Can someone give me the technical and/or practical reasons as to why many
of the Artistic filters are not available and are "grayed out" if an image
is in 16 bit mode?
Because they are 8bit!, but I think you knew that already. ;-) In simple words: Most of these filters are a combination of threshold, edge detection, dilation and blur operations, with some Fractal Noise thrown in here and there and there is no benefit in having them run in 16bit, as in most cases they will completely overwrite the previous pixel values. It would be possible, though.
Also, do you really gain anything by staying in 16 bit or lose any quality
converting to 8 bit?
It all depends on what you do. Higher bit depths provide greater precision which is in particular relevant for photo touch-up and color corrections. Depending on the resolution of your image it also affects smoothness of gradation for gradients, blurs and so on, which is a simple math thing - when the distance spanned by a gradation is greater then the number of available pixel values, not every pixel can have a unique color any more. Therefore neighboring pixels may be assigned the same colors (banding) or interwoven with alternating pixel colors (dithering). Once that has happened, there is no way to restore the original smooth gradients, so you may wish to keep that in mind...
Mylenium
there and there is no benefit in having them run in 16bit, as in most
cases they will completely overwrite the previous pixel values. It would
be possible, though.
OK then, this partially explains it, but if it is possible to make these filters work in 16 bit, then why don't they? I always assume that if something in PS is a certain way, then that is how Adobe intends me to do it. But the "8 bit only" filters thing seems to be at odds with keeping images at their highest quality throughout the work flow.
If the filter is going to mess around the pixels, what's the point of previous operations being in 16 bit?
The use of 16 bit is of limited value to all but a few who understand why they are using it and for what advantage.
Furthermore, there aren't many printers out there that can handle 16 bit.
Didn't you understand Mylenium's explanation?
No. That's why I asked for further clarification. Didn't you read my reply?
If the filter is going to mess around the pixels, what's the point of
previous operations being in 16 bit?
Well if you apply a filter as a Smart-Object, then it's not really messing with original pixels, now is it?
The use of 16 bit is of limited value to all but a few who understand
why they are using it and for what advantage.
Well those few who understand had to get their learning somewhere, now didn't they? I had hoped this forum could be mine. Your snarky reply is neither helpful nor appreciated.
And yeah, there's no real benefit to running them in higher precision.
This being said I am more than happy to cut Adobe some slack on the state of
filters in Photoshop. There are far more important things that needs to be
done to most of the filters in Photoshop than having them work in 16-bit.
Most of the filters in Photoshop are now approaching the Jurasic area and go
pretty much ignored when it comes to Photoshop updates. Things like being
able to render a lens flare on an empty layer, more lens flare options, a
much more sophisticated lighting filter, etc. are all more important things.
The simple solution to all of this is deal with it. Adobe does what Adobe
does that's it.
Robert
Historically, many filters were created when Photoshop supported only 8 bit
channel data. These filters were not updated when this situation changed.
Though the difference can be significant in certain situations, such as
black and white or ProPhoto RGB images, for the vast majority of
photographs, 8 bits works equally as well as 16 bits.
OK then, this partially explains it, but if it is possible to make these
filters work in 16 bit, then why don't they?
Well, you sure have a point, but as Chris said - even an ever so slight change in a feature needs coding work and testing and it would seem, that the demand for the artsy filters working native in 16bit is not that high to justify the effort. I would not take this as "Adobe wants me to work this way", though. As someone originally coming from 3D programs and compositing with After Effects, I can find simialr examples everywhere. The point really is, that it does not make sense to convert all types of effectsas to higher bit depths. Toon shaders in 3D programs are still mostly 8bit for apparent reasons and likewise, there would be no visual difference calculating a circle effect in After Effects in anything other than 8bit. If you want to attribute a failure to Photoshop, then it is its inability to mix different color depths easily. Still, not all is lost. If you encounter such situations, you can always duplicate the image, reduce the bit depth or change color space, run your filters and then copy&paste or drag the processed layer back to the origianl document. A similar workflow could be established by using smart objects, though then it will be a bit more tricky dealing with color profiles and such.
Mylenium