Ramblings of a Grouch

Before we delve more deeply into what DigitalMemoriesonline can do for a photograph let's consider how we are going to store the digital file.

""Let's store it as the best quality possible." I hear you cry. (I can't really hear you, but it sounds more friendly if I say I can). Perhaps surprisingly, that is the wrong answer in most cases. Keeping the technical bits to a minimum, let's see why.

I scanned a photo, restored it and then produced a 10" x 8" print (yes - I still use inches). The only technical bits we need to consider at the moment are Dots Per Inch (DPI) and Pixels Per Inch (PPI), which are the number of dots which make up each inch of the image (when viewed on a computer monitor these dots are called 'pixels', hence Pixels Per Inch). This is the image resolution. The other technical bit is the size of the file, which is measured in bytes. Suffice to say that, roughly speaking, one dot or pixel takes one byte to store (for a black and white photo). The type of file should also be taken into account but we'll come to that later.

Right, so I scanned the original at 600 DPI. Or rather I scanned a copy which had been made on a high resolution laser copier, as I couldn't take the original. Normally I would scan at 300 DPI, which happens to be the ideal resolution for printing. Less than this and the final image will appear indistinct and 'blocky' when printed out. More than this and the human eye will be hard pushed to tell any difference. So why scan at 600 DPI? Well, remember this was a copy of a photograph and I wanted to be sure I got every detail as sompletely as possible, though normally 300 DPI is fine. This is what a section of that image looked like at 600 PPI after restoration:

600 PPI, filesize 20Kb

That part of the image is actually 20 Kilobytes in size. That's pretty big for such a small image. The whole photo was just over 62 Megabytes. That's over 65 million pieces of information - enough to make the computer groan every time a part of the image was restored, and to make me groan as I waited for Photoshop to process each piece of work.

When fully restored, I saved it at 300 PPI, which resulted in the the part of the image shown above coming down to 16 Kilobytes and looking like this:

300 PPI, filesize 16Kb

That's a decent reduction in size of around 20%, and still high enough resolution to produce a good print. But the whole image was still a 13 Megabyte file. If you wanted to email it to Aunt Flo then it would take forever to send and she would take forever to download it, assuring that there would be no more knitted socks for you at Xmas. Perhaps that's a happy ending but it's still impolite to send such large files unannounced. And that's assuming your internet provider allows large files to be sent in the first place - many put a limit of 10 Megabytes on email attachments. So what can we do about that?

Actually, there are two tricks - one takes advantage of the power of your computer, the other the limitations of your computer monitor. But that, as they say, is a story for another day.

Until next time ...

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