Amazing lens, incredible sharpness

c_henry wrote:

Great Bustard wrote:

c_henry wrote:

Great Bustard wrote:

So it's f1.8 no matter what the sensor size.

It's also 75mm no matter what the sensor size.

So the 75mm is the equivalent of a 150mm f1.8 on FF, except for DoF where you get more.

No. 150mm f/1.8 will also project 4x as much (2 stops more) light on the sensor for a given shutter speed, resulting in half (one stop less) then noise for equally efficient sensors.

Actually, it's yes. We've agreed f1.8 is f1.8 whatever the sensor size.

Not "f1.8" but "f/1.8", where "it" that "we've agreed" upon means the diameter of the aperture (entrance pupil), and the "f" in "f/1.8" means "focal length": 75mm / 1.8 = 150mm / 3.6 = 42mm.

No, we agreed that if the light meter said f1.8 it didn't matter what the sensor size was we'd set it to f1.8. Are you now saying that's not the case?

The light meter will say f/1.8 for a given ISO (assuming your light meter takes the ISO setting into account), regardless of the sensor size or focal length.  However, there is no reason to shoot the same ISO on different formats.  That is, if your light meter reads f/1.8 for ISO 100, it will read f/3.6 for ISO 400, and the *effect* of f/3.6 on FF, in terms of DOF and the amount of light falling on the sensor, is the same as the *effect* of f/1.8 on mFT.

If you want to go off talking about noise then, well, whatever floats your boat, but that's not what I was asking.

Aside from DOF and noise, why would anyone care about the aperture? And if f/3.6 on FF has the same DOF as f/1.8 on mFT for a given perspective and framing, and f/3.6 on FF puts the same total amount of light on the sensor as f/1.8 on mFT for the same shutter speed, resulting in the same noise for equally efficient sensors, well...

That's good to know. Appreciate the help.

Glad to help! So now you understand that 150mm f/1.8 on FF looks rather different than 75mm f/1.8 on mFT, whereas 150mm f/3.6 on FF looks very similar to 75mm f/1.8 on mFT (for a given shutter speed and sensor efficiency).

Again, not really relevant to my question, but appreciate you taking the time to miss the point.

So, your question has nothing to do with the visual properties of the photo, but rather numbers used out of context? Apologies! I did indeed miss that "point".

No my question was simple, *you've* somehow made it about numbers out of context, light falling on sensors, efficiency, noise etc. I for the life of me can't understand why you're trying to make it so difficult.

Perhaps you read where I asked, "Aside from DOF and noise, why would anyone care about the aperture?"  Well?