[I]"If my objective is to get the least noise in low light video, is it true that 1080i60 at the default 1/60th shutter speed will produce lower noise video than 1080p30 or 720p30 also shot at the default 1/60th shutter speed? If so, why is this?"[/I]

Yes, because when shooting interlaced compared to shooting progressive the camera will use [I]line pair averaging[/I] to avoid line twitter. This averaging process reduces noise.

Of course there's no free lunch here, the line pair averaging also reduces vertical resolution. That 's exactly the intent of employing it.

Bob.

mudmsith said:
[I]"Considering how video is shot (lines are picked up over the full length of the time of the frame), it must be that the standard time for the shutter to be open (except when you induce an artificial frame rate like shooting 24p over a 29.97i tape format, which induces odd motion artifacts between frames) would be for the entire time of the frame.....in order for all lines to be picked up by the sensor/scanner mechanism......This is different from a stills (or film) situation, where the entire frame is exposed at the same time for whatever length of time the shutter is open."[/I]

The global V rolling shutter is irrelevant here and even still cameras can employ a rolling shutter i.e. the "roller blind" shutters in old large format stills cameras create some fantastic motion artefacts. Video cameras can and do have a global or rolling shutter, CMOS sensors typically have a rolling shutter, CCD sensors have a global shutter. There's no imperative in video that the frame is scanned line by line.

Bob.

Re: interlaced vs progressive, my understanding is that many (or most) modern devices don't actually shoot interlaced footage; instead, it is recorded into a progressive container and then "tagged" as interlaced video. Therefore, 60i=30p in those cases.

Maximum aperture and a slower shutter speed will give the least noise, but shutter speed shouldn't go too slow, it should follow the 1/2x frame rate rule for good motion blur although this can be corrected with something like ReelSmart Motion Blur.

Some cameras have dynamic range optimizers which work well to bring out details in the shadows without changing highlights.

"There's no imperative in video that the frame is scanned line by line."

.....Not being fully aware of the current mechanism, you may be correct in that statement, but there certainly was this imperative in the pre-digital pickup mechanism prior to the current HD revolution. A real time line scan was taking place at the camera sensor and being sent to the monitors/recorders and switchers in that form.

I could see that it would be possible these days for a full image scan to be put into a buffer and then converted to a line scan, and would love to know if that is really what is going on with cameras now.....but it certainly is not what was going on with SD video cameras when I was working as an EIC 12 years ago....or maybe I am missing something about the physics of the situation.....Just don't see how a camera sensor could be scanning two sets of lines (interlaced pickup) from top to bottom twice while the shutter was closed during part of that 30th of a second. The light has to be hitting the whole sensor in the first and second half of the open shutter period/framerate. I do see how a modern sensor could take a full frame image during a lessor period and place it in a buffer and clcok it out in the serial line format necessary for either progressive or interlaced output, but don't really see any other way of doing what TV caneras used to do in real time.

I am open to the explanation......A rolling shutter at a fixed frame rate of either 30 or 60 (having slats at the appropriate intervals for either, and rotated to achieve this) will work to do what I describe above, and when you alter the shutter rate in an old school TV camera away from the core line rate, you still get recordings at the core line rate, but get stutter across the shutter motion between the new artificial frames. In other words, the lines are still pumped out at the same rate from top to bottom, but the slats are creating break points in the motion that are noticable when something is moving quickly.

When I was overseeing live concert recordings, my video operator would sometimes change the shutter rate on her cameras to match the 60 cycle output of the lights so that there would be no pulsing when she "chipped" the cameras. When we began noticing finger stuttering during the closeups of the upright bass soloists hands, however, I realized what was going on and had her ignore the 60 cycle pulsing during setups from then on. This worked and fixed the problems. The lines were still being pumped out for 29.97frames and 59.94 interlaced fields while the 60fps shutter was working. The lines mattered and were imperative.

Even though this was digital video, it was still standard def and using the best technology from 1998, so I freely admit that this may have changed.....and would love to know if it had.....or if my understanding of how everything was working in 1998 is inaccurate. I don't claim to be all that deep in my understanding of everything.

mudmsith,
this a way too big a topic for me to cover here so I'm going to be brief, sorry.

CCD sensors transfer the charge from every photosite in a very short period of time to a Charge Coupled Device.

CMOS based sensors are different, each pixel or row or groups are read out sequentially. The time taken to read them out may very well not have any relationship to frame rate or shutter speed. In my EX1 the readout time is fixed at 1/60th, even when the "shutter speed" is 1/250.

The rolling band and other problems that you saw on cameras is not fixed by changing shutter speed, the Clear Scan mechanism works by controlling the phase between the shutter and the scan. My EX1 has a number of menu controls for this but sadly I've struck a number of problems with projectors and lights that it cannot mitigate.

Video today is basically transmitted as a data stream, gone are sync pulses and front and back porches. Everything you knew from back in the days of Plumbicon tubes is obsolete, flush it out of your head or it'll really hinder you coming to grips with how things work in the digital realm.

Bob.

Yes, you're correct. 1080p at 24fps is best. That lets you slow the shutter down to 1/48th or 1/50th, whatever you got. I have done 1/30th in order to get enough light, but only if I'd be underexposed otherwise.

At least get some on camera mounted Chinese LED lights for when you're in a jam. And NeatVideo is your friend.

On low light stuff with a locked down camera and not too much movement I find I can get away with a longer shutter (1/30 for 30fps) and I have done this a couple of times with good results.

On LEDs, be aware that they are not all equal. Some Chinese units produce noticeably green light, so check with other users before buying on the web. Some more expensive units aren't free of the green caste but can be corrected with a magenta filter.

What I find with the cheap LEDs is that they are missing parts of the visible spectrum and thus are fine for augmenting natural light, but horrible for completely lighting an otherwise dark scene. I love my Z96s for augmenting natural light, but I would never completely light a scene with LEDs.

Two words on this: Stokes Gap!

OK, some more words....

I've been a follower of this chap for the past 10 years: Mr Jonathan Harrison : here he is being interviewed at IBC 2013 about the Xmas present Bob is going to buy me - the CELEB400. Thanks Bob!



And this other interview, at IBC this year, where he explains in much detail the "holes" in the LED spectrum. I've attended 4 of Jonathan's seminars and if there are any holes (little pun there!) in what he is saying, I'd like to hear them.



Again, Stokes Gap! (o..k.. just for you Bob . .)

Toodles

Grazie

This is what we're getting: BBS Lighting AREA 48 LED

With a CRI of 97 I doubt there'll be too many complaints. Being able to change the light to five different types of light in seconds is a big plus and one of those options is chroma key green.

My go to light though is still my Z96s, I use them exclusively to light small objects, particularly candles Two Z96s, a couple of mic boom stands, roll of Cinefoil and gaffe tape, that's it.

Bob.

"CCD sensors transfer the charge from every photosite in a very short period of time to a Charge Coupled Device.

CMOS based sensors are different, each pixel or row or groups are read out sequentially. The time taken to read them out may very well not have any relationship to frame rate or shutter speed. In my EX1 the readout time is fixed at 1/60th, even when the "shutter speed" is 1/250."

Thanks....this parallels what I was thinking was possible....i.e., that the modern sensor is essenially "buffered" (actual mechanism may be a bit different) into the sequential feed of line/pixel data.....which must be flowing through the output of the camera.....since this ultimate sequential feed will take place across the basic frame rate, there has to be a way that the bottom lines will transmit light that hit the bottom of the sensor, even if the shutter was not open at that point in time because the shutter speed was so much faster than the frame rate.

The CCD, according to your description above, makes this possibility obvious, but the CMOS does not, and implies a similar buffered readout in order to make the quick shutter rates possible. Everything has to be clockable at the ultimate frame and line rate at the output.

Too much true buffering would be unworkable in a live/broadcast kind of situation, so I am curious as to how it works.

I appreciated being pointed in the right direction.