A reminder for some memebers as to what the F stop is all about.

Started Jan 26, 2014 | Discussions thread
DonSC Senior Member • Posts: 1,032
So what is your answer to this?

Great Bustard wrote:

Wow. Just wow. Everything you wrote is entirely incorrect, and I will prove it wrong with a single example that you can all do at home.

Let's take a photo of a scene with an E5 + 35-100 / 2 at 50mm f/2 1/200 ISO 3200 and 100mm f/2 1/200 ISO 3200 (note that we have used the same lens, same f-ratio, same shutter speed, same ISO, same sensor, and thus same sensor efficiency and pixel size).

We now crop the 50mm photo to the same framing as the 100mm photo and display both photos at the same size. Which photo is more noisy and why?

(Hint: while the sensors are the same size, the cropped photo uses only 1/4 the area of the sensor, and thus only 1/4 as much light makes up the cropped photo as the uncropped photo.)

We have a 300mm f/2.8 on a Canon 1Dx and a 300mm f/2.8 on a Olympus E-M1. Same ISO. Both cameras are 16 MP. Now crop the shot from the 1Dx to fit the FOV of the E-M1. What image has less noise? What image has less detail?

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