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11-01-2009, 10:37 PM   #61
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rawr, here are some clips

YouTube - PENTAX K-x Movie Sample ???? 7260? ??????

YouTube - PENTAX K-x Movie Sample ???? ????????? ??(2)

as well as heavy moire in the grass and other textures in tiny's clip and falconeye's camel clip.






I really hope they gonna fix it maybe with some firmware update, it's a real turn-off


Last edited by karl79; 11-01-2009 at 10:45 PM.
11-01-2009, 10:41 PM   #62
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Good for stills, bad for videos.

Depending on the readout rate, they could blend pixels together since the AA filter appears to be weaker.
11-02-2009, 01:28 AM   #63
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QuoteOriginally posted by karl79 Quote
rawr, here are some clips
Thanks for those. I couldn't see much of anything like moire but that just shows I don't understand video.
11-02-2009, 04:14 AM   #64
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QuoteOriginally posted by rawr Quote
Thanks for those. I couldn't see much of anything like moire but that just shows I don't understand video.
Here you go for moiré

(click for full size)


In the camel video, look at the grass in the background. While it looks pretty "normal" in one frame, if you watch the movie you'll see the grass color is flickering. This is from the same color moiré as in the single test frame above. All video dSLRs have it to a certain extent. This extent is larger for a K-x compared to a K-7.

It can be somewhat reduced by a mild defocussing. There is a sweet spot where color moiré is weaker but softness isn't distracting. YMMV

11-02-2009, 04:37 AM   #65
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QuoteOriginally posted by falconeye Quote
Here you go for moiré ...
In the camel video, look at the grass in the background. While it looks pretty "normal" in one frame, if you watch the movie you'll see the grass color is flickering. This is from the same color moiré as in the single test frame above. All video dSLRs have it to a certain extent. This extent is larger for a K-x compared to a K-7.
Aha. Thank you. I am edging closer to an understanding of the issue, I think. But it seems that it might be hard to distinguish moire from chromatic aberration sometimes.
11-02-2009, 08:35 AM   #66
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ok, I thought about getting the K-x for it's video, I'm pretty sure now I won't do it, the aliasing/moire issues make it unusable for me


YouTube - PENTAX K-x Movie Sample ???? ????????? ??(1)
11-02-2009, 09:16 AM   #67
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Gray anti alias video filter

QuoteOriginally posted by karl79 Quote
the aliasing/moire issues make it unusable for me
I wouldn't go this far. Of course, I don't know your requirements.

On the positive side is the outstanding fine detail contrast, on the negative side is the moiré issue. Two sides of one medal, actually. This is most visible with high contrast fine detail like the runway in the above video (or text, usually).

There are gray filters to reduce the effect (basically, a plate with many little holes) which create disks of confusion (by diffraction or refraction) about the size of one pixel in video mode). A slight explicit defocus helps as well (may require mild sharpening in video editing).


INVENTION


A gray anti alias video filter can be self made like this:

1. Place a large number of screws, head down, onto an UV filter.
2. Paint the remaining part black (use spray).
3. Remove the screws and let dry.

The diameter of the screw head should be such that one Airy disk roughly covers one pixel in video.

A. Airy disk radius for screw head with diameter D: r = 1.22 * 0.555 µm * f / D
(f is the lens focal length, green light)
B: r = 1.5 * pixel pitch = 1.5 * 5.5µm * 4288/1280
(pitch of video pixels, 50% overlap)

=> D ~= f/40.8 or 0.44mm for a 18mm lens

Note that one could approximate the effect by using f/32 in bright sunshine.


It may be difficult to obtain and handle screws this tiny. Here are steel balls this small and can be used if spray is applied from a constant angle:
http://www.nanoball.de/de/component/virtuemart/?page=shop.product_details&fl...&category_id=2

Also, one can print out the pattern on transparency sheet. There are special zone plate inspired hole patterns for this purpose (as the holes must not be too dense).


Last edited by falconeye; 11-02-2009 at 09:33 AM.
11-02-2009, 06:09 PM   #68
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This reminds me of the effects I saw in some experimental "video" I did with the K20D's 21fps mode. Lots of flickering color issues, unnexplainable CA (not visible in full-res stills), etc.
11-02-2009, 08:17 PM   #69
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QuoteOriginally posted by karl79 Quote
ok, I thought about getting the K-x for it's video, I'm pretty sure now I won't do it, the aliasing/moire issues make it unusable for me


YouTube - PENTAX K-x Movie Sample ???? ????????? ??(1)
Yeah I am in the same boat. My many reason for my next dslr is video and the k-x videos are just not doing it for me. My hv20 and 35mm adapter does better but doesn't take awesome stills.

I am now looking at the k-7 but really wish it had more control and 24p, and 1080. I would have bought yesterday if it had all that...
11-03-2009, 04:41 AM   #70
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QuoteOriginally posted by 0100 Quote
really wish it had more control and 24p, and 1080.
For 1080p. Yes, it would be great. But to obtain alias-free 1080p from a SLR it needs to scan higher than this, like 1500 or 2000 lines. No SLR does it yet. So, the best you can currently buy is 720p with scanning at about 1000 lines. 5D2 and K-7 are in this boat.
11-03-2009, 07:35 AM   #71
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QuoteOriginally posted by falconeye Quote
For 1080p. Yes, it would be great. But to obtain alias-free 1080p from a SLR it needs to scan higher than this, like 1500 or 2000 lines. No SLR does it yet. So, the best you can currently buy is 720p with scanning at about 1000 lines. 5D2 and K-7 are in this boat.
Absolutely right. What makes 1080p footage of DSLRs look sharper is mostly aliasing: what may appear to be fine details are in fact faked details, "invented" and added by the camera. This false reproducing of the image (aliasing) causes all of the above mentioned issues.
Except for lowlight performance, K-7 offers the best video of all DSLRs so far in my opinion.
11-03-2009, 07:54 AM   #72
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^yeah guys I am pretty much sold on the k-7.
11-08-2009, 04:36 AM   #73
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Henley Beach, Adealide South Australia
Recorded 08/11/09

YouTube - Henley Beach Marina
11-08-2009, 08:54 AM   #74
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That is very sweet.
11-12-2009, 08:10 PM   #75
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I am in utter shock with this one:



Wow. Make sure you download the AVI. Looks really clean for pure night footage.
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