T2i: Weird color splotches flickering?!

[kmp77]

Sometimes when I shoot I get sections of the video where areas will flash little yellow splotches and then revert back to the normal image. I saw it bad in a brick wall once and ruined the shot. This just happened today when testing a new lens.

http://i56.tinypic.com/2eav0au.gif

These yellow spots are not on the metal flag. It's being added. My shooting mode is neutral with the tp turned off etc. The other shot of the brick wall was way worse, looked like the wall was flashing.

Anyone know what this is?

[HueyNRolf]

That's aliasing. Welcome to HDSLR video.

[kmp77]

That's aliasing. Welcome to HDSLR video.

That just ruins a shot

[wildside50]

That just ruins a shot

You're going to run into that a LOT unless you specifically work around it. There's really very little you can do about it besides not shoot DSLR video.

[drapeama]

That's aliasing. Welcome to HDSLR video.

I'm glad I still own my HV40 and not "completely" moved to HDSLR...

There's really very little you can do about it besides not shoot DSLR video.

Well, HDSLR is good, but like every camera/camcorder/tool: there is weakness.

[Braceface]

It doesn't sound like he's describing aliasing to me. Sounds like a camera defect. I've never heard the term splotch for aliasing, and yellow splotches on the flagpole? That is definitely a weird issue.

[kmp77]

I think its this same effect:



I've seen my camera do this too on a brick wall.

[HueyNRolf]

I think its this same effect:



I've seen my camera do this too on a brick wall.

Yup that's aliasing alright.

I'm not knocking DSLRs for video. In fact, I'd say that the people who didn't make the switch are in the minority (on here at least). The low light performance and flexibility that comes with interchangeable lenses, makes them very attractive at a reasonable price. It's like a lot of choices you have to make, there are often downsides.

[jet]

This is why i switched to Pana ,With the GH2 if ever there is aliasing its barely noticable compared to the 550D i had.

[drapeama]

I'm not knocking DSLRs for video. In fact, I'd say that the people who didn't make the switch are in the minority (on here at least).

Each tools their strenghts and weakness.

[Janke]

Yes, it's aliasing, also called moirés.

I got that problem once only with my T2i/550D, shooting a speech by film director Matti Kassila, who happened to wear a corduroy jacket. I had to selectively defocus and desaturate the area of the jacket to get rid of the splotches...

[mkkid28]

Alias isn't just an issue with DSLR cameras though, I've seen a lot of examples of it on TV programmes.

[Janke]

I've seen a lot of examples of it on TV programmes.

Oh, yes. We used to have a news anchor famous for his almost psychedelic, almost-alive, moiré ties...

[Janke]

I got that problem once only with my T2i/550D, shooting a speech by film director Matti Kassila, who happened to wear a corduroy jacket.

Old thread, but here's a still frame showing the problem:

kassila.jpg

That little area on the lapel looks much worse in motion, when it constantly flickers and changes colors...

[racer-x]

Probably a combination of aliasing and your avc decoder...............

[racer-x]

It appears that the Aliasing/moire problem is caused by the crappy resizing algorithm used by Canon to reduce the image size of the large sensor. Even a simple Bicubic Resizer would yield substantially better results and would work just fine in Real-Time.

There is no excuse for this other than Canon intentionally reducing PQ so that the DSLR's wont blow away the much more expensive "Professional" HD Camcorders. That's my theory and I'm sticking to it.........

[Yellow_]

I've only experienced moiré like that brick / tile image when using the kit lens and a particularly sharp 20 yr old Tokina 30-200 ATX (OM System).

Comparing the kit lens / Tokina 30-200 to older low contrast / non coated lenses, I have a range of Meyer Optic lenses, including the Orestegoen 400mm (x1.5 crop) also known to be sharp that gives no moiré problems. But generally I also have a FaderND MKII in front and like to physically lock the lens aperture wide open, both of which soften the image before it hits the sensor.

I rarely use the kit lens, the focus on the outer ring doesn't make using a Vari ND any easier either. :-)

The moiré problem is not just a video DSLR problem, I've also seen it on point and shoots. But made worse by the line skipping that the Canons do to reduce resolution from full image res and final minimal upscale to 1920x1088.

I've also seen small amounts of Red/Blue chequerboard type effects to edges in some shots, only really noticable pixel peeping or uprezzing that are attributed to chroma bleed from the 4:2:0 subsampling done in video mode.

90% of the video's I've shot have no moiré problems so must be a combination of some of the above. Not sure if that helps at all.

[Dr. Benway]

Guff:

Reducing/removing moire: http://forums.creativecow.net/thread/2/926421

Something more technical: http://thebrownings.name/WHP034/

from Addendum 39: Assessment of a Canon 5D DSLR

Colorimetric and Resolution requirements of cameras
Alan Roberts
ADDENDUM 39 : Assessment of a Canon 5D DSLR
The Canon 5D is a full-size digital single lens reflex camera. Unusually, it also offers HDTV recording.
Although there are few of the usual controls that go with video cameras, it was thought worthwhile to check
its performance as an HDTV camera. The results were not encouraging.
The tests were done on a pre-production model, serial number 0039900173, software version beta 3.6.1.63..

I love that, not encouraging.

[racer-x]

........Or you could shoot most things with a shallow DOF. Lowering the camera bitrate also helps as the images will be slightly softer. This can be done with ML firmware.

I've only noticed moire pasterns in one shot so far and you'd have to look real close to see them.

[drapeama]

Reducing/removing moire: http://forums.creativecow.net/thread/2/926421

I might check to try that.