I'm trying to make sense of CSS media queries for a mobile-only page. My final goal is to have the font size on my page be about the same in physical units (inches/centimeters) regardless of decice physical size and resolution. But what I see reported by the media queries has nothing to do with the device specs.
I'm testing on an HTC One M7, which is 1080x1920, 467dpi - manufacturer specs.
The precise numbers reported by the media queries is:
width (as reported by min-width/max-width): 1080px
resolution (as reported by min-resolution/max-resolution): 288dpi or 3.0dppx
First, shouldn't the pixels reported for the width be in logical pixels, not physical? I mean both iPhone3GS and iPhone4 report a width of 320px, even though the latter is actually 640 physical pixels. See How to target iPhone 3GS AND iPhone 4 in one media query?
How should I know what the browser meant by "pixel" when it matches a given query?
Second, the reported 288dpi has nothing to do with the actual device 467dpi. And how is this 3dppx calculated?
This is an interesting question. I'm familiar with the way media queries work for iOS devices, but less so with Android devices. I'll take a stab at it anyway.
Let's start with dppx, which you probably know is a measurement of how many physical dots fit into each pixel (let's use your terms "physical pixels" and "logical pixels"). 3dppx means that each of the screen's logical pixels is composed of a 3x3 grid of physical pixels. To use iOS terminology, your display has a #3x resolution, like the iPhone 6 Plus.
You can see a list of various device dppx values here:
http://bjango.com/articles/min-device-pixel-ratio/
(The site refers to -webkit-min-device-pixel-ratio, which predates dppx, but I think means exactly the same thing.)
If you know a device's physical width and dppx you can use the following formula to calculate its logical width, which you can use in media queries:
device width / dppx = logical width
For your device this should be:
1080 / 3 = 360
I would therefore expect the following media query to target your device in portrait mode:
#media only screen and (max-width: 360px) { }
As for the 288dpi: A 1dppx device has 96dpi, and 3 x 96 = 288. I'm not sure where the manufacturer's 467dpi comes from, but it doesn't seem relevant to writing media queries.
Related
The CSS inch unit seems to be accurate until the user changes his/her screen resolution to something lower. I assume there are a number of potential users for any app who will have adjusted their screeen resolution for performance, and just to be consistent Im wondering if there's a way I can ensure that the CSS inch unit always matches a physical inch on the screen.
Use #media for different resolutions to separate your css into blocks based on the ppi. You can get the device's screen resolution and determine the PPI from that. then one inch is = PPI.
PPI = Pixels per inch
use px instead of in. Also on average there are 96px/inch
When doing media queries in CSS I noted that the value in pixels that is used for min-width and max-width when working on mobile do not seem to correlate to the device's actual width.
For example, if I was to target a landscape iPhone 5 I could use max-width:568px and it gets triggered but if I google iPhone 5 resolution I see that its long side is actually 1136px.
Why is half the device's resolution being used in media queries?
More importantly, how can I stop this from happening while still using the same queries for desktop?
First of all, take a look at this chart chart here. In the terms of that chart, this happens because iPhones (and other phones as well) render points to the several rendered pixeles (so called "device-pixel-ratio").
Sometimes it even gets a little more confusing, because some devices uses upsampling or downsampling techniques to fit the physical display size.
For example:
IPhone 5s
Points: 320 x 568
Rendered pixels: 640 x 1136
Device pixel ratio: 640 / 320 = 1136 / 568 = 2
In your queries you should use points (320 x 568) as your measurement.
This article, where you can find resolutions of different devices, can be very helpful as well.
I can not resist to mentions, that it is a good practice to make breakpoints based on a content rather than targeting specific devices. See #DaveEveritt's post.
This is not a duplicate question, because I don't want to target the iPhone 6 specifically, I want to target ALL smart phones and mini tablets, icluding the iPhone 6, 7, 8, etc and Android, etc
I'm trying to find out a useful CSS media query to detect smart phones.
So, I was thinking, the following would fit perfectly since the screen resolution in px on an iPhone 6 is almost the same as the one from a desktop screen with a pixel ratio of 1:
#media (max-device-width:16cm){ /* I need the PHYSICAL device width */
...
}
However, I'm not sure if this translates interally ALWAYS to 529.2px (1cm == 37.8px) or does it really respect the actual device width in cm of the hardware?
Because, in my opinion, what really matters is the physical space available, and I don't care at all how many pixels there are to represent this area in order to decide how much content I want to show.
You can't use centimeters because some devices have their pixels further apart.
However what you could do is check the device's pixel density. Here is how you can use a media query with the pixel density.
#media all and (min-resolution: 150dpi)
{
body
{
// do something
}
}
The second way would involve some JavaScript as described here.
Media query in pixels is all you need. Screen resolution and viewport width are 2 different things.
You can check http://viewportsizes.com/?filter=iphone for view port width. The link has the iphone filter but you can remove it to look at other phones.
I usually use 768px as a cut of point. Anything above or equal to 768 I use a desktop view and anything below I use a mobile layout. It's not device-dependent, you are simply checking the view port width or browser width to determine what should be shown.
http://www.lexus.ca uses this cut off point, I am just linking this to give you an example
'Resolution' seems to be often used as a term to describe viewport dimensions/device pixels expressed in terms of a x b:
e.g. 960px x 640px (for iPhone 4)
However from what I understand that's a bit of a misappropriation as used in media queries, at least, resolution denotes the density of pixels of an output device.
Can I confirm that the media feature 'resolution' is essentially expressing pixel density?
i.e. the diagonal pixel resolution of the display divided by diagonal size (in inches)
So, taking the example of the iPhone 4 again, the resolution would be defined as 330 ppi? (or 330dpi)
I'm essentially interested to know whether the resolution feature could be used to target a device(s) with specific pixel density.
In Brian LePore's
article he suggests mobile devices round the actual dpi value to "120 DPI for a low density screen, 160 DPI for a medium density screen, 240 DPI for high density, and finally 320 DPI for extra high density".
Is this correct and would that mean that you can't actually target a specific dpi?
i.e.
#media screen and (resolution: 330dpi) {}
and
#media screen and (resolution: 311dpi) {}
will ultimately both be treated as /rounded to
#media screen and (resolution: 320dpi) {}
Yes, resolution is definitely expressing pixel density.
If you want to be as targeted as possible for iPhones, you might try using several of the available queries, and setting the values specifically to iPhone specs.
iPhone 5 would be something like this:
#media screen
and (-webkit-min-device-pixel-ratio : 2)
and (device-aspect-ratio : 40/71)
and (device-height : 568px)
and (device-width : 320px)
You can test media queries of different devices by going to the page http://pieroxy.net/blog/pages/css-media-queries/test-features.html on that device. The only strange result I'm getting is that it doesn't return a resolution value for iPhone 5. However, I'd be surprised if the above query targeted anything other than iPhone 5. (Sorry I don't know more specifics about resolution to answer your second question.)
More info at:
MDN: Media Queries
iPhone 5 CSS media query (device-aspect-ratio for iPhone)
Media features for common devices
this is mentioned every article about mobile web, but nowhere I can found an explanation of what exactly does this attribute measure.
Can anyone please elaborate what does queries like this check?
#media only screen and (-webkit-min-device-pixel-ratio: 1.5),
only screen and (min--moz-device-pixel-ratio: 1.5),
only screen and (-o-device-pixel-ratio: 3/2),
only screen and (min-device-pixel-ratio: 1.5) {
//high resolution images go here
}
Short answer
The device pixel ratio is the ratio between physical pixels and logical pixels. For instance, the iPhone 4 and iPhone 4S report a device pixel ratio of 2, because the physical linear resolution is double the logical linear resolution.
Physical resolution: 960 x 640
Logical resolution: 480 x 320
The formula is:
Where:
is the physical linear resolution
and:
is the logical linear resolution
Other devices report different device pixel ratios, including non-integer ones. For example, the Nokia Lumia 1020 reports 1.6667, the Samsumg Galaxy S4 reports 3, and the Apple iPhone 6 Plus reports 2.46 (source: dpilove). But this does not change anything in principle, as you should never design for any one specific device.
Discussion
The CSS "pixel" is not even defined as "one picture element on some screen", but rather as a non-linear angular measurement of viewing angle, which is approximately of an inch at arm's length. Source: CSS Absolute Lengths
This has lots of implications when it comes to web design, such as preparing high-definition image resources and carefully applying different images at different device pixel ratios. You wouldn't want to force a low-end device to download a very high resolution image, only to downscale it locally. You also don't want high-end devices to upscale low resolution images for a blurry user experience.
If you are stuck with bitmap images, to accommodate for many different device pixel ratios, you should use CSS Media Queries or the HTML picture Element to provide different sets of resources for different groups of devices. Combine this with nice tricks like background-size: cover or explicitly set the background-size to percentage values.
Example
#element { background-image: url('lores.png'); }
#media only screen and (min-device-pixel-ratio: 2) {
#element { background-image: url('hires.png'); }
}
#media only screen and (min-device-pixel-ratio: 3) {
#element { background-image: url('superhires.png'); }
}
This way, each device type only loads the correct image resource. Also keep in mind that the px unit in CSS always operates on logical pixels.
A case for vector graphics
As more and more device types appear, it gets trickier to provide all of them with adequate bitmap resources. In CSS, media queries is currently the only way, and in HTML5, the picture element lets you use different sources for different media queries, but the support is still not 100 % since most web developers still have to support IE11 for a while more (source: caniuse).
If you need crisp images for icons, line-art, design elements that are not photos, you need to start thinking about SVG, which scales beautifully to all resolutions.
Device Pixel Ratio == CSS Pixel Ratio
In the world of web development, the device pixel ratio (also called CSS Pixel Ratio) is what determines how a device's screen resolution is interpreted by the CSS.
A browser's CSS calculates a device's logical (or interpreted) resolution by the formula:
For example:
Apple iPhone 6s
Actual Resolution: 750 x 1334
CSS Pixel Ratio: 2
Logical Resolution:
When viewing a web page, the CSS will think the device has a 375x667 resolution screen and Media Queries will respond as if the screen is 375x667. But the rendered elements on the screen will be twice as sharp as an actual 375x667 screen because there are twice as many physical pixels in the physical screen.
Some other examples:
Samsung Galaxy S4
Actual Resolution: 1080 x 1920
CSS Pixel Ratio: 3
Logical Resolution:
iPhone 5s
Actual Resolution: 640 x 1136
CSS Pixel Ratio: 2
Logical Resolution:
Why does the Device Pixel Ratio exist?
The reason that CSS pixel ratio was created is because as phones screens get higher resolutions, if every device still had a CSS pixel ratio of 1 then webpages would render too small to see.
A typical full screen desktop monitor is a roughly 24" at 1920x1080 resolution. Imagine if that monitor was shrunk down to about 5" but had the same resolution. Viewing things on the screen would be impossible because they would be so small. But manufactures are coming out with 1920x1080 resolution phone screens consistently now.
So the device pixel ratio was invented by phone makers so that they could continue to push the resolution, sharpness and quality of phone screens, without making elements on the screen too small to see or read.
Here is a tool that also tells you your current device's pixel density:
http://bjango.com/articles/min-device-pixel-ratio/
Boris Smus's article High DPI Images for Variable Pixel Densities has a more accurate definition of device pixel ratio: the number of device pixels per CSS pixel is a good approximation, but not the whole story.
Note that you can get the DPR used by a device with window.devicePixelRatio.
https://developer.mozilla.org/en/CSS/Media_queries#-moz-device-pixel-ratio
-moz-device-pixel-ratio
Gives the number of device pixels per CSS pixel.
this is almost self-explaining. the number describes the ratio of how much "real" pixels (physical pixerls of the screen) are used to display one "virtual" pixel (size set in CSS).
Device Pixel Ratio has direct correlation with Pixel density of the device.
Best concise description I could find:
Purpose of DPR is to keep consistent size of CSS pixels and therefore
consistent size of letters, symbols, images and everything else on
screen, across a variety of devices with different physical pixel
densities.
Source: screenresolutiontest