A few questions about screen resolution

[Neurotic_mortal]

Hey everyone, I generated a few questions that I'm still a bit unclear about. If anyone could help me answer them, that'd be great. Thanks so much.

What are some of the standard HD resolutions that we're seeing today? Do they require the same amount of PPI (72)?


Is there a reasonable difference between 720p and 1080p?


What is the difference between I and P when working with resolution.

 

[ALB68]

If you create content for the web, 72 is sufficient. If your going to print you need about 300 dpi.

Don't understand "reasonable difference", 1080 dpi file would be a higher quality file because it has more pixels.

DP I and PP I (hopefully this is the question) are used interchangably. PPI is used by Photoshop for Pixels per inch other is DPI and stands for Dots per inch.

 

[dv8_fx]

This could be a bit confusing with regards to usage .

DPI (dot per inch) is an old term and represents the specification for resolution of output devices ie. printers. Generally, the higher the DPI, the better the tonality and color blending of the image output.

A 1200 dpi printer uses 1200 dots of ink in every inch to make up the colors. thus, a lower DPI means fewer ink dots making up each pixel, which makes a lower color output. A higher DPI would have more ink dots for each pixel and gives more accurate colour (especially under close examination).


PPI (pixels per inch is your image's true resolution from pixel-based applications such as Photoshop. And this affects the print size of your photo and will affect the quality of the output.

From adobe with regards to your monitor question....

This brings up another point: Photoshop matches your image to your monitor's resolution for 1:1 pixel-on-pixel resolution at 100% size to provide the sharpest view of your work. Therefore, because monitors are relatively coarse at roughly 72 to 96 ppi (depending upon your monitor's settings), a common 300 ppi Photoshop image appears about 3- or 4-times actual size when viewed at "100%" on your monitor. And if you are changing your image size on screen to view or work on it, choose, say, 25%, 50%, 200%, or 300% scaling, rather than 33% 67% or odd percentages, to avoid scaling artifacts (although the ragged edges you see do not affect the actual image file and do not print).

Devices that have output specified in ppi include flatbed and film scanners, and computer monitors.

 

[Tom Mann]

re: "If you create content for the web, 72 is sufficient."


This is a very common misconception and bad advice. If you are creating for the web, it makes absolutely no difference what ppi setting you use. The only thing that matters is the total number of pixels in each dimension of the image.

To show this, look at the two attached images (taken from a recent PSG "help me tweak this photo" thread). As you can see, there is absolutely no difference in the sizes of these two images, nor any difference in the sharpness. However, one has its ppi set to 72, whereas the other has its ppi set to 300, but the dimensions in pixels is the same for both. If you don't believe this, check it out using EXIFtool or any other program which allows you to see the metadata.

The only time the ppi setting ever makes a difference (assuming the pixel dimensions are held constant) is if you are printing to a device that honors this setting, typically, a printer attached directly to your computer. However, if you are giving your image to someone else to print, eg, Mpix, a local photo shop, a photo kiosk in a store, in almost all cases, the ppi setting will be disregarded because they ask you what size print you want (ie, in inches or cm), and then their software intelligently resamples your image to bring its ppi to the optimal value for that particular piece of hardware.


HTH,

Tom M

 

[Tom Mann]

Oh, and to answer the OP's question, the terms 1080p and 720p are video/TV standards and are almost never used when dealing with still photographs. They terms imply that the pixel dimensions for each frame of video are 1920×1080 and 1280×720, respectively. Put in different terms, this is only 2.1 and 0.9 megapixels, respectively - hardly high definition by the standards of today's digital still cameras.

To answer your question about whether or not the dpi /ppi settings matter for these video formats, the answer is that if you are generating an image to be displayed on a particular output device (eg, a specific widescreen TV), the only thing that matters is the dimensions of your image in pixels - you want to fill the screen with your pixels.

However, if you are comparing different output devices (eg, different TVs), ie, feeding the same image to a TV with more pixels per inch will display a smaller but sharper image compared to the same image being displayed on a TV with fewer pixels per inch.

HTH,

Tom M

 

[ALB68]

Tom,
Yes your right. What I normally do is create my originals at like 300. In the interest of file size, (many forums have a limitation) if uploading or e-mailing I resize a copy to 72 to make the uploads faster and not use too much disc space. Sorry if I was not clear in my reply.