Understanding File Resolution and Why It Doesn't Matter When Showing Your Photos On-Screen

It is a common misconception, and it has been addressed before on photography groups, forums and news sites many times. However, for the new year starting today (2016, for those reading in the future), I reasoned a quick video review of the concept of file resolution versus pixel dimensions, and the interplay between them, would be in order. 

The short version of the story is simple: pixel dimensions are all that matters when showing your work on-screen.

The long(ish) version of the story is also simple, but could be a little murky for those with no graphic design experience (and there are plenty of skilled photographers that have no graphic design background).

The key points to keep in mind, as I mention in the video, are as follows:

  • Resolution (e.g. 300dpi, 240dpi, etc) only affects how your photo looks printed, in any form. This is a big part of what makes an image sharp (or not) when printed.
  • Pixel dimensions (e.g. 3,000x2,000, 900x600, etc) affect how your image is seen on-screen, and I do mean any digital display at all.
  • Web browsers, including and especially mobile ones, resize images on-the-fly as needed, and your pixel dimensions can be altered by this. However, they do not become any resolution higher than what the display's pixel settings are set to.
  • Send your files to your web designer at the very-specific settings of "Whatever your designer asks for."
  • Exporting from Photoshop, Lightroom or Capture One at any specific resolution means exactly nothing to your final image when displayed on-screen, provided you aren't also resizing the pixel dimensions upon export.

Check out the video above or on my channel, drop me some discussion or derision in the comments, and have a fantastic 2016, friends.

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23 Comments

Ariel Martini's picture

- so what resolution you want the pictures?
- 300 dpi
- yes, but what size?
- 1 Mega

true story. repeating story.

Eric Lefebvre's picture

Client:
But are your images HD? Are you shooting (stills) in HD?

Me:
Uhm ... I'm shooting with a 5dMk2 so 21MP or 3745X5626 pixels, HD is a video term that means 1080X1920 pixels so about 2MP more or less ... so I shoot at way more than HD.

Or when you see an ad on Kijiji, Craigslist or FB where the photographer claims to shoot HD pictures ... LOL

I've run into this problem many times, and it drives me up a wall every time. Frequent

"Oh, it's for the web, so you need it at 72dpi?"
"IDC, I just want it at 2040 pixels on the long edge"
"yeah, but at what resolution"
"....."

OR

"They said they need a high res file that's under/over 1MB"
*face-palm*

Fino Balanza's picture

Thank you!!! So frustrating sometimes! Especially with clients

Michael Clark's picture

vvvvvvvTHISvvvvvvv

Spike S's picture

Unfortunately, this post doesn't matter. You can tell people this over and over and over and they don't get it, especially graphic designers who were told to ask for images at 300dpi when they started. Also, too many photographers have a hard time comprehending this. I've written articles on it and explained countless times but there is constant denial on this.

Mark James's picture

I use 2044 wide, 96DPI and 500K max on my web exports and they as good as the high res ones when viewing on screen. I only raise the DPI when exporting for printing. That may change when 4k monitors become mainstream.

TImothy Tichy's picture

If you're setting pixel dimensions then the DPI setting shouldn't matter. I don't adjust file size or DPI on web exports, I just set the long axis at 1024 pixels and go.

AJ Barlas's picture

It probably should also be noted that DPI does not exist on screens. It's a print term that relates to the amount of dots the machine will place within an inch. On screen is PPI (pixels per inch). This is what Photoshop and Lightroom (at least) use in their export settings—unless something changed… and what should be refered to when talking about images on a screen.

Mike Leland's picture

Whether you use DPI or PPI, it doesn't matter one bit if you're specifying a pixel dimension.

user-24049's picture

DPI stands for "dots per inch" and it's referring to scanners and printers. For example: file has a resolution of 300ppi but it will be printed @ 9600dpi.... Unless you have a monitor with dots not pixels.. In a way, you're right but you're also terribly wrong...

While I agree that resolution doesn't matter for on screen viewing and that the dpi/ppi settings similarly don't matter for viewing, they certainly matter for file size. The big bugaboo in years past, and even still today, was the actual size the file took up on the disk (and subsequently had to be transmitted over telephone lines). Make your file too big and doom it to never be seen on the web.
This is why webmasters would tell the graphic designers to limit the resolution to 300. It gave a file size that would, normally, be small enough to transmit over the web in our lifetime. Even then, conversion tools would be used to compress the image to make the file size smaller. Faster load times equals more visitor happiness.
Until everyone in the world, or at least your intended audience, has a high speed connection to the Internet, the time it takes to download your image, which is directly related to the disk space used, will be important.
Of course, if you never intend on putting your image on the web, then my point is mute. :)

Mike Leland's picture

Pixel dimension and compression affect file size. If you're specifying a pixel dimension on output, your resolution has no bearing on file size. Don't believe me? Try it yourself.

Please don't add to the confusion James. As Mike says, try outputting an image set to 300ppi, and the same image with the same settings, and same pixel dimensions, but set to 30,000ppi. You will see that both images are the same file size.

To repeat what Nino said, Resolution (e.g. 300ppi, 240ppi, etc) ONLY affects how your photo looks printed, in any form. (the amount of compression applied to jpegs will affect file size)

Andrew Gerard's picture

I learned a lot, thanks.

A friend working at a web-hosting company would get complaints that images took forever to load. Clients were uploading 5MB files to their page, and wondering why they never opened.

So, the author explains resolution not having an effect of image while viewing on screen. What is not explained ... if the resolution remains the same the file size remains sometimes much high then ever needed for screen viewing. Not sure why the author didn't take this video a step further and explain after pixel dimensions were set, then to curtail the bloat of the image .... select resample image, change to 72 and Voila ... everything is the same except a smaller file size. Or, perhaps the very best recommendation ... just adjust pixel dimensions and select save for web. And, yes, some post resampling sharping is often done before saving for web ... maybe I do it wrong all these years. DK

Michael Clark's picture

2048 pixels at 300ppi is exactly the same file size as 2048 pixels at 72ppi. There's no difference in file size. The only time it matters is when dropping an image into a page setting program such as InDesign or a word processor that actually pays attention to the ppi setting. Even most printing applications nowadays rescale the image to fit a specified output size, regardless of the ppi value in the metadata.

There's also the equivocation of the term "resolution", some people refer to the pixel dimensions (ie. X times Y) when in all actuality "resolution" refers to the density of said pixels.