How can I get a strongly blurred background when my subject is far away?

Question

I’m new to DSLR photography and use a Canon 1100D with the 18-55mm kit lens. I want a strong blurred-background look even when the subject is relatively far away (for example around 10m), not just in close-up shots. Do I need a different lens, and what settings or shooting setup help maximize background blur?

canon-eos depth-of-field lenses bokeh beginner

Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0

Photography Stack Exchange contributor

8y ago

user75526 · Accepted Answer

Gear Selection

What lens to use depends on what effect you want to achieve and how much post-processing you intend to do. The 18-55mm/F3.5-5.6 kit lens is a good general-purpose lens. It is fully capable of producing background blur when appropriate camera-subject-background distances, focal lengths, and apertures are selected.

Since you are relatively new to photography, it may be more beneficial for you to maximize your ability to use your current equipment than to purchase new gear. Try using longer focal lengths with open apertures.

If you feel the 18-55mm range is too limiting, the 18-135mm/F3.5-5.6 IS USM has reasonable quality, performs well, and is fairly inexpensive.

Bokeh on a budget: kit lens demo.

Amount of Blur

To maximize the amount of blur, modify the following parameters:

Focal Length: Longer (100mm > 50mm).
Aperture Size: Larger, faster (F1 > F22).
Distance Ratio: Subject much closer to camera than to background.

You can determine what focal length (f) and aperture combinations (N) will produce more blur by comparing f/N. For example, using an 18-55mm F3.5-5.6 kit lens. If the subject is 10m away, you want the background to be far, 100m away. If you take a picture zoomed in to 55mm at F5.6, the background will be blurrier than if you take the picture zoomed out to 18mm at F3.5. (55/5.6 = 9.8; 18/3.5 = 5.1)

Does amount of background blur change with focal length given equal framing?

Since you already have an APS-C sensor, chasing sensor size would be counterproductive. The effect that sensor size has on background blur comes from modifying the above parameters to obtain the same field of view. When distance, focal length, and aperture are kept constant, the crop sensor images a portion of the same scene that the full-frame sensor would have. The amount of blur, relative to frame size is magnified (1.5x for APS-C). Relative to subject size, the amount of blur is the same.

Quality of Blur

The quality of blur is known as Bokeh. It depends on characteristics of the lens, such as the aperture and number/types of elements. The crop factor can multiplied by the aperture to roughly compare the amount of blur that can be expected in lenses designed for different sensor sizes.

Shaped Bokeh – Why is the bokeh shaped like the aperture?
Swirly Bokeh – What swirly bokeh technique is this and how can I achieve it?
Bubble Bokeh – Besides mirror lenses, what can cause ring-shaped bokeh?
Donut Bokeh – What's so bad about a mirror lens?