How is depth of field altered on video cameras?
Discussion
I get the relationship between aperture and depth of field on a stills camera, but there is of course the added element of exposure time on that. This being the case, how do you vary depth of field on video cameras, where presumably the aperture has to be set according to ambient light without the time of exposure element?
GetCarter said:
Short answer... you don't. Long answer (very long), 'proper' video cameras use DOF adaptors.
Thanks. It was 'proper' video cameras I had in mind. I'd been watching things on the telly and wondering how it was done.If you can cut & paste the very long answer from somewhere without too much effort, I'd be interested to know more!
Iris.
Open the iris (to match the lighting conditions, whether natural or artificial) to get the correct exposure, and this has a direct effect on the DoF.
To shorten the DoF in bright natural light, that stick ND filter over the lens, and open up the iris. Most pro cameras will have at least two, possible three ND filters built into the camera that you can add in by turning a knob (these filters sit between the lens and the back end of the camera) - and they are actual filters, rather than electronic ones.
When I shoot "head and shoulder" type interviews, and want to throw the background way out of focus, I generally use ND on the lens, open up the iris to get the exposure right (and reduce the DoF), and then move the camera away from the subject, and zoom in, so I am working off the end of the zoom - can give some very nice results.
Open the iris (to match the lighting conditions, whether natural or artificial) to get the correct exposure, and this has a direct effect on the DoF.
To shorten the DoF in bright natural light, that stick ND filter over the lens, and open up the iris. Most pro cameras will have at least two, possible three ND filters built into the camera that you can add in by turning a knob (these filters sit between the lens and the back end of the camera) - and they are actual filters, rather than electronic ones.
When I shoot "head and shoulder" type interviews, and want to throw the background way out of focus, I generally use ND on the lens, open up the iris to get the exposure right (and reduce the DoF), and then move the camera away from the subject, and zoom in, so I am working off the end of the zoom - can give some very nice results.
the main issue with video cameras is that they have quite small ccd's in comparison to stills cameras- small ccds = wide dof.
but even with a small chipped vid camera, you can get a shallow dof if you like- iris wide open, get far back from your subject and zoom right in. Use ND or shutter speed to control exposure.
High end pro video cameras have much larger CCD's, so its much easier to achieve a shallow dof.
Theres not too much different between photogrpahy and video. the same kind of principles apply regarding lenses, sensor sizes and so on. Only with video, faster shutter speeds (or exposure in photography terms) can give a stuttery or juddery look to motion.
but even with a small chipped vid camera, you can get a shallow dof if you like- iris wide open, get far back from your subject and zoom right in. Use ND or shutter speed to control exposure.
High end pro video cameras have much larger CCD's, so its much easier to achieve a shallow dof.
Theres not too much different between photogrpahy and video. the same kind of principles apply regarding lenses, sensor sizes and so on. Only with video, faster shutter speeds (or exposure in photography terms) can give a stuttery or juddery look to motion.
Fordo said:
Theres not too much different between photogrpahy and video. the same kind of principles apply regarding lenses, sensor sizes and so on.
What surprises me is how video camera lenses seem to get such massive zoom ranges whilst stills camera lenses can't... is it just that video is less discerning of quality?Simpo Two said:
Fordo said:
Theres not too much different between photogrpahy and video. the same kind of principles apply regarding lenses, sensor sizes and so on.
What surprises me is how video camera lenses seem to get such massive zoom ranges whilst stills camera lenses can't... is it just that video is less discerning of quality?Its like crop factor- a 50mm lens will look wore 'zoomed in' on a DX sensor, than a 35mm sensor.
So small sensors require much smaller lenses to get a long zoom, than large sensors do- so, for a vid camera with tiny sensors, you can make a massive zoom range without having an enormous lens on the front.
Trade off is, as you mentioned quality- small sensors and small amounts of glass up front, as well as an enormous zoom range, mean quality isnt top.
But most people prefer camcorders that are pocket sized, over quality.
Also, dont forget- some stills cameras do have huge zoom ranges, put usually theyre point and shoot cameras. and again, most people prefer pocket sized cameras over quality.
On the pro video side, most producers prefer to cut costs by going with cheap equipment, so they go with smaller prosumer 'corders. I regularly have to work with all sorts of HDV cameras, and i hate the things. I can get great footage out of them, but im constantly fighting the chromatic abberation, the lack of shallow dof, poor low light response and so on. Its a breath of fresh air when i get to work with bigger cams.
In cinema, and higher budget TV stuff, they use primes, and zooms with quite small zoom ranges, which makes far superior optical quality. Got a friend whos a focus puller on casualty, and then regularly work with digiprimes. Primes, as im sure you know from photogrpahy, can have much bigger irises, so you can get dof nice and shallow, which can make stuff shot on video look muchmore filmic
hope all that makes sense. At the risk of sounding pompus, I have a pdf somewhere that i wrote on the subject, for some guys im training, if you'd like to geek out on the subject?
Edited by Fordo on Thursday 16th April 12:37
Pleased to see that someone still trains cameramen after all! From the efforts of most ENG types there isn't much, namely:
1) Never use a tripod because it's boring, and too much to carry anyway.
2) Set camera to manual focus so you can get the background sharp whilst keeping the subject soft.
4) Set white balance to be wrong.
5) If there's a monitor in shot, don't synch but make sure it strobes like a b
d.
6) Don't use any lighting; the fluorescent tube just above the subject's head will do.
7) Set lens to wide angle.
8) Shove it in their face and say 'action'.
1) Never use a tripod because it's boring, and too much to carry anyway.
2) Set camera to manual focus so you can get the background sharp whilst keeping the subject soft.
4) Set white balance to be wrong.
5) If there's a monitor in shot, don't synch but make sure it strobes like a b
d.6) Don't use any lighting; the fluorescent tube just above the subject's head will do.
7) Set lens to wide angle.
8) Shove it in their face and say 'action'.
Simpo Two said:
Pleased to see that someone still trains cameramen after all! From the efforts of most ENG types there isn't much, namely:
1) Never use a tripod because it's boring, and too much to carry anyway.
My pet hate. It is very, very rare that I shoot anything without the camera being on legs, or other non-shaking surface (for instance, I have been known to use a beanbag to get a suitably tilted shot in a confined space, yet still keeping the camera suitably still.)1) Never use a tripod because it's boring, and too much to carry anyway.
Simpo Two said:
2) Set camera to manual focus so you can get the background sharp whilst keeping the subject soft.
To be fair, I can't think of any reason that someone would use automatic focus - if they can't focus the subject properly, they shouldn't be behind the damn camera. Plus, most of the kit I use doesn't have an auto-focus function anyway! 
Simpo Two said:
4) Set white balance to be wrong.
Arghhhhh!!!!! 
You would not believe the number of times that I have heard professional camera operators uttering the sentence "They can sort that out in the edit....."
Simpo Two said:
5) If there's a monitor in shot, don't synch but make sure it strobes like a bd.
Some people cannot understand the concept of a variable shutter......d.Simpo Two said:
6) Don't use any lighting; the fluorescent tube just above the subject's head will do.
Stop it John...... I am feeling every one of your frustrations!Worse still, why not use a couple of 800W redhead lights to burn out your subject.... and whilst at it, leave one without any scrim or gel, and stick a full blue CT correction on the other one.......
It's good to know there are at least three professional cameramen left - all on here!I've heard a lot of cut backs in ENG mean sometimes the presenter is set out alone, and theyre given minmal training about cameras- everything on auto, point at person, press red button.
Every other morning i seem to spot some inexcusable camerawork on BBC breakfast.
The crt unsynced in the background bugs me. I was on a shoot once, as a steadicam op, and i noticed nothing had been done to cure this in a particular shot being setup- i mentioned to the dop, being as nice as i could- didnt want to come across as the patronising 'know it all' - and suggested how we could stop the flickering. He replyed 'thats nice', and shot it as it was. Later, in post, they had to motion track the screens and overlay pictures on the screen. sigh
Every other morning i seem to spot some inexcusable camerawork on BBC breakfast.
The crt unsynced in the background bugs me. I was on a shoot once, as a steadicam op, and i noticed nothing had been done to cure this in a particular shot being setup- i mentioned to the dop, being as nice as i could- didnt want to come across as the patronising 'know it all' - and suggested how we could stop the flickering. He replyed 'thats nice', and shot it as it was. Later, in post, they had to motion track the screens and overlay pictures on the screen. sigh
Meeja said:
Worse still, why not use a couple of 800W redhead lights to burn out your subject.... and whilst at it, leave one without any scrim or gel, and stick a full blue CT correction on the other one.......
ive seen someone use a HMI, and put a full CTB gel on the front! So your taking your daylight light and making in bluer? The chap had no idea what the blue gel was for, he'd just 'seen it done before', but obviously on a tungsten lampNice to know theres quite a few people on here on the same wavelength- i can see some sort of pistonheads short movie coming on here......
Edited by Fordo on Thursday 16th April 19:17
Fordo said:
I've heard a lot of cut backs in ENG mean sometimes the presenter is set out alone, and theyre given minmal training about cameras- everything on auto, point at person, press red button.
I worked at an event in Leeds a few weeks ago, where a high profile former athlete was the main focus of attention. Local BBC sent someone out to cover the story, and it indeed was a one-man ENG crew. He set his tripod, placed his PD170 on it, used no lighting (relied on a combination of daylight through the window, and the sodium lighting in the room), and unhooked the camera's standard shotgun mic to record the audio (and held the mic far too far away from the subject).I very nearly went over to offer to shoot it for him, as I had with me a DSR570WSP with a J17 lens, a Vinten Vision 11, along with a decent paglight, and a 416 mic.
I remember watching the BBC local news that evening, and seeing clips of his interview. Truly appalling.
Fordo said:
The crt unsynced in the background bugs me. I was on a shoot once, as a steadicam op, and i noticed nothing had been done to cure this in a particular shot being setup- i mentioned to the dop, being as nice as i could- didnt want to come across as the patronising 'know it all' - and suggested how we could stop the flickering. He replyed 'thats nice', and shot it as it was. Later, in post, they had to motion track the screens and overlay pictures on the screen. sigh
That is where I would have come unstuck...... In situations like that I sometimes struggle to hold my tongue, and the DoP would have been told what a cock he was being.......Fordo said:
I've heard a lot of cut backs in ENG mean sometimes the presenter is set out alone, and theyre given minmal training about cameras- everything on auto, point at person, press red button.
That's what I don't understand. At least if they had a consumer auto-everything job at least the interviewee would be in focus! For the sake of five minutes' learning, the channel gets ste. Bt hey, as long as it's cheap, and who wants quality anyway when da kids only want wobbly 300x200 YouTube ste?Many thanks for all the tips here guys, really appreciate it. Been looking for advice on DOF for a while. I currently use a Sony Z1 mainly for video for the web.
Any general advice on using an on camera light? I have a pag light and only use it in low light conditions (usually interviewing in nightclubs for promotional clips) . Would you recomend using in interview situations where there is various clashing light sources (eg windows and tube lights)
Any advice is really appreciated many thanks
Any general advice on using an on camera light? I have a pag light and only use it in low light conditions (usually interviewing in nightclubs for promotional clips) . Would you recomend using in interview situations where there is various clashing light sources (eg windows and tube lights)
Any advice is really appreciated many thanks
TwistingMyMelon said:
Many thanks for all the tips here guys, really appreciate it. Been looking for advice on DOF for a while. I currently use a Sony Z1 mainly for video for the web.
Any general advice on using an on camera light? I have a pag light and only use it in low light conditions (usually interviewing in nightclubs for promotional clips) . Would you recomend using in interview situations where there is various clashing light sources (eg windows and tube lights)
Any advice is really appreciated many thanks
Use a decent quality PagLight at all times, and in all situations, balance the light with gel to match your ambient light and you won't go far wrong.Any general advice on using an on camera light? I have a pag light and only use it in low light conditions (usually interviewing in nightclubs for promotional clips) . Would you recomend using in interview situations where there is various clashing light sources (eg windows and tube lights)
Any advice is really appreciated many thanks
Better still, use "proper" lighting if you have the setup time/space to do it. (Three point lighting as a minimum) - But I guess in a nightclub situation, that is going to be a non-starter!
FWIW I did those type of gigs many, many years ago, (Fly-on-the-wall type stuff) and I thoroughly enjoyed it..... Always amazing what people will do once a broadcast style camera, and a soundman with a boom mic appear on the scene!
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