I suspect that they are measuring something different than the way type is measured in ID.
Being based on printing tradition, type size in ID is measured according to the height of the slug on which the type would have been cast at the foundry. That height includes space for ascenders and descenders, as well as the possibility of some space between lines. Not all fonts have glyphs that have the same heights at the same size, but the metal slug would have the same height and the space between lines would change. I suspect you are trying to measure some paricular aspect of the glyph height -- perhaps the Cap Height which is the distance between the baseline and the top of capital letters, or maybe the Ascender Height, the distance from the baseline to the top of ascenders -- but those hieghts bear no absolute realtionship to type size and will vary with the font.
I'm not a web person, so I don't know what browsers think when they see text specified in Pixels, but in ID you'll get the same size type specifying pts or px. You can specify px in the size field, but ID will instantly convert it to pt for you.
Thank you for your responses. I don't understand how pixel - points - it doesnt work that way in Photoshop! Which we are having a whole different set if issues with due the the new scaling of text in Photoshop CS6 which Adobe says they are aware of and maybe changing this back to the way it was in CS5.
For now I am going to go with in InDesign points = pixels.
Photoshop is a pixel editor, and InDesign is a layout application, and they have essentially nothing in common. I have no idea at all what Photoshop is measuring when you spec type in pixels, but the size and measurement value remain constant relative to the size of the image when you change the resolution values. If you spec the type in points and change the resolution, the type will remain the same size relative to the image, but the measurement value will change in reverse proportion to the resolution change.
This isn't directly related to type, but it might help you undeerstand the relationship between Photoshop and ID. Although you can list a resolution, it has no meaning inside photoshop itself and only becomes relevant when you place the object on a page (as in ID). ID reads the pixel dimensions, divides by the resolution and determines how large that is at 100% scale in units of measure, like inches or points. Becasue there are 72 points in a postscript inch it was convenient to map pixels to points as a ruler unit when web layout functionality was "added" to ID, but it really isn't working in pixels, it's just a relabeling of the rulers. When you place an image, in a pixel-measured document, if you want it to come in at 100% and have the size on the rulers match the pixel dimensions you have to save in Photoshop at 72 ppi.
72 points = 1 inch
1 point = 1/72 inch
You're working at 72ppi so one point will equal exactly one pixel.
It is my understanding that points DO NOT = pixels
12pt = 16px
see this site for conversion table http://reeddesign.co.uk/test/points-pixels.html
A pixel is 1/96 inch
96/72 = 1.3^
and 12pt x 1.3 = 15.6px (or rounded up as a pixel is on or off so 16 px)
Eugene Tyson wrote:
A pixel is 1/96 inch
No it is not, it depends on your monitor size and resolution. Which is why Adobe's lame solution for InDesign 'one pixel equals one point' was an *extremely* Bad Decision.
The difference with Photoshop is that in PS, you have total control over the pixel-to-Physical World Measurement ratio with the Image Size dialog.
So can you use your influence with Adobe to get them to fix this hiccup? I lay out books in ID, but they also go onto the web and for certain uses I need to specify type size in pixels to make sure my math works out right.
And another thing, for certain e-pubs, Kindle is telling me I need to save pages as GIFs. Could you please ask them to restore exporting ID pages in that venerable format?
Despite what you might think, I have very little influence at Adobe. You should make your requests at Adobe - Feature Request/Bug Report Form and lay out a strong case for why it would benefit most users.
At the risk of not letting sleeping dogs lie, I'd like to just +1 this answer as of June 2015. Knowing this would have saved half a day's head-scratching.
It is still the case IMO that *in InDesign*, one point = one pixel.
This is because one point (1/72 inch) maps to one InDesign reference pixel that is based on a 72dpi screen.
This is in contrast with the CSS reference pixel whose heritage is based on 96dpi: 12pt = 16px (CSS).
Fortunately there is more documentation available about this, but I haven't found very much that says what BobLevine has said so clearly and concisely.
There are two separate InDesign measurement issues, pixels as a ruler measurement vs. how the Zoom Level percentage is measured (or what a 100% view means).
There was a change in the Zoom Level in CS6. In earlier versions the 100% view was a 1:1 monitor to image ratio, which is how it works in Photoshop. In IDCS6 and later 100% equals actual print output size—InDesign looks to your system and gets the monitor resolution to calculate and display the print size, so if you show rulers in inch units 1 inch will physically measure as 1 inch. In earlier versions it was difficult to get your page to display as actual print size because of the variation in display resolutions.
The confusion over the new zoom measurement comes up a lot, and it has created problems if you are designing for screens:
Pixels as a measurement unit is a recent addition, and as others have noted a pixel = 1/72", and a 720x720 pixel page would output as 10"x10". An InDesign page doesn't have a set resolution—different image resolutions and vector art can live side-by-side on the page—while Photoshop images can be at any single resolution, so the output dimension of a pixel can be anything and depends on the ppi of the image.
Adding pixels as a measurement unit with a set dimension lets you design for screens at a specified pixel dimension. So now in Document Setup you can spec a 1024x768 pixel page, export it as a 72ppi PNG or JPEG and it will open in Photoshop at 1024x768. Or you can export it as a PDF and open it at 72ppi in PS and again it will be 1024x768. In earlier versions you could do the same, but had to spec Points.
Here's a comparison of 48pt type in IDCC2014, exported to PS at 72ppi, and 48px HTML in Safari. It's important to note that the Photoshop view is at 100% or 1:1, and the ID zoom level is 66%, which is 1:1 for my monitor setup (see the scripts for setting ID's zoom to 1:1 in the linked threads above):
Wonderful discussion here. Just to add more detail than you wanted: a typical average LCD flat-panel screen is often physically about 90-108 ppi. Unless you have a Retina display, which is physically at 220 ppi (MacBookPro). Unless you have this display ... unless you have that display ... etc, etc: Different manufacturers' monitor panels have a lot of difference in pixels per inch physical display.
From my reading, it seems that the venerable 72 ppi number originates with the mid-1980s Macintosh Classic 9" display being 72 ppi physically. But physical pixel size rapidly moved up to 96 ppi before 1989, as I remember it.
So the comment that 72 PostScript points = 72 pixels, along with the old tradition of making all web graphics set to 72 ppi was/is scarcely ever physically true. It borders on urban legend, and continues to confuse all of us.
I am a bit surprised that monitors have been kind of stagnant for ppi for a while, unless you buy super high-priced ones.
But physical pixel size rapidly moved up to 96 ppi before 1989, as I remember it.
An InDesign page doesn't have an output resolution, but for screen design you might want to design a page to a specified pixel dimension. In that case the pixel unit has to be assigned a single dimension so that you can export to the desired pixel dimensions. Adobe could have chosen another arbitrary size for a pixel, but it wouldn't matter—if they had chosen 1/96" then we would have to export our 1024x768 page at 96ppi to keep those same dimensions in Photoshop.
Displaying a page at a 1:1 ratio (which is needed for screen design) is a real problem in the current version. In CC you could double click the Zoom tool and get 1:1, in CC2014 you have to use a script.
rob day wrote:
Adobe could have chosen another arbitrary size for a pixel, but it wouldn't matter—if they had chosen 1/96" then we would have to export our 1024x768 page at 96ppi to keep those same dimensions in Photoshop.
Had this been the case, then it would correspond with the W3C definition of a CSS pixel (CSS Values and Units Module Level 3) and my InDesigners' visuals would have been the same size as my initial web prototypes :-)
Right, when I design for screen out of ID I use px in my styles. So if I'm going from InDesign to Photoshop I export as 72ppi, which opens the page as the same pixel dimensions at 72ppi. In Photoshop when the image resolution is 72ppi and you are setting text a point also equals a pixel, so then it's just a matter of using pixels in the CSS.
You are right, if there's some advantage to points vs. pixels in your CSS that I'm not considering then you would have to make the conversion (pixels x 1.3333=CSS points).