D800 or 8000E

Started Jan 10, 2013 | Discussions thread
Leo360 Senior Member • Posts: 1,141
Re: moire in DX mode: D800E versus D800

Robin Casady wrote:

Leo360 wrote:

I am actually comparing apples to apples. The scene is the same, the angle of view is the same. The only things different are the sensor size, the focal length (to preserve angle of view) and the aperture f-number (to preserve the DOF). And then DX and FX have different angular sampling rates and this is what matters for aliasing.

Another way to look at this is you are using the same sensor, but changing lenses. Let's say you are using a 50mm and a 35mm lens. The pixel pitch of the sensor remains the same. Only the size of the projected image changes.

Whether you would get moiré will depend on the size of the repeating pattern in the subject, distance to subject, and focal length of the lens—as these determine the size of pattern projected onto the sensor.

I don't see why you would be more likely to get moiré with a 35mm lens than you would with a 50mm lens.

It is the pitch of the sensor grid that makes a camera subject to moiré. The MP on its own is not how you measure susceptibility to moiré.

Robin, in DX mode the same scene is sampled by lesser number of pixels than in FX mode. Therefore, angle sampling rate (Nyquist frequency) is lower in DX than in FX. Without AA filter the spatial patterns with frequencies higher than Nyquist gets pushed (frequency shifted) into the sampled freq. domain and create artifacts (aliasing). Moire is just one manifestation of aliasing. In FX the mechanism is exactly the same but the Nyqist freq. is 1.5 times higher. Therefore, statistically speaking, getting pronounced artifact is less likely. This is why camera makers always use AA filter on sensor with 20MP or less. In 36MP+ territory AA filter is more or less optional.

I think your lens change analogy is incorrect. If you have the same scene (the same angle of view) with the same sensor you have the same sampling frequency no matter what lens you use. If changing the lens changes the scene (angle of view) than you are comparing apples to oranges.

Leo

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