|With RAW, you record all the data picked up by the camera's sensor and process it on your computer long after shooting. |
This means that a lot of technical decision-making can be left until you're in better shape to do it rather than while at the centre of the action under water. It also gives you a fantastic range of controls with which to play.
Today, most digital SLRs can record in RAW mode, although it seems that the manufacturers of most compact cameras offer only direct recording of jpegs onto the media card (the Olympus SP550 is an exception).
Camera buffs tend to ramble on about megapixels and dynamic range, but I have found that the camera is only half of the story.
One of the most important aspects of digital image quality comes from the software used to convert these RAW camera files to more familiar tiff and jpeg files.
There are plenty of RAW converters available but I have found the one supplied with Photoshop to be the most intuitive when it comes to working quickly. I have used the original RAW converter that came with Adobe Photoshop CS, upgraded to CS2 and recently upgraded yet again to CS3. I want to tell you about the latest RAW converter of CS3.
This is a diving publication, not a computer magazine, so I won't dwell on the fact that the latest version of Photoshop CS3 has 9000 tools whereas the previous version had only 7000.
I tend to use fewer than half a dozen!
Manipulating a picture in Photoshop trims away data and can be very destructive if overdone. Re-arranging the RAW camera data rather than trimming data is a much better way to achieve the highest-quality results, and the new CS3 RAW converter has some tools to do this that are a wonder to behold.
Upload your images to your computer and open each one in the RAW converter's working screen, using one of seven selections of control. These include the basic controls that allow you to adjust colour quality, exposure, brightness, contrast, depth of blacks and so on.
But new useful features include a fill-light effect and recovery for lost highlights.
You simply move the sliders to get the effect you want, or an Auto setting gives you what the software thinks is best. Other helpful guides include a histogram that allows you to see if you have lost details in highlights or shadow areas.
The next slice of controls includes an adjustment for the characteristic tonal curve of the image. This now has a 'parametric' option that allows you to make subtle adjustments, using up to four sliders rather than trying to mark accurately points of adjustment on the curve itself (still an option).
Why would you want to do this? Images shot on film are characterised by an S-shaped tonal curve, whereas digital images are normally linear (straight line). By adjusting the shape of the tone curve, you can get a more pleasing image that looks as if it was shot on your favourite film. It's what Hollywood directors call a 'filmic' quality.
Another set of controls covers sharpening and noise-reduction. This comes in useful when shooting at high ISO values in low light conditions. For images to be reproduced by a mechanical printing process, it's best to turn the sharpening off, but you can still use it for looking at the preview image.
The next slice of controls concerns hue, saturation and luminance. Here eight sliders allow you to make adjustments to the colour, which is useful when you have got it totally wrong while shooting under water - for instance, when using natural light at depth without any ancillary flash. Another set of controls splits hue and saturation levels between highlights and shadows.
A useful raft of sliders concerns lens corrections. This comes into its own when shooting through a flat port, or when using a wide-angle zoom that suffers chromatic aberration. Colour-fringing so caused can be adjusted by sliders, or you can simply hit the 'defringe' button.
Another useful feature on this level allows you to control lens vignetting. Camera lens designers try to give even illumination across the frame, but I often find with underwater subjects that they can be enhanced by increasing the vignette or unevenness to draw the eye in towards the subject.
This allows you to control how much the picture becomes darker towards the corners.
There is also a set of controls for camera calibration. I usually go with that supplied by the camera manufacturer but there is the option to reset the three levels of colour sensitivity (red, green and blue) plus the shadow tint (black).
Finally you'll find a raft of settings called 'Presets'. I have yet to discover how to take advantage of this!
While previewing the effects of your adjustments, you can enlarge parts of the image up to 400%. You can also rotate an image, and there are a few tools derived from the main Photoshop palette that allow you to make localised adjustments, too.
If you are worried about your own judgment as to how a picture should look, another option is to turn on an indicator system, so that if highlights or shadow areas are left devoid of information they are highlighted in blue (too black) or red (too white).
You can then open your image in Photoshop proper, either directly in 8-bit colour depth or
at the maximum provided by your camera (up to 32-bit). There are even seven levels of interpolation, to help you provide files of the right size to satisfy those difficult magazine art editors!
Once in Photoshop proper, it's time to clone out or heal those annoying bits of detritus in the water (or remove that offending diver who got in the way of your shot!) before saving the image as an uncompressed tiff file, a compressed jpeg or any of the other file types available on the Photoshop menu.
The RAW converter lets you do batches of pictures at the same settings.
If you are looking for a mathematical solution as to what makes a good result, don't bother. We are dealing with art. You just need to move the various sliders around until you have rearranged the digital data in a way that pleases the eye.
No data is destroyed. It is simply re-arranged, and you can make the adjustments in any order, reverting to a previous slider adjustment if needs be.
Don't worry if you think your first settings weren't right. Your original RAW file remains exactly as it was when you recorded it, so you can always go back and make a new conversion with different adjustments.
No longer will you lose pictures because they failed to come out correctly. And while under water, you can concentrate on things like finding the right subject, composition and focus.
|The picture as shot RAW in the camera. |
|Adjusting the tonal curve. |
|Adjusting basic colour. |
|Split toning. |
|Eliminating colour fringing and adding vignetting. |
|Adjusting the basic settings. |
|How you want the final result to look is up to you. |
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