Setting 'sharpness' for analogue capture

"The Sharpness control adjusts the amount of detail enhancement or high frequency peaking to be added to the video signal. In this picture the transitions from the gray background to the black lines are clean. In most sets, increasing the Sharpness control will add extra edges to at least some of the transitions in the picture, making them stand out. The problem is that you are adding information to the display that is not part of the original signal. Noise is also added to the picture when increasing the Sharpness control. While this added noise may give the impression of more detail, it actually has little or nothing to do with the original signal or any real picture detail. In both cases, turning the Sharpness control up to the point of adding false information is pushing it beyond its correct setting. The correct position of the Sharpness control is just below the point where extra lines are being added to the picture."

(From http://www.videoessentials.com/products_history.php)

Here are a couple of frame captures of the "Indian Head" pattern. It's best to download and zoom in to see the effects I'm talking about.

1. 2.

On the first, the sharpness is I think about right. You can still see some extra edges, but the sharpness control on my capture card doesn't give a smooth adjustment, the next step down is extremely blurred. (Also, around the centre circle you can see an example of rainbows from imperfect Y/C separation).

The second shows what happens if you increase the sharpness. The image looks more detailed, but if you zoom in you can see the white halos to the dark edges that have been artificially added. There is also a lot more noise in the image.

Just to add to this thread: I found I could get better results (sharper image with less haloing) by using the luma peaking adjustment in the BT8x8 Tweaker from within VirtualDub.

This is only useful if your card uses the old BT8x8 chipset.

Are these test patterns of any use in the PAL world?  Can we use these to help calibrate the sharpness for our LD PAL settings, or is switching sources to the NTSC Video Essentials disc just going to confuse things?

I would say probably yes, but I don't know for certain.

Apparently there were PAL test patterns included as an extra on the Encore Jason and the Argonauts LD. I haven't managed to track down a copy, yet.