1st Digital Meeting of the Session 7th October 08

Norman Piper DPAGB, AFIAP, was our guest speaker to begin the new session of Digital evenings. Norman’s brief was to assume nothing and set the scene for the future evenings so that new people in the audience would not be put off. This was a difficult thing to ask but Norman rose to the occasion. He considered briefly the History of photography, the film process and the advent of the electronic sensor. He listed the advantages and disadvantages of the digital camera, and noted the rapid turnover of new models, each one claiming to do more than the previous one. This was not surprising in an industry barely 22 years old, but he warned about un-necessarily changing to the latest model. The photographer had to consider what he/she really needed from a camera, and ignore the latest gizmo’s. Once set up with Camera, computer, and suitable software, digital photography became relatively cheap.

Starting with how the eye perceived a coloured scene, Norman moved on to how the electronic sensor used filters to mimic the effect. He explained the difference between Additive colour mixing (the eye & the sensor) and Subtractive Mixing (the ink-jet printer). He briefly discussed bits and bytes (usually 8 bits) and how the binary system worked. Jpeg images were typically 8 bits (256 levels) for each primary colour giving over 16 million possibilities. He illustrated the (zoning) effect of reducing the number of bits in a colour.

Memory cards (eg Compact flash cards) had increased exponentially in capacity from 16 or 64 Mb to 16 Gb so there was, nowadays, no problem with storage of images. He noted in passing that whereas film had typically a few % efficiency in converting light to an image, the electronic sensor was more like 70% efficient; and that very high effective speeds (ISO nos) were now possible.

After the refreshment break Norman considered several of the basic image manipulation tools a photographer was likely to use in PhotoShop He suggested that changes should always be made via the adjustment layer, so that they could be undone and the initial data of the image retained. The LEVELS adjustment allowed the full tonal range to be achieved. The Contrast could be varied using the centre slider, and the centre picker used to choose the grey point and thus alter the colour balance. He demonstrated the use of the HIGH PASS FILTER to effectively sharpen an image. Selecting parts of an image allowed those parts to be lightened or darkened to maximise the overall clarity of an image. Norman used a variety of examples to illustrate these various points, and the way changes could be progressively undone via the HISTORY tab.

In his vote of thanks Bill Chadband thanked Norman for his wide-ranging introduction to digital photography. Norman had successfully set the scene for the future talks which could now explore topics in greater depth.

Bill recalled Norman’s visit to the club in the year 2000 when Norman had explained how digital photography had given his photography a new lease of life. A worry, then, had been how one could produce a slide for competitions from a digital record and Norman had explained how photographing his 19inch Monitor had worked well. Another point which had stuck in Bill’s mind was Norman’s assertion that he could get perfectly good A3 prints from a 2 or 3 Mp camera and that one need not forever seek higher pixel numbers. Bill had verified the truth of this assertion for himself.

Whilst President Roger Dye did a brief presentation to the audience on producing the correct (1400x1050pixels; sRGB) image for digital projection on our Projector, Bill and Norman retired to the bar.

Bill Chadband