Are You Well Presented?

Now we look at presentation in all its guises

We continue the series of related articles on the subject of presentation. This can take many forms from preparing images for the web, for a DVD show, for a wall portrait, for your display for wedding fairs or for a competition entry. While there are many approaches to the problems, one thing remains – in a commercial world you ignore how you look to your clients at your peril and this runs right through your business from your studio, your personal presentation, your albums, viewing room, wall display, stationery and your website. We start with getting images (and sets of images) the correct size, the first hurdle which often trips the unwary!

Sizing for Output

One of the things in digital imaging that persistently puzzles users is the matter of file size and resolution. Part of the problem is the mental gymnastics required to get your head around the rather large numbers and relate this to the real world. It is very like the situation in Italy in the days of the lire when you handed over so many millions of units to buy a washing-machine that it was easy to be ten times or even a hundred times out! In digital imaging, further misunderstandings arise between pixels per inch and dots per inch (ppi and dpi). If you are new to all this, or unsure, then read on, others may fast forward to the next section!

The Pixel

The picture element (pixel) is the basic building block of an image file. Indeed they are all that the computer really cares about – how many there are of them, where they are and what colour they are. The size of your file on your hard drive is roughly computed by counting the number of pixels and multiplying that number by three, (once for red, once for green and once for blue). We say roughly because the file also contains some housekeeping information – bits of the file that describe how you want the colour to look, copyright information, camera data and the like. Just to add more complexity we now successively divide the numbers by roughly 1,000, to make them easier to manage. We start with a byte, then a kilobyte, then a megabyte, then a gigabyte and finally a terabyte; each is about a thousand times bigger than the previous unit. We say roughly a thousand because the actual number we divide the pixel count up by is 1024, the binary number obtained by multiplying 2x2 a total of nine times to give the sequence.

248
16
32 Are you well presented
64
128
256
512
1,024

If you look at the numbers you should see some familiar ones from, for example, your compact flash cards (eg 512Mb) or computer hardware such as graphics card memory.

In a nutshell then, if your Nikon D100 has a sensor of 2,000 by 3,000 pixels your image size is 2,000x3,000 = 6,000 (ie a 6 mega pixel chip) and this gives 6,000x3 = 18,000 bytes as your file size and you divide by 1,024 to get the 17.6 megabyte file size that shows up in Photoshop. It is not surprising that people get confused but we have to take the time to explain it fully otherwiseyou ponder why Photoshop always reports a smaller file size than you expect if you are used to, say, kilometres which are actually 1,000 metres rather than 1,024 metres! Now remove the wet towel from your head and carry on reading.

As we have already said, all the computer cares about from a quality standpoint is how many pixels of information it has to play with. If the image is 1,024 pixels wide x768 pixels high and you display that image on your monitor at a resolution of 1,024x768 (the so-called SXGA), it will just fit nicely on your screen, providing the software which is driving the screen does not start making adjustments. The screen runs at a nominal 72 pixels per inch or 96ppi. This again causes no end of confusion. An image of 1,024 pixels stretched across a 24-inch screen will be displayed at a different resolution to one that is displayed on a 17-inch screen. You cannot even do the sums on that scenario easily, as the screen resolution is measured up and down the screen and the screen size often measured across the diagonal – once again we are being bamboozled by the advertising men who prefer the bigger number of the screen diagonal and measure under the bezel of the CRT screen! They have more recently been forced by advertising standards to tell us the truth about screen sizes and measure it across and accurately. Even so, they cannot even agree amongst themselves on which pixel number should equate to which ‘GA’ number, but one take on the subject is listed below. Some of the older ones originally expected to be totally phased out, but the arrival of mobile phones has partly saved their bacon, as the tiny screen can only display the smaller resolutions. At the big end of the scale the acronyms get ever-more hysterical; I wish somebody would take their pencils off them!

In amongst this mess, the notion of asking for a 1,024 pixel width image for digital image competitions has grown up. This complies with most (but not all) users’ systems so that they may comfortably fit an image on their screen. Often for web use, a limit of 800 pixels is specified, to allow for space around the image for the other bits of the web page. This fits nicely with an SVGA resolution image, (800x600 pixels, at 16 million colours), for better quality.

The Growth of Screen Resolution

Page1 - Page 2 - Page 3 - Page 4 - Page 5 - Page 6

Photo Quote: Think about the photo before and after, never during. The secret is to take your time. You mustn't go too fast. The subject must forget about you. Then, however, you must be very quick. - Henri Cartier-Bresson