Sunday, 14 February 2010

Even though the weather last Saturday (Feb 13th) looked worse than expected, we still went along to shoot on our planned photo walk around the Anzac Bridge and Sugar Dock areas. In fact we only got about as far as Bowman Road before the weather closed in completely but I suspect we got a few good shots in before the skies opened and forced us off the streets!

One of the biggest drawbacks to shooting in poor weather is brightness and contrast. It usually sucks so anything you see on the LCD is a big disappointment. But the trick is to make that work for you. As with most of my workshops, the emphasis on Saturday moved quickly to HDR shooting because, as a technique, it's perfect for recording a load of image detail in scenes that would otherwise be too dark or too light or 'tepid' at best. High Dynamic Range image making (HDR), for those that don't know, is technique for getting round the fact that you can't record all the tonal range in one shot - so you must shoot multiple
exposures of the same subject, then combine the best tones from all three bracketed frames using special software. It's reasonably simple to do on one level but a lot harder to get really perfect (see separate postings for more information on HDR).

You can use Adobe Photoshop Elements (8.0) to assemble one of these HDR images (using its new Photomerge Exposure feature) or Photoshop CS 3/4 (slightly easier). But the best software to do the job is Photomatix Pro, available from It costs US$99, pretty much does only HDR images and is terrific. Find the three/five or seven images used in the exposure bracketing sequence, import into Photomatix, make your 32-bit HDR 'master' file (which can be saved as a special .hdr radiance file format) for use at a later time) or simply process the file into a more useable format by pressing the program's Tone Mapping button, adjusting the Strength, Colour Saturation, Luminosity, Microcontrast and other sliders to make the HDR image effect look 'hot'.

Actually, what we are technically doing by processing the files in Photomatix is lowering the bit depth (the amount of colour) in the image to make it wholly viewable onscreen. We do this because nearly all monitors are incapable of displaying high bit depth (i.e. '32-bit') colour correctly so we have to do this processing to the master file to get it to fit visually onto the regular screen bit depth. This can be a frustrating time because what we see on the screen is not always what we get once the Process button (in Photomatix) is pressed. In fact most of the images I make have to be subsequently added to Photoshop for a final editing 'tweak' - to add sharpness and to get the colour intensity just right. Note I tend to keep the Saturation slider in Photomatix well down so as not to overcook the colours. Red, in particular, is a colour that seems to record too 'hot' in Photomatix so set the colour saturation slider to 40 or less. You can always increase colours later once you get a better idea of what they are really like in Photoshop.

The rusty steel float image was made by more dramatic by underexposing the ambient light setting (using the Exposure Compensation setting set to minus one f-stop) and filling-in the foreground areas using a speedlight. You can also do this using the on-camera flash but it's harder because its output is so much lower than the speedlight's. One tip to get round this power shortage is to increase the ISO rating (i.e. from 100 to 400). This effectively makes the camera's sensor more sensitive to the flash's illumination therefore making the picture 'look' like there's actually more light than there really is, therefore effectively making the flash appear more powerful...

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