Moire example

Laurence wrote on 12/1/2011, 9:02 AM
Here is what happens when you shoot video with a tile roof with a DSLR: horrible moire. You can also see artifacts on the concrete siding.

http://vimeo.com/32969932

Fortunately I anticipated this and shot some stills on the same shoot, so I could just use a still for the front of the building shot.

This is why I wish I had bought a Panasonic GH2 instead of the Nikon D5100. A Canon DSLR would have given me the same problem.

The rest of the DSLR footage from that day looked fine:

http://vimeo.com/32872446

I still need to replace the last shot with a shot of the boy in the video instead of the stock shot. I'm pretty sure I'll also hire out a voiceover from http://voicejockeys.com.

Comments

musicvid10 wrote on 12/1/2011, 9:13 AM
Wow, an iridescent roof. Now there's a business idea . . .
Laurence wrote on 12/1/2011, 11:07 AM
"Yeah, honestly guys, that's the way the roof looked when I shot it!" ;-)
JasonATL wrote on 1/15/2012, 6:23 PM
Laurence - Your post today following up on your D5100 reminded me that you had started this post. Your work with the D5100 looks great.

Like you, I've started using DSLR's quite a bit, having used conventional HD camcorders previously. In general, I love my DSLR. But, like you, I've been bitten in the rear by the ugly moire issues at times.

I have the Canon T3i/600D and I thought that you and others might be interested in the fact that there is a simple workaround to moire on the T3i/600D if you happen to have a wide-angle lens handy. The trick is to use the T3i's 3x digital zoom feature. This feature crops the camera's sensor to make it appear that it is zooming in. What is happening (apparently) is that it is just using the available sensor area and, therefore, does not have to perform the moire-inducing downrezzing.

For me, I already had the Tokina 11-16mm zoom. I love this lens without the side benefit that I'm using it for here. Its a bit expensive to buy just for this purpose, but if you wanted/needed one anyway...

The solutions is: on a shot that you'd use a 35mm on your DSLR and end up getting moire, you can put the Tokina on, zoom it to 11.67mm (optically) and then engage the 3x zoom feature on the T3i. This gives a nearly identical frame as the 35mm, but with no moire. For a shot using a 50mm lens, I use the Tokina at 16mm and the 3x zoom, getting a similar frame.

I confirmed that this works beautifully here: http://vimeo.com/35111205

I don't know if the D5100 has such a feature or not, but if it does, this might help in some situations.
Laurence wrote on 1/15/2012, 11:10 PM
No the D5100 does not have this feature. I wish it did.
Laurence wrote on 1/16/2012, 8:22 AM
In another thread I was talking about the Nikon D4:

http://www.sonycreativesoftware.com/forums/ShowMessage.asp?ForumID=4&MessageID=795395

26 seconds into the Nikon promo video "Why", the interviews start:



Two out of three of the interviewees are wearing tight patterned shirts that would be full of moire on my D5100. The Nikon D4 has three levels of sensor crop: full frame, 1.6 crop which matches my D5100, and a way zoomed in 1 for 1 pixel mode. The D4 also has some new sort of antialiasing technology that sounds like it uses some sort of low pass filter rather than pixel averaging like the Panasonic GH2. The tight patterns on the shirts look perfect in the interviews without a touch of moire, but I don't know if this is because oF the antialiasing filters or because they did your trick and zoomed into the 1 for 1 pixel mode with a wide lens. It looks like really shallow depth of field so I am pretty sure it is the new anti-aliasing filters, but I wish I was sure.
PeterDuke wrote on 1/16/2012, 5:48 PM
"some sort of low pass filter rather than pixel averaging "

You may not want to know this, but averaging is a simple form of low pass filtering, known as "Moving Average", which is a type of "Finite Impulse Response" or "All Zero" filter. Depending on how you weight the samples before averaging, you can change the shape of the filter. Of course more complex low pass filtering is possible too, which is what you were implying.