Viewing "Actual Size"

[Canned_Pug-Ng0EYk]

HI,

I've always wondered why, if I set the screen view to "Actual Size" or even 100%, that if measured against a ruler put up to the monitor, it does not correspond. Is there a view or setting that can do this without me zooming in or zooming out and measureing with a ruler every time? (I'm feeling this might be so simple I'm going to once again be embarrassed....

Thanks.

[Guest]

This has been discussed several times in the forum. You might search for one of those threads.

[Canned_Pug-Ng0EYk]

i did try "viewing size' and "actual view" with 0 results not sure

what else to ask...will look further

[Stix_Hart]

The search is busted...  Try this thread here.  Long story made overly short and simple: try 140%, it seems to work for most people.

[Canned_Pug-Ng0EYk]

Thanks!

[rob day]

here's a simplified version of the formula in the referenced script

(horizontal resolution / screen horizontal inches) / 72) * 100

a 23" Apple Cinema display running at 1920 gets you 137 — (1920/19.5)/72)*100

but on my laptop the formula result is 149, so there's no universal percentage that works on all monitors.

Photoshop's Print Size doesn't work either as the last poster in the other thread implies—unless your monitor is running at exactly 72ppi, which would be unlikely.

[Canned_Pug-Ng0EYk]

well, this is closer that I was able to get. This makes it that much

easier to knowing which size fonts will work best...gets you as close

as poss. before a print check.

Thenk Youse!

[Guest]

Your formula works -- except that I measure my 23" iMac screen at 20" wide. But this leaves me with a question: what exactly is this magic number 72?

Years ago, I read that native screen resolution was 72 ppi for the Mac, and 96 ppi for Windows. I never really thought about it, but it didn't seem to match my monitors and at the time I was using the same (non Apple) monitors on both PC and Mac. And now with my iMac 1920/20" is 96 ppi.

Your formula which divides actual monitor resolution by 72 indicates that there is an adjustment for what the application expects the monitor to display. But is this inherent to InDesign (and by extension all applications) or inherent to the OS (as per my old recollections)?

If I make a new document in Photoshop at 96 ppi, it displays acutal size at 100%. I'm left wondering why InDesign (and others) don't have a preference pane that allows to adjust the screen resolution.

[Canned_Pug-Ng0EYk]

Really! Wouldnt that be great!?

...from Miickii's iiPhone

[John Hawkinson]

M Blackburn wrote:

Your formula works -- except that I measure my 23" iMac screen at 20" wide.

23" is the diagonal length, from upper-left to lower-right. For a 16:9 ratio monitor, that means it would be 20"x11.25". Slightly different for other ratios of course.

Your formula which divides actual monitor resolution by 72 indicates that there is an adjustment for what the application expects the monitor to display. But is this inherent to InDesign (and by extension all applications) or inherent to the OS (as per my old recollections)?

If I make a new document in Photoshop at 96 ppi, it displays acutal size at 100%. I'm left wondering why InDesign (and others) don't have a preference pane that allows to adjust the screen resolution.

Let's not confuse resolution (total # of pixels, which you CAN change) with density or ppi... It's the job of the OS to tell applications how big a pixel is, sometimes that doesn't quite work. But that's why InDesign doesn't [and shouldn't!] have an adjustment. All programs should have the same idea of how big your screen is...

[Peter Spier]

M Blackburn wrote:

what exactly is this magic number 72?

It corresponds to 72 points per inch.

[rob day]

But this leaves me with a question: what exactly is this magic number 72?

The first Macs had builtin screens with a res of 72ppi—the mac plus 9", 512×342. When monitors became seperate items driven by third party graphics boards, the screen res became variable.

If you are designing a GUI for InDesign that shows rulers you have to settle on how many pixels there are in an inch when the zoom level is at 100%. In InDesign it's 72 pixels, in Photoshop it's the image's ppi. The size of the displayed pixels changes depending on the monitor capabilities—if you could find a screen running at 72ppi, ID's 100% zoom would show ruler inches measuring exactly an inch.

Dividing by 72 gives you the ratio that compensates for the actual screen ppi and the assumed 72ppi.

In case you thought there would never be a practical use for your long forgotten high school algebra, Marijan's javascipt channels Pythagoras to get the actual screen res, where your screen's diagonal is the hypotenuse.

[Canned_Pug-Ng0EYk]

i just want my booboo bear...waa-a!

...from Miickii's iiPhone

[Guest]

Rob,

Thanks for the info regarding the Mac. (Peter seems to had missed that my question about 72 was somewhat rhetorical and kindly informed that it refers to ppi) Am I to conclude the universal use of 72 dpi comes solely from those ancient Macs? This also leaves me to conclude that my understanding of Windows machines being 96 ppi must be from some Windows dude noticing that his monitor wasn't 72 ppi at a time that Macs could also using 96 ppi monitors, and that there is nothing inherent in either OS that would force the choice of 72 ppi as the default display resolution.

I fully recognize that a program without a variable display resolution such as ID has to settle on a value, and that that value has to be historical rather than speculative, but considering the number of people that are bothered by 100% not showing actual size -- and my assumption of how easy it would be to have a preference for screen resolution -- I would expect it to be part of the program.

(Derivative of the Pythagorean Theorum, eh? I’ve been out of touch with high school algebra for a long time now.)

A P.S. for John Hawkinson.

I am fully aware that the 23 is a diagonal measure, but that is a measure of monitor size and this discussion deals with resolution which has to be taken parallel to an edge.

Are you sure of your facts and your reasoning? Why must all programs have the same idea of how big the screen is if it results in all programs displaying 100% at something other than actual size? Especially when the capability to adjust resolution is acceptable (and easily implemented) in applications such as Photoshop?

[Peter Spier]

Peter said 72 POINTS per inch. In Photoshop, when you view at 100% you see a 1:1 relationship between screen pixels at the curent screen resolution and the image pixels, so each image pixels uses only one display pixel. At 400% you use four display pixels for each image pixel, and so forth. Rob may have explained it better, but ID measures in points, and at 100% view, you have a 1:1 relationship between display pixels and points.

[Guest]

Peter,

When I think 72 points per inch, I think pica points, and that is not what we're talking about here. No one uses ppi in reference to points. Points are discreet values. We are talking about resolutions. So I am legitimately confused by your reply.

While Photoshop considers 100% to be a 1:1 relationship as you describe, the discussion here is about 100% in reference to the rulers. If your resolution in Photoshop is 72 ppi, a 3" square image will not display at 3" at 100% -- but it will at 96 ppi (if that is your monitors resolution).

Image display of the rulers, that's the crucial point. But what do you mean by ID measures in points? It has to generate its display based on an assumption of pixels. And there is no reason that the formula it uses need be hard wired to an archaic standard.

Frankly, I'm starting to wonder how relevant 72 ppi is even to the future of the web. Browsers display per your systems actual resolution don't they? And they are becoming more adjustable and user customizable. I don't even know if the current resolutions of monitors are optimal. Maybe in the next 10 years the average monitor will be 150 ppi.

[Peter Spier]

I'm talking about points as in points and picas, and rulers.

InDesign's internal measurement system is points. Any other ruler units are just conversions. When you say view at 100%, ID is saying OK, let's show a 1pt x 1pt square as if it is a single pixel -- at least that's my understanding -- so if the screen is 72 ppi, your ruler will be accurate at 100%. If the screen is 96 ppi, your ruler will shrink to about 75% of "real" size on screen. My 27" screen with a horizontal measurement of about 22" displaying 1920 pixels is about 84 ppi, and my rulers on screen, at 100% view at around 86% of lifesize.

I'm not sure how you manage to show a .25 pt stroke at 100%, but my suspicion is that there are more phosphor dots or LCD cells or whatever than just one making up each screen pixel, but it also appears that the display is unable to show any difference, at least on my monitor, between 1 pt and .5 pt or .25 pt and .05 pt when zoomed out that far, so there has to be some rounding or rule that says light up SOMETHING if there's some detail to see. When I zoom out to 50% a 3 pt rule actually appears sligthly thinner than a 2 pt rule and from 1 pt down they all look the same. Some of this also depends on where the object is located relative to the boundaries of the screen pixels.

[Guest]

Peter,

Saying InDesign's internal measurement system is points and that any other

ruler units are "just" conversions is meaningless. Any discreet unit of

distance is nothing but a conversion of some other measurement system. The

only physical measure of a pica is in a museum somewhere, and that isn't

what anyone uses for points anymore.

And I doubt that your explanation of how InDesign calculates screen image

size is accurate anyhow: changing InDesign's preferences from postscript

points to traditional doesn't affect the display size. I am pretty confident

that the 72 refers to the traditional monitor resolution Rob refers to.

I'm not sure what point you're trying to make in your second post. All I am

saying is that 72 ppi is a legacy value. It has no intrinsic correctness and

is arguably an outdated default.

[Peter Spier]

You are totally misunderstanding me. The units ID uses internally are postscript points which are 72 per inch. It makes no difference what ruler units you use, at 100% ID is going to base the view on showing you the equivalent of 72 postscript points in the size it "believes" represents one inch, which is calculated by checking the number of pixels being displayed and dividing by the reported system resolution (I'm making a presumption, here).

Two different monitors may both be running at 1920 x 1200, for example but if one is a 24 " and the other is 27" the apparent size of what is on screen is going to be very different, even though Windows or OS X is using the same value for resolution in the OS. ID can't tell the physical dimensions of your monitor, so it displays the rulers using the same calculations on both monitors, and the size will be wrong, but differently wrong, on each one, unless the the "true" resolution of the monitor -- the number of pixels displayed divided by the physical size of the display -- is exactly 72.

In order to find the correct zoom level for a lifesize view you need to calculate that "true" monitor resolution and divide it by 72, the number of postscript points you want to display in one real inch of monitor space. It has nothing whatever to do with 72 ppi or 96 ppi beyond what those numbers may be doing to affect the size of the pixels on the screen, and you don't need to know what number the OS is using.

The second post was probably my misunderstanding you. Again, I don't believe the system resolution is particularly relevant. It's a constant, or at least can be treated as a constant, and your display depends on the physical size of the monitor and the number of pixels it displays. I keep hearing that Windows uses 96 ppi, and I don't understand where that number is even useful, if it has a real meaning, or is simply a relative value and not truly tied to a physical dimension (which is what I suspect). The number of pixels that will be displayed in an inch in your browser will still be determined by the same monitor resolution value/physical size calculation, modified by any zoom factor.

The same 600px wide image displayed in the same browser using the same settings will use the same proportion of the screen regardless of the physical dimensions of the screen if two monitors are set to the same resolution. If you change the monitor resolution setting, the image will be rendered larger or smaller and will take up a greater or lesser part of the total browser window.

[Guest]

Peter,

I do not think that I am misunderstanding you. Where did you ever get the

idea that I don't understand that two different sized monitors running the

same pixel dimensions would have different apparent images sizes? I think I

was fairly careful in pointing out when I was talking about effective

resolution, by which I mean actual numbers of pixels per inch of monitor.

What I said was that I don't believe you are correct in the assertion that

ID calculates the size of its display based on points. I doubt that because

I can see no reason a programmer would use typesetting points for

calculating screen display, and changing InDesign's internal calculation of

points from postscript to traditional doesn't effect the display. It just

doesn't make sense. Granted, I would change my mind if a technician from

Adobe set me straight.

[Peter Spier]

M Blackburn wrote:

Peter,

What I said was that I don't believe you are correct in the assertion that

ID calculates the size of its display based on points. I doubt that because

I can see no reason a programmer would use typesetting points for

calculating screen display, and changing InDesign's internal calculation of

points from postscript to traditional doesn't effect the display.

Of course it doesn't affect the display. Does an inch change size because you switch from fraction to decimals? Changing from psotscript to traditional points or mm changes the spacing between the tick marks on the ruler, not the distances between objects or the size that something has been drawn.

You can believe what you want about the internal units. 72 is actually a pretty nice number since it is divisible by 2, 3, 4, 6, 8, 9, 12, 24 and 36, compared to 2 and 5 for 10, for example. It could be angstrom units for all the relevence it has. The point here is that at a true 100 % view, exactly 72 postscript points will take up exactly 1 inch of space on the monitor, and you are trying to get ID to show you the ruler at actual size. If you measure the monitor dimensions in inches, 72 is the number that you need to use to calculate the correct zoom. If you measure your monitor in cm, 72 would not be the correct factor (and I haven't done the math, but it would be based on how many postscript points are in a cm).

[Guest]

Peter,

Postscript points and traditional points ARE different sizes. That's why

they have different conversion equations to other systems -- like inch.

Why I say typographic points would be a bad choice for programmers is that

points are part of a measurement system with 12 points to a pica making

calculation unnecessarily awkward. You must never have worked in a print

shop or traditional typesetting.

If you are going to suggest that all one needs to consider is 72 points in

an inch, there is no reason to assume that the 72 per inch is linked in any

way to points. You seem to forget that every other program converts its

screen image to 72 units per inch as well. Most of those programs don't even

know what a typographic point is.

[Peter Spier]

What makes you thingk ANY program converts anything to 72 units per inch?

And I have worked in print shops. And the reason that postcript points are not the same size as traditional (any of the several traditional point sizes) is precisely because those units do not divide evenly into an inch. But I'll repeat what I said before, You can convert ruler units all day long and it will not affect the size of anything, only the marks onthe rulers and the numbers used to describe the dimension.

I don't think this conversation is going to go anywhere.

[Peter Spier]

M Blackburn wrote:

Frankly, I'm starting to wonder how relevant 72 ppi is even to the future of the web. Browsers display per your systems actual resolution don't they? And they are becoming more adjustable and user customizable. I don't even know if the current resolutions of monitors are optimal. Maybe in the next 10 years the average monitor will be 150 ppi.

Resolution, if you are thinking in terms of a saved image resolution, doesn't exist on the web, or in Photoshop. Your browser shows image pixels in reation to the screen resolution, not in relation to how densly packed they are. Save the same 600px x 600px image at ten different resolutions (without resampling) in Photoshop, and when viewed at 100% they all look identical, because they are, and they will all look exactly the same in a browser becasue they all contain the same number of pixels. "Resolution" is a print concept describing how large the pixles are at the size you print. Take those same images with their different saved resoltuions and put them all on a page together in ID so the physical size of each image is the same, and they will again be identical because the same pixels are being packed into the same space. 300 ppi or 72 ppi only means something in reference to associated dimension that is also saved, and only describes the resolution if you print at the save dimension, which is why the "effective" resolution for your image is the one you need to watch in ID.

[rob day]

I don't even know if the current resolutions of monitors are optimal. Maybe in the next 10 years the average monitor will be 150 ppi.

If you increase the monitor resolution the displayed pixels get smaller and so the interface also is reduced in size—dialog boxes and text would be reduce by 65% if the display went from 98ppi to 150ppi.