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

Started Jan 25, 2014 | Discussions thread
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citizenlouie Contributing Member • Posts: 776
Take photos....

DoF equivalency has little to do with actual photography. When I got a new camera, I learn its differences and adopt the different shooting style.

If you must insist on knowing why (for example) a 75mm @ f/1.8 is the same across the platform, consider this: It's not the focal length, nor aperture that give a 75mm f/1.8 lens a greater DoF on a 4/3 per se. It's the fact on a 4/3 (or m4/3) camera, you simply have to stand twice as far to get the same field of view. Therefore the depth of field is lessened due to subject-to-focal-plane distance. This is further complicated by the fact 4/3 lenses are designed for a squarer format sensor. I have no idea how some of you guys can be so sure that a f/1.8 on a 4/3 sensor is exactly f/3.6 equivalent on a FF sensor, not to mention 4/3 sensor is squarish, so the angle of view calculation would be different so will be the lens design (and I have a feeling telecentric lens design will give a greater DoF, just a hunch, not proven though), so the DoF is a lot more complicated than simply double the number....  But does any of these calculations meaningful in actual photo taking?

If you want to compare apple to apple, go use a Nikon D800 on a tripod at a fixed distance, use a FX prime lens (for example, a Nikkor 35mm f/1.8G), and shoot one photo in FX mode and one photo in DX crop mode and everything else remains constant (e.g., 35mm @ f/1.8 @ ISO 200 @ 2 meters from subject). I assure you both photos will have the same DoF. It has nothing to do with whether it's FX (FF), DX (APS-C) or 4/3. If D800 could take a 4/3 lens, and do the exact same experiment, the DoF will be similar also at the given FL.

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