Why are 1 bit images black or white?

[AstroBenny]

I'm doing my Photoshop course on Lynda.com  and I've got a bit confused about bit depth..

I understand that a 1 bit image has two values: black or white. Why isn't a 1 bit image instead, say, two different shades of white, or two different shades of red, or two different shades of grey...
Why black and white? How would you even define what shade of black or white it is anyway..
 

[ShadowCaptain]

5 minutes ago, AstroBenny said:

I'm doing my Photoshop course on Lynda.com  and I've got a bit confused about bit depth..

I understand that a 1 bit image has two values: black or white. Why isn't a 1 bit image instead, say, two different shades of white, or two different shades of red, or two different shades of grey...
Why black and white? How would you even define what shade of black or white it is anyway..
 

You cannot define shades in 1 bit, it is either ON white or OFF black, think of it like binary

- HOWEVER you can use any 2 colours, so you could have light red and dark red, and it would still be 1 bit

(but you could not have any other colour or shade)

as you increase the bit depth, you increase the number of shades available as you can define more values

 

(also you can basically tell the computer which shade 0 and 1 should be) but you cannot mix them as that would require more than 1 bit)

[Djole123]

Because it doesn't make any sense. What are you going to do with 2 colors?

 

Also, you can merge and separate a couple of pixels to make shades of gray.

[ShadowCaptain]

1 minute ago, Djole123 said:

Because it doesn't make any sense. What are you going to do with 2 colors?

 

Also, you can merge and separate a couple of pixels to make shades of gray.

not in 1 bit

[Djole123]

1 minute ago, ShadowCaptain said:

not in 1 bit

 

Ahem

 

 

Mac 128K, for example, has a "gray" background, but if you look closely, it's black, than white, than black etc etc. And it's a 1-bit color pallette.

[ShadowCaptain]

2 minutes ago, Djole123 said:

SNIP

Yes so each pixel is either white or black, ie 1 bit

you just said "if you look closely" this proving my point

They are not "mixed" there, each pixel is a separate colour entirely, there are no grey pixels, only white and black

[soup]

7 minutes ago, ShadowCaptain said:

not in 1 bit

He could(ish), say a whole matrix of pixels, alteratively off and on gives a medium grey to the whole thing.  Now if two pixels were on one off (repeat) then a lighter grey to the whole panel.  I agree each individual pixel would be black or white but overall the effect would be of a one coloured panel.

  This assumes the pixels are of such a size as to become indistinct from each other.

[ShadowCaptain]

Just now, soup said:

SNIP

yes like the mac thing above

 

but I am only dying on a pixel basis, it can only be one colour or other, your perceived colour is irrelevant

just like, a computer cannot display yellow pixels because its made up of RGB, but they trick your eyes into seeing yellow, but they never actually HAVE yellow pixels

[Djole123]

1 minute ago, ShadowCaptain said:

Yes so each pixel is either white or black

you just said "if you look closely" this proving my point

 

My point was that you can make shades of gray by using a 1-bit pallette by merging and separating pixels. And optical illusions.

[ShadowCaptain]

Just now, Djole123 said:

 

My point was that you can make shades of gray by using a 1-bit pallette by merging and separating pixels. And optical illusions.

Sure I see what you are saying but the question was, "why are the values only one of 2 colours" and that is why

What you can do with 1 bit is a different story

[soup]

1 minute ago, ShadowCaptain said:

your perceived colour is irrelevant

just like, a computer cannot display yellow pixels because its made up of RGB, but they trick your eyes into seeing yellow, but they never actually HAVE yellow pixels

I would say it DOES matter which colour you percieve it is what it actually is that is irrelevant.

 

Surely it matters that you percieve a yellow it doesn't really matter that it is 80%red and 80%green with no blue?

[ShadowCaptain]

1 minute ago, soup said:

I would say it DOES matter which colour you percieve it is what it actually is that is irrelevant.

 

Surely it matters that you percieve a yellow it doesn't really matter that it is 80%red and 80%green with no blue?

 

OP was asking about facts about 1 bit colour and why when its 1 bit can the pixels only be one of two values

 

So it DOES matter what the pixels are doing because that is what he is studying

 

To an and user I would agree

[AstroBenny]

20 minutes ago, ShadowCaptain said:

You cannot define shades in 1 bit, it is either ON white or OFF black, think of it like binary

- HOWEVER you can use any 2 colours, so you could have light red and dark red, and it would still be 1 bit

(but you could not have any other colour or shade)

as you increase the bit depth, you increase the number of shades available as you can define more values

 

(also you can basically tell the computer which shade 0 and 1 should be) but you cannot mix them as that would require more than 1 bit)

So you couldn't have one shade of red and one shade of green for example?

(1000th post )

[ShadowCaptain]

5 minutes ago, AstroBenny said:

So you couldn't have one shade of red and one shade of green for example?

(1000th post )

Yes you could, the pixels could be any 2 colours

 

(but normally its just used for black and white)

[AstroBenny]

23 minutes ago, ShadowCaptain said:

Yes you could, the pixels could be any 2 colours

 

(but normally its just used for black and white)

 So what's the difference between 8bit Adobe RGB and 8bit Adobe sRGB?
 because they can both have 256 values of a colour...

(for one channel of 8 bit)
 

 

[ShadowCaptain]

17 minutes ago, AstroBenny said:

 So what's the difference between 8bit Adobe RGB and 8bit Adobe sRGB?
 because they can both have 256 values of a colour...

(for one channel of 8 bit)
 

 

https://fstoppers.com/pictures/adobergb-vs-srgb-3167

 

Adobe RGB covers a wider colourspace

[soup]

11 minutes ago, AstroBenny said:

 So what's the difference between 8bit Adobe RGB and 8bit Adobe sRGB?
 

 

This is avery complicated (and much argueddisscused) topic.

But I'll have a stab at highlighting the main point :-. 

Actual colour is only part of the story .  You have to also specify strength (i.e. is it a 'bold' colour is it 'pastel' etc).  sRGB tends to actually display fewer colours but has greater 'description' of what 'type' of colour it is  So RGB greater number of colours sRGB more information on the 'type' of colour.

 

If very interested (i.e more than me a very uninterested party:i.e. I am very much a colour philistine(as long as it is what is used for my monitor[sRGB] I don't really care  )) do some Googling on

" the difference between adobe rgb and srgb 8bit"

 

[Gachr]

I'm no graphics designer, but from the knowledge of CSS I have...

Numbers in colours represent how strong each of the RGB colours is. So (if 9 is max value, there are 3 fields) 990 makes yellow. However, you have 1 field with 2 numbers (0 and 1) which represent both 0% RGB (black) and 100% RGB (white).

 

Some other examples:

If you had one field with 8 options (a way of 8bit) you could actually do different shades of gray, since RGB would decrease in parallel.

If you had 4 bit with colours, you could do the basic ones with mixing (black, white, red, green, blue, magenta, cyan and yellow) plus transparency.

 

I'm not sure how one field white-black is called, but 3 field is rgb that stands for red, green and blue. There is also rgba, which adds alpha channel (transparency).

[AstroBenny]

18 minutes ago, ShadowCaptain said:

https://fstoppers.com/pictures/adobergb-vs-srgb-3167

 

Adobe RGB covers a wider colourspace

But how does that change the 256 possible values for each colour space?

[ShadowCaptain]

3 minutes ago, AstroBenny said:

But how does that change the 256 possible values for each colour space?

Because the darkest red in Adobe RGB is darker than the darkest red in SRGB, so even though there are only 256 values, there is more variance in the values so the overall colour depth of the image is greater

 

For examples you could have 100 shades of grey, or 100 shades going from black to white, which would have a wider range

[soup]

8 minutes ago, AstroBenny said:

But how does that change the 256 possible values for each colour space?

Roughly speaking one can describe 256 colours or 128 colours + strong/heavy/pastel etc.

[AstroBenny]

9 minutes ago, ShadowCaptain said:

Because the darkest red in Adobe RGB is darker than the darkest red in SRGB, so even though there are only 256 values, there is more variance in the values so the overall colour depth of the image is greater

 

For examples you could have 100 shades of grey, or 100 shades going from black to white, which would have a wider range

So for Adobe RGB would the 256 shades be closer together in shade or further apart?