DVC30 - Frame mode 50% resolution loss??!! at DVinfo.net

Dave Croft · September 14th, 2004, 03:55 PM

I thought the DVC30's frame mode had a similar dip in resolution of maybe 25% like some other Pany cams and possibly the GL2 have? Check this thread:

http://www.dvinfo.net/conf/showthread.php?s=&threadid=31845

Can this be right?

Boyd Ostroff · September 14th, 2004, 04:06 PM

Since the origin of that information is Adam Wilt's DVC-30 review, you might want to contact him directly and see how he determined this http://www.adamwilt.com. If this isn't correct I'd think DV Magazine would want to address it in a future issue...

Dave Croft · September 14th, 2004, 04:08 PM

Thanks for the link Boyd, I'll try to email him.

Rokta Bija · September 14th, 2004, 07:03 PM

I think anyone with a DVC30 should be able to tell us if this is true. A 50% loss would be very obvious, and I have a hard time believing panasonic would do it that way, especailly considering how good the frame mode is on the GS400.

Dave Croft · September 15th, 2004, 01:46 AM

Rokta you are right, it should be obvious. I will download a resolution chart and do some tests.

Dave Croft · September 15th, 2004, 04:32 PM

Here are four frame grabs from a resolution test I did with my DVC30 today. They are fairly compressed, but you can quite easily see the difference between the shots (if anyone can host the uncompressed shots let me know and I could email them).

http://www.villagephotos.com/pubbrow...lected=1008443

1. Interlaced 50i at 1/50th second shutter speed.

2. Frame mode 25p at 1/50th second shutter speed.

3. Interlaced 50i at 1/25th second shutter speed.

4. Frame mode 25p at 1/25th second shutter speed.

As you can see the interlaced 1st image is clearly the sharpest. According to Adam Wilt in his review of the DVC30 in DV magazine, the frame mode of the DVC30 has a 50% reduction in resolution over interlaced, due to the frame mode doubling fields. The 2nd image shows that although it is less resolution, it is not as bad as the 3rd image, which is interlaced 50i at 1/25 (50% resolution).

The 4th image using frame mode and a 1/25th shutterspeed has a near identical resolution to the 3rd (50i, 1/25).

From this test I feel assured that the DVC30 does not have as big a drop in resolution when in frame mode as suggested. To me it seems more like 25%, which is what I thought it was in the first place.

I am going to try and email Adam Wilt with the result of this test.

Boyd Ostroff · September 15th, 2004, 05:41 PM

I'm glad that you took the initiative to do some actual tests instead of just theorizing! However when I look at #2 and #3 I don't see a very big difference in vertical resolution as measured by the converging bars in the 9 o'clock position on the chart. The JPEG compression makes it difficult to tell though. Unfortunately you did not frame the chart properly to be able to really read the resolution. You need to frame such that the chart exactly fills the full frame to get a reading from those converging bars.

Also, I don't think you would really see a 50% resolution loss when comparing a 60i full frame to a field-doubled frame. All interlaced cameras do some field blending - see my post: http://www.dvinfo.net/conf/showthrea...504#post222504

I'll be interested to see Adam's response.

Dave Croft · September 16th, 2004, 02:48 AM

Hi Boyd, as usual I forgot that often a cameras LCD does not cover the entire frame, so what I thought was a carefully full framed shot turned out to not be.

I'm hoping to be able to host the un compressed shots on my brothers web space, I could even redo the shots at the proper full frame size.

Frank Granovski · September 16th, 2004, 03:19 AM

Adam Wilt most likely used a high-end wave-form monitor to measure and compare the resolution in these 2 modes. The 50% loss is a bit harsh. It could be a typo; but then again he could have discovered something that could force the DVC30 price down. Way down.

Bo Smith · September 30th, 2004, 03:48 AM

Here's his review:

http://www.dv.com/reviews/reviews_it...cleId=48800242

September 14th, 2004, 03:55 PM	#1
Dave Croft Regular Crew Join Date: Apr 2004 Location: Yorks UK Posts: 89	DVC30 - Frame mode 50% resolution loss??!! I thought the DVC30's frame mode had a similar dip in resolution of maybe 25% like some other Pany cams and possibly the GL2 have? Check this thread: http://www.dvinfo.net/conf/showthread.php?s=&threadid=31845 Can this be right? __________________ Dave Croft Experimental filmmaker, Nature video, Documentary work and more. Panasonic DVC30, XLR adapter, Shotgun Mic, Canon WD43 Wide angle, PC using Premeire + AE.

September 15th, 2004, 01:46 AM	#5
Dave Croft Regular Crew Join Date: Apr 2004 Location: Yorks UK Posts: 89	Rokta you are right, it should be obvious. I will download a resolution chart and do some tests. __________________ Dave Croft Experimental filmmaker, Nature video, Documentary work and more. Panasonic DVC30, XLR adapter, Shotgun Mic, Canon WD43 Wide angle, PC using Premeire + AE.

September 15th, 2004, 04:32 PM	#6
Dave Croft Regular Crew Join Date: Apr 2004 Location: Yorks UK Posts: 89	Resolution test stills Here are four frame grabs from a resolution test I did with my DVC30 today. They are fairly compressed, but you can quite easily see the difference between the shots (if anyone can host the uncompressed shots let me know and I could email them). http://www.villagephotos.com/pubbrow...lected=1008443 1. Interlaced 50i at 1/50th second shutter speed. 2. Frame mode 25p at 1/50th second shutter speed. 3. Interlaced 50i at 1/25th second shutter speed. 4. Frame mode 25p at 1/25th second shutter speed. As you can see the interlaced 1st image is clearly the sharpest. According to Adam Wilt in his review of the DVC30 in DV magazine, the frame mode of the DVC30 has a 50% reduction in resolution over interlaced, due to the frame mode doubling fields. The 2nd image shows that although it is less resolution, it is not as bad as the 3rd image, which is interlaced 50i at 1/25 (50% resolution). The 4th image using frame mode and a 1/25th shutterspeed has a near identical resolution to the 3rd (50i, 1/25). From this test I feel assured that the DVC30 does not have as big a drop in resolution when in frame mode as suggested. To me it seems more like 25%, which is what I thought it was in the first place. I am going to try and email Adam Wilt with the result of this test. __________________ Dave Croft Experimental filmmaker, Nature video, Documentary work and more. Panasonic DVC30, XLR adapter, Shotgun Mic, Canon WD43 Wide angle, PC using Premeire + AE.

September 16th, 2004, 02:48 AM	#8
Dave Croft Regular Crew Join Date: Apr 2004 Location: Yorks UK Posts: 89	Hi Boyd, as usual I forgot that often a cameras LCD does not cover the entire frame, so what I thought was a carefully full framed shot turned out to not be. I'm hoping to be able to host the un compressed shots on my brothers web space, I could even redo the shots at the proper full frame size. __________________ Dave Croft Experimental filmmaker, Nature video, Documentary work and more. Panasonic DVC30, XLR adapter, Shotgun Mic, Canon WD43 Wide angle, PC using Premeire + AE.

September 30th, 2004, 03:48 AM	#10
Bo Smith Regular Crew Join Date: Aug 2003 Location: Exit28, NY Posts: 64	Here's his review: http://www.dv.com/reviews/reviews_it...cleId=48800242 __________________ Bo Smith \| Camera Operator / Cinematographer web \| http://BoSmith.tv

September 14th, 2004, 04:06 PM	#2
Boyd Ostroff Wrangler Join Date: Dec 2002 Location: Mays Landing, NJ Posts: 11,787	Since the origin of that information is Adam Wilt's DVC-30 review, you might want to contact him directly and see how he determined this http://www.adamwilt.com. If this isn't correct I'd think DV Magazine would want to address it in a future issue...

September 14th, 2004, 04:08 PM	#3
Dave Croft Regular Crew Join Date: Apr 2004 Location: Yorks UK Posts: 89	Thanks for the link Boyd, I'll try to email him. __________________ Dave Croft Experimental filmmaker, Nature video, Documentary work and more. Panasonic DVC30, XLR adapter, Shotgun Mic, Canon WD43 Wide angle, PC using Premeire + AE.

September 14th, 2004, 07:03 PM	#4
Rokta Bija Regular Crew Join Date: May 2004 Posts: 61	I think anyone with a DVC30 should be able to tell us if this is true. A 50% loss would be very obvious, and I have a hard time believing panasonic would do it that way, especailly considering how good the frame mode is on the GS400.

September 15th, 2004, 05:41 PM	#7
Boyd Ostroff Wrangler Join Date: Dec 2002 Location: Mays Landing, NJ Posts: 11,787	I'm glad that you took the initiative to do some actual tests instead of just theorizing! However when I look at #2 and #3 I don't see a very big difference in vertical resolution as measured by the converging bars in the 9 o'clock position on the chart. The JPEG compression makes it difficult to tell though. Unfortunately you did not frame the chart properly to be able to really read the resolution. You need to frame such that the chart exactly fills the full frame to get a reading from those converging bars. Also, I don't think you would really see a 50% resolution loss when comparing a 60i full frame to a field-doubled frame. All interlaced cameras do some field blending - see my post: http://www.dvinfo.net/conf/showthrea...504#post222504 I'll be interested to see Adam's response.

September 16th, 2004, 03:19 AM	#9
Frank Granovski Outer Circle Join Date: May 2002 Location: Hope, BC Posts: 7,524	Adam Wilt most likely used a high-end wave-form monitor to measure and compare the resolution in these 2 modes. The 50% loss is a bit harsh. It could be a typo; but then again he could have discovered something that could force the DVC30 price down. Way down.