A few bits about EX1 shutter, blurs and transfer

[Craig Seeman]

You’re now dealing with the wonderful world of spatial vs temporal resolution and HD formats.

I’ll speak in terms of NTSC but the concepts hold true for PAL of course. I’ll try to keep the explanation simple.

59.94 Interlace frames per second (aka 60i) means the motion is being sampled at that rate . . . but any given field has only half the full lines of resolution (every odd or even line).

29.97 Progressive frame per second (aka 30p) gives you higher resolution per frame but more space between samples of a moving objects.

One simple way of thinking is 60 lower rez pictures per second vs 30 higher rez pictures a second. Of course I’m not touching on how the mind perceives this or how shutter speed has impact but I’m keeping this simple.

23.98 (24p) and the space between motion is even farther apart! It’s upside is that it’s sort of a “universal” since you can: go Film out easily, do a slight speed change to get PAL 25fps or add pull down to get NTSC 29.97 frames per second.

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Now want if you want the best temporal resolution of 59.94 interlace but the best spatial detail that progressive provides . . . that’s 59.94p (aka 60p).

Here in NTSC land the broadcasters themselves have gone in two directions. Some show HD in 720p60 (60 frames) and others do 1080i60 (60 fields which is 30 interlaced frames).

So your choices, all of them, are there in the EX1. That’s one reason the camera is SO GREAT. YOU get to make the choice.

Keep in mind the camera, just like the broadcasters, are moving data with limits as to what they can handle whether recording or transmission. 1080p60 might be an ideal but broadcasters aren’t pushing that much data and neither is the EX1.

So what might YOU do. It may depend on what you shoot. If it’s fast action sports you might choose between 720p60 or 1080i60. Keep in mind you might be thinking about what looks better when you do that slo-mo too. They’re both taking “snapshots” every 60th of a second. The eye MIGHT perceive 1080 as higher resolution but you’ll be faced with de-interlacing when you do that slow-mo. Take your pick the choice is yours.

If you’re shooting “slow moving” drama or talking heads you might opt for 1080p30 since you get the most detail per frame and the subject isn’t moving so much so 30 progressive snapshots might suffice compared to 60 snapshots (of either 1080i60 or 720p60).

Now if you’re facing the “universal” (film out, xfer to PAL and xfer to NTSC) you might chose between 720p24 or 1080p24. 1080p24 seems like a “no brainer” BUT if you want to shoot and integrate overcranked slo mos of 720p60 without any resolution changes you might stick with 720p24.

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Then there’s the shutter. When shooting Progressive one might compensate for the motion blur by shooting at a higher shutter speed (less motion is captured while the frame is exposed. But you may well need more light though to compensate for the fact that the sensor has less time to gather the light. Lower shutter speed – more blur. Higher shutter speed – more staccato motion (the famous “Saving Private Ryan” look). Again the choice is yours. Of course shutter speed affects interlace video too but I mention Progressive because these where one is most aware of the blur vs staccato look.

Data rate. Keep in mind that XDCAM HD (and the EX1) is VBR 35mbps. How those bits are used are dependent on the spatial and temporal resolution. at 24fps you got more bits per frame. Think about how this impacts what you shoot too. It’s a VBR (variable bit rate) codec so it does have some flexibility. This is one reason why it’s so much harder to “break” XDCAM HD compared to HDV. They’re both long GOP but they are NOT the same.

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Choices, choices, choices. You have so many to make. What you do can depends on subject, lighting conditions (shutter speed impact) and what you’re delivering it for. That’s why, with HD you have to become much more Director of Photographer than Camera Operator because all these resolutions are creative choices (and yes technical too) because they WILL impact the look of your production. There’s no “best” choice. What “look” are you going for?

[Mark Palmos]

Hi there Craig.
Most of our work IS for viewing on computer, or being projected onto a screen via a computer, so progressive 1080 would probably be best.

A question though… wouldnt shooting 1080p be the same thing as shooting 1080i and then rendering the final video to a HQ WMV file 1080 progressive? Or is there a difference?

Thanks for the detailed explanation.
Mark.

[Dean Sensui]

[Mark Palmos] ”
1/ i dont think one can set shutter angle AND shutter speed simultaneously… ie if you set shutter speed for 2000th and angle at 180 but leave the Menu Shutter setting saying “angle” then it appears only the angle will be changed, the shutter will be 100th. (pausing in mid pan one could see motion blur – which one would not if shooting at 2000th sec. Conversely, leaving the menu on “shutter” will mean the 180 degree angle will be ignored and it will be a 2000th of a sec exposure per frame.”

Shutter angle and shutter speed are two terms for what’s essentially the same feature.

Film cameras have a disk-based shutter and the number of degrees the shutter remains open is what determines shutter speed. A 180-degree shutter is open for twice as long as a 90-degree shutter, for example.

Dean Sensui — Imagination Media Hawaii

[Ron Shook]

Mark,

[Mark Palmos] “2/ maybe its my imagination, but shooting at 100th of a second 1080 50i HQ even a very gradual pan shows significant softening of the edges once the pan starts. When it stops again, everything is sharp. At the speed I was panning I wouldnt have expected the softening to be as extreme at 100th of a second. This happens regardless of Interlaced or Progressive.”

I think that I can answer this question adequately, and no, it’s not your imagination. Several things are at work here. First of all a shutter speed of 100th of a second is not that fast. It oughta be a bit better at a significantly faster shutter speed.

Secondly, and probably the bigger culprit, you are seeing the limitations of the long GOP Mpeg2 codec. The Sony 35mbps codec is better than it has any right to be, IMO, but it’s still compression defined over multiple frames of video. Particularly on a pan of a detailed subject where everything in the frame is changing with each frame, however slowly, it’s impossible for the codec to keep up with that amount of change, so the algorythm automatically cuts the detail to avoid blocking artifacts. You hear folks say the codec is nearly impossible to break, but they are essentially talking about blocking and other highly visible artifacts. Some situations, usually involving Pans, the codec has to break down the detail to keep up and avoid the more visible garbage. You’ll see much less problem if you have a subject that takes up far less than the whole frame, moving through a stationary shot. There’s considerably less to change from frame to frame and the long GOP algorythm is more successful at preserving the detail.

This speaks directly to the Sony/Pany controversy over the relative benefits of interframe (long GOP), v.s., intraframe compression. All other things being equal, although in most instances the opposite is true, the XDCam 35 mbps interframe codec is not going to look as good while panning a detailed subject or in subject movement that fills much of the frame as the DVCPro100HD codec because the Pany codec compresses each frame separately.

Matt Devino’s moving shootout footage, illustrates what I’m saying pretty nicely even though we are seeing full res footage that has all been compressed long GOP again for web delivery. In his case, all other things are not equal in that the EX1 has far better native resolution on the camera and in the codec than the HVX 200, yet when you watch the comparison when the respective cameras pan with the skateboarder, there’s very little difference in apparent comparative resolution, the HVX holds it’s own because of the codec differences. Yet on the wide locked frames of the skate through, the background looks sharper with the EX1, while it’s hard to see a lot of difference in the apparent sharpness of the skater himself.

It’d be great to see Matt’s tests natively from each camera. Perhaps he could comment on what he sees prior to compression for web delivery.

[Mark Palmos] “what on earth is so nice about progressive. I mean, ok, when you freeze it looks nicer, ie not interlaced, but when you pan it jerks and looks simply awful… almost as bad as having fields reversed by mistake. If our little EX1 did 1080 50p that would probably be the best of both worlds, but alas. I personally prefer a smoother looking 50i to the jerky 25p. I also know progressive is better for compositing as well as watching on computers, but for watching on a TV monitor, i far prefer interlaced.”

I gotta say that like you I don’t understand the 24/25p or die phenomenon, however things are a little different for us in NTSC land. When 24p goes to TV here pull down or pull up or whatever the heck it is, is applied here to deliver a 1080 60i signal, and that tends to mask some of the judder that you see in 25p but also lowers detail. IMO the most logical way to shoot relatively low action things here in 1080 is 30p where you get some of the best from both worlds.

Ron Shook

[Randy Strome]

Hi Mark,

I, like you, had never owned a camera with a shutter angle option. Turns out that the terms shutter angle and exposure time define the same thing: How long is the exposure. Shutter angle is a term that was used in film cameras. On the EX-1, it is an electric shutter, so no physical angle is actually changed. If you are already comfortable with considering exposure time in terms of fractions of a second, then there is no need to ever look at the shutter angle option. Here is the conversion chart if you are interested:

https://www.reduser.net/forum/showthread.php?t=3079

[Mark Palmos]

Aah, thanks Randy, yep, i could see no difference (probably because there isnt one!) Cheers, Mark.

[Job Van nuenen]

Hi Mark,

As for your point 4-, not beeing able to copy the footage to a laptop computer and import it: This works fine as long as you leave the structure of the folder including the name intact. try copying the folder named ‘BPAV’ that’s on the SxS into a new empty folder with chosen name. Now you should be able to import that folder into the clipbrowser using the ‘open containing folder’ command.

I personally prefer Sony’s XDCAM transfer utility for ingest, because it gives you more logging options, and has less of the ‘fisherprice-look’ the EX clipbrowser has 🙂 The described routine works fine in this application too.

Media100/after-effects/Combustion/FCP/Flint/Flame/Inferno..
Thank heavens; there’s a sign of progress here..

[Alexander Kubalsky]

I would like to see someone do a comparetive test of the EX1 and HVX200 codecs. Set them both in 24p modes, same shutter speed, to film the same pan shot of a jogger going by, then in post, break down a seconds of each cameras footage into the actual 24 frames and see the difference. I’ve just bought the EX1 after four torturous hours in the store trying to decide between it and the HVX. I wanted the most film like qualities in a camera. Would like to know I made the right decision.

[Randy Strome]

Question here that i have always wondered about. With interlaced frames, are the two “half” frames recorded at the same instant but played back one after another, or are they recorded sequentially and played back sequentially?

[Craig Seeman]

Interlace is recorded sequentially otherwise there would no difference in recorded motion between them. Just watch the jitter on an interlaced frame of any subject or camera movement, on a TV monitor.