TRV900 Progressive Scan

13 replies [Last post]
Christian Lett
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Joined: Apr 26 1999

One of the most common questions a video camera user who wants to shoot a movie (either feature or short) asks is: 'How can I make it look like film?'

Various answers will point you in the direction of contrast, depth-of-field, lighting, colour saturation, etc. Some will mention frames vs fields.

I must admit, it took me a while to grasp the concept of fields but now, I think (and please correct me if I'm wrong) that I understand.

If we assume that (for film to be transferred to video) film is shot at 25 frames-per-second (fps), when it is transferred to video for whatever reason, one frame is captured on both fields. When we shoot video, one field is captured by the CCD an instant before the other field, essentially recording two lower resolution 'frames' in place of one normal frame. Ideally, if a video camera could capture both fields at the same time and record them in such a way that the image doesn't advance until both frames have been recorded, a 'film look' would be achieved.

I have a TRV900E and was under the impression that progressive scan mode did precisely that - the user manual says that when in this mode, it 'takes in 25 fps'. It certainly didn't look like it did as the motion was rather jerky, so I did an experiment with a stopwatch, recording in PS mode.

On playback, I stepped through the frames: it required 2 pushes of the advance button before the image on screen updated. One second worth of footage actually only had 12 'frames' where the image changed, not 25.

So, am I doing something wrong? Is there another setting I've missed somewhere? Or is progressive scan just a near-useless feature, useful only for taking 'high-quality' stills (when the quality is really pretty poor compared to a proper digital stills camera)?

Christian.

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Christian J. Lett
[email=clett@nationalexpress.co.uk]clett@nationalexpress.co.uk[/email]

Christian Lett After Effects and Maya Artist www.quarterlightpictures.com

Unicorn
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Joined: Apr 12 1999

No, you're not doing anything wrong. The TRV900's 'Progressive Scan' video mode is a joke, as it records each frame twice! It's great for stills, but just a marketing gimmick for video.

P4-3.06/2GB RAM/2500GB IDE/SATA. Avid Media Composer, Liquid Edition, Premiere 6, Lightwave, Vue 6, eyeon Fusion 5. DV and HDV editing/compositing.

Christian Lett
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Joined: Apr 26 1999

Bummer!

Cheers Unicorn.

Christian Lett After Effects and Maya Artist www.quarterlightpictures.com

michiel
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Joined: May 13 1999

I recall a post on here saying that the DX100/110 and the XL1 do progressive scanning correctly?
Anybody with one off the above please confirm or otherwise, your comments on this would be appreciated as I am about to purchase and the ability or otherwise to do good progressive scan is important to me.

Thanks in anticipation.

M.P

Alan Roberts at work
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Joined: May 6 1999

I have a DX100, and in "Frame Mode" video or "Still" modes it seems to read the entire ccd at one go. So the exposure is from a single period of time (20ms in PAL/625).

Whatever the mode, the ccd is copied at high speed, once per integration period, into a RAM. This either in the field blanking or during line blanking, depending on precise type of ccd. The RAM is then read out to make the video signal. For interlaced video, adjacent pairs of lines are averaged, with a phase shift each field to achieve interlace.

If the ccd is copied at 50Hz, then we get conventional video. If it is copied at 25Hz, then the RAM is refilled only at frame rate and we get a "progressive"ly scanned image, but output to interlaced video. That's what normally happens for "Frame Mode". The integration period is still 20ms, otherwise there would be too much blur. Consequentially the exposure is reduced by one stop because alternate periods of 20ms are simply dumped into the ccd drain channels.

In "Still" mode, exactly the same happens, but there's only a single transfer of the ccd into the RAM, which is then read to video for 7 seconds.

Either way, the process ensures that vertical resolution is that of a 576 line image, rather than that of two temporally summed 288 line images.

Hope that's clear. Shout again if you want more details.

michiel
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Joined: May 13 1999

Thanks Alan.
I suppose my next question would have to be, from a creative perspective, does this mode produce the desired effect of "shot on film" ?
I usually capture by Y/C dropping one field to gain a similar "feel".

Thanks.

M.P.

Unicorn
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Joined: Apr 12 1999

Yes, the XL1 does it right, and yes, it does give a little more of a film look. However, it doesn't fix video contrast problems and the like.

P4-3.06/2GB RAM/2500GB IDE/SATA. Avid Media Composer, Liquid Edition, Premiere 6, Lightwave, Vue 6, eyeon Fusion 5. DV and HDV editing/compositing.

Alan Roberts at work
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Joined: May 6 1999

Mark (Unicorn)'s right, it goes some way to giving a film look, but not very far. The transfer characteristic of film is logarithmic over a long range, while video camera gamma correctors work reasonably well over a much shorter range. To get a decent film look you need to raise the gain near black to about 9 times (typical broadcast cameras are gain limited at about 4.5 to 5 times, while high-street camcorders rarely get above about 3.5 times). Also, you need to implement a "knee" function to cope with overloads in a gentle way, and to tone done or remove aperture correction.

This is a big subject that I could go on about for a long time, and was to have been the subject of a series of articles I offered to write for CV. Bob turned down the first because it was too mathematical

DVdoctor
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Joined: Apr 1 1999

If I remeber correctly the earlier camcorder VX1000 etc in photo mode only used one FIELD to create the image resulting in a poorer quality than folks were expecting.
The TRV900 in photo mode does capture the complete frame (576 lines)
I haven't tried to test the field rate, I'm curious why you are only getting 12 Fps Could be sony trying to make it look like film with the frame rate etc.

If for some reason your shutter speed were lower possibly only half the images would be captured (is shutter speed of 25)

Anyone else tried this?? My TRV900 is still in US so I don't have one to try on.
The XL1 seems to do it correctly at 25FPS

Problem is that until we get to a Progressive scan TV (like the High Def US units that are appearing) we just re interlace the image back again, we the effect is of questionable value and I have heard that folks doing a Video to film conversion DO NOT Recommend that you do it.
John

tom hardwick
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Joined: Apr 8 1999

I've been using my TRV900E for putting slides to mini DV, and it's great.

I select Progressive Scan and 1/25th sec. This allows me to hold the slide up to the lens, push the photo button and record 7 secs of full definition video.

I use 1/25th because the light source I've chosen means that this shutter speed allows me to use the best (middling) apertures. In combination with the inbuilt ND, and manual white balance, the results can be outstanding.

This "Photo" mode means there's no dancing grain - as you'd get if you simply took a 7 sec burst of moving video. There ARE quality differences, but I'm at a loss to describe them.

tom.

Main Man
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Joined: Jun 24 1999

If i understand correctly, the reason you want this "progressive scan" feature is so that the video looks more film like. In the films I have made in the past, i have always done what michiel has done, drop one of the fields oin the image, but this results in poor quality. But I have found a way of creating this "film-like" effect with out having progressive scan or dropping a field.

If will work if you have Adobe Premiere, simply drag your clip to the time line, right click on it, go to field options, and choose flicker removal. Now render it, and maybe put some widescreen bar at the top and the bottom of the screen to finish the effect using the "clip" filter.

Try it, and tell me if it works - it did for me!!

Main Man.

john harris
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Joined: Sep 14 1999

This is my first ever reply to messages on this bulletin board, although i've been reading it for some time. I work professinaly in TV and Video production and have been using the single field method of making video look like film since a chance discovery back in 1989 using a Sanyo VH5000 VCR which came with a range of Digital effects such as Picture in picture and freeze modes.I am in the fortunate position to have many items of current DV equipment including Sony DS30 Dsr200 Vx9000 Trv900 and a Panasonic EZ1. The TRV900 will give a filmic look if you use the 1/25th sec shutter speed but it is slightly blurry and does not look right. The panasonic EZ1 works superbly in frame mode giving a very fluid filmic feel to the image. The problem in both cases is that you are stuck with the look as you have recorded it. Try using the digital still effect on the TRV900 on analogue playback (does not work thru DV OUT) and set the playback frame rate using the thumbwheel. Alternatively, use premier and Deinterlace the video clip, I find this looks better than using flicker removal, you could try combining the two. A further option is to used Plug-in FX such as Aged film or Cinelook.

Alan Roberts at work
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Joined: May 6 1999

John, the reason why 1/25th looks blurry is because, while you're shooting at the right frame rate (25fps) you're keeping the shutter open for the full frame. Film cameras don't do that, they generally have a 180 degree shutter, which means that the exposure is 1/50th second. Fortunately, that's exactly what tv cameras do, so the real target is to expose for 1/50th, transfer the entire ccd image to the readout RAM once per frame and read the interlaced fields from there. And that's exactly what many DV cameras do in "Frame" or "Still" mode. Just occasionally there's a rogue that duplicates frames, to give 12.5fps, but that has to be a major mistake by someone in a software lab deep in the bowels of Sony

Christian Lett
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Joined: Apr 26 1999

I tried John Harris' suggestion and played some DV footage back on my TRV900 whilst applying the FLASH digital filter. Genius! By using the lowest setting, it looks like 25 frames instead of 50 fields. Although subtle, the effect was instant and it made my music video look even more amazing than normal (Not very modest I know but what the hell!)!!!

Anyway, cheers!

Christian.

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Christian J. Lett
[email=clett@nationalexpress.co.uk]clett@nationalexpress.co.uk[/email]

[This message has been edited by Christian Lett (edited 29 October 1999).]

Christian Lett After Effects and Maya Artist www.quarterlightpictures.com