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.