Tools for working with aliasing artefacts on a 7D

[Paul Curtis]

I'm still considering a 7D, it's just the aliasing artefacts that concern me.

Objectionable stair stepping is really an issue for me along with moire problems in patterned backgrounds.

Now has anyone spent any time trying to fix these things in post?

For example there are a number of plug-ins to help reconstruct 4:2:0 artefacts that could also be applied to this footage.

You could use instant HD scaling tools to take it to 4k then downsample back to HD to smooth off the stair stepping. In fact take it up, add a tiny bit of noise and back down again would improve visual resolution and also get rid of some of the watercolour AVCHD artefacts.

Topaz Labs have some interesting plugins for removing JPEG artefacts and noise that might be applicable in this case.

I'm quite happy to take a look at this if someone can give me some original source footage with the kind of artefacts i'm talking about?

cheers
paul

[Chuck Spaulding]

Or you can shoot around the 7D's limitations. I have had moire in a couple of shots, but most of the time its not that big of an issue.

I can't imagine putting 7D footage through that sort of post production gyration would yield the type of results or be worth it. If its that much of an issue for the type of shooting your doing I'd suggest getting a different camera.

[Alex Leith]

You could also try the Caprock Anti-Moire filter (that goes in-front of the lens).

7D Caprock 2.0 Anti Moire Filter on Vimeo

Or if you are really brave (or can get someone to do it) you could replace the camera's internal anti-aliasing filter with one that is better suited to video (at the expense of stills sharpness)

[Paul Curtis]

Alex,

I didn't know about that, very interesting, thank you. Shame the video doesn't feature a comparison with the filter off. Are you aware of any samples that do?

Chuck,

I'm trying to decide whether it's worth my while getting one. I'd love to because i use canon for stills however i've seen some truly awful results from it. I need something small for run and gun, could be a 7D, GH1, or a small camcorder. I'd love to get a bigger sensor size though as it would compliment the EX1 but i'm trying to use the resources i can find online to tell whether it would work for me. And i ponder how rescuable is the footage if there are problems. I'm not in environments that i control, nor in a situation where i will be able to review then and there. I'm looking for safety nets :)

thanks
paul

[Chuck Spaulding]

This is kind of a tough decision. It also really depends on what you mean by run-and-gun? I mean the EX1 is a very good camera for run and gun if your set up well for tapeless production.

I find the 7D to very stealthy, I can shoot in situations that would be very difficult to do with my EX1/3.

If you haven't already seen these (I've been pimping them out all over the place) in the first I had control over the shots but I shot the whole thing in about four hours. I had a few issues with aliasing but not bad:

Amused to Death on Vimeo

This is a concert where we had no control over lighting, had no idea who the bands were or what songs they were performing, and we had less than an hour to setup. This is about as run-and-gin as it gets. most of the CU from the stage are the 7D the rest was a JVC100.

LED ZEPPELIN'S THE OCEAN on Vimeo

Not so much aliasing issues as much as rolling shutter. The bad camera work is all me, not the camera. One thing about working with bands at concerts the beer flows freely...

I really like the 7D, but at the moment I'm not making money with it so I can play around with it all I want. If you already have an EX1 and your looking for an inexpensive camera to give you some great beauty shots then the 7D might be just what your looking for. I'm not sure I'd recommend it as a primary camera. But there are some great examples of wedding videos where they are using only the 7D.

My only point earlier was that I'm sure if you used the 7D quite a bit you'd quickly learn its quirks and easily and possibly subconsciously figure ways around them. It will be interesting to see if Canon takes what its learning from the 5dMkII and 7D and role that up into a really good video camera. But even if they do, that's probably two or more years away.

[Ram Shani]

the filter results look great were i can order one A S A P

[Chris Barcellos]

In the meantime, while I am shooting with a 5D, I had a theory that shooting super flat, and then transcoding to Cineform with Neoscene, then adding sharpness and levels in post might reduce moire and aliasing, but I conclude that doesn't make that much difference, as this test shows:

Moire Testing with the Canon 5D Mark II on Vimeo

[Paul Curtis]

Thank you for these samples.

Chris, that's a killer test. Very useful. Fundamentally the line skipping is missing chunks of information, so either softening the input or perhaps fixing in post is the only option.

I notice that Boris have a new set of their plugins and one is a 'dvfixer' which purports to help fix the aliasing

New After Effects Filters

Could be useful for some shots.

Chuck, they look great. Although all downsampled which can hide a multitude of sins. I think a lot of aliasing problems can be covered up by filtering then downsampling. Do you have any of the original source footage up anywhere?

cheers
paul

[Brandon Freeman]

I'm still trying to figure out the best way to soften the resolution to avoid moire/aliasing artifacts optically, but I am finding adding monochromatic film grain in Apple Color is taking the edge off of a lot of it. That combined with downsampling to 720p seems to help a lot. (Doesn't hurt that monochromatic film grain also hides compression artifacts and iso noise.)