f/1.8 on m4/3, ASP-C, FF; are they the same?

Started Nov 1, 2010 | Discussions thread
sacundim Senior Member • Posts: 1,111
You can definitely take night photos

Peiasdf wrote:

Hi everyone, I do not get why some people said the 20 f/1.7 lens on m4/3 equals to 40 f3.5 on FF so here is the thread asking about it.

If a picture is taken at 20mm, f/1/7, ISO 200, 1/100s on m4/3, will it come out similar (beside DOF) to a 40mm f/1.7, ISO 200, 1/100s picture on a FF?


Some people mentioned m4/3 lens only lets in a quarter the light of a FF lens. So does it mean the camera have to reduce speed by a factor of four to get the correct exposure. It does not make sense to me, as P&S cameras do not require 15 times the exposure.

You're missing the role of sensor size in this. The FF f/1.7 lens has to let 4x as much light in as the 4/3 f/1.7 lens because it has to illuminate a sensor that has 4x the area. Saying that the FF lens lets 4x as much light in at the same aperture is just another way of stating the fact that the FF sensor's size gives it an advantage over the 4/3 sensor.

I am thinking about going from D90 + 35 f/1.8 -> GH2 + 20 f/1.7 for a night out with friends camera but the exposure thing is throwing me off. Maybe I need a Nokton 25 f/0.95?

Depends on how bright the night is and the illumination where you take the photos, but you can definitely take night photos in brightly illuminated streets with the GH2 and the 20mm f/1.7. Here's some I took last night with my G1 and the 20/1.7 after the Giants won the World Series (ISO 1600, RAW, processed in Lightroom, noise reduction slider pushed to 25):

The blurriness comes mostly from the fact that I was taking photos of moving cars, and panning to follow them; I have photos of still objects that are sharp, but they're just not as good :-P.

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