Resolution test, between crop (18MP) and fullframe (12.8MP)

Started Mar 12, 2013 | Discussions thread
Great Bustard Forum Pro • Posts: 42,061
Re: true

Sovern wrote:

Great Bustard wrote:

Sovern wrote:

That wouldn't make any sense. Why would some lenses rate 8MP on a 12MP sensor and say 15MP on a 22MP sensor.....makes no sense especially if we're comparing a lens on a 5Dc to a 5Dmkii so pixel density is not the issue.

Put more pixels behind any lens, and the photo will resolve more detail (all else equal). Put a sharper lens in front of any sensor, and the photo will resolve more detail (all else equal).

In both cases, how much more detail depends on a great number of factors, not the least of which are motion blur, camera shake, diffraction, DOF, etc.

Not only is that not hard to understand, it should be intuitively obvious.

You're not comprehending or understanding my post and what I said.

Quite the opposite.  Read on:

If a lens can resolve a maximum of 8MP of detail. Why would it resolve more detail on a 22MP body over a 12MP body when they both exceed the limitations of the lens (both have more MP's than 8)?

Because the lens does not "resolve a maximum of 8 MP of detail".  Let's say R represents the total resolution, RL is the resolution of the lens, and RS is the resolution of the sensor.  Then:

1 / R² = 1 / RL² + 1 / RS²

is usually a good approximation for modern optical systems.

That mans that with the higher MP's sensor is is basically up scaling the image and is not truly creating 22MP photos with that lens.

Well, yeah, it is creating 22 MP photos, but not all 22 MP photos are equal.

Hope that makes my post easier to understand.

You're assuming, incorrectly, that the lens outresolves the sensor and/or vice-versa, and that's where you are going wrong.

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