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:

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!

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.

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.

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 ?

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


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!

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. ...
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'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 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.


I tried to set upper field after capture, but it didn't change anything.

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.


I have witness this stair effect in very few shots, so this could be the reason why you haven't seen this.

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.

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.
Thanks for your answer. I'm quite sure now that this is what is happening also in my case. FCP is not to blame.

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.
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.

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.

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.

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.


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.

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.

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.

I get quite bad stairs in thin lines [in 25F]. But I haven't ever seen this with 50i.

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?

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.

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?

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!

I had some stairs in my footage too.

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

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 ;-)

I had some stairs in my footage too.

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

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.


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

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.

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

That's not what I was saying at all. The technique Canon use is no different than how green ccd shift processing works that you should already be familiar with. Think of the system as temporal green ccd shifting.

The Digic processor can easily construct information from adjacent ccd samples. The limiting factor with this method is when a high contrast area is sampled and there is an absence of red or blue information thus there is a resolution drop which appears as stair stepping.

It is actually very good.

25F has much more resolution than a deinterlaced 50i stream. Other cameras in the XH-A1 price range suffer from more fundamental problems of either not having much native resoluton or have poorly implemented HDV codecs.

Message to Chris Hurd.

I can hardly access this site any more. I keep timing out and get sent to the archives section. Can you help please???

TT

That's not what I was saying at all. The technique Canon use is no different than how green ccd shift processing works that you should already be familiar with. Think of the system as temporal green ccd shifting.

Yes, I know the theory but shouldn't that just result in lower res images not stairstepping? I mean the stairstepping in those example images is exactly the size of one line. The exact same size of stairstepping is created by deinterlacing hdv footage. High contrast images also show regular deinterlacing way better so it doesn't necessarily have anything to do with not enough colour.

25F has much more resolution than a deinterlaced 50i stream.

How much? Is it possible to get a 50i screengrab vs the same image in 25f?

I have to agree with a previous post--I think all the stair-stepping is due to the sharpening that the camera does before saving to tape. If you look closely, the black stick is blacker and the sky is whiter where they meet each other--this is a clear symptom of software adding contrast (even though it is done in-camera). Try turning your sharpening down to -9. I have done that with my A1 and the pictures retain all of the sharpness of the original image without the "stair-stepping." Then you can add a little sharpening in post if desired.

The thing with that though, is that the stair stepping will reappear if you apply sharpening in post, and much worse. I think the sharpening is honestly 0 at 0, and -9 simply adds a blur. Honestly, Canon does such a great job, and I have not seen stair stepping to be really an issue at all. I have noticed it in some shots, but it doesn't merit concern or panic. At least for me. Again, when downrezzing to 720p, it's gone.

Mikko

I have got some grabs here that compare 25F to 50i to 50i_de-interlaced and categorically show how effective 25F is.

You'll have to take my word for that 25F has significantly more resolution than a de-interlaced 50i image. In order of resolution 50i has the most followed closely by 25F then a long way behind is 50i_DI.

Unfortunately I am not allowed to post attachments. Looks like I am still sat on the naughty step.

All the best

TT

Stairstepping or jaggies.
It's my greatest concern with the A1 (working with it for one year now). I shoot exclusively in 25F/shutter 50, but the stepping stairs, 'jaggies' specially in strong contrast situations, is bothering me. It is the weak spot in this camera. Sure, there are many situations you do not see them.

It has nothing to do with editing or capturing, it's in the signal, it is on the tape. You see it mostly on diagonals, but a green shirt with backlight on a yellow wall will show it all. I talk for the 25F here, don't know about the 30F, most complains I see are 25F related.

It is a interlaced chip to start with. What is the processing in the A1 doing? combining the two fields in a 2x Hz speed (for us 100 Hz) and placing them as a compressed progressive field back in the 50 Hz timing. And during that processing the jaggies occur in some particular situations. And although the final 25F signal is better then the interlaced interpolation during post, it is not problem free.

What to do?
I noticed it (jaggies) on contrasted situations, on diagonals, so sharpening (edges) is not recommended, but we can also 'play' with the:

SHARPNESS : 0
H DTL FREQ : MIDDLE
DTL HV BAL : 0

The detail frequency and the detail horizontal vertical balance, the first (H DTL FREQ) you like to set to [low] if working for film out or green screen, the latter can -also- influence the diagonals. I think Canon tried its best to make the 0 setting as good as possible, the standard balance with no shift to the sides. I prefer the sharpness at 0.

If you found a setting that is mostly doing good to prevent the jaggies pleas say so. I think however that the situation (light, edges,contrast) is most important in getting troubles with the jaggie.

BTW:
The BBC tested their Sony HDW900R HD cams to their studio situations, I read that to understand a little more.
http://www.bbc.co.uk/rd/pubs/whp/whp-pdf-files/WHP034_ADD22-Sony-HDW900R.pdf

I noticed the Detail freq 0 (-99~99) Frequency of detail compensation 99{v} that is a high setting for the video mode.

Hi,

Does anyone has an issue with horizontal lines when panning or camera tripod mounted line(s) appear on moving object across the frame...? Cutting in FCP 6, easy hdv 25p setup, none field dominance in sequence setup. Shooting in 25f/25 shutter.
Would there be a cure for this?


Many thanks.

Pavel

Refer to the post immediately above yours -- experiment with these Custom Preset options: HDF (Horizontal Detail Frequency or H DTL FREQ) and DHV (Horizontal / Vertical Detail Balance or DTL HV BAL). Please post the results of your findings as this is always excellent material for discussion.

Thank you Chris. I will experiment with it this summer and will post my findings.

Now, however I got almost 20 hours of footage and it drives me crazy to see these lines basically on majority shots where there is a movement in the frame on otherwise good footage... and of course the lines appear when the atmosphere of the shot is at its peak...

Would people share some post-production technique how to reduce this on already captured footage, just for the peace of my mind...?

The footage was captured:

Sharpness: 0
H DTL FREQ: MIDDLE
DTL HV: 0

Many thanks.
Pavel

Would people share some post-production technique how to reduce this on already captured footage, just for the peace of my mind...?


A small amount of vertical blur might help out. Sometimes slightly vertically blurring one of the channels can help without making a major impact on the overall sharpness of the video. YMMV of course. I've gotten a few shots that improved with a minor vertical blur in the red channel (maybe 1-2 pixels, if I recall). I use After Effects, I assume other apps have similar capabilities.