/500 sec.

I’ve heard that I should use the built-in flash as a last resort. Is this true?
Yes and no. The trouble is that the small size of the flash unit and its position on the camera means that the light it produces is direct and harsh.

Other limitations include the risk of red-eye, due to the close proximity of the flash to the lens, and the fact that you need to be fairly close to the subject, as the Guide Number of a pop-up flash is comparatively low.

What’s the Guide Number?
The Guide Number (GN) is a measure of the maximum power of a built-in flash unit or a flashgun – the bigger the number, the more powerful it is.

The Guide Number = distance x f/stop at ISO100. We know – it all seems to be getting complicated again! Knowing the Guide Number is useful if you’re shooting with manual flash, because it helps you calculate the aperture you need to set, or the distance the flash needs to be from the subject in order to get a good exposure.

However, these days, exposure can be taken care of automatically by TTL flash metering.

TTL flash metering? Things really are getting complicated…
TTL – or Through the Lens – flash metering actually makes things easy! The latest ‘intelligent’ versions, such as iTTL on Nikon and E-TTL on Canon, fire one or more brief flash bursts or ‘pre flashes’ are fired before the main flash.

The camera registers the amount of light returning through the lens (hence the name), and then works out the right amount of light to pump out for the main flash exposure.

However, just like normal exposure metering it can be fooled by dark, light or reflective backgrounds, 
and you may need to adjust the flash exposure to compensate.

How do I alter the TTL flash exposure?
The camera will automatically control the flash exposure for consistent results in TTL mode, no matter what aperture or ISO or shutter speed (as long as it’s slower than the flash sync speed) you choose.

That is, as long as the flash has enough power to reach the subject. If you’re too far away, your flash-lit subject will appear too dark, and you’ll need to move the flash closer, choose a wider aperture and/or increase the ISO setting.

If you want to fine-tune the flash exposure, the easiest way is to use flash Exposure Compensation (FEC). Look for the button marked with a zig-zag flash symbol and ‘+/-’. See the previous page for alternative ways to control the brightness of your flash.

Controlling flash exposure

Three quick and easy ways to ensure perfect results by adjusting the exposures of your flash pictures

1 Flash Exposure Compensation
This allows you to adjust the output from the flash, making the subject 
lit by flash either brighter (positive compensation) or darker (negative compensation). Flash Exposure Compensation can be applied on the camera, or on a dedicated flashgun attached to the camera.

2 Flash Exposure Lock
Some cameras (like Canon’s 7D) have an FEL (Flash Exposure Lock) or FV (Flash Value Lock) button. Ensure the main subject is in the middle of the picture, then press the Flash Lock button. The flash will fire without an exposure being made, but the exposure setting will now be locked in. Simply reframe and take the picture.

3 Flash Exposure Bracketing
If timing isn’t crucial, try taking a series of exposures at a range of Flash Exposure Compensation settings to improve the chances of getting the perfect ratio of flash to ambient light. Advanced flashguns and cameras offer Automatic Flash Exposure Bracketing.

How to get flash in sync

Slow Sync is useful when shooting in low light, allowing a long exposure to be combined with a brief burst of flash. Rear Curtain Sync allows you to fire the flash at the end of an exposure, rather than at the start.

Normal flash
Automatic camera modes default to a flash sync speed of 1/60 sec, which is too short to allow much ambient light in at night.

Slow Sync flash
By using slow-sync flash, a longer exposure can be used to allow ambient light to register on the sensor as well. Use a tripod too.

Front Curtain Sync
In a long exposure, subject movement recorded after the flash fires will appear as a trail in front – they’ll seem to be travelling backwards!

Rear Curtain Sync
The results look more natural, but it’s harder to predict where the subject will be when the flash fires at the end of the exposure.

Flash photography cheat sheet – what you need from a flashgun

Now that we’ve broken down some of the misconceptions about flash photography, let’s take a look at what you need from a dedicated flashgun.

In our flash photography cheat sheet below we’ve illustrated some of the most useful features for photographers and what you can do with them.

Simply click on the infographic to view the larger version of this cheat sheet, or drag and drop to your desktop.

How to photograph a reflection in an eye

jmeyer | Photography Tips | Portraits | 07/11/2014 00:01am

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Discover how to photograph a reflection in an eye ball with this simple step-by-step tutorial!

This is a quick and easy photo project that only takes minutes to shoot, but produces amazing results. If you’ve ever taken macro shots of eyes before you’ll know how much fun it is, but you can take things a step further by including a reflection of a local landmark.

Not only will this result in a more visually striking image, but if you choose a landmark that’s got some personal significance to your subject, you’ll end up with something that is also much more personal and intimate, not to mention more interesting.

The trick is to choose a landmark with a very distinctive shape, and ideally to set it against a brighter sky, as this will make for clearer, more recognisable reflections.

If the sky is blue, so much the better. Here we chose to capture a reflection of Beckford’s Towernear Bath.

SEE MORE: How to focus a portrait – get pin-sharp eyes in 3 easy steps

How to set up your camera to photograph a reflection in an eye

01 Get up close
A macro lens is essential for this project. We used Nikon’s 105mm f/2.8 Micro, which gives one-to-one magnification. This means we could focus close enough to fill the frame with an object the size of our camera’s sensor, which is roughly the size of someone’s eye!

 SEE MORE: Fashion and beauty portrait photos: 3 tips for instant success

02 Set your aperture
Next, set your camera to aperture-priority mode and decide on an aperture; something like f/13 should do the trick. Just ensure this gives you a shutter speed fast enough to shoot handheld – if it doesn’t, raise the ISO to 200 or 400 to enable a faster shutter speed.

Autofocus point options: what subjects should each be used with?

jmeyer | Photography Tips | 17/11/2013 00:01am

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Your DSLR offers a variety of autofocus points, which can be used in different ways. But which focus points should you use, and when?

Our quick cheat sheet below explains your different focus point options and when they are most opportune.

We used a Nikon camera for the purposes of this tutorial, but the same principle applies for other brands even though other cameras will have AF systems with a different number of AF points.

SEE MORE: How to take control of autofocus to get the shots you want

Click the infographic to see the larger version, or drag and drop to your desktop to save.

Auto Area AF: best for snapshots
In Auto Area AF mode, you’re leaving it to the camera to decide what to focus on. It will check all its focus points and choose either the object nearest to the camera or, on later Nikons, any faces the camera detects in the scene. This mode is a good fallback for novices, but the camera will sometimes focus on the wrong thing.

Single-point AF (51 points): best for precision
In single-point AF mode, you pick the focus point yourself. This gives the most control, provided you’ve got time to select the correct point (or you could use the ‘focus lock’ method, see overleaf). Single-point AF is ideal for relatively static shots where you’ve got a little more time to get set up.

Single-point AF (11 points): best for everyday
If you have a camera with a large number of AF points, you have a sophisticated autofocus system at your disposal, but it can take too long to select between them. On Nikons with 39-point or 51-point AF systems, you can restrict the number of AF points to 11 for quick manual focus point selection.

Dynamic area AF (nine points): best for action
Dynamic area AF mode is designed to make the autofocus system more responsive and more reliable for moving subjects. You still select the focus point manually, but the surrounding AF points act as backups to keep the subject in focus if it moves briefly away from your chosen AF point.

Dynamic area AF (21 points): best for erratic action
You can include more AF points in Dynamic area AF mode. Nine points offers greatest accuracy if you can follow your subject in the viewfinder, but for subjects which move more erratically, the 21-point option may be more effective. Try out the options to see which best suits your subjects.

Dynamic area AF (51 points): best for subject tracking
You can use all the camera’s focus points in Dynamic area AF mode. Some models offer 3D tracking, which uses information from multiple AF points to predict your subject’s movement. This suits shots where you want to keep the camera framing the same while shooting a moving subject.