Canon 5D Mark III - Polarizer improves sharpness?

[jcs]

This scene shot at 24mm with a FaderND gen 1 (works fine with the 24-105 lens) looks sharper than normal for a detailed wide angle shot: https://vimeo.com/40107424

It's not sharp, but it appears sharper than normal and requires less post sharpening (about 1/2 the amount). This example shows moire (church), which I haven't seen before with the 5D3 (well, have seen it before but very minor). More details in the vimeo description and original MOV available for download. Banding in sky likely due to using CineStyle and over-exposing the shot (could fix in post if this shot was needed using noise/grain or selective blurring with AE or Resolve).

If anyone has a FaderND (any version), Heliopan, etc., or clear linear/circular polarizers, would helpful to know if polarizers can help improve sharpness (some OLPFs use a polarizer- might be some kind of interaction with polarized light which reduces diffusion and blur).

[Andrew Reid]

There may be a reaction between the ND and OLPF that causes moire but I'm not seeing any extra sharpness or detail.

[jcs]

Compare the grass up close (ALL-I and IPB) to this footage, same lens, 24mm: http://www.youtube.com/watch?v=eTEV6_os4gY

Normally grass is mush- looks less mushy with the polarizers (ND affect achieved by two polarizers out of phase (either a linear and circular (made from a linear polarizer and 1/4 wave retarder), or two circulars)).

Again, I shot more than this clip, and each clip with the polarizer needs less sharpening. Lots of folks have polarizers & variable NDs- should be easy to validate or invalidate by testing.

[Andrew Reid]

Thanks for the test. But I'm still not seeing it!!

Edit: at least not the different IPB makes. ND - I will test that!

[jcs]

Just did a non-scientific line chart test. It's very subtle (not worth posting pics), but it looks like slightly less fuzz on the lines near the limit when using the polarizer (variable ND). Since the outer polarizer can be dialed, lots of variables (could test on an HDTV live and perhaps check for sharpness changes).

Also tested ALL-I- looked terrible compared to IPB: macroblocked everywhere (to be fair, was using SDHC (95Mbps card limited to 20MBps by 5D3) and not CF (can hit 45+MBps), though the ALL-I clip hit 48Mbps (6MBps).

Again, sharpening in post requires about 1/2 normal with bright outdoor shots with the polarizer in place.

Regarding IPB- if you can't see that it's better at 100% crop, then ALL-I has no advantage (except for slow computers). However, when you study IPB and ALL-I at 200-400% crop (and later start to see macroblocking in ALL-I at 100% once you know what to look for), ALL-I becomes even less attractive.

[Andrew Reid]

I'm using a SDHC 95Mbps and get 66-88Mbit footage in ALL-I mode.

What are you using to analyse and playback the footage? It must surely have a problem with ALL-I because there is no WAY the highly compressed IPB has better image quality from my experience.

[jcs]

[quote author=Andrew Reid - EOSHD link=topic=558.msg3680#msg3680 date=1334105485]
I'm using a SDHC 95Mbps and get 66-88Mbit footage in ALL-I mode.

What are you using to analyse and playback the footage? It must surely have a problem with ALL-I because there is no WAY the highly compressed IPB has better image quality from my experience.
[/quote]

I've gotten >101Mbps using 600X CF Lexar Pro with ALL-I (IPB had less artifacts (looked better) at 30Mbps, same scene & conditions).

Regarding IPB- the tree/sign scene below shows IPB outperforming ALL-I. The 400% crops posted here (see attachments) and elsewhere show macroblocking issues with ALL-I but not IPB. Some folks can see a quality improvement with IPB even on the youtube footage.

The best I have seen with ALL-I was using Compressor (old version from FCP7) to transcode before analysis. It came closer to IPB but still had a few hard macroblock edges (same scene as below).

If you have shot and analyzed ALL-I compared to IPB, and found IPB inferior, can you post crops to show ALL-I outperforming IPB along with the settings used? I have tried low- detail, high-detail, motion, still, etc., can't get ALL-I to perform better than IPB (using Faithful or CineStyle).

[jcs]

If there is any real effect, I think it involves the polarizer.

Testing a linear polarizer (in addition to circular), at different angles would also be interesting. Check this out: http://nikonusa.com/en_US/IMG/Images/Learn-And-Explore/2012/Camera-Technology/D-SLR-Series/Moire-D800-D800E/Media/OLPF_schematic.pdf
A polarizer might stop/reduce/change the last diffusion stage (if the 5D3 works similarly). A collimator might also have interesting properties: http://en.wikipedia.org/wiki/Collimator (check out the Söller collimator drawing):
[img]http://upload.wikimedia.org/wikipedia/commons/5/52/Collimator.jpg[/img]

Ah, interesting, another clue from the Nikon link:
[QUOTE]By converting polarized light into circularly polarized light with the wave plate, two points are divided into four points at low-pass filter 2.[/QUOTE]

Since a circular polarizer is a linear polarizer with a 1/4 wave retarder (phase shifter, "wave plate"), curious if this might explain a real effect when a circular polarizer is placed in front of this optical assembly. Intuitively, based on testing, it could be a circular polarizer reduces the effect of the OLPF by 1/2 to 1/4. If the OLPF works by providing two light paths, perhaps pre-polarizing produces one light path (or narrows the net separation).