Aliasing and Moire in fine details question(s)

[Lou Bruno]

I have noticed, at times, fine lines such as telephone wires tend to shimmer. Also, moire lines appear on patterned shirts and even leaves on hedges and bushes. Like the "old days" with a proc/enhancer amp.

I was able to correct this for the most part by using a -7 on the sharpness and bringing up the coring as well as lowering the sharpness on the HDTV. However, I have not observed this on any of my other cameras which are AVCHD and HDV. I have observed the above with the IAF off, no auto-focus and even with the stabilizer off as to eliminate these as potential issues.

My question is this:

Has anyone else observed this and what was your solution?

NOTE: It is more present when rendering to AVCHD Blu-ray but is present in the original material.

Could it be the MPEG-2 compression?

Does anyone have a menu setting for the Vertical and Horizontal detail?

Very little is actually written in the instuction manual/book. I found some information in the Canon 5D threads and am even wondering if this oversharpening is lens related as well.

[Charles W. Hull]

Lou, I am just starting to look at aliasing with the XF100. I have been using a 5DMkII where aliasing is a big issue, so I would like to see it go away with this new camera. I shot a powerline scene that has shown significant aliasing with the 5D, and it is much better with the XF100. And the XF100 shows more detail as well; in one case it resolved two power lines where the 5D only showed one fat line. But there is some effect with the XF100, perhaps what you are calling shimmer. The XF300/305 undoubtedly resolves even better than the XF100, so it could be more pronounced with that camera.

But my tentative conclusion is that I am seeing simple pixelation, and as I scan the camera the pixel edges shuffle. In this case it shows with pixel peeping, but it does not show at a normal HD viewing distance. If you view the video at a normal distance, something like 2.5 x the diagonal screen width, do you still see shimmering? Chuck

[Philip Lipetz]

With the XF100 I experimenting with reducing the red channel to lower shimmer. In cam display it works.

Alan Robert's XF300 BBC settings have a reduced red channel, but red is much stronger in the XF300. Will let you know if I can then properly compensate in post.

[Glen Vandermolen]

Lou,
Are you referring to the XF300 or XF100?

[Chris Hurd]

I suppose I should add a thread prefix selector to delineate topics pertaining to the XF300 series vs. the XF100 series.

[Lou Bruno]

Yes...the XF-300. Both vertical and horizontal lines actually shimmer. Looks somewhat like what happens in downconversions, but not related to that process.

I am not the only person observing this anomaly. I was contacted via e-mail from another user observing the same thing.


Chris,: May be a good idea to differentiate the cameras via another topic. There will be many questions relating to the less expensive XF-100, though they are tied-in very much.

[Lou Bruno]

Yes....I adjusted the red channel as per the BBC white paper on the XF-300 This is more related to what may be resolving issues-too sharp. The secret must be an adjustment encompassing the sharpen menu, coring menu. This would also include in the sharpen menu an adjustment to vertical and horizontal detail. The manual is pretty weak. I may have to contact CANON PROFESSIONAL shortly-this week.

NOTE: This shimmer does not appear om my professional JVC HD monitor, on a computer screen or in the actual display. It appears on a HDTV. Never appeared before on my other HD cameras.
I am good with this "stuff" and this has stumped me. The fact that it is being displayed on other owners HDTV's may help to isolate the problem and come to a plausable solution.

So far -7 sharpness in the menu BBC Horiz/Vert set-up, and increased Coring I also lowered the sharpening on my HDTV and all is passable. Trying to find a good default setting to avoid shimmering.

Lastly, the power-line example is a true example of the shimmering.

Originally Posted by Philip Lipetz

With the XF100 I experimenting with reducing the red channel to lower shimmer. In cam display it works.

Alan Robert's XF300 BBC settings have a reduced red channel, but red is much stronger in the XF300. Will let you know if I can then properly compensate in post.

[Dave Partington]

Yes....I adjusted the red channel as per the BBC white paper on the XF-300

I'm about to start testing the XF300, where can I find this white paper? No point re-inventing the wheel!

[Glen Vandermolen]

Originally Posted by Dave Partington

I'm about to start testing the XF300, where can I find this white paper? No point re-inventing the wheel!

http://thebrownings.name/WHP034/pdf/..._XF300-305.pdf

[Dave Partington]

Awesome - thanks!

[Antony Michael Wilson]

Lou, this is definitely something to look into on this camera, I agree. It is so sharp out of the box AND with the BBC settings that you will often get aliasing on very fine detail, which will only get worse on SD deliverables. The BBC tests were done on static charts, as far as I know. While they are a great starting point, it seems that - when pictures start to move (!) - you will have problems, particularly on a baseband 1080/50i or 1080/60i output. You get interline twitter, which is what you are probably seeing. As you get further down the post-production chain (such as encoding for Blu-Ray in your case) what is actually very, very minimal aliasing will be exacerbated. I'm running a hardware down-convert from XF material shot with the BBC settings right now. I'm using a Teranex and even with all sharpening/enhancement disabled, I'm still getting exacerbated aliasing. The aliasing is certainly visible on our HD production monitor when you look carefully but could never have been spotted on the shoot. It didn't show up when we tested with charts to start with and this is a great example of how important it is to test/calibrate with charts and scopes AND by actually shooting something!!!! I'm very glad we remembered that before unleashing this camera on a big job!!

I'm confident this has nothing to do with the codec. We're seeing the same phenomenon going into the Avid and FCP uncompressed. Most existing AVC and HDV cameras just don't have the optics and/or the sensor specs to resolve this much detail. The issue here is that the lens and the sensor on the XF are pin-sharp. By disabling all sharpening that the menus will allow, it will be possible to get a better idea if the OLPF is doing its job well.

I have a 305 on test at the moment and I'm having the same problem. If I can find the time and a confirmed solution, I'll report back. A combination of sharpening reduction/elimination and noise reduction should do the trick.

FWIW, I was on an Alexa test a couple of weeks ago and it has the same problem on the 1080 output/internal ProRes recording. It will be interesting to compare to the ArriRaw footage...

[Lou Bruno]

Antony,

Thank you for your comprehensive answer. I must agree with your findings. I did not think it was a CODEC issue.

I have lowered the sharpness and will contact CANON technical help as it relates to some of the other settings that will, hopefully, rectify this situation. Ex: Horizontal and Vert. detail adjustment.

I have been involved in video since 1982. This has to be the sharpest and crisp picture I have observed on a camera of this level. Too sharp. My AVCHD and HDV camera do not exhibit this anomaly.

[Matt Ford]

Im shooting and reviewing footage in the field, no access to a decent screen.

BBC V CP. 25p. Sharpness -3. Looks great on the camera screen. Appalling on my Macbook Pro in XF Utility, shimmering, moire the lot! Hope its just the Macbook screen, if so why?

What coring levels are people using? Has anyone discovered the best CP settings to minimise this?

The XF is meant to be much better then the HD SLR, they must really suck!



Matt

[Lou Bruno]

Here we go MATT:


Sharpness Level: -7 or even -9

H Detail 8

HV Detail 2

Coring Level 5

Lower the sharpness on a HDTV as well.

Good luck.

[Matt Ford]

Thanks for sharing Lou, will give it a try tomorrow!

Matt