On Printing Large from Small Files

by Miserere


Yesterday's post by Yvon about printing photos from K20D files reminded me of the day I found out I had been lied to by the camera business. It was about 1 year ago.

I had been thinking about what present to get my parents for Christmas, and being that they were in Spain and I was in the US, it couldn't be anything big. It took me a while to realise that a photograph would make a great gift, especially if it were one I had taken. What would make it even better is if it were a photograph that was meaningful to them. I immediately knew which photographs they would like (I have a good memory for images and the majority of my "good" photographs are stored in my head...finding them on my hard drive is another story).

After a while of cursing under my breath at my appalling photo cataloguing system I found what I was looking for in the depths of my laptop disk. I thought about it for a while and decided that a photograph wouldn't do; I wanted to print a poster for each of them. These are the images I chose:

© 2007 Miserere

The tiny village where my mother was born.

© 2007 Miserere

Canes and farming utensils my grandfather left unfinished after his passing away.

I hadn't planned on visiting my parents for Christmas last year, but my lovely wife miraculously found us some cheap tickets and insisted that we go. I carried the poster tube with me across the Atlantic and over the Alps (we flew via Zurich) and was able to see my parents' faces when I gave them their gifts. They were very touched and it meant a lot to them emotionally.

What does all this have to do with printing sizes and being lied to? My mother's poster was printed approximately 20x26 inches (51x66 cm), while my father's was 15x26 inches (30.5x66 cm). Oh, and the photos were taken with a 6MP Pentax Optio S60 point-&-shoot. This computes to around 130ppi (pixels per inch). Of course, you cannot see the prints for yourselves, but I can assure you they look great from a normal viewing distance, and even close up they hardly appear pixelated. When I first saw those posters I knew for certain that you must print at least at 300ppi was an old photographer's wives' tale perpetuated by camera sellers wanting you to upgrade to the newest camera with higher megapixel count. I believe it to be (maybe) applicable to ink-jet printing, but not for prints we order online which are done on laser printers.

Those posters are now hanging in my parents' living room. And I'm glad I could make them so happy with so few ppi.

Merry Christmas, Mum & Dad!

Using the Pentax 14.6MP K20D, how can my 300 DPI printed photos get any better with my Epson R-1800 @ 1440 DPI?

Hi Pentaxian friends,

Here I go again with the Pentax K20D!

I got to think , after writing yesterday's post, that the K20D won't be available forever. There are so many new DSLR cameras being introduced, and Pentax may also introduce a replacement for the K20D soon. I assume that it would have more pixels or a larger Full Frame CMOS sensor, video capabilities, but the bottom line, I'm still very happy with the K20D. I'm seriously thinking of buying another K20D body, brand new and at about half the original price and keep it in the original shipping box, unopened, until my current K20D dies.

The K20D does more than any camera I have ever owned. The K20D, along with the post-processing software available today, renders photographs that cannot currently be improved upon. The K20D sensor produces images that can be enlarged to 11" x 14" for print at 300 Image DPI. The recorded resolution of the sensor is 4672 pixels x 3104 pixels. Divide these numbers by 300 (for a printer with 300 Image DPI resolution) and you get the optimum print size of 10.35" x 15.57" - round that off to standard US print sizes and you get 11" x 14". Actually, I understand that 240 Image DPI is about the maximum resolution that our eyes can discern. The same calculations using 240 Image DPI would thus render prints sized at 12.93" x 19.46", or roughly 13" x 19" which is exactly the maximum size that my Epson R-1800 can print. I don't think that many of us print larger than that very often. Until they re-invent printing technology, my pictures won't get any better than what my K20D gives me. Actually, I am (as photographer) the weakest technical link in the digital picture taking process. The only real benefit I bring to the table is my composition skills, and that needs some constant improvements. But wait...my R-1800 is supposed to print at 1440 DPI according to Epson.

Well, before we continue, let's all understand the difference between Image DPI and Printer ink DPI (dots per inch). One color image pixel requires many printer ink dots. This is why we need a 1440 DPI printer (ink dots) to print an image at 240 to 300 DPI (pixels). Attempting higher resolutions on color printers simply limits the pixel size area, allowing fewer ink dots, which then limits to even fewer possible color tones. We need several ink dots in that space to simulate the correct color of one image pixel. As example, to print one "green" pixel on our inkjets, we know it must mix some blue, some yellow, some white and maybe some black. There is no white ink, white is the paper color. To make green, the printer only has the CMYK (Cyan, Magenta, Yellow, and black and some in-between colors on newer printers), ink colors and so must use a few cyan and yellow ink dots, not necessarily equal numbers of each, to achieve a certain shade of green. To make lighter shades of green, blank white space are used in the right amount. Black ink dots are used to darken colors. The average visual effect of all these individual cyan and yellow ink dots, white paper, and sometimes black ink too, looks green to us. But all of these multiple ink dots represent or simulate the color of only one green image pixel. (I found the above a while back while Googling "Printer resolution". It made sense to me)

So...it doesn't matter if Pentax were to introduce a 50MP DSLR, I am still constraint by the printing technology. Yes, some DSLR cameras can produce better colors, operate in almost darkness with higher sensitivity, take pictures at 10 FPS, but in the end, all these attributes just make a photographer's life a little easier. You can achieve the same picture taking with old fashion know-how and modern post-processing software. In my opinion, the final representation of one's photo quality can only be appreciated when printed.

So go ahead and spend thousands on a new DSLR, in the meantime I will keep taking pictures with my K20D until it dies. Chances are, that print for print and size for size, my printed photographs will be just as good as anyone's printed photographs. When my K20D dies, I will open the box containing my newer K20D, and I will be ready to go, and at half the price I paid for the first one and at a fraction of the DSLR cameras available then, on that future date. I bet you that printers will not make the 13" x 19" photographs much better than they do today. It would seem useless as our eyes won't be able to see the difference.

Thank you for reading,

Yvon Bourque