difference between Frame mode and 1/30 shutter? at DVinfo.net

Michael Fossenkemper · November 13th, 2005, 11:46 AM

I just shot some stuff in a dark club and slowed the shutter speed down a bit to 1/30. Loaded it into the computer and noticed that it's not interlaced. I shot with a setup that was in normal and not frame mode. do the CCD's act the same in both of these modes? besides more light hitting the CCD's, it also kind of resembles the look of frame mode on some of the edges, but not quite as bad. when I go back to normal shutter speed, the interlacing lines are there. Oh, using a DVC30.

Michael Fossenkemper · November 13th, 2005, 03:02 PM

I've done some more testing to see if there is any visual difference between these two. Initially I thought there would be a different in resolution thinking that 1/30 would be shooting at full resolution. I hooked up my DVC30 to a monitor and switched between frame mode and normal mode at 1/30 shutter speed. other than the light difference, the image quality looks exactly the same. on a 45 degree sharp line, you see the same stair step junk.

Chris Hurd · November 13th, 2005, 03:22 PM

"Stair stepping" is a by-product of the DV format. It's especially noticeable on 45-degree lines.

Michael Fossenkemper · November 13th, 2005, 09:20 PM

But I don't see it in 60i and 60 shutter speed. only in frame mode or 1/30 shutter speed.

Philip Hill · November 14th, 2005, 08:43 AM

doesn't shooting in 1/30 reduce your res by half? i don't think the camera is able to charge both fields on the CCD for 1/30th as that would take 2 seconds, as the CCD cannot capture the whole frame at once (because the CCD is interlaced) hence slow shutter speeds on interlaced CCD's capture half the res but with no interlace artifacts.

that's my understanding of it

Joshua Provost · November 14th, 2005, 09:01 AM

Michael,

Yes, you will lose vertical resolution in both modes. In Slow Shutter 1/30, the shutter speed in 1/30 (obviously. In Frame Mode, by default, the shutter speed will be the default 1/60. In light of that, Frame Mode should need a wider iris and/or more gain to get the same exposure.

Josh

Jheronimus Nunca · November 14th, 2005, 10:24 AM

Quote:

Originally Posted by Joshua Provost

Yes, you will lose vertical resolution in both modes.

The manual for the AG-DVC30P recommends shooting in 60fps for frame mode. What I noticed is that if you capture the footage at this mode and open the file in quicktime pro and select 'high quality' under the video properties menu and then toggle 'de-interlace' there is a noticable loss of resolution. So to me you do gain some resolution with this mode over shooting 30fps slow shutter but you loose sensitivity.

This is probably not a very reliable test, but I tend to shoot in the 60fps frame mode when I have enough light because I don't have to de-interlace in post and it looks better to my eyes, esp. while editing.

I do remember reading a thread here a while ago on editing in FCP with progressive footage. It seems there is some setting especially for editing progressive footage in the timeline so that slow motion effects, freeze frame, etc. are rendered better using both 'fields' of the progressive frame. I could not find this setting, so perhaps someone who knows could chime in?

Thanks.

Michael Fossenkemper · November 14th, 2005, 09:43 PM

Well you wouldn't need to select de-interlace in quicktime if you were shooting in frame mode. It's progressive at that point. The resolution shot has already been taken. I mistakenly took what i read in another forum as truth when they said that shooting interlaced video, if you shoot at 1/30 shutter speed, the CCD's capture both fields at the same time. I like the feel of 30fps but not the look on the DVC30. I have a 16:9 HD LCD tv and the resolution degrade on the DVC30 at either frame mode or 1/30 shutter speed is pretty noticable. I guess i'm asking more from this camera than I paid for it. I guess I was hoping to shoot at 1/30 shutter and not take a vertical resolution hit, but now it's getting through my thick head that it's not possible with interlaced CCD's.

November 13th, 2005, 11:46 AM	#1
Michael Fossenkemper Major Player Join Date: Sep 2005 Location: NYC, weeee. Posts: 417	difference between Frame mode and 1/30 shutter? I just shot some stuff in a dark club and slowed the shutter speed down a bit to 1/30. Loaded it into the computer and noticed that it's not interlaced. I shot with a setup that was in normal and not frame mode. do the CCD's act the same in both of these modes? besides more light hitting the CCD's, it also kind of resembles the look of frame mode on some of the edges, but not quite as bad. when I go back to normal shutter speed, the interlacing lines are there. Oh, using a DVC30.

November 13th, 2005, 03:02 PM	#2
Michael Fossenkemper Major Player Join Date: Sep 2005 Location: NYC, weeee. Posts: 417	ok I've done some more testing to see if there is any visual difference between these two. Initially I thought there would be a different in resolution thinking that 1/30 would be shooting at full resolution. I hooked up my DVC30 to a monitor and switched between frame mode and normal mode at 1/30 shutter speed. other than the light difference, the image quality looks exactly the same. on a 45 degree sharp line, you see the same stair step junk.

November 13th, 2005, 03:22 PM	#3
Chris Hurd Obstreperous Rex Join Date: Jan 2001 Location: San Marcos, TX Posts: 27,368 Images: 513	"Stair stepping" is a by-product of the DV format. It's especially noticeable on 45-degree lines. __________________ CH Search DV Info Net \| 20 years of DVi \| ...Tuesday is Soylent Green Day!

November 14th, 2005, 09:01 AM	#6
Joshua Provost Major Player Join Date: Sep 2004 Location: Phoenix, AZ Posts: 493	Michael, Yes, you will lose vertical resolution in both modes. In Slow Shutter 1/30, the shutter speed in 1/30 (obviously. In Frame Mode, by default, the shutter speed will be the default 1/60. In light of that, Frame Mode should need a wider iris and/or more gain to get the same exposure. Josh __________________ Owner/Operator, 727 Records Co-Founder, Matter of Chance Productions Blogger, Try Avoidance

November 13th, 2005, 09:20 PM	#4
Michael Fossenkemper Major Player Join Date: Sep 2005 Location: NYC, weeee. Posts: 417	But I don't see it in 60i and 60 shutter speed. only in frame mode or 1/30 shutter speed.

November 14th, 2005, 08:43 AM	#5
Philip Hill Tourist Join Date: Jun 2005 Posts: 2	doesn't shooting in 1/30 reduce your res by half? i don't think the camera is able to charge both fields on the CCD for 1/30th as that would take 2 seconds, as the CCD cannot capture the whole frame at once (because the CCD is interlaced) hence slow shutter speeds on interlaced CCD's capture half the res but with no interlace artifacts. that's my understanding of it

November 14th, 2005, 09:43 PM	#8
Michael Fossenkemper Major Player Join Date: Sep 2005 Location: NYC, weeee. Posts: 417	Well you wouldn't need to select de-interlace in quicktime if you were shooting in frame mode. It's progressive at that point. The resolution shot has already been taken. I mistakenly took what i read in another forum as truth when they said that shooting interlaced video, if you shoot at 1/30 shutter speed, the CCD's capture both fields at the same time. I like the feel of 30fps but not the look on the DVC30. I have a 16:9 HD LCD tv and the resolution degrade on the DVC30 at either frame mode or 1/30 shutter speed is pretty noticable. I guess i'm asking more from this camera than I paid for it. I guess I was hoping to shoot at 1/30 shutter and not take a vertical resolution hit, but now it's getting through my thick head that it's not possible with interlaced CCD's.