Diffusion at DVinfo.net

Marty Baggen · September 5th, 2005, 09:11 PM

I would be very curious if someone could conduct a simple test:

If the HD-100 could be pushed to create visible artifacting (shooting shimmering water for instance), then reshoot with a diffusion filter to see if the artifacting is minimized.

I'm not talking about masking the problem, but rather reducing the work that the compressor has to do.

Werner.... please jump in on this line of thinking.... Barry too?

If MPEG dislikes contrast and hard edges, it makes sense that diffusion and perhaps a pro mist to raise black levels would help.

Seems as though you could really cheat black levels up in the field, and correct in post. Much easier than dodging artifacts in post.

Speaking of black levels.... does HDV use 0 IRE or 7.5?

Barry Green · September 5th, 2005, 11:10 PM

It's almost certain that yes, lower detail will lead to less artifacting. It's a little counterproductive though -- the whole point of shooting high-def is to get a sharper picture with more resolved detail...

I'd try to devise some test circumstance but I don't have an HD100 yet.

Marty Baggen · September 5th, 2005, 11:32 PM

On a technical level I agree with you Barry, but from an artistic one, a very slight diffusion offers a nice look.

However, your comment has got me thinking about how HD may present different objectives.... but since the holy grail amongst most here is to mimic a "film" look, then skillful use of diffusion will most certainly be a common approach, or at least a solution that should be considered.

Werner Wesp · September 5th, 2005, 11:52 PM

MPEG2 likes 'blurred' edges and smooth transitions (within one frame). this is the way to reduce artifacting, yes. but indeed, what's the point of shootin' hi-def, then?

Guy Barwood · September 6th, 2005, 12:20 AM

higher resolution blur?
;)

Robert Castiglione · September 6th, 2005, 03:22 AM

I have been shooting with the camera with a reduced detail setting of minus 9 and together with 24 P and a compressed black setting it gives a great film like image.

Rob

Werner Wesp · September 6th, 2005, 04:14 AM

What MPEG2 really has difficulty with is lots of randomly arranged hard edges (indeed as in water - with small waves - that has light reflecting on it, indeed). Someone posted some footage of gravel already (from the HD100) and it was handled very, very well (beyond my expectation). In that clip there is movement too, so that makes the performance even more impressive.

You have to remember, all in all, the bandwith (19 Mb/s) isn't that low - because it is MPEG2. The bandwith is about the same as the interframe, lower compression of DV (25 Mb/s). Seen the effectivity of the codec and the relativey high bandwith I won't expect too many problems for this resolution. 19 Mb/s or 25 Mb/s won't hold up anymore for 1920x1080 progressive or even 1440x1080 progressive. That's probably one of the reasons the HVX *HAS* to choose P2 (otherwise they would need some higher bandwith like JVC might be developing with the ProHD XE...

Marty Baggen · September 6th, 2005, 07:21 AM

Ironically, I think, yes.... hi-res blur is precisely what you end up with.

It's a technique used in the 35mm and 16mm worlds, as well as SD video.

Tiffen makes a host of filters that achieve the goal, and I don't know a shooter that doesn't carry a bag of filters that diffuse, raise black levels, or both.

I realize now, how paradoxical it seems to be wondering how to defocus areas of a high def picture, but I can tell you that it has given very pleasing results for my film and SD work for years. I'm curious to see what affect it could have on HDV.

Werner Wesp · September 6th, 2005, 08:29 AM

Using them or not using them is up to you, and it is indeed in the first place an artistic decision.

HDV would handle difficult situations better with these filters (the image is 'easier' to compress by MPEG2 standards)

September 5th, 2005, 09:11 PM	#1
Marty Baggen Major Player Join Date: May 2005 Location: monroe, or Posts: 572	Diffusion I would be very curious if someone could conduct a simple test: If the HD-100 could be pushed to create visible artifacting (shooting shimmering water for instance), then reshoot with a diffusion filter to see if the artifacting is minimized. I'm not talking about masking the problem, but rather reducing the work that the compressor has to do. Werner.... please jump in on this line of thinking.... Barry too? If MPEG dislikes contrast and hard edges, it makes sense that diffusion and perhaps a pro mist to raise black levels would help. Seems as though you could really cheat black levels up in the field, and correct in post. Much easier than dodging artifacts in post. Speaking of black levels.... does HDV use 0 IRE or 7.5?

September 6th, 2005, 07:21 AM	#8
Marty Baggen Major Player Join Date: May 2005 Location: monroe, or Posts: 572	Ironically, I think, yes.... hi-res blur is precisely what you end up with. It's a technique used in the 35mm and 16mm worlds, as well as SD video. Tiffen makes a host of filters that achieve the goal, and I don't know a shooter that doesn't carry a bag of filters that diffuse, raise black levels, or both. I realize now, how paradoxical it seems to be wondering how to defocus areas of a high def picture, but I can tell you that it has given very pleasing results for my film and SD work for years. I'm curious to see what affect it could have on HDV. Last edited by Marty Baggen; September 6th, 2005 at 08:57 AM.

September 5th, 2005, 11:10 PM	#2
Barry Green Barry Wan Kenobi Join Date: Jul 2003 Location: North Carolina Posts: 3,863	It's almost certain that yes, lower detail will lead to less artifacting. It's a little counterproductive though -- the whole point of shooting high-def is to get a sharper picture with more resolved detail... I'd try to devise some test circumstance but I don't have an HD100 yet.

September 5th, 2005, 11:32 PM	#3
Marty Baggen Major Player Join Date: May 2005 Location: monroe, or Posts: 572	On a technical level I agree with you Barry, but from an artistic one, a very slight diffusion offers a nice look. However, your comment has got me thinking about how HD may present different objectives.... but since the holy grail amongst most here is to mimic a "film" look, then skillful use of diffusion will most certainly be a common approach, or at least a solution that should be considered.

September 5th, 2005, 11:52 PM	#4
Werner Wesp Major Player Join Date: Aug 2005 Location: Belgium Posts: 497	MPEG2 likes 'blurred' edges and smooth transitions (within one frame). this is the way to reduce artifacting, yes. but indeed, what's the point of shootin' hi-def, then?

September 6th, 2005, 12:20 AM	#5
Guy Barwood Major Player Join Date: Mar 2005 Posts: 423	higher resolution blur? ;)

September 6th, 2005, 03:22 AM	#6
Robert Castiglione Major Player Join Date: Mar 2003 Location: Fremantle, Western Australia Posts: 253	I have been shooting with the camera with a reduced detail setting of minus 9 and together with 24 P and a compressed black setting it gives a great film like image. Rob

September 6th, 2005, 04:14 AM	#7
Werner Wesp Major Player Join Date: Aug 2005 Location: Belgium Posts: 497	What MPEG2 really has difficulty with is lots of randomly arranged hard edges (indeed as in water - with small waves - that has light reflecting on it, indeed). Someone posted some footage of gravel already (from the HD100) and it was handled very, very well (beyond my expectation). In that clip there is movement too, so that makes the performance even more impressive. You have to remember, all in all, the bandwith (19 Mb/s) isn't that low - because it is MPEG2. The bandwith is about the same as the interframe, lower compression of DV (25 Mb/s). Seen the effectivity of the codec and the relativey high bandwith I won't expect too many problems for this resolution. 19 Mb/s or 25 Mb/s won't hold up anymore for 1920x1080 progressive or even 1440x1080 progressive. That's probably one of the reasons the HVX HAS to choose P2 (otherwise they would need some higher bandwith like JVC might be developing with the ProHD XE...

September 6th, 2005, 08:29 AM	#9
Werner Wesp Major Player Join Date: Aug 2005 Location: Belgium Posts: 497	Using them or not using them is up to you, and it is indeed in the first place an artistic decision. HDV would handle difficult situations better with these filters (the image is 'easier' to compress by MPEG2 standards)