Fs700 moire

P

PrimeHD

Well-known member
How do you deal with moire on FS700? I noticed especially annoying moire along the vertical lines with high contrast, such as contour of gold metal letters etc. Killjoy.

Sony website says:
"Super-sampling: Spectacular HD or 4K

Does a 4K camera make sense in an HD world? Perfect sense. Even if you’re not planning on 4K production, the 8.9 megapixels of Sony’s 4K image sensor enable you to shoot fine-textured, super-sampled HD now and learn how to get the best from the camera."

Okay, but what exactly does it mean in practical terms and why do we still have significant moire, even after the upgrade to firmware 3.0 (4K)?

Note: I'm referring to the in-camera AVCHD recording, did not have a chance to use an external recorder yet. Alas, same moire will likely show on the external recorder?
 
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It's a 4k sensor feedng HD output. How does Sony downsample? Lineskipping, dithering algorithms? Just how do they do it?
 
I don't know, but I wish it was done better than it looks now. No AB comparisons here, but I have a feeling that my GH2 used to be significantly better - less moire. Yet GH2's sensor had even larger pixel count than Sony's, so shouldn't it have worse moire issues then??
 
just to be clear. the 4 k upgrade does nothing for the in camera avchd recording ,except. maybe some new picture profiles? and they are meant for the 4k output?
 
so nothing different ,for in camera upgrade avchd . but you will get the power zoom controller to work but is that just for the one new pz 18 200 lens or all nex pz lens?
 
Moire is an optical efffect that's the result of superimposing two patterns. In the case of an image sensor, it's the pattern of the photosites interacting with a pattern in the image. Optical Low Pass Filters are applied by a manufacturer such that it reduces or eliminates moire. The problem with an OLPF is that it's optimized for one particular focal length. So, clearly, with a zoom lens or with an interchangeable lens camera, the OLPF applied to the image sensor works well, or it doesn't.
 
cuervo said:
Moire is an optical efffect .... the OLPF applied to the image sensor works well, or it doesn't.
Click to expand...

All I know is that GH2 was both sharp, and virtually moire-free. And Panasonic apparently did have to downsample, too - just like Sony does - because GH2's sensor was much larger than HD resolution.

Not only that, but with GH2, I did not see any significant moire at any focal length of the particular lens used.

So then, it can be done.

My question: is there a way to make Sony FS700 to appear as moire-free as lowly Pana GH2 was?
 
What I see in that clip doesn't look like moire, but aliasing. And you're likely seeing it for a couple of reasons. One, the fact that you're overexposing the letters that seem to be showing it. And two, you may have your sharpness set a bit to high. Can you tell me what your FS-700 settings are?
 
I don't think there was any way to expose for the highlights in that situation. Museum lighting was rather dim overall, yet ceiling lights were right next to the lettering.

FS700 settings: I don't believe the cam records meta info readable by anything including its own CMU... so from memory:: CineGamma4, Detail 0, ISO 640, 1080p30 FX @ 1/60 shutter. Lens Canon 24-70mm L MK II (yum!) with Metabones MK II adapter.
 
cuervo said:
It's a 4k sensor feedng HD output. How does Sony downsample? Lineskipping, dithering algorithms? Just how do they do it?
Click to expand...
Best guess is that they do a similar trick to Canon with the C300 (and Canon have been very open about it). Basically treat the Bayer sensor as 2x2 blocks, with therefore 1920x1080 blocks in the sensor. Since each block has one red, one blue, and two green photosites, direct reading gives R,G,B values for each HD (1920x1080) pixel - with no deBayering or scaling. That's the beauty of the approach - together with the option of being able to read the sensor RAW, and do a normal deBayer to get even higher resolution.

Adam Wilt did some very good tests, and his charts show that the FS700 performance in normal modes is very, very good with little moire/aliasing.

You're not in a slo-mo mode, are you? At 240fps, it can only read fast enough by ignoring three blocks out of every four - so skipping every 3rd and 4th column, and every 3rd and 4th line. This also seems to be something like DSLRs do, and probably the GH2 as well.
 
PrimeHD said:
All I know is that GH2 was both sharp, and virtually moire-free.
Click to expand...
The GH2 is definitely not moire-free, it can exhibit significant moire if the pattern lines up just right.

What was different about the GH2 is that it never showed the purple/orange color artifacts in its aliasing (or moire patterns). It was always strictly black & white aliasing. That makes a huge difference in people perceiving it. It's still there, there's still noticeable aliasing, but because it doesn't get accentuated with orange and purple color artifacts, people don't notice it as much.

The Sonys, and the Canon EOS Cinema line, have a little bit of aliasing (which can lead to moire patterns in certain circumstances), and both of them do exhibit the color fringing on their moire or aliasing, so when it shows up you're likely to see it.

I don't think it's likely fair to say that the GH2 has less aliasing than an FS700, but I think you're probably noticing it more because of the color artifacting in it.

Even so, the FS700 (and C100/C300/C500 etc) show vastly less aliasing and moire than the BlackMagic camera, which has no optical low pass filter at all. The FS700 (and F3 and FS100) all have an OLPF, but it seems to have been tuned a little aggressively, in a chase for more sharpness, which left it slightly susceptible to the purple/orange chroma fringing on fine detail.
 
Barry, but did you watch my sample? The moire (or aliasing, whatever it is) on the edges of the lettering is very pronounced, even though the lines are NOT as fine as I'd expect to induce the moire normally. If FS700 is so good, then what is going on there?
 
Yes I downloaded it and watched it.

Understand that I don't have an FS700 and so can't replicate this effect.

It's an odd clip in that it does indeed look like aliasing, but it appears to only be affecting the blown-out sections. If it was conventional aliasing you should be seeing it and noticing it on the other letters too; it's showing up nastily on the "D"s, but the equally-curved "O"s aren't showing it at all. The only difference is that the areas where it's showing up, are on completely blown-out portions of the video.

So I don't know what to tell you. It could be something like the sunspot issue that affected the Red and Epic (filming the sun, the very centermost portion would show up as a black pixel). Or it could be some bug in the codec? Only way to rule that out would be to recreate the issue and view it on a live output.

But this doesn't look like typical aliasing. I mean, it does, but it clearly isn't, because you're not seeing the same effect on the non-blown-out stuff. So it appears to be related to gross overexposure.

If I had an FS700 I'd try to recreate it and figure out what's going on here. Maybe Stephen or some other FS700 owner will be able to do that and offer advice.
 
I've got an FS700, and I've not seen anything like this. But I can try to recreate it tomorrow, with Canon L lenses and my Metabones adapter.
 
Ideally PrimeHD would find a controlled scenario for reproducing it, and then share the circumstances under which it happens. I usually don't buy into the idea that it would be a hardware issue, but really, if this was a common thing with FS700s you would think we would have heard about it long ago. So, if you can reproduce it, that's solid info, but I would guess it would be pretty hard to recreate, so it MAY be something related to only PrimeHD's camera?
 
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