Have you ever gotten asked if your photos are high resolution or if your photos are a specific DPI? What do you say when you get a request that doesn't make sense?
When delivering photos to multiple different clients and venues, I regularly get asked if my photos are high-resolution or asked for a specific DPI. I've worked with print fairly extensively, but have been in the mostly screen end of things for the last few years. When people ask about high resolution, I tend to question why they are asking for high resolution and what high resolution means to them.
Maybe "high resolution" are trigger words for me. Most people dealing with files that are not photographers confuse the terms "high resolution," "DPI", "megapixels," and many others. It's the bane of my photographer life, you would think. I'm going to hopefully make this article a resource that people can reference if they need to when dealing with clients. If that doesn't work, at least it will be cathartic for me.
Dots Per Inch. Think of this as the density of pixels within an image. I've heard people referencing a five-inch file, and to me, that is just an old way of saying I'm taking the file and using the total pixels to make a file that has a long edge of five inches. I find this useless, because we don't know what DPI this person is actually using or the total pixels in the image. Knowing and setting DPI is important for printing, but only then really.
Listen. Most cameras these days are high resolution. You know highway billboards that are 50 feet wide? Those don't even use the full resolution of my Nikon Z 50 typically. In my experience, only gallery-quality mural prints actually require a real high-resolution camera. Print something six feet tall or wide, and if you want it to stand up to people putting their faces right in the image, then, yes, you may want a really nice medium format camera. Even then, I've seen D850 images blown up to 30 feet tall, and they still look great. Beyond this, every job I've done would be happy with D750 or Z 50 levels of resolution.
Megapixels? Really? Remember when they used to put the megapixel number on a sticker on the front of the camera, like fuel injection, or ABS on old cars? Despite the somewhat relegated term, megapixels actually offers some level of description of the image file that the previous two terms do not. Megapixels just means the total amount of pixels in your image. On my Z 50, 5,568px by 3,712px = 20,668,416, which is basically the 20.9 megapixels (million pixels) that this camera is rated at. But ultimately, who cares? Phones shoot more pixels than real cameras, but that doesn't make them better.
Why None of the above Matters
Let's think about images like we are thinking about megapixels. Each image, either straight from the camera or sized and edited, has a pixel dimension. That could be 5,000px by 3,000px, or that could by 800px by 600px. With this pixel dimension, we instantly know how big the image is and if it satisfies our personal requirement for total resolution. If we make it a little simpler and just start referring to the long edge of the image, we can make this even simpler. It's like we have started measuring video resolution with 4K, FHD, etc. The measurement we are referring to is a single edge dimension. If we say we're delivering 5,000 px wide images, we know we can print these for most applications and they will serve as a high-resolution file. In the end, if the file you are delivering is destined for print, more than likely a photo editor or designer is altering and placing that photo anyways, so why bother with specifying DPI in the first place?
I believe the long-edge pixel dimension specification is the best way to describe and share image data. Now, it just needs a fancy name.