A step-by-step guide to ensure your images are optimised for display and printing.
From time to time it pays to run through a checklist of the key steps in your digital photo editing workflow to make sure you’re including all the necessary processes that can make the difference between ‘keepers’ that look just right for sharing and printing and shots you’ll set aside. In this feature, we’ll outline the most important steps to incorporate into your workflow in the order in which they should be tackled.
You may not necessarily use all of them every time you open an image for editing. But you should check them all as a matter of routine.
1. Monitor calibration and working conditions
Is your monitor calibrated ““ and is the calibration up-to-date? This is the best way to ensure that what you see on your screen is an accurate representation of the subject that will display on other monitors or TV sets and print out with the correct colours and tonal balances.
Colorimeters (the tools required for monitor calibration) are now affordably priced and well worth the investment. See our Colorimeter reviews to help you make a choice.
When editing images it is best to work in an environment with relatively low light levels, ensuring no direct light falls on the monitor screen to create specular reflections. Most colorimeters can measure ambient light levels on your desktop and allow for them when measuring your monitor’s output.
A properly calibrated monitor will display image colours accurately, enabling them to be printed with correct tonality and the right colour balance.
2. Raw file conversion
If you want to get the most out of your images, you will shoot raw files because they give you the maximum amount of data to work with. This provides much greater flexibility to adjust key parameters without adversely affecting the tonal balance in the image.
The best raw file converters provide plenty of scope for correcting image deficiencies before producing an editable image file.
Choose an effective and flexible raw file converter, rather than simply accepting the software bundled with the camera. Most of it is inferior to third-party applications like Adobe Camera Raw (a plugin associated with Photoshop, Photoshop Elements and Lightroom), Phase One’s Capture One or the freeware RawTherapee application. It takes a while to ‘learn’ any of these programs but most of them will enable you to make initial adjustments to exposure levels, colour balance, contrast, sharpening and noise levels and correct lens aberrations like chromatic aberrations, distortion and vignetting before producing an editable TIFF or JPEG file that can be opened in your image editor.
3. Brightness, contrast and colour correction
Simply getting these three parameters right will make a huge difference to the appearance of your image. Use the histogram in the Levels tool to check the distribution of image tones before making adjustments.
Starting out with excessive contrast often gives you an image with blown-out highlights or blocked-up shadow detail. Many cameras and editing programs can overlay ‘clipped’ highlights and shadows with colours that draw them to your attention.
If you’re adjusting a raw file prior to conversion you can often tweak the exposure and contrast sliders to bring the image tones back to a usable balance. Bias your contrast adjustments towards low contrast as it is easy to increase contrast when working in your image editor but impossible to restore details if highlights or shadows are clipped.
This illustrations shows how careful you must be when using the Levels adjustment on a high-key subject. In the top image, only the right hand slider has been moved, thereby preserving the predominant light tones in the subject. In the lower image, the left hand slider has been also moved inwards with unfortunate results on tonality and colour reproduction.
Be particularly careful with Levels adjustments for high-key and low-key subjects as this tool has been mainly designed for images with a relatively even distribution of tones from black to white. Follow the system we outlined in issue 65 for using the Levels control to fine-tune the colour balance with individual channel adjustments. If the colour balance isn’t as you remember it, the middle arrow on each channel’s histogram can be used to shift it slightly in the required direction.
Pay particular attention to shots with dramatic lighting, such as sunsets and poorly-lit interiors, which are often rendered incorrectly by the camera’s auto white balance control. If there’s a part of the scene that should be neutral grey you can use the white point dropper tool to re-align the colour balance so it is subtracted from the rest of the scene.
Be judicious with the adjustments you make, particularly when working on JPEGs, which are easily posterised when tones drop out. Increasing exposure can make noise more visible in the shadows, whereas decreasing it too much will increase the risk of blown-out highlights. If you can’t avoid either (or both), the fault lies in the original image, which was probably incorrectly exposed.
4. Noise reduction
Images captured with high ISO settings are likely to benefit from noise reduction adjustments, which are best applied straight after exposure level and colour adjustments. Some types of noise are easily correctable; others aren’t and all adjustments have limitations.
Noise reduction will counteract sharpening because it works by blurring edges, which ‘softens’ the image. So your objective should be to make the noise less obvious without causing the subject to appear unnaturally smooth.
Some noise is tolerable, particularly in shots like this one, which could only be captured at the high ISO 25,600 setting.
Remember some noise can be acceptable in shots taken in low light, where it is expected. It’s a bit like film grain, which can add character to some types of shots.
5. Lens corrections
These days most cameras will automatically correct the most problematic lens aberrations ““ but only in JPEG files. That’s why it’s important to have corrections in your raw file converter.
Adobe Camera Raw provides manual adjustments for chromatic aberration (shown here) as well as rectilinear distortion. If the lens you used is included in the Camera Raw database, one-click correction of these aberrations is available.
Unfortunately, Adobe can be slow to add the latest lenses to its Camera Raw database and it provides no corrections for Olympus or Panasonic lenses and is limited in its support for lenses from some other manufacturers. There are sliders in Camera Raw for correcting all the common aberrations (including coloured fringing) and you can save the corrections for subsequent use.
Be judicious when making adjustments. A little vignetting can be useful as it will draw the viewer’s attention to the centre of the image. But it might also increase noise levels near the corners of the frame.
Low levels of barrel or pincushion distortions will have little effect on the appearance of landscape shots, although they won’t be acceptable in architectural photographs. The rule here is to correct them only when necessary, since over-correction can reduce corner resolution and change the composition of the shot.
6. Clarity and contrast enhancement
These tools help to correct the inherent flattening of contrast resulting from the camera’s sensor and lens. The Clarity slider in Adobe Camera Raw adjusts mid-tone contrast to make the image appear sharper (although it doesn’t actually add sharpening). The further to the right you drag the slider, the more the mid-tone contrast is increased. Moving the midtone slider to the right in the Levels adjustment dialog box will achieve a similar effect but it’s not so easy to control.
Most editors provide several ways to adjust image contrast, ranging from an auto contrast setting to a dedicated contrast slider. Contrast can also be adjusted with the Levels tool. Moving the end points of the Levels histogram inwards will increase contrast, while moving them outward reduces it.
Work carefully. Drawing in the black and white points too much can make low-contrast subjects look unrealistic and destroy the impact of misty scenes (as shown in the illustration above). Increasing contrast can also make colours appear more saturated
Output sharpening is normally the last step in the editing workflow. When applied correctly, sharpening can improve the amount of detail you can see in the subject. The trick is to choose the right tool and apply it just enough to make the necessary improvement without introducing unattractive sharpening artefacts.
Most image editors support unsharp masking and provide adjustments for the amount, radius and threshold parameters.
Most image sharpening is done by unsharp masking, which works by emphasising the edge brightness differences within the image. There are usually at least three adjustments available:
Amount is usually listed as a percentage. It controls the overall strength of the sharpening effect. If in doubt, start with 100% and work backwards until you have the level of sharpening you want.
Radius controls the size of the edges you wish to enhance, with a smaller radius used for emphasising small-scale detail. When selecting the radius setting aim to match it with the size of the smallest detail in the image.
Threshold controls the level of brightness at which sharpening will be applied. With the slider at zero, every pixel is sharpened, while at 255 no sharpening is applied. The best setting is always in between, with a position between 3 and 10 giving the best results in most cases.
8. Selective enhancements
Having made all the other adjustments you can now address issues like spot and dust removal, selective sharpening (for example of the eyes in a portrait) and eliminating noise from otherwise smooth areas such as blue skies or areas of skin. Create layer masks to isolate the areas you will work on and use the healing brush, cloning tool and adjustment brushes to make the necessary corrections. Flatten the image to combine all the layers when you’re done.
9. Save a copy of the end result separately from the original
Keep originals as archives that you can return to when you want to re-edit the image. Save edited images in a format that preserves image data. JPEGs should be converted into TIFFs to prevent loss of quality each time the image is re-opened and re-saved. Saving an edited image ensures you won’t have to redo everything if you plan to use the image again.
10. Cropping and resizing
Many shots will be improved by cropping, particularly if the original aspect ratio isn’t ideal for the subject matter. You may want to crop an image to exclude a large area of uninteresting sky or to make it match a specific paper size or aspect ratio.
This 3:2 image was cropped to a 16:9 aspect ratio to remove an uninteresting area of sky and so it could be displayed properly on a widescreen TV set.
Images may also need to be resized to match a specific paper size (although most printer drivers can handle this automatically). You may also want different outputs for different display formats. In general, downsizing is less destructive than upsizing and the greater the reduction or enlargement the more likely the image quality will suffer. Resizing strategies will vary, depending on whether you want to upsize or downsize.
If you want to enlarge an image for printing it’s better to do it with your image editor, rather than leaving it to the printer. Choose the Bicubic Smoother or Preserve Details resampling method and watch for haloes around sharp edges, which indicate over-sharpening. When downsizing images for posting online or attaching to emails, select the Bicubic Sharper method and watch for moirø© fringing and other artefacts.
Article by Margaret Brown
Excerpt from Photo Review Issue 67