HDV - interlaced and progressive question.
Discussion
I really ought to know the answer to this 
We have an event coming up that needs something moving very quickly to be captured on HDV. We normally set the shutters on the video cameras to +500 so we at least get 25fps of sharp images. These will then look relativly normal when played back at normal speed as well as giving you a whole series of stills.
If I shoot progressive, I assume I get 25fps of higher res images compared to interlaced but it will look very jerky playing back as interlaced TV. We really need the highest quality of the event to analyse but I also want pictures that look good as "normal video".
Any suggestions please?
(The cameras are Sony Z5s and we are also shooting stills with a D3X and D300s...can't get hold of D3S for love nor money in the next 2 weeks!)
We have an event coming up that needs something moving very quickly to be captured on HDV. We normally set the shutters on the video cameras to +500 so we at least get 25fps of sharp images. These will then look relativly normal when played back at normal speed as well as giving you a whole series of stills.
If I shoot progressive, I assume I get 25fps of higher res images compared to interlaced but it will look very jerky playing back as interlaced TV. We really need the highest quality of the event to analyse but I also want pictures that look good as "normal video".
Any suggestions please?
(The cameras are Sony Z5s and we are also shooting stills with a D3X and D300s...can't get hold of D3S for love nor money in the next 2 weeks!)
Interlaced vs progressive is a minefield. - according to a beeb r&d paper, which is far too technical for me, the actual resolution of sonys Z7 and Z5 cameras is the same, regardless of being interlaced or progressive, but i couldnt understand why!
But in practical terms- if your interested in analysising footage, it would be easier shooting progrssive- when looking at freeze frames, you'll have a nice clear frame rather than interlace combing But, progressive is as you say, a little more - 'jerky' - 25 frames per sec just isnt really enough to render smooth motion, which is why interlaced was invented- You get 50 fields per sec, so its smoother, but your still actually only transtiing 25 frames per sec, so you dont take up more bandwidth. anyways, im sure you know all this!
Also, i understand why your shooting a higher shutter speed- so you have nice crisp frames- but that wont help judder. Motion blur on camera movement helps disguise judder a bit! Tricky situation- you need crisp sharp frames, but also want nice smooth footage.
Whenever im shooting progressive, i change my shooting style. Film is progressive, and films are shot very different to tv. Most news cameramen whill throw a camera around all over the place, because you can with an interlaced cam, it'll look pretty smooth. With progressive, either pan fast or very slow. Medium speed pans will look juddery. I try and follow a subject when panning- the viewer will look at the subject, and ignore any judder in the background. I try and have less camera moves and let the action happen in frame.
That said, some cameras are more juddery when shooting progrssive than others. Film, or digi cine cams have large sensors, with shallower dof- when the backgrounds soft, subject sharp, and you're panning, following a moving subject, any background judder wont really be noticeable due to the softness of the background. The subject wont judder as they will essentially stay the same place in the frame as you follow them. Film cameramen really have a completely different way of shooting.
Hdv cameras have tiny sensors, so everything tends to be in focus, which doesnt help judder. I've noticed the more expensive cameras tend to judder less- wether its down to the operator, the sensor size/ dof, or how the circuitry handles motion, i dont know- its probably all of the above!
What is it your shooting? Do you have the opportunity to do some test progressive footage? Could do a test, and see what looks sharper, footage shot progressive, versus footage shot interlaced, and then de-interlaced in post.
If i were in you're position, id most probably shoot interlaced, and de-interlace in post. Or beg / steal / borrow a cam that can shoot 50fps progressive! With those extra frames per sec it would look smoother and being progressive it'll look sharp, and be dead easy to convert to 25fps 50i for a dvd or blueray. Know anyone with a sony ex1 or ex3? I think they can shoot 50fps or 60fps at 720p resolution. Or a canon 7d- that'll shoot 50 or 60 at 720 too
But in practical terms- if your interested in analysising footage, it would be easier shooting progrssive- when looking at freeze frames, you'll have a nice clear frame rather than interlace combing But, progressive is as you say, a little more - 'jerky' - 25 frames per sec just isnt really enough to render smooth motion, which is why interlaced was invented- You get 50 fields per sec, so its smoother, but your still actually only transtiing 25 frames per sec, so you dont take up more bandwidth. anyways, im sure you know all this!
Also, i understand why your shooting a higher shutter speed- so you have nice crisp frames- but that wont help judder. Motion blur on camera movement helps disguise judder a bit! Tricky situation- you need crisp sharp frames, but also want nice smooth footage.
Whenever im shooting progressive, i change my shooting style. Film is progressive, and films are shot very different to tv. Most news cameramen whill throw a camera around all over the place, because you can with an interlaced cam, it'll look pretty smooth. With progressive, either pan fast or very slow. Medium speed pans will look juddery. I try and follow a subject when panning- the viewer will look at the subject, and ignore any judder in the background. I try and have less camera moves and let the action happen in frame.
That said, some cameras are more juddery when shooting progrssive than others. Film, or digi cine cams have large sensors, with shallower dof- when the backgrounds soft, subject sharp, and you're panning, following a moving subject, any background judder wont really be noticeable due to the softness of the background. The subject wont judder as they will essentially stay the same place in the frame as you follow them. Film cameramen really have a completely different way of shooting.
Hdv cameras have tiny sensors, so everything tends to be in focus, which doesnt help judder. I've noticed the more expensive cameras tend to judder less- wether its down to the operator, the sensor size/ dof, or how the circuitry handles motion, i dont know- its probably all of the above!
What is it your shooting? Do you have the opportunity to do some test progressive footage? Could do a test, and see what looks sharper, footage shot progressive, versus footage shot interlaced, and then de-interlaced in post.
If i were in you're position, id most probably shoot interlaced, and de-interlace in post. Or beg / steal / borrow a cam that can shoot 50fps progressive! With those extra frames per sec it would look smoother and being progressive it'll look sharp, and be dead easy to convert to 25fps 50i for a dvd or blueray. Know anyone with a sony ex1 or ex3? I think they can shoot 50fps or 60fps at 720p resolution. Or a canon 7d- that'll shoot 50 or 60 at 720 too
Edited by Fordo on Tuesday 18th May 19:37
quoting the R&D paper: " 12
This camera has another mode, Rec Type
Progressive, in which the entire 1080-line
image is compressed as one.
Figure 4 shows the result. There is no
visible difference in resolution,
confirming that there is no image quality
advantage in using this mode, apart from
the slight advantage in recording, which
should result in a slightly lower level of
compression artefacts. Note that
recordings made in this mode can not be
played back in a standard HDV player,
only in one compatible with this
recording mode. "
can be downloaded from http://thebrownings.name/WHP034/pdf/WHP034-ADD34_r... has some useful info, but its scarily technical. I point the glass end at things and press the record button
and a more useful article on judder: http://www.nav.co.uk/understanding-hd.php
sorry - im probably not helping, im probably making your decision even more complex!
This camera has another mode, Rec Type
Progressive, in which the entire 1080-line
image is compressed as one.
Figure 4 shows the result. There is no
visible difference in resolution,
confirming that there is no image quality
advantage in using this mode, apart from
the slight advantage in recording, which
should result in a slightly lower level of
compression artefacts. Note that
recordings made in this mode can not be
played back in a standard HDV player,
only in one compatible with this
recording mode. "
can be downloaded from http://thebrownings.name/WHP034/pdf/WHP034-ADD34_r... has some useful info, but its scarily technical. I point the glass end at things and press the record button
and a more useful article on judder: http://www.nav.co.uk/understanding-hd.php
sorry - im probably not helping, im probably making your decision even more complex!
Edited by Fordo on Tuesday 18th May 19:26
Brilliant bits of info - thank you!
As you say, its such a minefield. Your explanation of DOF on HDVs answers a lot of other questions of mine as well. I had a freelancer do a shoot for me recently and he shot progressive HDV for some odd reason, it looked horrid on any moving shots.
We did some test shots outside the office with dropping some objects and I really couldn't see any better detail on the progressive so I'll not compromise the footage for later use. As to the trial...its a sort of big boys firework
Fordo, I'll be in touch - I have seen your profile before then completely forgot your user name!
As you say, its such a minefield. Your explanation of DOF on HDVs answers a lot of other questions of mine as well. I had a freelancer do a shoot for me recently and he shot progressive HDV for some odd reason, it looked horrid on any moving shots.
We did some test shots outside the office with dropping some objects and I really couldn't see any better detail on the progressive so I'll not compromise the footage for later use. As to the trial...its a sort of big boys firework
Fordo, I'll be in touch - I have seen your profile before then completely forgot your user name!
Decide what you want, clean stills (with potentially lots of inherent motion blur) or smooth looking motion
and then pick your camera
You can't really have your cake and eat it too .. unless you are shooting with say a Phantom or an I-speed 3. Even if you process interlaced with something adavanced like Magic Bullet the stills will never look right for really fast motion.
and then pick your camera
You can't really have your cake and eat it too .. unless you are shooting with say a Phantom or an I-speed 3. Even if you process interlaced with something adavanced like Magic Bullet the stills will never look right for really fast motion.
Gassing Station | Photography & Video | Top of Page | What's New | My Stuff