Corner sharpness: Four Thirds vs 35mm (bandwidth warning)

Started Oct 27, 2007 | Discussions thread
YellowBullet Senior Member • Posts: 1,374
Re: Corner sharpness: Four Thirds vs 35mm (bandwidth warning)

Andy Hewitt wrote:

Hi Amin,

While I wouldn't want to criticise your efforts, I have to say that
this test was rather useless, being perfectly honest.

It's infinitely more useful than MTF charts at same f-stops.

You compared a Pro level SLR,

Since when is the 5D a Pro level SLR? It's a 20D with a FF sensor and slower FPS.

using a prime lens,

Valid point. A zoom such as Tamron 28-75 or Canon 28-70 would be more appropriate.

that had the
aperture stopped down,

Aperture was stopped down to get the same DOF. Higher ISO was used to get the same shutter speed. Absolutely valid comparison.

with a prosumer level camera using a kit lens,
that was used almost wide open.

It's not Canon's fault that the Oly lens doesn't open to f/1.4.

To make this a valid test, you need to use cameras from the same
level in the market, and use identical lenses, and identical settings.

So we should put a 50mm Oly on an E3 and a 50mm Canon on a 5D, stop them both down to f/8 and test them like that?

What IN THE WORLD would such a test be useful for?

Different FOV, different DOF, different noise levels, completely different images.

I really cannot understand for the world of me why people have absolutely no problem comparing different focal lenghts on different formats (28mm on FF, 14mm on 4/3, to get the same FOV), but then they cry foul when someone compares different f-stops on different formats to get the same DOF.

Different system use different parameters to achieve the desired result. When you use a 50mm lens at f/8 and ISO 800 on FF, you would use a 25mm lens at f/4 and ISO 200 on 4/3 to get a similar picture. It's as simple as that.

Changing only one parameter (focal lenght) to fit the format but then ignoring everything else and keeping all the other parameters the same makes absolutely no sense whatsoever.

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