Will a 2x teleconverter on an 18-55mm kit lens improve portrait background blur?

Asked 7/8/2017

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I want stronger background blur for portraits with an 18-55mm f/3.5-5.6 lens. If I add a 2x teleconverter or a macro adapter, will that help separate the subject from the background? Does the effective f-stop become larger or smaller, and is this a good way to get more out-of-focus backgrounds?

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

Photography Stack Exchange contributor

9y ago

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No.. in fact you will get somewhat horrible results.

The lens you'll end up with is a 32-110mm f:7-f11 (ish) lens because not only does the focal length multiply by two, but you are also reducing the maximum aperture by two stops.

The depth of field of 55mm @ f5.6 is exactly the same as 110mm at f8, but the big problem is that at f8 maximum aperture your camera is likely to struggle with autofocus and the viewfinder will become pretty dim.

Not exactly sure what you are trying to achieve but if it's portraiture then on you crop sensor camera you could maybe buy a 50mm f1.8. That's going to be a whole new world of background blur for you.

Originally by user64503. Source · Licensed CC BY-SA 4.0

user64503

9y ago

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A 2x teleconverter is generally not a good solution for this. It doubles the focal length, but it also costs about 2 stops of light, so your 18-55mm f/3.5-5.6 effectively becomes roughly 36-110mm f/7-11. That means a dimmer viewfinder, more autofocus difficulty, and usually poorer image quality on a kit zoom. In practice, it won’t give you the kind of portrait background blur people usually want.

A macro adapter is for close-up work, not normal portrait distances, so it won’t help here either.

For the best blur with your current lens, use it at 55mm, set the widest aperture available, keep the subject well away from the background, and get relatively close to the subject. If you want a much stronger background blur effect, a fast prime such as a 50mm f/1.8 is the more useful upgrade.

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9y ago

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