25F - stairs in thin objects
 

I haven't used much 25F until now and here's a question about it. I get quite bad stairs in thin lines, as if 25F was interlaced (showing only another field). This happens only when a thin object is in front of bright background. But I haven't ever seen this with 50i. So am I capturing my 25F-material wrong or is this normal behavior with F-mode? I use FCP6 (HDV-1080p25 settings) to capture/edit.

Click the picture to enlarge it:

Same here...
 

I have exactly the same problem, and it gets worst when you downsize it. Sometimes i use the Flicker filter to hide it a little.

I read an article stating that Canon produces it's frame mode by using a vertical pixel shift; this is because the image sensor is interlaced, and they are not able to give us true progressive. This may explain why you see the effects you are talking about. This also reduces the vertical resolution when compared to the interlaced frames. They are approximating a progressive scan.

This doesn't bother me too much as the "pixelation" around the details.
I shot some 25F yesterday and it shows the same. Could be downsampling from HD to SD (DVD). I have not checked on HD screen. And, looking directly at Parkinson (ITV?) after my test DVD I found out that the XH A1 is really a crappy camcorder ;) But they are on another budget... Don't rave. I like the A1 very much. Yet another concert to shot tomorrow!

Yes. Sadly this might be the case. I was hoping that there is something wrong with my capturing method.
It is absolute possible to get great 25p picture from A1, if there isn't a bright background behind. I'm shooting mainly nature, so there are lots of situations when stairs appears.
I've been reading here that many of you are using only 24F. Do you have some settings or tips to reduce this problem?

It looks like it has been deinterlaced. What capture/editing software settings are you using? Do you happen to use FCP 6 with "no fields" in the settings? If so it is possible that it's deinterlacing the image.

I'm using:
HDV 1080p25 preset to capture
HDV 1080p25 (HD 1440x1080 / Field Dominance None) for a timeline.

The problem is that I can only see 'stairs' when objects are in front of a bright background. There are limited situations where stairs appears. Otherwise picture is good.
Exactly where I can find that "no fields" setting in FCP (or did you mean Field Dominance)?

It has to do with the way Canon creates progressive frames from an interlaced ccd. The sampling means that alternate lines have 1/3 of colour information to build the picture from hence the stair stepping.

You'll only notice it on high contrast areas and has absolutely nothing to do with capture settings.

i konw this problem since my first test with that 25f mode...and i came to the
conclusion that i recieve better results when i film in 50i and use a good
deinterlacer afterwards(blending fields and move detection). hoped also to save those steps in my workflow...

So does the 24F have this problem or is it just PAL modes. It seems that all who have noticed this issue uses 25F-version of A1 ?

Try setting field dominance to upper. I know it makes no sense, but FCP 6 WILL DEINTERLACE video material if field dominance is set to none. Then take another screen capture and show us the result.

FCP 5 did not do it and this has caused me many headaches. I don't want it to deinterlace, but I also don't want it to create interlacing in effects. It blows. I'm willing to bet that this will cure your problem. I've seen many images from the a1 that don't have any stairstepping artifacts and it shouldn't have them anyway!

I'm not a FCP guru, but isn't it impossible to choose upper field for capturing 25p(F) material via firewire? I think FCP forces you to 'none' field order if the preset is set 1080p25.
I tried to set upper field after capture, but it didn't change anything. Also it seems that stairs are already in the tape, though I can only check this via component out which forces me to use 1080i.
Are you sure about that "FCP6 will deinterlace", because the picture doesn't normally look like that. I'm quite sure that my captured material is 25p without any interlacing.
I have witness this stair effect in very few shots, so this could be the reason why you haven't seen this.

Still I'm wondering has anyone with NTSC 24F -version seen this happen?

I had a 960x720 DVCPRO HD sequence and FCP deinterlaced it if field sequence was set to none. After capture, it doesn't do anything to the during capture. Maybe your FCP understands that those XH A1 files are progressive, but my FCP didn't understand my P2 files.

Did you export an image and look at it? The preview window also deinterlaces if it's smaller than 100%. You could also try opening the files with quicktime and take a look at the direct stream.

That's because 1440x540 is still enough resolution that you won't see those stairs everywhere. But they are there, just simpler to spot with high contrast edges.

I've done all that. Only step where deinterlacing could happen is capture, but I can't change those settings (1080p25 is field none like it should be). I can view material in Full HD scale (FCP and QuicktimePlayer), so what I see should be ok.
Here's the original clip you can download. It's very foggy shot with low light, but the 'stair effect' is really visible. Captured with 1080p25 preset.

Download clip here (25Mb):
http://aavekammari.pp.fi/stairs.mov

I can see the stair-stepping in 24f, to answer an earlier question. Not terrible, though, I find it to be very faint, only noticeable on contrasty edges, and if you go down to 1280x720, it's gone.

are these final, rendered clips or artifacts that you see on the timeline? i though i had a serious issue as well but discovered that wasn't the case after exporting. i see it only in editing, when vegas stretches the 1440 to simulate device aspect ratio. when rendered, monitored, or reviewed from in-camera the footage looks fine. here's before and after.

Thanks for your answer. I'm quite sure now that this is what is happening also in my case. FCP is not to blame.
Now that I've made some test more, I can confirm that I see those same stairs in all steps (in camera, imported clip, timeline, rendered).

And again, stairs are visible in very few shots / situations. Otherwise 25F-mode looks just great.

I couldn't get your clip open, but I believe you. Well that's a bummer. I guess I won't be using the 25p mode if I get an xh a1.

The good news is that while the stepping artifacts can sometimes show up under some circumstances, they're generally not visible when watching the video on a TV set. Virtually all of these more affordable camcorders fall short in some area when scrutinized closely. But play it back on an HD TV and voila; beautiful video.

I know I've had people over to watch some 24F footage on my 42" TV and they've always been stunned by how awesome it looks. Are there some shots with jaggies in there? I'd bet on it. Anyone notice them? Nope.

I've been watching "these stairs" all the time via HDTV, my 2nd monitor is 40" Full HD TV, so stairs are there, but you're absolute right that I do look the picture much more careful than people who just watch the contents.

It's not that bad. The reason why I see it is that I shoot mainly nature. There are just lot of hard situations for 25F (and also for mpeg2). I just watched 3 hours of 25F material and (visible) stairs were only in couple of shots.

Does the xh a1 encode 25p material better is it has less information than 50i? Does it look better encoding wise?

I would say no, but I'm not really sure about that, because it does look different, even if the picture has no moving objects. Is it encoding difference, don't know.

Well that's a bummer. If the stepping is enough where its bothering you while viewing on a TV, you might try a horizontal channel blur. Sometimes just blurring a single channel by a pixel or two does a nice job of reducing some jaggies without appreciably softening the image. It ain't perfect, but it can help sometimes.

Can you post samples of the same scene shot in 25F and 50i?

What is your sharpness setting? Having it too high will certainly cause stairs. Does turning it all the way down make a difference?

Perhaps the JPG algorithm is causing such a severe stair stepping. What program are you using to make you're jpegs? What is the quality setting for the JPEG?

Do you have screen caps off a high resolution hot screen we can see to compare the level of stair stepping? Is the stair stepping even there in a full rez hot cap with biometric compensation?

http://aavekammari.pp.fi/stairs.mov

There is an original FCP captured file (HDV Quicktime 1080i50, 25Mb). This has nothing to do with jpeg. It's there in the original file also and when viewed directly from cam.

I'm going to be very busy in coming weeks, but I'll try to create an example (25F/50i) as soon as possible.
My sharpness setting is set -1. I haven't test it yet, but I'm quite sure that turning it down will decrease stairs. Of course this would also make all shots too soft. I have to try this also in real life when I have more time.

As I earlier wrote, stairs are visible in very few shots.

Still can't open that file, can you give a straight m2t file without any encodes to a different format?

You need a QuickTime Pro to view FCP HDV files. I made H.264 clip. Of course it isn't the original anymore.. but at least you should be able to watch it.
http://aavekammari.pp.fi/stairs2.mov (8Mb)

I had some stairs in my footage too.

LOL!! I love that!

Again, easily solved with a subtle blurring technique. If you scrutinize the frame, you may notice some softening of the image.

It's amazing what you people are doing with the new 33bit extrapolated algorerhythms.

Or just have a strong drink or a beer too many. Results may vary, but what you will see may also be similar to 33 bit... whatever :)

... and just want to add that 33 bit algorithm is perfectly reversible with proper sharpening, as seen in attached example ;-)

Uh.. really bad looking stair-stepping you have there. Haven't ever seen that bad in my shots :D

Completely off topic and random questions, but I like the seriousness you approach your camera:

1) How do you protect for overexposure, since zebra didn't show 100 ire. Just guess once used to how lcd behave?

2) How do you like your Cineform+FCP workflow? (..well, maybe nobody use it since it would probably involved in stair stepping issues conversation)

For whom had previously a DVX:

2) How do you like/dislike focusing ring feel?

3) Better sd (also in 4/3) now or before (intentionally not talking about 16/9 where advantage has to be obvious)?

Cheers

The stair steps are cause by the way the Canons create progressive frames from interlaced ccds.

The XL-H1 and XH camera clock the greed CCD a field out of sync with the blue and red CCDs like so.

rbrbrbrbrbrb
gggggggggg
rbrbrbrbrbrb
gggggggggg

This obviously means there is a green sample or a lower luminance same in the field sampled by the red and blue CCDs hence the slight loss in resolution seen as stair stepping round areas of high contrast.

TT

So it creates the same artifact as your basic hdv-deinterlacing would? Hmm. Not good.

I think Canon's technology is much better than that. Images speak for themselves. XL-H1 and A1/G1 produce the best images below $10k imo and do not exhibit painful problems that software deinterlacers do.