5dsr cacelling 5ds low-pass filter

[patflynn]

General question here that I didn't find elsewhere on a search of this forum.

 

The EOS 5DS and 5DSR each offer 50MP sensors, with the difference being that the R version introduces a separate filter to cancel the

effects of the S version's low pass filter, for the ultimate in detail capture.

 

Mine is a basic question: doesn't ADDING one filter to cancel the effects of another, deteriorate image quality? Placing MORE media

between the original light and the image capturing sensor seems like putting another filter on the front of the lens - you wouldn't do it

unless your vision required it (like a ND filter or polarizer, etc).

 

I assume Canon chose this route for the 5DSR for mass manufacturing reasons. But my question is, does this inevitably degrade image

quality? In much the way that it is supposed to enhance it?

 

If it isn't obvious, my understanding of the low pass filter is minimal. But shouldn't basic physics prevail? Since Canon itself thinks no, I

am looking for a plain English explanation to educate me. Thanks for any feedback.

[AzDavid]

<p>Don't know if this counts as "plain English" or not, but ... Adorama's comparison of the two cameras states that the low pass filter in the 5DS adds a slight blur to ward off moire. The extra filter in the 5DSR, Adorama says, "re-aligns the original pixel shift and thus eliminates the blur resulting in extreme sharpness in images." (http://www.adorama.com/alc/0015137/article/Canon-5Ds-vs-5DsR) So, the claim is that the extra filter actually makes images better (sharper) in the 5DSR. </p>

[JDMvW]

<p>It's not "less", it's moiré, so to speak.<br>

Here is a short, but reasonably clear explanation of how this works on the Nikon D800 and D800E<br>

(<a href="https://photographylife.com/what-is-low-pass-filter">link</a>)</p>

[Dieter Schaefer]

<p>It is my understanding that Canon used the same trick Nikon did with the D800/D800E pair. Here, the D800 had the AA (anti-aliasing) low pass filter, and the D800E added another one to cancel the effect of the first. Hence, the D800E is a bit more prone to moire than the D800 but the fact that the D800/D800E pair was replaced by a D810 without an AA filter is a good indicator that moire is not a major issue when using high MP cameras. A direct comparison of D800 and D800E reveals that the D800E is producing sharper images (no surprise here since the blurring effect of the AA filter is gone).</p>

<p>While the AA filter appears to have been a necessity with lower MP cameras, the higher the MP count, the less the need for such a filter. Essentially, moire is triggered by regular subject pattern with the same or similar pitch as the sensor pixels; and the finer that pitch, the less likely that such a pattern occurs in nature. If it does, however, then moire is hard or even impossible to get rid of in post processing.</p>

[ilkka_nissila]

<p><em>doesn't ADDING one filter to cancel the effects of another, deteriorate image quality?</em></p>

<p>Basically the first layer of the filter splits light according to polarization and shifts some of it by a step equal to the spacing between adjacent photodiodes under the CFA, and the second layer (in the self-cancelling configuration) moves the shifted light back on its original trajectory but doesn't change the path of the light with the orthogonal direction of polarization. Thus the result should be similar to having a clear glass. </p>

<p>DXOMark tested a lot of lenses on the D810 (which doesn't have an AA filter) and didn't find any differences in resolution between the D810 and D800E (which has the self-cancelling AA filter). Thus it seems this is not a real issue. This technology works as intended.</p>