Comparing Olympus 4/3lenses to FX "Full Frame" offerings

Started Jan 25, 2014 | Discussions thread
bobn2 Forum Pro • Posts: 60,233
Re: The sad thing is both sides are right

JiminDenver wrote:

Which is often the case with equivalency discussions because in a sense we are comparing apples to oranges.

Does a full frame lens deliver more light to the sensor box than a 4/3s lens....YES

Let's get this straight. A FF lens delivers more light to a FF sensor than a FT lens of the same f-number does to a FT sensor.

Does that extra light amount to a hill of beans on a 4/3s sensor...NO

More light is more light. More light is more photons is less noise.

Why? Because it is not light from the part of a full frame scene that a 4/3s lens CAN see. It is the light that would deliver the REST OF THE SCENE to a full frame sensor. That's why all that extra light doesn't change the shutter speed even if you use a full frame lens on a 4/3s sensor.

That's not the situation that we are talking about. The thread is all about FF (in this case Nikon) equivalents to FT (in the case Olympus) lenses.

Let's take for instance one of the comparisons that Dave makes, the Olympus 35-100/2 with the Nikon 70-200/2.8. Dave says the Nikon is deficient because it is the same size and not f/2. I say that the Nikon is 'faster' than the Olympus, so if it's the same size and cheaper, then it's relatively a bargain.

So, the question is, what set's the shutter speed? My argument is that it is the lowest image quality that you can bear. Why? Because if you aren't getting as fast a shutter speed as you want, and you think (knowing your camera) that you have IQ to spare, you'll go up a stop's ISO to get the shutter speed that you want.

So, with the same shutter speed the Olympus at f/2 is putting the same amount of light on the sensor as the Nikon at f/4, and it is the amount of light that determines the noise and thus IQ. So, if Nikon and Olympus and their sensor manufacturers have done an equally good job, the photos taken at f/2 (FT) and f/4 (FF) will have the same image quality, and thus the same shutter speed will be acceptable - so the lenses are equally fast. But the Nikon lens can open out one stop more, to f/2.8, so for the same quality result you can get one stop faster shutter speed. the lens is faster.

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