Confused about CF25 and shutter speed

Garry Matthews · January 6th, 2005, 02:20 AM

I think Toke has a point.

So anyway, getting back to the original topic of this thread;

Is there a difference between CF25 and 1/25 shutter?

Heath McKnight · January 6th, 2005, 08:43 AM

1/25 shutter looks like slow motion, sort of, with tons of motion blur that's really slow.

heath

Dennis Adams · January 6th, 2005, 05:44 PM

> Is there a difference between CF25 and 1/25 shutter?

Yes. In CF25 you can shoot with faster than 1/25 shutter. Otherwise, they look pretty similar to me.

///d@
Sony Media Software

Barry Green · January 6th, 2005, 06:06 PM

Quote:

Nobody in Sony says that pd150/170 is a progressive camera. Nevertheless it records progressive frames with slow shutter.

Well, not really... it records one field, duplicated. It's still an interlaced image, but instead of getting information from both fields, it just uses one field and duplicates it.

Tim Ashbrooke · January 6th, 2005, 08:30 PM

Hmmm.....If 1/25th second shutter speed only uses one field and duplicates (or interpolates) it, that would mean there's a theoretical 50% loss of resolution. The only way I can see of getting the filmlook cadence and still have full res is to use dvfilm deinterlacer or something else. Please tell me I'm wrong! ;)

Garry Matthews · January 6th, 2005, 09:52 PM

I don't know where you get your information from Barry, but you're so wrong!

I just filmed a still scene in HD, first at default settings (no cf, 1/50shutter), then with 1/25 shutter; then with CF25 and 1/25s, then with CF25 and 1/50s. I then viewed the TAPE on a hi-def plasma, and there was no discernable difference! (remember, this was a still scene, no motion).
There's no way that the camera drops 1 field, and just doubles the other! This would result in an image with less lines than standard DV. From what I see with my very own eyes, the camera has to recombine the 2 field scans to form a frame.

I think some people here are getting confused with progressive CCD scanning, and progressive images. The JVC cam for example, reads the CCD progressively, then records the progressive image to tape. The FX1 always reads the CCD in interlaced mode, BUT it then recombines the scans (in CF mode or slow shutter), and records the image to tape (which for all intents and purposes, is now *progressive*, though in the mpeg TS it may be tagged as interlaced).

Because the FX1 CCD is always read interlaced, there is always some drop in resolution (slight cross-talk between scan lines etc.) and that's why you never get 1080 lines of real optical resolution...

My 2c.

Barry Green · January 6th, 2005, 10:34 PM

I wasn't talking about the FX1, that was in reference to the PD150. The PD150 doubles fields, the FX1 does not.

As for where I get my information, it's from first-hand scientific testing. Shoot a resolution chart and you'll see that the FX1 loses about 200 lines when going to CF30 mode (and presumably when going to CF25 mode). Which is nowhere near half... in interlaced it does about 775 lines, in CF30 it does about 575.

Marc Martin · January 7th, 2005, 12:08 AM

Is it possible to set the shutter speed somewhere between 50 and 25 fps?

Toke Lahti · January 7th, 2005, 03:29 AM

<<<-- Originally posted by Garry Matthews: I just filmed a still scene in HD, first at default settings (no cf, 1/50shutter), then with 1/25 shutter; then with CF25 and 1/25s, then with CF25 and 1/50s. I then viewed the TAPE on a hi-def plasma, and there was no discernable difference! (remember, this was a still scene, no motion).
There's no way that the camera drops 1 field, and just doubles the other! This would result in an image with less lines than standard DV. From what I see with my very own eyes, the camera has to recombine the 2 field scans to form a frame.
...
The FX1 always reads the CCD in interlaced mode, BUT it then recombines the scans (in CF mode or slow shutter)... -->>>

Sorry, but this might be possible with 1/25, if there is no readout time from ccd or the actual exposure time is little less than 1/25 s.
Then again, it is impossible with eg. 1/12, because exposing one field takes longer than recording the whole frame, so there is absolutely no time for exposing and reading the second field.

_Ooorr_, would the camera use a frame buffer with 1/12 where it would blend two frames each having the other fields? This way it could have full resolution with slow shutter and still be interlaced.
I just wonder why they didn't introduce this buffer technique before if they now use it...

I'm used to use slow shutter with low light situations with sony's dv cameras and because the sensivity of fx1, it would be very useful to use slow shutters with it also, especially if it doesn't halve the resolution.

January 6th, 2005, 08:43 AM	#17
Heath McKnight MPS Digital Studios Join Date: Apr 2003 Location: Palm Beach County, Florida Posts: 8,531	1/25 shutter looks like slow motion, sort of, with tons of motion blur that's really slow. heath __________________ My Final Cut Pro X blog

January 6th, 2005, 02:20 AM	#16
Garry Matthews New Boot Join Date: Jan 2005 Location: Melbourne, Australia Posts: 5	I think Toke has a point. So anyway, getting back to the original topic of this thread; Is there a difference between CF25 and 1/25 shutter?

January 6th, 2005, 05:44 PM	#18
Dennis Adams Regular Crew Join Date: May 2003 Location: Madison, WI Posts: 123	> Is there a difference between CF25 and 1/25 shutter? Yes. In CF25 you can shoot with faster than 1/25 shutter. Otherwise, they look pretty similar to me. ///d@ Sony Media Software

January 6th, 2005, 08:30 PM	#20
Tim Ashbrooke Regular Crew Join Date: Apr 2003 Location: Grafton, NSW, Australia Posts: 38	Hmmm.....If 1/25th second shutter speed only uses one field and duplicates (or interpolates) it, that would mean there's a theoretical 50% loss of resolution. The only way I can see of getting the filmlook cadence and still have full res is to use dvfilm deinterlacer or something else. Please tell me I'm wrong! ;)

January 6th, 2005, 09:52 PM	#21
Garry Matthews New Boot Join Date: Jan 2005 Location: Melbourne, Australia Posts: 5	I don't know where you get your information from Barry, but you're so wrong! I just filmed a still scene in HD, first at default settings (no cf, 1/50shutter), then with 1/25 shutter; then with CF25 and 1/25s, then with CF25 and 1/50s. I then viewed the TAPE on a hi-def plasma, and there was no discernable difference! (remember, this was a still scene, no motion). There's no way that the camera drops 1 field, and just doubles the other! This would result in an image with less lines than standard DV. From what I see with my very own eyes, the camera has to recombine the 2 field scans to form a frame. I think some people here are getting confused with progressive CCD scanning, and progressive images. The JVC cam for example, reads the CCD progressively, then records the progressive image to tape. The FX1 always reads the CCD in interlaced mode, BUT it then recombines the scans (in CF mode or slow shutter), and records the image to tape (which for all intents and purposes, is now progressive, though in the mpeg TS it may be tagged as interlaced). Because the FX1 CCD is always read interlaced, there is always some drop in resolution (slight cross-talk between scan lines etc.) and that's why you never get 1080 lines of real optical resolution... My 2c.

January 6th, 2005, 10:34 PM	#22
Barry Green Barry Wan Kenobi Join Date: Jul 2003 Location: North Carolina Posts: 3,863	I wasn't talking about the FX1, that was in reference to the PD150. The PD150 doubles fields, the FX1 does not. As for where I get my information, it's from first-hand scientific testing. Shoot a resolution chart and you'll see that the FX1 loses about 200 lines when going to CF30 mode (and presumably when going to CF25 mode). Which is nowhere near half... in interlaced it does about 775 lines, in CF30 it does about 575.

January 7th, 2005, 12:08 AM	#23
Marc Martin Regular Crew Join Date: Jan 2003 Location: Paris, France Posts: 80	Is it possible to set the shutter speed somewhere between 50 and 25 fps?

January 7th, 2005, 03:29 AM	#24
Toke Lahti Major Player Join Date: Oct 2004 Location: Helsinki, Finland Posts: 158	<<<-- Originally posted by Garry Matthews: I just filmed a still scene in HD, first at default settings (no cf, 1/50shutter), then with 1/25 shutter; then with CF25 and 1/25s, then with CF25 and 1/50s. I then viewed the TAPE on a hi-def plasma, and there was no discernable difference! (remember, this was a still scene, no motion). There's no way that the camera drops 1 field, and just doubles the other! This would result in an image with less lines than standard DV. From what I see with my very own eyes, the camera has to recombine the 2 field scans to form a frame. ... The FX1 always reads the CCD in interlaced mode, BUT it then recombines the scans (in CF mode or slow shutter)... -->>> Sorry, but this might be possible with 1/25, if there is no readout time from ccd or the actual exposure time is little less than 1/25 s. Then again, it is impossible with eg. 1/12, because exposing one field takes longer than recording the whole frame, so there is absolutely no time for exposing and reading the second field. _Ooorr_, would the camera use a frame buffer with 1/12 where it would blend two frames each having the other fields? This way it could have full resolution with slow shutter and still be interlaced. I just wonder why they didn't introduce this buffer technique before if they now use it... I'm used to use slow shutter with low light situations with sony's dv cameras and because the sensivity of fx1, it would be very useful to use slow shutters with it also, especially if it doesn't halve the resolution.