sharpness / acutance ? at DVinfo.net

Gints Klimanis · August 4th, 2003, 06:12 PM

Hi,

What exactly does the vx2000 Sharpness parameter do?
I read in a previous post that this adjusts acutance. I
What exactly is this in digital video?

Mike Rehmus · August 4th, 2003, 06:39 PM

If you look at the video on an edge in the picture closely, you will see what happens. Best to grab a still and then blow it up in your picture editor.

Every one I've seen just increases the contrast of the edge by driving the darker side darker and the lighter side lighter. Some only affect the light or dark.

An extreme case of this is the viewfinder on the pro cameras. They have a peaking circuit that causes a sort of halo to appear around the edges when the camera is exactly in focus.

Boyd Ostroff · August 4th, 2003, 07:09 PM

Actually I was just playing with this, but on my PDX-10. If possible, connect the camera to a decent monitor, then try turning the sharpness up and down in the custom preset. See which setting produces the effect you like.

Recently, I've begun to tire of the over-enhanced edges this produces, both in my digital still and DV cameras, and have taken to turning it all the way down. The PDX-10 really seems to suffer from this, look at the fringes around the trees in this frame grab. I think the PDX-10 is a bit more pronounced than the VX-2000 actually.

I plan to do some shooting with the sharpness turned all the way down and see how I like it. I can always enhance in post if needed...

Matt Stahley · August 4th, 2003, 09:23 PM

Boyd this is a little off the subject but those sets on the Green Mist site are excellent. Is that a combination of projections and physical sets or are the backgrounds painted?

Boyd Ostroff · August 4th, 2003, 09:46 PM

Hey thanks Matt! Depends on exactly what you're looking at, but just about everything seen in a photo on the site is "real". I like to do big backdrops, relatively cheap way to fill the stage with a high resolution image :-)

The Trovatore is what we're working on now, and it will also utilize DV footage (computer animation and real images) projected at about 44'x25' on a downstage scrim to create (we hope :-) an epic, cinematic feeling. The video sequences will be shown during the time the real sets are being changed and allow the opera to continue without pausing for scene changes. But everything depicted in these sketches would be "real", with 60'x32' translucent seamless backdrops at the rear of the stage.

Apologies for wandering off topic.... but I do own a VX-2000 and am using a PDX-10 for the video shoots :-)

Gints Klimanis · August 5th, 2003, 11:54 PM

Well, I'm a DSP programmer and am wondering how various functions map to video terminology. A "high frequency shelf" filter with a > 1 gain ( could boost/cut frequencies by a fixed amount above specified filter frequency) will increase the sharpness of edges as well as boost overall noise. Given that I only see the fringes on the right side of the brandes in Boyd's example image (thanks !!!), I'm guessing that this is an analog filter. Also, I doubt that these cameras have enough DSP power to process images digitally in one dimension, let alone in two. The fringes appear to be the ringing of the analog filter (time domain step response) in reaponse to a major change in contrast.

August 4th, 2003, 06:12 PM	#1
Gints Klimanis Inner Circle Join Date: Jun 2003 Location: San Jose, CA Posts: 2,222	sharpness / acutance ? Hi, What exactly does the vx2000 Sharpness parameter do? I read in a previous post that this adjusts acutance. I What exactly is this in digital video?

August 4th, 2003, 06:39 PM	#2
Mike Rehmus Wrangler Join Date: May 2002 Location: Vallejo, California Posts: 4,049	If you look at the video on an edge in the picture closely, you will see what happens. Best to grab a still and then blow it up in your picture editor. Every one I've seen just increases the contrast of the edge by driving the darker side darker and the lighter side lighter. Some only affect the light or dark. An extreme case of this is the viewfinder on the pro cameras. They have a peaking circuit that causes a sort of halo to appear around the edges when the camera is exactly in focus. __________________ Mike Rehmus Hey, I can see the carrot at the end of the tunnel!

August 4th, 2003, 07:09 PM	#3
Boyd Ostroff Wrangler Join Date: Dec 2002 Location: Mays Landing, NJ Posts: 11,798	Actually I was just playing with this, but on my PDX-10. If possible, connect the camera to a decent monitor, then try turning the sharpness up and down in the custom preset. See which setting produces the effect you like. Recently, I've begun to tire of the over-enhanced edges this produces, both in my digital still and DV cameras, and have taken to turning it all the way down. The PDX-10 really seems to suffer from this, look at the fringes around the trees in this frame grab. I think the PDX-10 is a bit more pronounced than the VX-2000 actually. I plan to do some shooting with the sharpness turned all the way down and see how I like it. I can always enhance in post if needed...

August 4th, 2003, 09:23 PM	#4
Matt Stahley Major Player Join Date: Jun 2002 Location: Waynesboro, PA Posts: 648	Boyd this is a little off the subject but those sets on the Green Mist site are excellent. Is that a combination of projections and physical sets or are the backgrounds painted?

August 4th, 2003, 09:46 PM	#5
Boyd Ostroff Wrangler Join Date: Dec 2002 Location: Mays Landing, NJ Posts: 11,798	Hey thanks Matt! Depends on exactly what you're looking at, but just about everything seen in a photo on the site is "real". I like to do big backdrops, relatively cheap way to fill the stage with a high resolution image :-) The Trovatore is what we're working on now, and it will also utilize DV footage (computer animation and real images) projected at about 44'x25' on a downstage scrim to create (we hope :-) an epic, cinematic feeling. The video sequences will be shown during the time the real sets are being changed and allow the opera to continue without pausing for scene changes. But everything depicted in these sketches would be "real", with 60'x32' translucent seamless backdrops at the rear of the stage. Apologies for wandering off topic.... but I do own a VX-2000 and am using a PDX-10 for the video shoots :-)

August 5th, 2003, 11:54 PM	#6
Gints Klimanis Inner Circle Join Date: Jun 2003 Location: San Jose, CA Posts: 2,222	Well, I'm a DSP programmer and am wondering how various functions map to video terminology. A "high frequency shelf" filter with a > 1 gain ( could boost/cut frequencies by a fixed amount above specified filter frequency) will increase the sharpness of edges as well as boost overall noise. Given that I only see the fringes on the right side of the brandes in Boyd's example image (thanks !!!), I'm guessing that this is an analog filter. Also, I doubt that these cameras have enough DSP power to process images digitally in one dimension, let alone in two. The fringes appear to be the ringing of the analog filter (time domain step response) in reaponse to a major change in contrast.