Controlling Moire on the 7D

[Ted Ramasola]

A test I did on the eos 7D using wide lenses and the caprock filter 1.0.

I've done the chart tests but will show a scene thats most likely
to show moire and aliasing.

It includes a speaker grille and monitor vents.
Tiny repeating patterns that will trigger moire on the 7D.

Draw your own conclusions.
The caprock has different range for filters from 1.0 to 2.8
and different numbers fit different focal lengths.

Controlling moire on the 7D

Hope this test will help those with similar problems.

[Ryan Mast]

Would you mind posting full-rez stills?

[Ted Ramasola]

Ryan,

The moire and aliasing problem is normally found and triggered in video mode. Its when the camera does line skipping.

The file, while its still newly uploaded is still in wmv format in full HD 1080. You can still download it and scrutinize the image.

A couple of weeks later and the hosts in XR and Vimeo usually compress it to mp4 file.

I'll try to grab a before and after frame for you in case you have problems downloading.

[Ted Ramasola]

Ryan,

Here's two grabs with the 20-40mm lens @ 20mm.

Ted

tip; looking at thumbnails both seem to have moire, but clicking them to enlarge the frames will show a big difference.

[Robert Buchanan]

In the stills it seems to loose some sharpness with the filter. Is that true or as noticeable in the original video?

[Ted Ramasola]

Robert,

yes, using the filter will let you lose BOTH sharpness AND contrast.

My tests came on the heels of Barry Greens own test with the entire caprock line found here.
Caprock Anti-Moire Filters Tested on the 7D - DVXuser.com -- The online community for filmmaking

And as just as he recommended, when using these on your DSLR, you need to compensate either in-camera or in-post.

In the video I posted, I DID NOT compensate.

I'm posting a couple of test charts which i just shot to show how compensating "brings back" sharpness and contrast with the aliasing and moire controlled.

The chart with NO Filter had camera settings at lowest on sharpness & contrast or at none.
The chart WITH Filter is compensated at sharpness at 2 and contrast at mid or 0 setting.

[Jon Fairhurst]

Nice test, Ted!

It would be interesting to see how consistent this is on a variety of lenses at a variety of distances.

I did some tests with some Tiffen soft/fx filters and found that the softening that it added depended on the lens.

In any case, it looks like you have a solution for your 20mm lens - at least at short distances, and probably at long distances too.

[Ted Ramasola]

Thanks Jon,

Thats true, the caprock filters is not one-filter-for-all, its effectivity depends on the lens focal length.

I got the 1.0 purposely for my wide lenses as I have more problem with aliasing and moire on my wide shots.

I have pushed the 1.0 filter as to its limit and at 20mm it is very effective.

I have tried it on the 11-16 tokina and it is partially effective. The largest ring the caprock has is only 67mm thus I can only use around 15mm-16mm of the tokina without vignetting.

At 16mm, it still has a little color aliasing on the chart.
In the real world, it is highly probable that it will be usable.

The 1.0 is not so good with 50mm and is unusable on the 80mm and longer.

[Jon Fairhurst]

It's good to know that you've confirmed the same phenomenon. And, yes, wides are more likely to alias. The exception is when the subject wears clothing with fine patterns, since that can be right in the center of focus. On portraits, I often use a GlimmerGlass #1, mostly to give people an attractive look. It doesn't remove aliasing, but reduces it slightly. I also have a GG #3, but it's a bit strong for my tastes.

Too bad the Caprock isn't available in larger sizes. I have the 5D2, and FF wides generally have large threads.

Ideally, we would be able to snap an anti-aliasing filter right on the sensor. You wouldn't want to remove/replace it in the field, but such a filter could actually act as a protector for the sensor. And with that arrangement, it wouldn't matter what focal length lens was on the camera.

[Ted Ramasola]

I think thats what the caprock is implementing for the phase one sensors. They place the filter on the sensor itself.

What I'm hoping for is they just get rid of the aliasing and moire on the next generation of these cameras. The GH1 doesnt have it but thats not a platform I believe I would go to. -But who knows! These are exciting times.

[Ted Ramasola]

Jon,

Could you tell me about this Glimmer Glass? Its the first time I heard of it. -forgive my ignorance. Whats the maker? What does it do basically? is it like a diffuser of some kind?

[Jon Fairhurst]

Tiffen makes the GlimmerGlass filter. It comes in warm and normal versions in grades #1 through #5. (#2 and #4 are not available in round, threaded versions.) It is a diffuser that is achieved with what looks like small specs of glitter in the filter - silver for normal, gold for warm. The #1 gives a nice, subtle glow without being too boudoir. The main reason I like it is that it diffuses specular highlights. It gives skin a nice look.

Here's an example:
http://www.dvinfo.net/forum/film-loo...erglass-2.html

[Ted Ramasola]

Thanks Jon.