How much better is f/1.8 or f/1.4 than f/3.2 for low-light shooting?

Asked 9/18/2012

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I use a Fujifilm FinePix S2980, whose widest aperture is f/3.2. In dim light, without flash, image quality is not very satisfying. Friends suggested moving to a camera with a larger sensor and a faster lens such as f/1.8 or f/1.4.

How much practical difference does a lens at f/1.8 or f/1.4 make compared with f/3.2 if shutter speed stays the same? Also, how much does sensor size matter for low-light performance compared with aperture alone?

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

Photography Stack Exchange contributor

13y ago

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From 3.2 to 1.8 is a little over 3 times the amount of light - yeah, it makes a difference. If you still want something that is a pocketable camera, but great quality look at the Sony RX100 (review here).

The Fuji you have has a really small sensor, which is going to limit low-light ISO performance. The RX100 has a sensor 4 times larger than your Fuji. Not only is the higher ISO performance of the RX100 far better than your Fuji, the lens is f/1.8 - so you'll be increasing the ability to take low light images in 2 ways.

Originally by user11295. Source · Licensed CC BY-SA 4.0

user11295

13y ago

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Yes—going from f/3.2 to f/1.8 is a big improvement in low light. Aperture works in stops: each stop lets in 2× as much light. f/3.2 to f/2.2 is about one stop, and f/2.2 to f/1.6 is another, so f/1.8 is a little over 1.5 stops faster than f/3.2—roughly 3× more light. f/1.4 is about another 2/3 stop faster than f/1.8, and about 5× more light than f/3.2.

That means at the same shutter speed you can use a much lower ISO, or at the same ISO you can use a faster shutter speed. Both help in dim light.

Sensor size matters too. Your Fuji has a small sensor, which generally produces more noise at higher ISO settings than cameras with larger sensors. So a larger-sensor camera plus a fast lens improves low-light results in two ways: better high-ISO image quality and more light from the lens.

So yes, a camera with a larger sensor and an f/1.8 or f/1.4 lens can perform considerably better than an f/3.2 small-sensor compact in low light.

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13y ago

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