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View Full Version : Canon 7D Moire meet the Dutch Angle



stephenvv
10-22-2009, 10:58 PM
Okay, just got a 7D couple of days ago and wanted a better handle on aliasing color moire issues. I found a perfect test to shoot and test my theory that angle is everything based on looking at Barry G's test charts.

I think this test shows that long horizontal lines +- 10-15 degrees are the issue. Dutch the angle enough and it appears to my eyes that the effect vanishes and nothing but nicely sharp footage remains.

Shot factory default, 1080 24p, very high shutter as I had no ND plus it keeps motion blur from hiding result. Download the WMV as compressed Vimeo is not 100% accurate of what moire I see on with camera directly in 1080p monitor.

7214842

MOIRE IN FULL FORCE
http://www.sv2studios.com/clients/7d/moirebad.jpg

MOIRE GONE
http://www.sv2studios.com/clients/7d/moiregone.jpg

sunburst
10-22-2009, 11:10 PM
interesting!

I guess now well see a thousand remakes of the THIRD MAN :engel017:

stephenvv
10-22-2009, 11:20 PM
Indeed - I"m lucky - my last name is Dutch - "van Vuuren", so I'm all set:2vrolijk_08:

MovieSwede
10-22-2009, 11:23 PM
Handy in case you gonna make Battlefield Earth 2. ;)

morgan_moore
10-22-2009, 11:30 PM
If you decide - Im shooting 720 - its all this cam is good for

it does indeed ad another tool the the box

Tram needs to write a 16:9 frameguide that rotates

S

Matthew Bennett
10-23-2009, 05:50 AM
Ha! Great test...
I actually really like your test shot too... it has sort of a David Lynch in the suburbs feel...

Eddy Robinson
10-23-2009, 10:14 AM
That's interesting. If you're making more tests, the Canon 7d has an 'artificial horizon' built in so you can see the forward and lateral tilt - maybe you can measure the exact angles. your theory certainly seems consistent with everything we know about how Canon bins pixels on their sensor.

sblfilms
10-23-2009, 10:22 AM
That could come in handy big time. Not optimal of course, but shooting off angle just enough to get rid of the Moire and the cropping and reorienting in post is one more workaround to consider if you just can't seem to get rid of the really nasty moire as shown here.

stephenvv
10-23-2009, 10:27 AM
Eddy - good point. I don't have a laser level or anything to check that the ground is flat, but if someone does, the exact angle range of the effect which lessens by degree off true horizontal, could be determined.

And I wonder if smart programmer people could use this data if the 7D records the angle in metadata to create a moire-removal plugin. It's clearly an effect that only regular people see when it's the moving moire on strong horizontal lines.

Kholi
10-23-2009, 10:47 AM
It works. We were doing this with the MKii when everyone attempted to find out how to cure aliasing and if you're purposely framing just a tad wider you can crop out of the image enough to be able to tilt it in post BACK to a proper horizontal composition.

It's easy if you're going to finish at 720 or anything smaller than 1080.

However, the method does not work with various laterals in the frame: buildings, powerlines and vehicles for example. One surface may be cured, but the others become plagued.

In Stephen's example, you can see the chairs on the deck are now jagged.

stephenvv
10-23-2009, 11:07 AM
However, the method does not work with various laterals in the frame: buildings, powerlines and vehicles for example. One surface may be cured, but the others become plagued.

In Stephen's example, you can see the chairs on the deck are now jagged.

I understand technically the chairs are jagged but for real-world viewing, it works fine. I had my wife 6ft from a 24" 1080p monitor staring at the shot asking her to find the image flaw - she is totally non-technical but a good eye - she can pick out progressive/24p footage, interlace issues, low resolution etc. as well as anyone here.

But she saw none of the jaggies despite repeated prompting from me to look for image problems and flaws - moire, yes of course, easily, but only if it was large in frame. In fact, she kept remarking how good it looked compared to my HV30. That's what counts for me in being able to live with 7D as pro cam until this is solved down the line.

So, to me, as long as I have shots without the colorama moire, jaggies be damned - only some pixel peepers see them some of the time - if they are looking. Which probably means my film is boring them anyway.

Kholi
10-23-2009, 11:11 AM
I understand technically the chairs are jagged but for real-world viewing, it works fine. I had my wife 6ft from a 24" 1080p monitor staring at the shot asking her to find the image flaw - she is totally non-technical but a good eye - she can pick out progressive/24p footage, interlace issues, low resolution etc. as well as anyone here.

But she saw none of the jaggies despite repeated prompting from me to look for image problems and flaws - moire, yes of course, easily, but only if it was large in frame. In fact, she kept remarking how good it looked compared to my HV30. That's what counts for me in being able to live with 7D as pro cam until this is solved down the line.

So, to me, as long as I have shots without the colorama moire, jaggies be damned - only some pixel peepers see them some of the time - if they are looking. Which probably means my film is boring them anyway.

Well, technically, pixel-peeping got you to figure this out in the first place... I've got footage from a shoot in Japan that I'm scrubbing right now (7D) and it was used for the all dangerous wide on a three camera shoot (2 x Red and 1 x 7D) and I can spot the aliasing... the producers can't. They only notice the great light and the Japanese Pop Star, the important things. If anyone's noticing any moire or aliasing in your footage, doesn't matter if it's pixel peepers or a thirty year old moviegoer, then you've got more issues than technical ones.

So, it's not REALLY a question of what non-pixel-peepers can or cannot spot, it's about an all inclusive solution to aliasing since this is a technical post on the subject, not a subjective one.

In the end, I only said that it does not cure all. It works for some scenarios, will not work for all. This from having done it with the MKii earlier on and learning first hand that if you try to do this on a wide city shot it just flops the aliasing and moire to another plane.

stephenvv
10-23-2009, 01:25 PM
What I'm arguing is that aliasing only becomes an issue with ruining a shot when it make the moving moire patterns - when those are not present, I consider the shot in most cases, very usuable, even for filmout or VFX.

Osslund
11-25-2009, 07:06 AM
I did two interviews yesterday and rigged the 7D. The subjects shirt had a pattern and it looked awful. It was so bad I had to switch camera and used the GH1 instead. No moire what so ever! In this area I'm very disappointed at the 7D. I can't trust it.

bwwd
11-25-2009, 08:09 AM
Or you could tell them to wear specific t-shirt without patterns.

Ian-T
11-25-2009, 12:22 PM
Isn't that the same type of rule when shooting film?

Osslund
11-25-2009, 03:13 PM
Moire is always a problem in video sure. But in this case I couldn't use a 7D but it work with a GH1. Same lens, same shirt...

Barry_Green
11-25-2009, 05:07 PM
Isn't that the same type of rule when shooting film?
? Film has no trouble resolving any sort of patterns or details. Not sure what you mean here.

ROCKMORE
11-25-2009, 05:51 PM
I did two interviews yesterday and rigged the 7D. The subjects shirt had a pattern and it looked awful. It was so bad I had to switch camera and used the GH1 instead. No moire what so ever! In this area I'm very disappointed at the 7D. I can't trust it.

If you ever have time, can you shoot a side by side with the GH1 and the 7D on a moire problem shot? I'm still on the fence which camera to go with.
Thanks in advance.

Osslund
11-26-2009, 12:38 AM
I'll try to squeeze in some sort of test. Maybe next week...