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

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.

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...ny-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.

25f horizontal lines XH A1
 

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

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.

If possible Pavel, try to shoot with shutter 50 not 25, only in static low light situations you shoot in 25 shutter. Or maybe you had a good reason to do so.
Generally shoot shutter 50, if there is to much light: add an extra ND.

btw: the mentioned detail settings-->

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

are the mainstream settings, I played with them, changed and tested them, and easely could see the difference in the "jaggie" forming. I am sure you can see that too. But, you have to adept to the shooting situation, like high contrast, diagonal lines etc.
Maybe a preset for those situations? Anyhow, if you go to SD after the edit you wan' t notice the jaggies too much.

Thank you. I shall rest in peace today.

All very good points. Perhaps I could render the whole clip in HDV and import to After Effects and apply the vertical blur to the whole thing, and then down sample to any other resolution. (While writing this I feel it might not the best idea. :) How about FCP 6? Friend of mine has Sapphire plug-ins they might have some remedy. Philip, if you get a chance (and time) could you please elaborate of the procedure in AE? I am new to AE. Many thanks.

Raymond, the reason for shutter 25 - I shot documentary in India for my Uni course and was under impression that slower speed will reward me with less TV look. Was I under right impression?

Add yes, I should really create presets for specific shooting situations. Good idea!

BTW I used a preset from this site - TERRA1 consistently throughout the photography.

I love the picture just this was quite unexpected shock.

Regards,
P

Hello,

Just a question, would this 'stairs' and jaggies be solved when the footage is recorded on the FireStore hard-drive unit? (I imagine to record on the tape as a backup at the same time)

If yes, I am seriously considering to get one.

Thank you for your input.

Regards,
Pavel

Hi Pavel. The tape and the hard disk record exactly the same video data, so it shouldn't make any difference.

Richard

Besides the 'stairs-effect' I also get a flickering effect in straight horizontal lines at 25 f. At 50i this effect is not present, or much less at least. So I shoot in 5Oi mainly.

Why shoot progressive with interlaced ccds? You lose temporal resolution without gaining any image sharpness; it really is a big mistake. Interlaced is better than fake progressive in almost all respects.

Because interlaced video has lower resolution and worse artifacts when shown on a progressive display.

The fact is that a large and growing portion of the audience will see the video on their progressive display. Last year, just LCD television sales alone outstripped all interlaced TVs, not counting the myriad of other video display devices.

Many distribution formats only support 30p/24p, such as most Internet options, which negates the temporal resolution "advantage" of interlaced, assuming you even like the look in the first place.

Even fewer distribution formats support 60p, which prevents you from doing a high-quality deinterlace in post-production because it would, again, negate the temporal resolution.

If their display can deinterlace properly, at least they wont get the nasty flickering that interlaced TVs have, but they'll still have combing, loss of resolution, and probably more defects depending on the quality of the display's deinterlacer.

Things get even more ugly if you're extracting 24p in post-production, the motion is different from true 24p and suffers problems that 30p doesn't have. (PAL excepted.)

Finally, progressive video will look equally good on interlaced and progressive displays. So aside from temporal resolution and the artifacts discussed here, it has every advantage over interlaced video.

I don't agree. Not for the XH-A1. 24F loses vertical resolution due to it being produced from native interlaced chips. You're point would be better made toward the Sony EX1 which gives its highest resolution in 24/25p.

And progressive displays will eventually need to properly deinterlace anyway, because 1080 interlace will remain a broadcast standard for some time, which looks fantastic on tv sets that can properly handle it. For those monitors that can't properly deinterlace, why would I want to be targeting to the lowest common denominator, when 1080i60 looks stunningly great on sets that can do it right?

What we should be insisting on are progressive displays that also properly deinterlace and reverse pulldown 1080i until the day when 1080p60 becomes a broadcast standard, which today it is not.

The Canons lose 15% resolution, sure, but progressive television deinterlacers lose far more than that, usually over 30%. The ones that don't blend away that much detail are leaving in combing, flickering, and other interlaced artifacts.

If a television display had motion-compensated deinterlacers, it would only soften the moving part of the image by 30+%, and the static portions of the image would be full resolution. But televisions don't have one because mo-comp is still far too slow.

I disagree. You're lumping the progressive monitors with known poor deinterlacers to the ones that pass full bandwidth. See link below to Gery Merson's testing article:

Are You Getting All the the HDTV Resolution You Expected? Round 3

When viewing 24F or 60i on a Pioneer Kuro or Elite Pro FHD1, the 60i from the Canon A1 is sharper and more artifact free as well, whether static or in motion, than the 24F which has the stairstepping jaggie due to the inherent loss of vertical resolution on the A1, which was the subject that fostered this thread.

I'll read the entire link when I have time, but from a cursory glance I didn't see any mention about normal interlaced artifacts such as combing and flickering; just references to artifacts caused by incorrect pulldown detection.

I've compared my A1's 30F and 24F against 60i with a variety of deinterlace-to-60p algorithms (tdint, yadiff, a few mocomp) and in every case, the interlace artifacts are always visible in high motion scenes or the motion is blurred enough to remove the artifacts.

Finally, it should be said that these resolution and artifact issues are secondary to the desired look of the production.

Wholeheartedly agree.

Hi, I also agree. How about if your desire is to have your production artifacts free as an objective for the desired look of the piece? Basically the ideal is to achieve balance between the quality of the picture and the content.

I like canon xh a1 very much, especially the 24f/25f quality. I guess will just have to live with the occasional stairs in contrasty and fast moving situations. In my view it is ultimately about the feeling, whether the picture feel like real...

25f after compression
 

Hi,

just like to report that the 'stairs' after sending the footage through Compressor (mpeg2 HDV 1080p setting) came out less visible, in some cases almost disappeared. Nice.

Stairs Update
 

Ok, recently I shot water fall on a bright day and then I looked at the footage. Basically the horizontal line or stair was traveling across the frame all the way through from bottom direction up. Terrifying.

Then I have noticed that using camera filters helped the images. I shot with 6x4 Low Contrast 1 and 3 strength and Diffuser number 1. The picture was clearer in a sense that it did not have the infamous stairs on it even on a bright day and with some movements in the frame. But I did not change any setting in the camera, mainly using Panavision 2 and Terra 2 present but with more sharpening added (-2 to -4).

I can't help myself but thinking and hopefully seeing too that the 25f mode appears better in FCP than 50i.

Regards,
Pavel