ASK DAVID SHERWILL...

Now in semi-retirement, David takes a great deal of pleasure, passing on his 45+ years of photographic knowledge to amateur and fledging photographers around the world with help, advice and tutorage..

Whether your questions are film or digital photography-based, large, medium or 35mm format, technique-related or associated with studio lighting or darkroom; feel free to Ask The Expert and get direct email help from one of the UK's most experienced photographers. Some corrispondance will appear on these pages so that others might benefit from the advice.
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LATEST Q&A's...

Q.Someone has suggested to me that I should make some of my black & White images into Duotones. What are Duotones?
BEN THAW, CORNWALL, UK

A. Duotones are used to increase the tonal range of a greyscale image. Although a greyscale reproduction can display up to 256 levels of grey, a printing press or most mono Inkjet photo printers can reproduce only about 50 levels of grey per ink. This means that a greyscale image printed with only black ink can look coarser than the same image printed with two, three, or four inks, each individual ink reproducing up to 50 levels of grey.

The fact that duotones use different colour inks to reproduce different grey levels, means they are treated in PhotoShop and Paint Shop Pro as single-channel, 8-bit, greyscale images. In Duotone mode, you do not have direct access to the individual image channels (as in RGB, CMYK and Lab modes). Instead, you manipulate the channels through the curves in the Duotone Options dialog box.

To apply a duotone effect to only part of an image, you must convert the duotone image to Multichannel mode. This converts the duotone curves to spot channels, allowing you to erase part of the spot channel for areas that you want to appear as standard greyscale.

Duotone effects are all achieved by manipulating the image settings by altering the percentages that make-up the digital information contained within the image. In practise, this simply involves pulling and pushing the curves around and changing the colour saturation until a desired effect is created.

 

Q. I find that my exposures are perfect outdoors but inconsistant indoors. Do you have any tips on getting better exposed images?
IAIN QUINN, CUMBRIA, UK

A. It's impossible to get 100% perfectly exposed images 100% of the time. In print-film terms, it always pays to bracket exposures and given that digital photography cuts out the costs of film and processing, it is also perfect for bracketing, in-fact some digital cameras have auto-bracketing facilities.

Bracketing is the process by which multiple photographs are taken of a particular subject with some of the settings slightly modified, such as shutter speed, f-stop, or aperture. Obviously, some of these elements can also be tweaked after the fact with digital photography, but the more extreme the under or over exposure, the harder it is to correct post-shoot. So, bracket really is the best way to get better exposure results.

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