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Some very imp. basic questions.. !


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#1 amanchopra

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Posted 16 October 2005 - 10:52 AM

I am a photographer and am new to cinematography

Can some one here please tell me what exatcly is the difference in FILM camera and DV camera and Digital?

Also what is 30, 60i etc and all..

I am going to get started with a project , will be using a PD 170 , dont no much at all , i am confused what should i use 60i or all 30, or like what is it

Also like how in photograophy anything below 100 shutter speed causes blur in the picture, how does it work with Cinematography. What shutter speed to keep etc ?

thanks
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#2 David Mullen ASC

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Posted 16 October 2005 - 11:36 AM

Surely you can tell a film camera apart from a video camera...

Mainly the differences between film and digital are ability to handle a wide exposure range (film is superior), resolution (depends on the film format and the digital format, but 35mm film, for example, would exceed most digital video formats in resolution), lack of digital artifacts in film (unless digitized), lack of grain in digital (but it has noise, which is similar).

Consumer DV tends to have deeper focus (more depth of field) than 35mm or Super-16. Depth of field is mainly governed by focal length of lens used, what f-stop you shoot at, what distance you focus at. Smaller target areas, whether film or digital, require shorter focal lengths on average, which give you a deeper focus look. 35mm is a fairly large target area and therefore gives you less depth of field compared to Super-16 or a professional 2/3" CCD digital camera, which are similar in target area size. A DV camera often has 1/3" CCD's and therefore uses very short focal lengths and you get a very deep focus look compared to 35mm.

Typically a film camera shoots 24 whole frames at a time per second, with a 180 degree shutter, meaning the shutter is closed 50% of the time. So that's a shutter speed of 1/48th of a second at 24 fps. Since 24 fps is a rather low frame rate, barely fast enough to create the illusion of continuous motion, you tend to have problems with fast motion looking strobey or choppy. So a certain amount of motion blur per frame helps smooth that out, which is why stop motion animation, with no frame blurring, often looks too crisp in terms of motion. If you shoot at 24 fps at 1/100th per second shutter speed, then fast motion would look very choppy and crisp, almost jerky.

Traditional video cameras have been interlaced scan, as have traditional TV sets. Instead of capturing and displaying a whole frame at a time, they capture (in camera) and display (on a TV) only every other horizontal scan line, called a field, then the next field contains the alternate lines. So two fields make up one whole frame of video. NTSC video is 60 fields per second, or 30 frames per second, depending on how you want to think of it. A standard video camera (like the PD-170) would capture motion 60 times per second as fields.

Since slicing motion into 60 segments is more samples than a film camera capturing at 24 times a second, 60i video motion tends to look much smoother and more fluid, which is one of the looks that are difference from the strobiness of film. Typically you would shoot 60i video with no shutter on, meaning 1/60th per second shutter speed, capturing 60 fields per second.

Some video cameras have a feature called progressive scan, which captures whole frames at a time instead of fields. Some monitors (like on a computer) also display progressive scan. Progressive scan video capturing at frame rates like 24, 25, or 30 fps mimic the motion effects of a film camera running at those speeds more closely than 60i video does.

The PD-170 does not have a progressive scan feature for 30 fps though.

The Canon XL2, and DVX100A are the most common DV cameras that offer 24P and 30P options. The older Canon XL1 had a fake progressive scan look called "frame mode" which could give you a 30P look.
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#3 Michael Collier

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Posted 26 October 2005 - 09:35 PM

yup. david said it all.

the only thing I have to add is that with video sometimes its so quick, so easy so immediate, that most begginers and a lot of professionals I have seen dont take the time to do things right.

With film you have such a large exposure lattitude that adjustments dont affect the immage quite as much as with video. If you increase a light just one stop it would look like a huge increase compared to a one stop ajustment in film. also your whites and highlights are zones that will give away the 'film look'

dont think that because video is quicker than film, that lighting for video will be. you must be very careful with your lighting. i've said it in a million posts, i will say it here....use a vectroscope.
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