what is PROGRESSIVE SCAN?

[Adi Head]

i'm reading through my pal PD-150 manual.

can someone explain what exactly PROGRESSIVE SCAN means?
i understand from the manual that if you intend to use frames as still photos, you should set progressive scan to ON. and that if you use progressive scan, camera motion may look jumpy.

but what is it exactly? what manipulation does it do to the footage? is progressive scan ONLY for making still photos?

thanks.

[Henrik Bengtsson]

Normally your footage is made out of fields, every second line being from Field 0 and every other from Field 1. Progressive scan means it stores everything as frames instead. The term is usually used with DVD players where it means that it does a frame interpoliation (usually) between field 0 and field 1 to create one full frame. This is then outputted to the TV or Projector as a full frame.

[Adi Head]

ok. but why does it do the things that it does?
isn't it possible to shoot NOT in prog scan mode and still make still photos later?
why does prog scan mode cause jumpy motion?

if i don't plan to make still photos of my footage, are there still reasons why i should use prog scan mode?

i've read posts about using prog scan mode as something that has to do with generating a "film look", but since my camara is a PAL 150, i'm not sure how relevant this issue is for me.

i just want to be clear on all the issues concerning this feature. thanks.

[Marc Betz]

Say you are panning across a block of wood.

Progressive scan will give you 25 FPS (pal) and each frame will look like this

_____________
_____________
_____________
_____________

A clear picture in each frame.

Normal video will look like this at 50 field per sec.

_______________
() _______________
_______________
() _______________

(ignore the parenthesis, the spaces I used to offset the 2nd line dissapeared when I posted)

Since each field in video is shot at a differnet point in time and displayed in still mode as one frame. The percieved motion in field mode will be smoother as the movement sort of overlaps. In progressive scan, the movement is not blended and can look jerky because the distance the objest travels between each exposure is greater.

Video mode is smoother but makes crappy stills
Progressive mode is jerkier but makes great stills.

Try this link to see the difference (pretty simplistic description but shows what I mean).

http://www.canondv.com/xl1s/f.html#

Click Interactive video

Then click on Shooting Modes

People love progressive scan/frame movie mode because is takes away some of the smoothness that makes video look like video.

[Frank Granovski]

You might try these links about progressive scan. (I haven't tried to see if they're still up.)

http://www.digitalconnection.com/FAQ/multimedia2.htm

http://www.pulnix.com/imaging/i-techC.html

http://www.theperfectvision.com/howto/howto_tech_9.htm

[Adi Head]

thanks for the links.
i still don't get one thing. since my camera is a pal camera, won't it shoot 25 frames/sec anyway? isn't that what pal is? as opposed to ntsc's 30 frames/sec?

i'll take a look at the links. thanks again.

[Adi Head]

ok.
i tried the links. no luck.
but searched myself in google and found some good information (if anyone reading this thread is interested) here:

http://www.camcorderinfo.com/content/progressive_video_ntsc.htm

(copy n' paste, don't know how to make it a hyper link)

by the way, in this article, they state the following:

- - -"Interestingly, in 1995 Sony issued a press release announcing the development of their new line of CCDs, of which the big buzz was that they would be able to shoot at sixty full frames per second in progressive scan. Only a few of their prosumer cameras, namely the VX1000, VX2000 and TRV900, ever used it, and were only limited to 15 fps. The latest cameras do not incorporate progressive scan at all, but rather, something called progressive shutter.

Sony, and other camcorder manufacturers recently, have learned that the average consumer doesn’t appreciate the difference between regular interlaced video and progressive scan and have apparently shelved the technology for higher-end cameras. In its wake however, it has left a progressive shutter system. This technology is used only in still picture mode, and emulates progressive scan by using a mechanical shutter to cut on motion blur." - - -

what about the 150? is this a true progressive scan mode? or is it what they call "progressive shutter"?
also, does the 150 have some kind of fps limitation?

[Mike Rehmus]

Sony, and other camcorder manufacturers recently, have learned that the average consumer doesn’t appreciate the difference between regular interlaced video and progressive scan and have apparently shelved the technology for higher-end cameras. In its wake however, it has left a progressive shutter system. This technology is used only in still picture mode, and emulates progressive scan by using a mechanical shutter to cut on motion blur." - - -

I do not believe there is any mechanical shutter in current Sony camcorders. What you read as progressive shutter is still progressive scan.

[Bill Ravens]

for your pal system.....normal record mode would record 50 FIELDS per second, which when interlaced to make a frame would be 25 FRAMES per second. In progressive scan mode, a true progressive scan camera would record 25 fields and 25 frames per second. IOW, each field is also a full frame, instead of a half frame. Because normal mode takes two fields per second, each field is acquired about 1/2 second apart, resulting in a "rasterizing" of the image when there is rapid horizontal motion. Normally, in video, the rasterizing is kinda hard to see. In still frame capture, the jagged edges would be horrible. If you want to see an example, go to this site:

http://www.lukesvideo.com/

In cameras like the XL1s, which has a "frame mode" two interlaced images are still acquired, but, they are acquired at the same instant in time instead of 1/2 sec apart, thereby removing the temporal differences in each field. It's not true progressive scan, but, it gives the same effect. The difference is a slight loss in vertical resolution. For my money, you can't tell the difference on a TV screen, and only the trained eye can see the difference on a VGA monitor.

[Adi Head]

i think i understand now what "true progressive scan" means more or less and how it differs from the normal interlaced fields. and i'm pretty sure i understand how the xl-1s "frame mode" simulates this by using both fields at once and doesn't alternate between the two.

so what is the PROGRESSIVE SCAN MODE on the sony pd150 (pal)?

is it "true progressive scan"?
is it like the xl1s "frame mode"?

[Mike Rehmus]

yes and yes but at a slower rate that is not really suitable for video. But it makes great stop-frame-animation!

[Andre De Clercq]

I don't own a VX2000, but if one wants to get prog pictures from all available CCD pixels, there are only 3 possibilities
1. One needs to have a prog readout structure together with the underlaying buffers and processing structures (DVX100)
2. One needs to use an optical ( mechanical?) shutter (VX2000?). These shutters (like iris shutters) are suffering from short lifetime if continiously used and are slow (reason for the 15 fps on VX2000?). The CCD (electronic) shutter needs to be slightly different in this situation.
3. A progressive electronic (CCD) shutter which is the electronic equivalent of the curtain shutter in SLR photocamera's. Here too, the readout and processing needs to be changed for this mode.
If somebody having the VX2000 could verify if in the 15 fps mode the picture would show geometric distortion(apart from the motion blurr) with a fast pan/tilt , we could accept possibility 3. Otherwise there must be real prog readout (difficult if the CCD layout is not being designed forit) or an optical (LCD?) or pure mechanical shutter in the system.

[Adi Head]

mike, so what you're saying is that if i'm shooting video (not for stop frame animation, or still photos) with my pd150p, there is no apparent reason to shoot in progressive scan mode. and if i want to achive a 24 fps "film look" i'd be better off shoot in normal mode (NOT progressive scan) and manipulating the footage in post.
is that right?

[Frank Granovski]

Sorry about those links. It was a while ago that I printed out these articles sitting in my top desk drawer. They're good reference. perhaps try:

http://www.adamwilt.com

I'm sure he's got something about progressive scan on his great site.

[Mike Rehmus]

I supose if your talent is moving slow enough that 15 fps works, then ok. Otherwise, you will get some very strange video with 15 fps.

I think you have to use normal modes for normal subjects.

Light your scenes very carefully and they will transfer to film reasonably well. They never will be HD at 24 fps but it will work.

I have a friend that wrote, shot, and edited Blood, Guts, Bullets & Octane with a GL1 (I think) and then had it transferred to 35mm. The film was bought by Tom Cruz for distribution. That wasn't a technically great film but the story worked and his talent came through. Joe Carnahan is currently directing Tom Hanks in his next film.

BGB&O cost under $8,000 to shoot IIRC.

Somy advice is to shoot with what you've got. The camera is the least of the issues in front of you if you are going to do a feature-length film.