Proper way to shoot footage for 60i to 30p deinterlacing

[Graeme Nattress]

1/60th shutter is what video is normally shot at. Shooting at 1/30 will probably, depending on camera, put it into a fake progressive mode that might just look crap. The most “open” shutter you can have shooting 60i is 1/60th, where each field is lasts 1/60th second and is fully exposed.

In de-interlacing you can adjust the use and balance of the two fields and blend to either give 30p with 1/30th shutter or 30p with 1/60th shutter (ie 180 degree shutter) or somewhere inbetween.

Might be good to experiment to get the look you want.

Graeme

– http://www.nattress.com – Film Effects and Standards Conversion for FCP

[Bret Williams]

I woulh think 60i woulh have a max 1/120th shutter. No?

[Graeme Nattress]

On interlace, the shutter is per-field, and as each field lasts 1/60th second, the shutter cannot be longer than that.

– http://www.nattress.com – Film Effects and Standards Conversion for FCP

[Bret Williams]

Ok, I’m just learning on this one, but I thought 60i meant 60 frames per second, interlaced. Which would be 120 images per second, thus a max 120 th shutter? Or does 60i just mean 30i?

[Graeme Nattress]

60i is 60 fields per second, interlaced.

Graeme

– http://www.nattress.com – Film Effects and Standards Conversion for FCP

[Bret Williams]

Gotcha. Yeah, sorry, brain fart. Yeah, so 1/60th is as slow as you can get without the shutter just staying open. Cool effect though using a slow shutter. And motion picture film is usually 1/48th shutter speed at 24fps, so I guess you’d still want 1/60th even at 30p. Seems to me that on pans and other high motion shots you might want slower to achieve more motion blur and not get that staggered look. But then, the hurky jerky look is what everyone wants to make their stuff look more like film.

[Gary Adcock]

[Bret Williams] “And motion picture film is usually 1/48th shutter speed at 24fps,”

No one in film talks in fractions, Film shutters are indicated in angles of degrees, and unlike digital captures, in film shutter angle is independent of the capture. Not all film cameras use 180* shutters ( the film equivalent to the 1/48th you mention).

Shutter Angles can be used for a a myriad of uses, longer shutter angles, say 240 degrees, can show more motion blur, smoothing the look “juddery” look of 24p materials for those unfamiliar with shooting 24 frame systems.

“Seems to me that on pans and other high motion shots you might want slower to achieve more motion blur and not get that staggered look”

Correct — but your math is wrong, the longer the shutter is open the longer the blur. So smaller fractional numbers are in order for more motion blur. 1/4 is open longer than 1/60th.

gary adcock
Studio37
HD & Film Consultation
Post and Production Workflows

[Keyframe]

[gary adcock] “Correct — but your math is wrong, the longer the shutter is open the longer the blur. So smaller fractional numbers are in order for more motion blur. 1/4 is open longer than 1/60th.”

I understand Gary to state that:

Longer the shutter is open -> Longer the blur;

1/4 [sec.] [shutter speed] is open longer than 1/60 [sec.] [shutter speed];

[Accordingly, 1/4 sec. shutter speed results in longer blur than 1/60 sec. shutter speed.]

However Gary also states:

“So smaller fractional numbers are in order for more motion blur.”

Gary,
I thought that 1/4 (0.25) is a larger, not smaller, number than 1/60 (0.016666…). Did you mean “smaller denominators within fractional numbers [assuming equal numerators]?” Or am I missing something?

Steve Grimes

[Gary Adcock]

[keyframe] “Gary, I thought that 1/4 (0.25) is a larger, not smaller, number than 1/60 (0.016666…). Did you mean “smaller denominators within fractional numbers [assuming equal numerators]?” “

correct,

I was referring to a smaller denominator.

gary adcock
Studio37
HD & Film Consultation
Post and Production Workflows

[Keyframe]

[gary adcock] “correct,

I was referring to a smaller denominator.”

Thank you for the clarification.

Steve Grimes