Dots and DPI vs Pixels and PPI: This topic comes up often here on UHH ending in pages of aimless passionate debate. Here is my take on the subject as one who was there when the...

Strodav Loc: Houston, Tx

This topic comes up often here on UHH ending in pages of aimless passionate debate. Here is my take on the subject as one who was there when the discussion between dots and pixels first started back in 60s.

Certain methods for displaying images, both reflective and luminescent, are made up of DOTS OF ONE SIZE AND ONE DENSITY. The dot is either on or off, there is no in-between. The resolution is the number of dots / inch or DPI. The old B&W dot matrix and pin printers were such devices. How do you get them to display PIXELS that vary in density? The technique was to group dots together to form PIXELS. For example, to get a 256 level pixel a 16x16 array of dots is used. For a dot printer, all dots off gives paper white, all dots on you get black at the density of the ink, but you've reduced your display resolution from the inherent DPI of the printer by 16x, which gives you Pixels per Inch PPI. So, PIXELS are fixed size that vary in density.

The loss of resolution can be overcome to some extent by shaping the matrix. For example, if my original image has a vertical line of value 128 running through the middle of some of my 16x16 arrays of dots. I could turn on just one side of the matrix or 8x16 dots to show the edge of the line which improves apparent resolution. Modern color photo printers shape their matrices of dots to improved perceived resolution, but their inherent "dot" resolution is so high (5760 x 1440 for my Epson XP-15000) and they can slightly vary ink droplet size the discussion of dots almost becomes moot as prints look photographic.

So what's a PIXEL. Besides Picture Element, it is characterized by a FIXED SIZE ELEMENT THAT CHANGES IN COLOR AND BRIGHTNESS. In our cameras, it ends up as an r, g, b element with a size related to the camera's sensor resolution. On my D850 I get 8,256 x 5,504 14 bit r, g, b PIXELS. Let's not get into Bayer filters and de-mosaicing at this time.

So, dots are of fixed size and density and either on or off. DPI is the number of dots per inch. Pixels are of fixed size but vary in color and density. Dots can be used to make Pixels and while many use DPI and PPI interchangeably, they really are different.

Let the melee begin.

PixelStan77 Loc: Vermont/Chicago

Strodav wrote:

This topic comes up often here on UHH ending in pages of aimless passionate debate. Here is my take on the subject as one who was there when the discussion between dots and pixels first started back in 60s.

Certain methods for displaying images, both reflective and luminescent, are made up of DOTS OF ONE SIZE AND ONE DENSITY. The dot is either on or off, there is no in-between. The resolution is the number of dots / inch or DPI. The old B&W dot matrix and pin printers were such devices. How do you get them to display PIXELS that vary in density? The technique was to group dots together to form PIXELS. For example, to get a 256 level pixel a 16x16 array of dots is used. For a dot printer, all dots off gives paper white, all dots on you get black at the density of the ink, but you've reduced your display resolution from the inherent DPI of the printer by 16x, which gives you Pixels per Inch PPI. So, PIXELS are fixed size that vary in density.

The loss of resolution can be overcome to some extent by shaping the matrix. For example, if my original image has a vertical line of value 128 running through the middle of some of my 16x16 arrays of dots. I could turn on just one side of the matrix or 8x16 dots to show the edge of the line which improves apparent resolution. Modern color photo printers shape their matrices of dots to improved perceived resolution, but their inherent "dot" resolution is so high (5760 x 1440 for my Epson XP-15000) and they can slightly vary ink droplet size the discussion of dots almost becomes moot as prints look photographic.

So what's a PIXEL. Besides Picture Element, it is characterized by a FIXED SIZE ELEMENT THAT CHANGES IN COLOR AND BRIGHTNESS. In our cameras, it ends up as an r, g, b element with a size related to the camera's sensor resolution. On my D850 I get 8,256 x 5,504 14 bit r, g, b PIXELS. Let's not get into Bayer filters and de-mosaicing at this time.

So, dots are of fixed size and density and either on or off. DPI is the number of dots per inch. Pixels are of fixed size but vary in color and density. Dots can be used to make Pixels and while many use DPI and PPI interchangeably, they really are different.

Let the melee begin.

This topic comes up often here on UHH ending in pa... (show quote)

Here we go again. No thanks!

Longshadow Loc: Audubon, PA, United States

Getting popcorn.

Cany143 Loc: SE Utah

Longshadow wrote:

Getting popcorn.

I keep suggesting people sprinkle some parmesan cheese on their popcorn, but nobody listens! <sigh!>

Longshadow Loc: Audubon, PA, United States

Cany143 wrote:

I keep suggesting people sprinkle some parmesan cheese on their popcorn, but nobody listens! <sigh!>

Never tried that.
White cheddar is good.

Cany143 Loc: SE Utah

Longshadow wrote:

Never tried that.
White cheddar is good.

Oh? I'll have to try that.... soon.

CHG_CANON Loc: the Windy City

This is laughable, too laughable to bother responding in a serious way, the kind of misinformation that makes the internet such a cesspool.

The attachment has a DPI = 1. Check the file properties. Why doesn't the image show as blotch of overlapping red+green+blue color? Will it print to just 1 inch or 960 inches?

(Download)

Longshadow Loc: Audubon, PA, United States

CHG_CANON wrote:

This is laughable, too laughable to bother responding in a serious way, the kind of misinformation that makes the internet such a cesspool.

But with popcorn.

CHG_CANON Loc: the Windy City

Longshadow wrote:

But with popcorn.

And real butter, imported sea salt and parmesan.

Longshadow Loc: Audubon, PA, United States

CHG_CANON wrote:

And real butter, imported sea salt and parmesan.

Wow, that's two for parmesan.

Cany143 Loc: SE Utah

CHG_CANON wrote:

And real butter, imported sea salt and parmesan.

Real butter? Sorry, but mention of that should be relegated to the *DUH* file. Some things are so a priori obvious that the mere mention of them surpasses the limits of disbelief. But rawthah than quibbling about it further, let me just say, harrumphhhhh!

Got a preferred brand of imported sea salt, Paul? I've only used domestic brands, and if I've somehow been missing out.....

CHG_CANON Loc: the Windy City

Cany143 wrote:

Real butter? Sorry, but mention of that should be relegated to the *DUH* file. Some things are so a priori obvious that the mere mention of them surpasses the limits of disbelief. But rawthah than quibbling about it further, let me just say, harrumphhhhh!

Got a preferred brand of imported sea salt, Paul? I've only used domestic brands, and if I've somehow been missing out.....

Technically, I just use kosher salt from the box, but I've been reading about the flaky sea salt from Brittany (Fleur de sel).

TriX Loc: Raleigh, NC

I WAS going to start a diet today since I have added an inch to my waist this winter as I spend lots of time reading and snacking, But NOW my plan has been derailed by all this talk of popcorn - fortunately I keep Parmesan (and not that stuff in the green container). You all should be ashamed for taunting me 🤬

Cany143 Loc: SE Utah

CHG_CANON wrote:

Technically, I just use kosher salt from the box, but I've been reading about the flaky sea salt from Brittany (Fleur de sel).

Lady who used to live around the corner from me is named Brittany! I'd go around the corner and ask her if she'd front me a little Fleur de sel, but she doesn't live there any more.

Now I'm feeling deprived. Shall I go out and try to find something to photograph that visually conveys the depths of my deprivation? Or would it be better to pop some popcorn? Granted, lacking any of Brittany's flowery sel, this feeling may not completely abate, but it could form the kernel of a beginning. Ah! the fardels we must bear!

CHG_CANON Loc: the Windy City

It's important the popping is done the old fashion way too, with an authentic Whirley Pop Popcorn Maker ...