# Naked Lies

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 1215922.  Sun Dec 11, 2016 5:46 am The question was "How many shades of grey are there?". The answer given was 104 because that's how many there are in the Pantone colour reference. But that's the answer to the question "How many shades of grey are there in the Pantone colour reference?". Unless we are to believe that a colour only exists if Pantone have defined it. A computer can display 256 shades of grey and the eye can distinguish many more... or only 8 depending on who you ask, but that's a whole other can of worms. Basically this one was wrong on every level and the elf responsible should be bound and flogged. (See what I did there?).

 1215980.  Sun Dec 11, 2016 12:03 pm Good point! Thank you for that and welcome to the forums.

1216053.  Mon Dec 12, 2016 3:30 am

The show did mention shades of white (black + white) too...

 Quote: A computer can display 256 shades of grey

Assuming 24 bits per colour. Correction: 255 if white is a neutral grey, 254 if it isn't. Black is not a shade of grey.

 1216073.  Mon Dec 12, 2016 5:28 am You are assuming that "grey" is any colour where R=G=B and 0 < (R,G,B) < 255. There are many colours taht would be called "grey" where R, G and B are not equal values. Therefore when you look at the available permutations there are probably something over 10,000 [gestimate] "shades of grey" which can be displayed using the common 24-bit computer colour model. Not that this means anything - it's just constraning your choices to the chromic resolution of the display. It's like saying "All objects more than a mile away must be at least 2 metres tall because that's the size of a single pixel at my camera's highest possible zoom". I can assure that even though Swot is dozens of miles away and rather less than two metres tall she does actually exist. PDR

1216211.  Mon Dec 12, 2016 7:45 pm

 Quote: Good point! Thank you for that and welcome to the forums.

Thanks! My pedantry finally got the better of me on this one and I was compelled to sign up.

1216213.  Mon Dec 12, 2016 7:52 pm

 Quote: Assuming 24 bits per colour. Correction: 255 if white is a neutral grey, 254 if it isn't. Black is not a shade of grey.

Fair point. I could claim that the black displayed on a monitor is highly unlikely to be truly black but that might be grasping...

1216214.  Mon Dec 12, 2016 7:57 pm

 Quote: There are many colours taht would be called "grey" where R, G and B are not equal values.

True, I was of course only referring to neutral greys. But it makes me wonder at what point grey officially stops being grey.

 1216216.  Mon Dec 12, 2016 8:02 pm When it's ajar!

1216225.  Tue Dec 13, 2016 3:00 am

 Slimypants wrote: But it makes me wonder at what point grey officially stops being grey.

Surely that would be when it has so fully integrated with the human culture and society that people need to be reminded it is actually one of the alien overlords...

PDR

1216230.  Tue Dec 13, 2016 3:07 am

Slimypants wrote:
 Quote: Assuming 24 bits per colour. Correction: 255 if white is a neutral grey, 254 if it isn't. Black is not a shade of grey.

Fair point. I could claim that the black displayed on a monitor is highly unlikely to be truly black but that might be grasping...

Grasping is not unheard of around here, so if it'll help your case, go for it :-)

1218248.  Mon Dec 26, 2016 11:09 pm

 PDR wrote: Therefore when you look at the available permutations there are probably something over 10,000 [gestimate] "shades of grey" which can be displayed using the common 24-bit computer colour model. PDR

Let's get past the guestimate phase of the discussion, shall we? An 8-bit camera in monochrome (gray scale) mode can record 256 distinct shades of gray (2^8), including absolute black (0) and pure white (255). However, 8-bit images are considered VERY low resolution in scientific imaging.

I teach astronomy & astrophysics at a small observatory, and we commonly use a 16-bit camera for astronomical photography that records 2^16, or 65,536 distinct shades of gray, and when we do mathematical manipulations to these images, we routinely convert them to 32-bit images, in which there are no fewer than 4.29 billion distinct shades of gray (2^32 = 4294967296), so there are no errors in rounding up or down.

Typical RGB color images from cell phone cameras are 8-bit, but much higher resolution is used in most scientific imaging. In theory, there is no limit to the number of divisions, or gray scale values, between pure black and pure white.

 1218298.  Tue Dec 27, 2016 12:07 pm Welcome aboard, Vermonter. You appear to be a very QI addition to our ranks. We allow Very Interesting to the merely QI.

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