OK Experts-PseudoGrey

[Steve Cat]

I came upon this while on the retouchPro forum. It is essentially a way of getting more than 256 shades of gray and still look like B & W.

In Paintshop Pro there is a function that counts colors. using the plugin I get 1736 colors. Looking very closely one sees the different shades. Cool but

1. Does Elements have a function that tells how many colors are in an image?

2. Is this any different than using HSV and setting saturation a tad above 0?

Theory link http://r0k.us/graphics/pseudoGrey.html

Free Plugin link, note also includes many other more or less useful effects, but the one we're interested here is monochrome and Deep Gray http://www.redprince.net/pixie/

[Steve Cat]

I should have pointed out that Pixie Dust is bunch of free actions

[TonyW]

One telling comment in that link:

"I don't think anyone can actually see the difference between 256 and 1786 levels of grey."

Makes me wonder why even try :confused: . On the other hand I see a lot of geeky things that people do because they can not because it does anything useful :D

Tony

[Wendy]

Tony ...

You beat me to it :D :D

Wendy

[Chuck S.]

8-bit images (like JPEG's) have a maximum of 256 shades of gray. However, 16-bit images (such as those generated by some scanners) have the capability for 65,536 shades of gray. Each bit of information added to the image increases the number of shades of gray (and color) by a whole bunch (scientific term!). It sounds like this pseudo-gray plug-in is adding a bit to allow interpolation between the JPG normal 256 shades. It sounds a little like resampling, in that it's inventing some information that didn't exist in the original image - unless it was 12-bit RAW or 16-bit scan.

[Steve Cat]

I said 1736 colors. Looking very closely one sees the different shades

you said "I don't think anyone can actually see the difference between 256 and 1786 levels of grey."

also "Tony ...You beat me to it"

So your saying I don't see them. That really isn't very friendly. Nor does it contribute to the overall knowledge of the board.

[Juergen D]

you said "I don't think anyone can actually see the difference between 256 and 1786 levels of grey."
Steve,
Tony was merely quoting from the link that you had posted... :)

Juergen

[Steve Cat]

There is no magic here. Its the same old 8 bit jpeg or bitmat or gif, I don't believe it is format specific. What they are doing is using a color picture that in this case only has 1736 colors 256 of which are grays, the remainder of which appear to be greens and purples that are very close to gray, and trick the eye into believing, it is a fuller range that 256.

I have noticed this same effect, i.e., similar colors, by reducing the saturation using HSV, a method again for getting a more realistic "B&W" by having more "colors" present. It doesn't seem to make much difference whether on uses 16 bit tifs or 8 bit jpegs for this approach.

I have yet to experiment with using the new jpeg/raw conversion and using that saturation slider.

The other interesting thing that I discovered is that what we consider a grays scale is just one of many possible. It was developed of the old B & W televison picture, hence, the name NTSC. Computer Monitors and printers are not like black and white telelvison. The developer believes that a more accurate one he calls PIC produces more pleasing black and white. In my opinion it does. Same number of colors with either method. The free Pixie Dust plug in has an option for PIC should you wish to try it out for you self. I am in way over my head here and just am attempting to convey what I have learned in hopes of improving my B & W work.

[Steve Cat]

The old brain just ain't what it used to be.

I just remembered, the reason people try to get more that 256 grays is because many times the conversion process ends up with more grain than the original, because your eye can just tell the difference between the "gaps" between two adjacent gray tones in a 256 scale. Even though the eye may not be able to perceive 1756 shades of gray, it may perceive two adjacent tones as gapless, and hence finer grained. This is often noticeable in the sky. Now this may be fine, no pun intended if you are trying to simulate Kodak Tri-x, but what if you want fine grain Ansel Adams skys? Pseudo-Gray is an attempt to do so.

[Wendy]

Hi Steve ...

I was also simply quoting from the link ...

... and I am always friendly :(

Wendy

[Steve Cat]

Ask yourself "for what purpose" did I quote. Would the reader think I agreed with the link or disagreed with the link? What was my motive, to enlighten, to support, to be critical?

[Chuck S.]

Steve, re the 'near-gray' colors, that's a pretty neat trick. Short of going to 16-bit, which really will give you more true grays (i.e., R=G=B values), the 'tinging' of a gray with a little red, green, or blue really would generate a different color that might be distinguishable from the nearest true gray. Will have to try it one of these days.

And thanks very much for the link!