A Little Background
A recent discussion got me thinking about this topic. In a nutshell, when the question of “How big can I print?” is raised, you’ll get a lot of opinions. Someone will invariably state that bigger prints are meant to be viewed from farther away, and so the degradation in resolution that comes from making enlargements is no problem. By this logic you can print as big as you want because the bigger you print, the farther away people will stand to view the image. Well, it’s not quite so simple as that.
I’m in the process right now of making a number of prints for an upcoming exhibition, and in particular just had one print which I thought looked questionable printed too big and had to reduce the size a bit. So the issue resonated with me. It’s something I’ve always had in the back of my mind, so I thought this would be good opportunity to codify my thoughts on the topic.
So first, let’s get the basics out of the way. Digital images are made up of pixels. When you send an image to a printer, you have to specify what the resolution of the image will be in pixels per inch (ppi). You can print a smaller image with more resolution (more ppi) or a bigger image with less resolution. There are some nuances as to whether you actually send an image to the printer at reduced ppi, or whether you resample the image up to larger pixel dimensions. The latter actually creates more pixels so you can send the image to the printer as a bigger file without reducing the ppi, but since these pixels are interpolated, there is no new data actually being created. Regardless, the fact of either scenario is that the larger you print the more quality you lose.
So, how big can you print before you actually notice the loss in quality? I see people not infrequently post things in photography forums like “I’ve got a 24×36 inch print from my 12mp camera and it looks great.” And I’m thinking to myself, “Huh, I just made a 24×36 image from my 21mp camera and I don’t think it looks that good.” What gives?
We need to take into account two things: content and context.
The content of a print can make a real difference. Think about a traditional landscape print, for example, where fine details are generally considered to be very important. It’s not at all desirable to have smudgy foliage, blurry textures in tree trunks, etc. But in portrait photography, fine details are usually less important. In fact it’s often desirable to not show a lot of texture in the skin. In general (please note this should be should be taken to mean “more frequently but not always”), it can be easier to get a larger print from a portrait than a landscape. Or at least less objectionable when you interpolate the image up.
Speaking more broadly, when you have a well-isolated subject where much of the rest of the photo is dedicated to bringing out that subject (through techniques such as depth-of-field, lighting, compositional framing, etc.) then it becomes easier to print that photo larger and have it be acceptable. Essentially, resolution matters in a much smaller portion of the overall photograph. That’s not to say the rest of the image isn’t important; it just matters in a different way which is not dependent as much on resolution. It’s also not to say resolution isn’t impacted in that smaller area of the photo; but the rest of the photo is there to isolate the subject. So the subject might be perceived as having better resolution than if it were not isolated.
On the other hand, when you have a photograph where fine detail and textures are key components across a large portion of the image, upsizing the image too much and smudging those details will more strongly impact the perceived quality of your print.
Consider the following examples.
The above photograph I actually did print at 24×36 inches. The subject is well isolated through depth of field and lighting. Outside of the isolated flower, there are no other fine details to worry about in this image. If you were to look at a printed version of the flower itself (which would be an area about four inches wide) without having the rest of the image surrounding it, you’d see that it actually is not very sharp after having been interpolated to that size. However, in the presence of the rest of the scene, it comes across as looking quite sharp.
Now here’s another photograph:
This image relies heavily on fine detail and texture stretching all the way across the frame. The native resolution was the same as the previous example. But in this case, the largest print of this image I’d make and still find acceptable is 16×24 inches. Anything larger, and those details and textures lose a lot of their impact.
So what about the argument that you can print a photo larger and people have to stand back farther to look at it, so the loss in fine detail really doesn’t matter because you’re looking at it from farther away? This is where context comes into play.
I come across people making comments like “you don’t need high resolution cameras unless you’re printing billboards.” Maybe. But on the other hand, maybe not. Because depending on how big the billboard is and how far away you are standing from it, you might not see any difference at all. Once you are interpolating images to that size, the differences in resolution are probably going to seem minor.
But there is a big difference between an image printed for a billboard and an image printed for a gallery. That is why we have to consider the context for which the print is intended.
So, let’s get back to this question of viewing distance. If you make a bigger print, does that mean people will typically stand farther away to view it? Maybe. But it depends on the context. As an example, I printed a bunch of project photos to hang in the conference room of an engineering firm at 24×36 inches. Upon close inspection, many of these photos are less than ideal in terms of fine details. But, to someone sitting at the conference table, or walking by in the hallway, they look great. And that is the context in which they are meant to be viewed.
But, the situation is different in a gallery. Say I took my 16×24 inch print from above and printed it at 24×36. It would probably look good from 10 feet away. Maybe even from five feet away. But not from two feet away. And I’m not going to rope off a five-foot perimeter in front of my print in a gallery to ensure no one gets too close.
Yes, in some cases bigger prints are supposed to be viewed from farther away. But as is often the case with an art print, people enjoy getting closer to them. I know that I do. I love seeing another photographer’s big print, walking up to it, getting lost in the details as my eyes wander around the image. We don’t make prints big just for the sake of making them big. We make them big for a purpose. In the case of a billboard, that purpose is to be seen from far away. But in the case of an art print, that purpose is necessarily tied to impacting a viewer in a more intimate setting.