Recently, a Facebook friend posted a question about how large a print one can get from a smartphone WITHOUT resorting to resampling software. Back in 2011, I did some research into image resolutions and print sizes, after being told that an image I’d sent through email for a CD cover was only suitable for a postage stamp! My report can be read on http://www.mobitog.com where I was a moderator for a year.
Here is the thread: http://www.mobitog.com/threads/image-resolutions-and-resizing.1563/
Of course, things have moved on since.
However, whilst smartphone cameras are getting better if not bigger, and photographic Technology is improving by leaps and bounds exponentially, the co-relation of image resolution and print size is still a very valid argument.
Okay, before you read any further, remember these 3 Very Important Things:
1) we are not talking about DSLR cameras here, we are discussing smartphone cameras, with the emphasis on smartphones having access to either iOS Apps (Apple) or Google Play Apps (Android). If you have a hybrid camera that also makes and takes calls, yay for you, and consider it included in the smartphone category. If you have a DSLR and rely on traditional photography methods, then your best bet is still Photoshop, Perfect Resize, or any of a growing number of image resampling/resizing software.
2) we are not going to talk about resampling/resizing software here, we will instead concentrate on image print sizes “straight out the box”, and in practical terms, notwithstanding advances in processing software and Apps.
3) I’m not going to talk about the difference between dpi and ppi here. Suffice to say that dpi relates to the number of ink Drops Per square Inch in a printer, and ppi relates to the number of Pixels Per square Inch on a camera. The difference between the two is explained further in a number of the weblinks listed below as we go along. From the mobile photographer’s practical point of view, consider both dpi and ppi interchangeable (oh, I know they’re not!), file it away in the recesses of your memory, and let’s get on with the real stuff.
I did some digging around on the internet, and here are links to several sites that attempt to shed light on the eternal Megapixel vs Print Size question. I have no affiliation with any of these sites, and some of the information may be outdated/moot especially in regard to the iPhone and Apps. However, you will see that most concur that the industry standard for professional printing should be 300 dpi, and then explain what happens when the dpi drops. In a nutshell, the relationship between dpi and print size is converse – the bigger the dpi, the smaller and more “picture perfect” the photo, the smaller the dpi, the bigger the photo but with possible loss of detail i.e the dreaded pixelation.
A recent post by experts in the field of mobile photography, with salient points especially in relation to the iPhone.
MARTY YAWNICK’s article about this, which goes back to 2011 around the time I was doing my research, an oldie but still a goodie, as it’s been updated to include later incarnations of the iPhone
For those of you curious about how your iPad camera photos will look “in real life”. Of course it looks bigger on a bigger screen, but how will your photo come out in print? Griffintechnology explains.
Explains pixelation in Photoshop. And how you must never assume that Photoshop will resize your low-resolution images without pixelation…there’s a different algorithm involved in resampling pixels and not just blowing up the size of existing pixels.
Compares different smartphone cameras and how they print at 300 dpi.
Contains a useful colour chart showing maximum print sizes in relation to Megapixels
Explains it from a different viewpoint, literally. Billboard posters are generally printed at 72dpi, which looks great from a distance, as that’s how they’re meant to be viewed…however, if you go close up to the poster, pixelation is immediately obvious. So, for up close and personal viewing, it is highly advisable to choose to print at 300dpi.
Icon Photography School has a useful colour chart made by one of its students explaining Megapixels and maximum print size, again at the industry standard of 300dpi.
Explains the difference between ppi and dpi
From a DSLR photographer’s point of view, if you don’t use resampling or have no recourse to Apps via your imaging device
Again, another site that explains the difference between ppi and dpi
From a DSLR user’s point of view.
Just a couple more things to remember:
1) The number of Megapixels on your smartphone is not actually the same as the output. To give you an extreme example, the Nokia Lumia 1020 boasts a whopping 41MP camera, however, when the image output resolution is calculated, it comes out more like 34-38MP. I don’t use my iPhone anymore, so I’m not sure if the iPhone offers the same facility, however, on my Samsung Galaxy S4, the camera gives me a choice of resolutions to take pictures at, so I can essentially choose whether I want to use my full 13MP resolution for each shot (which naturally takes up more room on the phone), or to shoot at lower resolutions and thus save on storage space.
2) Again, what goes in isn’t necessarily what comes out. If you choose to save your images at the highest resolution, and then process the image through various Apps, bear in mind that some Apps, especially the free ones, will reduce the size of your output to postage stamp sizes. So, the caveat is to check whatever App you’re processing your image with, and make sure it will save at a high enough resolution for you for printing later. I’ve been there, done that…processed images that look wonderful on the iPhone/Galaxy screen, only to realise afterwards that the App/s used only saved at a measly 600×800 pixels, which means I can’t print a large size without first having to resize it in Perfect Resize. Again taking the Nokia Lumia 1020 as an example, straight out the box you can get huge, quality prints…however, if you tried to “app” your image first and then print it out, you will find that most Apps (iOS or Android) simply do not cater for such high resolutions and will just reduce your image to their default saving resolution. The Nokia Lumia 1020 is a Windows smartphone, however, and the Windows Apps Store has a long way to go before it catches up with the 2 front runners, iOS and Android, so my guess is most users will simply buy that as a point-and-shoot, as there aren’t many photo editing Apps in the Windows Store. Then again, I’m fairly sure of 2 things – that Apps will be updated offering higher and higher resolutions, in keeping with the trend for bigger and bigger Megapixel counts on smartphone cameras, and that the Windows Apps Store will be playing ball with the big boys within the next 3 years.