Talk:Amiga Hold-and-Modify

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Merge with what now?

The description of the control bits is wrong. I believe 01 changes the blue component and 11 changes the green component.

Contents

[edit] Aspect ratio

I remember creating some HAM graphics with a Photoshop export plug-in. It seemed HAM used a very wide pixel ratio. What was the screen resolution of HAM images?

The screen resolution was LoRes or LoRes-Laced. In PAL areas, this was 320x256 or 320x512. In NTSC areas, this was 320x200 or 320x400. HiRes (640 width) didn't support HAM, at least not on OCS/ECS Amigas, I believe that the AGA Amigas could do this though (I never had one, so can't be certain).
--193.120.178.201 16:46, 26 July 2006 (UTC)
AGA did allow HAM mode to be used on 70ns (HiRes) and 35ns (SuperHiRes and Productivity) resolutions. --Safalra 16:20, 19 December 2006 (UTC)
OCS and ECS did not have the bandwidth to support fetching more than 4 bitplanes in Hires mode, hence they could not support HAM in Hires or higher. AGA could display all 8 bitplanes in all modes, thus it could display HAM in any mode. 62.31.67.29 15:57, 16 February 2007 (UTC)

[edit] lossy compression?

I would say it's more quantisation than lossy compression. What do people think? 62.31.67.29 15:57, 16 February 2007 (UTC)

Isn't all computer graphics quantisation? I think that "lossy compression" is a better term. Val42 19:39, 17 February 2007 (UTC)
Since it takes 3 pixels to modify one color to another color, HAM effectively reduces the color resolution to 230 horizontal. DVDs also reduce color resolution (350 across) as does NTSC/PAL broadcasting (~160 across). All of these are lossy compression techniques that seek to squeeze the color information into a lower resolution that the original source. - Theaveng 16:58, 2 September 2007 (UTC)

[edit] Sliced HAM (SHAM or SHM)

No discussion about Sliced HAM? This was a technique used on the original Amigas to use all 4096 colors without the "blur" of HAM. It required the full attention of the CPU (i.e. minimal multitasking), but the pictures were beautiful and crystal-clear. I stopped using HAM after I discovered Sliced HAM mode. - Theaveng 17:02, 2 September 2007 (UTC)

We need external references to add this information to the article. If you can find such references, go ahead and add it. — Val42 16:07, 3 September 2007 (UTC)

[edit] Rename this article

The Hold-and-Modify article just redirects to here, so this article should take that name. At least, it should be renamed to "Hold-and-Modify (Amiga)". — Val42 19:12, 3 September 2007 (UTC)