nikon D7100 - how will Canon respond?

Started Feb 21, 2013 | Discussions thread
noirdesir Forum Pro • Posts: 13,561
Re: Hopefully with no AA filter on the 7D II...

bobn2 wrote:

noirdesir wrote:

bobn2 wrote:

noirdesir wrote:

And is this an option in reality? Do we know AA function exactly and does have LR a tool where I can input the parameters of the AA function?

No, but I believe that DxO does have one where they have already put in that correction. There are several ways to do it in practice and theory, if you wish. First step is to find the MTF of your AA filter. The way to do this is to project a slanted edge on the sensor (I would suggest a knife edge held close to the sensor illuminated by a laser pointer) and use a slanted edge MTF program (quite a few available) to find the MTF. Actually what you want is the PSF. When you find the PSF, you apply a deconvolution to the image to correct out the filter. You can get plugins for ImageJ which do both the PSF analysis and the deconvolution.

Roughly since the D800E came out (but probably also before in reference to Leica or MF) people here (including you) have discussed the MTF of an AA filter. Somebody then posted MTF curves for one or two AA filters in a thread where you also participated. But that was about it, until Marianne showed some of her results. So, while it is naturally measurable, essentially nobody beside DxO has ever done it.

Because practically it is not of much interest.

Point is though, this really is not necessary for many. For instance, I have a 36MP camera. rarely do I produce images which require the 36MP, so I'm working where the AA filter characteristic is irrelevant.

But isn't cutting short a discussion about the general effects of an AA filter by saying that it isn't relevant in most situations, a little bit of a cop out?

There are two 'general effects of an AA filter'

i) A droop in the spatial frequency response near Nyquist.

ii) The reduction of aliasing artefacts.

In most use situations with a high MP camera (i) is not greatly significant. (ii) is.

Did I say anything else?

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