What is the difference between resolution and dpi ?

Smaller dpi makes things smallers, enabling me to put more stuff on screen, same as higher resolution.
So whats the difference ?

Also, how can I change the contrast on my E1505 ? I have the brightness controls, how do I change contrast ? Black has a whitish tint on it right now.

 

wheras resolution is the actual number of pixels on the screen, dpi is a more softwarey measurement that describes how big in pixels to make windows and things.

 

DPI is dots per inch. It measures saturation of the pixels. The screen resolution measure physical size of dots -the higher the resolution, the greater the clarity, but smaller everything is.

DPI is seen with printing primarily. Old laser printers were prized from black and white since they could do 300dpi, although today, this is nothing (since lazers do upwards of 1200dpi)

 

The difference is that resolution says nothing about how compact the pixels are, or how big the monitor is. It just says "This monitor has AxB pixels". For all the resolution cares, the monitor could be the size of a building. The resolution would stay the same, but the DPI would be close to zero.

DPI tells you how many pixels the are on the screen *per inch*
So you might have a low resolution, but really high dpi (for example, say, a 4" screen running 800x600. The resolution in itself is lousy, but the DPI would be insanely high)

 

Jalf almost has it correct.

However, pixels and dots are NOT always interchangeable words.


Resolution, is determined by pixels. Pixels measure how much information a screen/monitor can display. And DPI measures the physical clarity of each pixel. But to understand resolution and DPI you have to understand the EFFECTS of resolution first...

Imagine looking at a 8'x6' wall painting, through a toilet paper tube from very close up. You placed a postcard on the painting with typed sentences on it that are 1/2 inch in height. You can only see a little bit of the painting, but what you can see will appear very large to you, and the 1/2 inch letters on the postcard are large, because you are close up. this is what a lower resolution is like.. you can see less but it looks bigger. And it has nothing to do with clarity, just perception of how much information (how much of your painting) you can see right now. We'll call this 800x600 pixels.

Now, keep the paper toilet roll to your eye, and slowly move backwards 3 steps.. .two things happen.. first.. you can see more of the painting, and second, the little lines, brush strokes.. details.. look smaller to you. The letters on the postcard also seem smaller but are still readable. So you can see more of the whole painting, not all of it, and little details seem smaller, slightly jaggier not blurry, but not as sharp, just not as easy to see because your perceieve them as smaller. Have they actually changed physical size? No. They just appear smaller from that distance. We'll call this 1024x768 pixels.

Now, move back even further until you can see the whole painting. You can no longer read the typed sentences on the postcard, they seem too small. You can see the whole canvas of the painting, but you cannot make out the small details such as individual brush strokes. They're too blurry, they're just too small from your perspective to see them. We'll this 1600x1200 pixels.

Now move back even further, until you can see the painting frame and a little bit of the wall behind it too. We'll call this 1920x1080 pixels.

All of this is about perspective.. that is the *effect* of changing resolutions.. is changes how much you can see. If you moved back until you had 3840x2160 pixels, you could "see" two paintings on the wall and not just one, but the details would seem very small. If you wanted to read the sentences on the postcard on the first painting, you'd have to reprint them on a large piece of paper and make the size of the letters bigger.. like increasing your font size from 12 to 72 in MS Office or Openoffice on your computer.

Those are the *effects* of resolution. The higher the resolution, the more you can see on your screen. If you keep increasing your resolution, you can put more 8x6 foot paintings on your desktop at the same time.

If you reduced your resolution to 1024x768 for example, you would have to make the paintings much smaller, in order to fit more than one on your screen, or be stuck seeing only part of 1 large painting.

The problem here is that if you shrink the painting too much, to fit on the lower resolution screen, you lose detail.. here is where DPI comes in..

Now, the effect of DPI, simply makes things easier or harder to see/read by giving them more or less definition. More DPI makes them sharper, more defined. Less DPI makes the edges seem blurry or jagged.

So higher DPI can help balance out resolution to a point, by making fonts and images seem sharper, clearer when you use higher resolution. (there is a point at which no matter how much you increase the DPI, if the resolution is too high, it won't help)


Now, imagine you are using the 1600x1200 pixel resolution with a high DPI, so the fonts are sharper instead of being blurry. They may still seem a bit small, but they're readable now and not jaggy or blurry.

And lets say you have a 17" LCD monitor, that you are using this high DPI 1600x1200 resolution on. You can have alot of windows open, so lets say you have 8 windows/documets open side by side on the screen in columns, and they fill up the screen from side to side and top to bottom.

So, what happens when you move up to a 24" LCD monitor with the same DPI and same 1600x1200 resolution? What are the effects? Can you see more on the screen? Before the screen was filled up, does this larger monitor mean you now have space along the sides of the 6 columns? The answer is no. You can see the same amount of information, because the resolution is the same. The 9 windows still fill up the screen.

But something does change. The text looks a little blurrier. Because the DPI stayed the same. Why?

Remember I said at the very beginning how DPI measures the effects of the *physical clarity* of pixels? Well here's how...

Lets assume we have 2 monitors, both are 17" and at 1600x1200 pixels/resolution. Well, one of these monitors has big dots, and the other has smaller dots. Yes, the dots from one monitor to another, or one printer to another, can have different sizes! (this is why all this DPI/resolution stuff can be so confusing!)

So the monitor with smaller dots can fit more dots into one inch. This means each pixel will have more dots, and any image made of pixels with smaller dots, will be sharper, clearer.

You ask why would each pixel have more dots, wouldn't more dots mean more pixels? Well, it could, but remember we have the monitors resolution set to 1600x1200 pixels. That's a fixed number for us right now, on both monitors.

So smaller pixels means more dots per inch means a sharper, clearer image, means each pixel is sharper, and in the end, yes.. technically you can fit more pixels into the same space but that last one is a different issue.

So remember we moved up to a 24" LCD monitor with the same DPI and same 1600x1200 resolution? And the columns on the screen still filled up the screen? And the text was a little blurrier? We asked why would the text be blurrier....

Well, look at what we did.. we took the same DPI from a 17" monitor, and looked at a 24" monitor with the same dpi. But we stretched out the resolution across a bigger space. The same 1600x1200 pixels have to cover more space.. which means the pixels have to be larger on the 24" monitor than they were on the 17" monitor. The pixels have to be larger. Not the dots. We did say it was the same DPI...

So, even though every inch of the 24" monitor has the same number of dots, and the pixels are bigger (which means they cover more dots), you would have to sit further back from the monitor to "see" the image as clearly as you did when you sat in front of the 17" monitor.

It's like sitting too close to a large TV. The closer you get, the more pixelated/blocky the little bits of the image get. The further back you sit, the less blocky the picture gets.

Now if we increased the resolution on the 24" monitor, but left the DPI alone, what would happen?

Well, now the pixels don't have to stretch out to fill the 24" screen with 1600x1200 pixels.. we're using a larger resolution, let's say 1920x1080

(yes I know it's a different screen ration, that's another issue, shhh this is just the basics.. for you people learning this, forget about this comment for now)

This means each pixel will again have the same number of dots (or close enough) that you had on the 17" screen, and the pixels aren't stretched anymore. But, you now have much more resolution, so remember those 8 columns of windows on your screen? NOW they have some empty space surrounding them.. but also.. text will look smaller, you might need to use a larger font.. and perhaps a higher DPI to sharpen it out, so each pixel using in building each letter is sharpen it out.


Honestly, if you use some brainpower, you'll get it from here yourself. I hope this helps, i doubt you bothered to read this far, and below.. as some old attempts I took at explaining this issue... so to reiterate..

Resolution is the size of your field of view on your computer desktop..your screen, and it's measured in pixels. And dots, are the tiny bits of visual information that your screen displays, pixels are made up of dots, and different monitors may have different sized dots.. which means DPI can change from monitor to monitor. Which means they way the same resolution looks on one monitor can look differently on another monitor.

yes, lots of apples to oranges when trying to figure out resolution and DPI.

enjoy your new knowledge or added confusion.

(below here are old aborted attempts at explaining this issue.. it helps some people..)




That all depends on your resolution. let's still with the 1600x1200 resolution



Those are 3 different resolutions and their *effects*. Now..

So..

Image #1 = 96x96 pixels, 1 dot per pixel = jaggy/blurry

Image #2 = 96x96 pixels, 4 dots per pixel = less jaggy less blurry

Image #3 = 96x96 pixels, 8 dots per pixel = sharp, clear


This is really a complicated issue that even most experts don't explain well. Because it depends on a variety of factors.

You start by asking 3 questions: (and this is the basic info)

How big is the medium being used to display information (on LCD or other monitor/paper). What size is the monitor? Is it a 17 inch monitor or a 20 inch monitor? Is it an 8x11 inch sized paper, or a 4x6 inch sized paper?

How many pixels does it have, and how many dots per pixels does it have? (yes, dots per pixel).

Basically, DPI - dots per inch determines how clear/sharp an image is. The more dots per inch, means the more dots per pixel. A pixel can have 1 dot, or 4 dots or 8 dots...etc. So DPI measure how much information a pixel can display. The more dots per inch (which means the more dots per pixel too) the clearer/sharper the image will be.

If you pack more DPI into just one screen element, say.. a font.. all that means is the font, whatever size it is.. will be sharper, easier to read, no matter what resolution, or screen size.. the more DPI, the easier to read, the sharper the font or picture.



Short version:

DPI.. dots make up pixels (sometimes 1 dot = 1 pixel, sometimes 8 dots = 1 pixel...etc) so the higher the DPI, the clearer/more focused, less jaggy an image..on screen or on paper.. will be.

Resolution (pixels): Pixels are the measurement of how much information can be displayed on one screen. If you have a 1024x768 resolution you will be able to "fit" less information on a screen than if your resolution was 1600x1200. Think of it this way...

picture 2 square cardboard boxes. One large, one 1/4 the size of the first. The large box will be 1200x1600 pixels and because it's large, you can fit more in it.. (or your can write more information on one of it's sides).

The smaller box will be 1024x768 pixels and can hold less (and could hold less information if written on one of it's sides, assuming you write your letters the same size on both boxes).

because the 1600x1200 box is bigger, if you wrote letter A's all the same size, on its side, you might fit 6,000 letter A's on that one side.

but if you write letter A's *the same size* on the 1024x768 box, you might only fit 2,000 letter A's on its side.

Now, the letter A's on the big box would look smaller, because the box is bigger. But they aren't smaller, and you fit more letters (more information) on the bigger box.

Now, back to DPI.. whichever box has *more DPI* will make the letters sharper, clearer, easier to read.

these issues change a bit if you use two boxes of the same size, and try to fit more "pixels per inch" onto the box. What this means is..

if Box A was


The longer explaination:

Multiple "dots" can make up one pixel. So DPI, or dots per inch, can differ from medium to medium (from printing to LCD display) and from different implimentations of the same medium (one LCD vs another LCD, or one printer vs another printer.)

Yes, with DPI it's a more complicated term than most people realize, which is why you'll rarely get the same answer 5 times in a row from 5 different people, even if they're "experts."

Now, Pixels are another story. A pixel is a unit of measurement that defines how many individual spacial elements make up an image.

So a 1024x768 screen will have 1024 horizontal "picture elements" for each column of 768 "picture elements". Sort of like a pre-defined spreadsheet.

Now, the more dots per pixel you have (pixels can be broken down by 1/4 pixel, 1/8th pixel, 1/2 pixel..etc) the more colors that pixel can display, and the sharper and image made of pixels can be.

So, here comes the part where more people get confused..

The more pixels something has, means that thing can display more information. For example...

if you have a 17 inch monitor, with a "resolution" ( in this case a measurement of how many pixels the screen displaying) of 1024x768, and you compare it the same monitor with a resolution of 1600x1200...
all this means is that the second monitor can display more visual information than the first monitor. It does NOT mean the CLARITY of the image is better or worse. It just shows that more pixels allows you to display more information.

Now if the first monitor (1024x768) had 64 dots per pixel, and the second monitor (1600x1200) had 32 dots per pixel, this means the first monitor would have a clearer image, but could show less information on the screen. (Note: I'm not getting into the issue of SIZE of the dots.)

To put all of this together for you:

If you have an image that is 300 "dpi" and measures 5'x2' (yes feet) then..

A) monitor 1 (1024x768x64PPI) can show LESS of the picture (just a piece of the corner), but what it does show will look better, be clearer/sharper/more defined.

B) monitor 2 (1600x1200x32PPI) will show alot MORE of the picture, but what it does show will be less clear, more jaggy than the first montor.

So what if you have a screen that is only 4"x2" ? The same thing. The more resolution (pixels) it has, the more information it can display on one screen. But, the more dots *each pixel* has, the clearer the image will be.



Yes, using DPI

 

Huh? Sorry, I was lost after chapter 4, verse 12

 

oh uhh, maybe this guys link makes more sense?

http://cambridgeincolour.com/tutorials/digital-camera-pixel.htm

and yeah, the whole issue is *complicated* which makes explaining it *convoluted* (at least for me) it's like doing quadratics before learning order of operations. If you don't already know the fundamentals, working out the details won't happen quickly.

Like I said, even most experts get it wrong, or don't explain it correctly on purpose because there are too many factors to include, so they skip over alot.

 

You seem to indiacte taht dpi only effects the clarity of a picture. Then why does increasing dpi make things look smaller on the screen ?

 

Increasing resolution makes things on the screen look smaller.

Increasing DPI makes them look better. But, many images on the screen have dithered edges, such as fonts. If the DPI is increased, the need for the dithering decreased, and the edges become sharper.. making them look smaller, when they aren't.

Unles you mean in an illustrating or photo/drawing program? Something like photoshop or illustrator? because then, when you increase the DPI of an image (not the same thing as increasing the DPI of a monitor), you are effectively increasing the visual size of the digital image (not the printable size) and so the image software zooms out (usually too much) making the image appear smaller, when all it did was reduce the magnification (aka: zoom out).

Also, *software based* DPI changes on-screen (such as when you increase or decrease the DPI of windows system fonts), are rendered by the video driver and video card. So you may have a different visual effect with different manufacturers video cards/drivers, as they try to draw the screen with different visual settings. This may be the reason you see things smaller when changing DPI in software.

As I mentioned, it's a difficult issue to address because there are soooo many factors that can effect the *image* you see, even if logically there should be no difference.

 

Oh hell, yes, changing dpi makes everything smaller on my M90, when it came it was like 132 dpi, things were big, so I scaled down the dpi to 96, and now things are much smaller, menus, fonts, everything.

 

Thats because you changed the system font/icon DPI, NOT the "screen" DPI. Basically, you made the font smaller, so the menu tables will accomodate the smaller text, hence the menus will be smaller too. It's like changing the font size in a web page or MS word. If the text is enclosed in a table that does not have a defined size, then the text, and its surrounding table will be smaller.

So again, you only changed the system font/icon display size by reducing the system font DPI. You didn't change the DPI of your screen. And it has nothing to do with the resolution, other than at higher resolutions, which makes *everything* look smaller, some people prefer to increase the system font DPI (size), to make the text easier to read. (Calling it DPI in stead of system font/icon size is just another windows issue that makes little sense even if the technical issue behind it is accurate)

 

Hello all. I came into this thread late, but I thought I should add my part for future readers. I work with dpi and resolution in my profession so I deal daily with the question “what is the difference between resolution and dpi”.

If you just want the answer and don’t care about the explanation jump to the conclusion at the end.

Dell_Lied put a lot of time into explaining the meaning of resolution and dpi and I am sure many will find his/her analogy to the painting useful. Unfortunately, Dell_Lied has fallen into the same trap that so many have. He/she has confused various definitions “resolution”.

The problem is that “resolution”, and strangely enough “dpi”, are very generic terms. Resolution is used in many fields for many different things. Saying the word “resolution” is similar to saying the word “unit”. This ambiguity causes a lot of confusion in the computer world when it is applied to the “screen”.

The screen of a notebook has a specific quantity and density of pixels. These values are fixed physical attributes of the notebook screen and cannot be changed. The measurement of quantity is always described in resolution. For example, a 1600 x 1200 monitor is 1600 pixels wide and 1200 pixels high. The density is measured differently depending on the manufacturer - some use DPI. Therefore, the post by Jalf is completely correct when talking about the physical screen.

The operating system on the other hand, has its own definition of a screen. The screen is the interface to the operating system and is most often referred to as the desktop.

In Windows, when you change the screen resolution in display properties, you are changing how many pixels wide and how pixels high of the desktop you want to see. Please refer to Dell_Lied’s analogy to understand why that makes everything on your screen appear bigger or smaller.

A problem that arises is that, unlike CRT monitors (the old style, large, tube monitor), the physical resolution of a laptop screen cannot be changed. This can leave objects looking a little distorted or unclear on your notebook when you change to a resolution that is not equal to the actual physical resolution of your screen.

So what do you do if you want to make objects bigger on your notebook screen so you can see them better?

The solution many graphic card manufactures have come up with is to change the “DPI”. Changing the “DPI” allows you to keep the resolution setting at the screens native resolution but still have control over how large objects appear on the screen.

The confusing part is that you are not actually changing the DPI in the traditional sense. The fuzziness of objects will not change as Dell_Lied suggests. This setting actually only changes how large an inch will appear on the screen. Another term for this is “Zoom”. Why they didn’t just call this setting Zoom I have no idea. It would have saved us a lot of confusion.

The worst part is that this explanation of DPI and resolution only applies to screens. We cannot apply this explanation to describe the difference between DPI and resolution in other computer related things such as digital cameras, or printers, or JPEG images. In fact, in the world of printers DPI is a unit of measurement for resolution – there is no difference. That’s why there is so much confusion, people so often learn what the terms mean in one context and try to apply the same definition to all situations. Unfortunately this is wrong.

Concluson:

Although changing the screen resolution or changing the DPI achieve a similar effect, if you have a flat panel monitor or notebook, and the DPI option is available, always set the screen resolution to the screens native resolution and use the DPI setting to make objects bigger or smaller.

Note: This refers to the DPI setting in Advanced settings in the Display properties. If you only want to change the font size use the Font Size setting in the Appearance tab.

 

For CRTs we also had the notion of "dot pitch", which was the distance between phosphor dots on the screen. A "pixel" usually spanned a number of such phosphor dots. So running a too high resolution on a low-quality CRT display (high dot pitch) didn't necessarily give you a better picture.

On an LCD displays, the "dot pitch" is the distance between cells of the same color (say green). So all is simpler....