Understanding the Depth of Field

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Understanding the Depth of Field

Depth of field is refer to the amount of element that are in focus or the portion in the scene that appears acceptably sharper in the image. The depth of field is focusing on one specific element in your field of view.In photography the depth of field comes into play when you want your subject to be in sharp focus while the rest of the image is blur in order to draw the viewer attention towards the subject. Depth of field is mainly required in portrait, wildlife and macro photography like as shown in downward images.

The shallow depth of field means your main subject is in sharp focus against the blurry background. Where you select a portion of the frame while composing what you want to be in focus and by setting your lens aperture to wide open.

The macro/wildlife photographer mostly used wide aperture lens for their works because they want their subject to be in sharp focus by  keeping the background blur as shown in downward photographs where I used wide aperture to get sharp focus on subject by keeping the background.

When I go out for taking photographs, the first question I ask to myself what kind of background would be the best to pop out my subject correctly. As i going out for macro photography I want my subject to be in sharp focus by keeping the background blur, so for this situation I use wide aperture by adjusting smaller f-number (like f-5 or f-4). At the wide aperture (low f-number) the opening of your lens is wide open creating a shallow depth of field. Great depth of field is also useful when you are photographing wildlife/macro. If your aperture is too wide like f-4 only your subject will be in sharp focus only

Four factors control depth of field

 

  • Lens Aperture

Photographing is all about painting with lights, you are creating a story in a split second. That is what photography is all about . in a technically your camera is measuring the light in the scene and you are telling it how much of that lights you want to use to create a properly exposed image. Shutter speed captures movement. ISO helps control how sensitive your camera is to the available light in a scene. Finally the aperture create depth of field. This is where the real story began. It is the aperture that you control what is in focus and what is out of focus(background). Aperture is the opening in your lens that lets light pass through to the sensor of the camera. Think of it as a pupil for your lens. It dilates to let more light in, and contracts to restrict light when it is bright. Aperture is probably the first thing most photographers think of when they want to adjust the depth of field.

Large apertures, which correlate to small f-stop numbers, produce a very shallow depth of field. The shallow depth of field is used in wildlife/macro photography. On the other hand, small apertures, or large f-stop numbers, produce images with a large depth of field. Large depth of field is used in landscape photography where we want most of scenes in the frame to be in focus.

In macro photography, the aperture choice is conditioned by subject distance and focal length choices.

On the one hand, you’ll need to get pretty close to the subject, depending on the focal length you use. On the other hand, you’ll be using a macro lens ( 150-200mm). Both settings will lead you to get a very shallow depth of field.

In portrait photography, your aperture choice will depend on the desired level of shallow depth of field, you want.

For a shallow depth of field effect, wide apertures like f/2.8 and f/4 are great. Using them will help you keep your subject sharp while blurring all background elements.

Let’s say you need more depth of field because you’d like include interesting background elements that are close to the subject. Here, an aperture of f/8 would be a fantastic choice.

Finally, if you want to go for a deep depth of field, use smaller apertures like f/11, f/16 or less.

Getting close to capture animals is very difficult. Wildlife photographers generally use telephoto lenses (300-600mm), whose depth of field is extremely shallow.

To increase depth of field and capture the whole animal in focus, you may be tempted to use small apertures (f/8, f/11). In practice, the truth is that the aperture choice will depend on whether the animal is in motion or staying still.

Small apertures might work when animals stay still, because you’ll be able to freeze them and maintain a correct exposure by slowing the shutter speed (increasing exposure time).

But when animals move, you need a fast shutter speed (exposure times under 1/1000s) to freeze most movements and avoid blur. As a consequence, you are forced to use the widest aperture possible in your lens if you want to get a correctly exposed photo.

Therefore, you need to find the right balance between aperture (depth of field) and shutter speed (ability to freeze movement).

One possible workaround is to push the ISO up. Depending on the camera you have, it’s a good idea to shoot with the ISO setting in auto mode. For example, shooting at 1/1000s, f/8 and ISO auto mode between 400 and 12800 will work perfectly well in many cases.

  • Focal length

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

Keeping all the settings equal (focus distance, aperture, sensor size, CoC), larger focal lengths produce a much shallower depth of field. For example, a 100mm lens focused at 20ft (6m) will have much less depth of field than a 24mm lens focused at 20ft (6m).

  • Distance from the subject

The distance between the camera and the subject greatly affect the depth of field of your photographs.

The shorter that distance, the smaller the depth of field. But you can’t get the entire subject in focus, even with a small aperture? This is because the closer you are to your subject, the shallower the DOF.

when you’re close to the subject, depth of field is rather evenly distributed around the focus point. But, as you move away from it, the percentage of depth of field in front of the focus point decreases while increases behind it.

  • The size of the film sensor in camera

The full frame cameras produce shallower depth of field than APS-C cameras at the same effective focal length and aperture. Shooting portraits using a full frame camera results in more pleasant images, since it gives you more control over 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.

 

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