Progressive versus interlaced shutter speed at DVinfo.net

Frank Aalbers · January 2nd, 2005, 11:32 PM

Sadly I don't have a camera yet to test this out, so I'll ask it here for those who maybe know.

Lets say I set my shutter speed to 1/60.

In progressive this means my shutter angle is 180 degrees on one frame which is 1/30th of a second.

What does this setting do when in interlaced ? Since each field frame is 1/60th of a second, will the shutter be open all the time ? As if it had a 360 degree shutter angle on a 1/60 s field ? Or will it still use 180 degree shutter angle on a 1/60 s field, which actually means a 1/120 shutter speed ?

I hope my question is clear enough ...

Thanks !

Frank

Graham Jones · January 4th, 2005, 02:52 AM

Perhaps having the shutter speed set at twice the frame rate, while it produces a nice effect when shooting progressive, might be too low when shooting interlaced. After all the shutter would, as you say, sort of match the number of images (choppy interlined images) coming per second..

I think having the shutter speed set at twice the frame rate comes from shooting film where they are known to shoot 24fps at 48. I recently shot video at 25fps progressive and had the shutter at 1/50: it looked lovely but I wouldn't have done that had I been shooting interlaced because, as you may be considering yourself, that would seem to create the danger that the shutter pulses wouldn't have fed the frames amply enough and I don't know how the might effect the overall image? You know.. only giving 25 frames 25 shutter openings! Not enough.

I'm really just waffling - things like this have to be tested or does anyone else have any thoughts?

January 2nd, 2005, 11:32 PM	#1
Frank Aalbers Regular Crew Join Date: Oct 2004 Location: Oakland,CA Posts: 135	Progressive versus interlaced shutter speed Sadly I don't have a camera yet to test this out, so I'll ask it here for those who maybe know. Lets say I set my shutter speed to 1/60. In progressive this means my shutter angle is 180 degrees on one frame which is 1/30th of a second. What does this setting do when in interlaced ? Since each field frame is 1/60th of a second, will the shutter be open all the time ? As if it had a 360 degree shutter angle on a 1/60 s field ? Or will it still use 180 degree shutter angle on a 1/60 s field, which actually means a 1/120 shutter speed ? I hope my question is clear enough ... Thanks ! Frank

January 4th, 2005, 02:52 AM	#2
Graham Jones Major Player Join Date: Jan 2004 Location: Europe Posts: 489	Perhaps having the shutter speed set at twice the frame rate, while it produces a nice effect when shooting progressive, might be too low when shooting interlaced. After all the shutter would, as you say, sort of match the number of images (choppy interlined images) coming per second.. I think having the shutter speed set at twice the frame rate comes from shooting film where they are known to shoot 24fps at 48. I recently shot video at 25fps progressive and had the shutter at 1/50: it looked lovely but I wouldn't have done that had I been shooting interlaced because, as you may be considering yourself, that would seem to create the danger that the shutter pulses wouldn't have fed the frames amply enough and I don't know how the might effect the overall image? You know.. only giving 25 frames 25 shutter openings! Not enough. I'm really just waffling - things like this have to be tested or does anyone else have any thoughts? __________________ www.irishfilmmaker.com