Chapter 6 Basic RAW Processing

The word processing has been associated with photography since its existence. For many years it referred primarily to the processing of exposed film into negatives, which was done in temperature-controlled tanks filled with chemicals to process the film and water to clean it. Once the negative was produced, the photographer used to process the photographs by placing the negatives onto an enlarger, thus exposing light-sensitive paper to the light passing through the negative. The paper was then developed to produce the image, using developer, stop-bath and then a fixer. This was known as print processing. Generally speaking, once the film became a negative the ability to ‘edit and retouch’ began, with various darkroom techniques such as dodge and burn, although the choice of film and chemicals used to process the film could hugely affect the finished image.

Things have not changed much in the digital age, except that we now work with digital negatives or RAW files. To some degree the task of post-processing images has become hugely more accessible and affordable, if not completely automated on some occasions. As most photographers no longer process film, the term post-processing has generally become accepted as anything that manipulates or changes the RAW file once the shutter has been fired.

Professional and experienced photographers tend not to rely on post-processing techniques to save an image that does not succeed; however, some post-processing is inevitable and to some degree expected in today’s market. Whilst I will cover a few RAW processing basics, it is important to bear in mind that the world of post-processing, editing and editing software, such as Adobe Photoshop, are worth an entire book of their own. To this end, this chapter is a very brief and basic insight into how to process your RAW files using the industry standard software, Adobe Camera RAW (ACR).

RAW – THE DIGITAL NEGATIVE

Many people new to the world of digital photography fail to appreciate that their standard compact camera processes photographs in-camera. Any camera that shoots in JPEG or even TIFF format will process the images to some degree and then compress them into one of the recognized file formats.

JPEG may be convenient, allowing you to get many exposures on a single storage card; however, it also massively impacts on flexibility and image quality, introducing unwanted artefacts, colour casts and tonal curves. RAW on the other hand undergoes no or little in-camera processing and needs importing into the camera manufacturer’s proprietary software or a recognized RAW converter, such as Adobe Camera Raw, to be processed.

Shooting in RAW allows the photographer to process the images by way of fine-tuning and other adjustments prior to editing. The amount of adjustment that can be made to a digital negative prior to editing is huge, ranging from exposure to vignetting, so it is worth spending a little time exploring the various RAW processors on the market and the effects that you can achieve with them.

OTHER RAW CAPTURE UTILITIES

Note: For simplicity, I am referencing Adobe Camera RAW, as it is the most popular and widely available of RAW capture utilities. However, most major camera manufacturers, plus several third-party software developers, produce their own software to process RAW files. The techniques utilized here may be applied in the majority of RAW capture software; however, the tools and menus will vary.

There are a few useful basic tools and visuals you should be aware of when editing digital negatives that are particularly helpful when fine-tuning colour balance, exposure and even reducing digital noise. These techniques are quick, basic and simple adjustments that will have you improving your images in minutes.

Histogram

The histogram will give you an instant visual graph of all the tonal information in your image. It will instantly tell you if you have clipped shadow detail or highlight detail. It will also give you a visual indication as to where the majority of the image data resides, such as the shadows, mid-tones or highlights. The histogram is something that many new photographers ignore; however, it can be a very useful tool when judging exposure or even to ascertain if you are clipping certain colours.

Fig. 6.1 Adobe Camera RAW Histogram. Image © Christian Hough.

When looking at the histogram, you will see shadow detail to the left, mid-tones in the middle and highlights to the right. As a rule of thumb, if your histogram is more dominant to the right, then your image is possibly overexposed. On the other hand, if your histogram is more dominant to the left, then it is possible that your image is underexposed. It is important to remember that it is only a guide and you will find that shooting on dark and light backgrounds may push the histogram either way, yet your photograph will be properly exposed.

If you are seeing a large spike in the histogram it is usually a sign of clipping (where image data is being lost). It may be that the dynamic range of the scene is wider than your camera can capture; however, small adjustments to exposure will usually help.

BASICS TAB

White Balance Slider

Accurate white balance is of utmost importance in any genre of photography. For the most part, a camera’s auto white balance (AWB) will do a reasonable job in the studio; however, over many frames its consistency can vary, leaving you the arduous task of colour-correcting many images.

There are a couple of simple things you can do to assist you in achieving a more accurate and consistent white balance, and they are to avoid AWB and to use a grey card.

Fig. 6.2 White balance: XpoBalance by Lastolite.

Avoid AWB

Auto White Balance is very convenient, but not necessarily accurate. The most consistent and professional way of setting your white balance is to do it manually, either in-camera, via your capture software, or in batch processing using the White Balance tool and a grey card.

18% Grey Card

Grey cards are cheap. They are neutral (with no colour) and have 18% reflectance across the visible spectrum. At the start of each shoot or setup, it is advisable to take a single properly exposed frame of the 18% grey card, and this may be used as your white balance. You may find that different reflectors will reflect colours at slightly different temperatures, so when you change your lighting it is useful to shoot a frame with your grey card so that you may adjust your RAW settings later.

If you are processing your images using RAW processing software, such as ACR, then you can simply select the White Balance tool from the tool bar and click it onto the grey card. You will find that there is an instant colour shift as the software makes all the necessary adjustments. This setting can then be copied and applied to several RAW photographs without the need to open them. Of course, if you have shot without a grey card and are experiencing a strange colour shift in your image, then it is possible to use something that is a neutral black, grey or white within the frame. It may not necessarily be perfect, but may get you closer to a more neutral white balance. It will then be a case of using the Temperature and Tint sliders to fine-tune your image.

Fig. 6.3 WB before…. Image © Christian Hough.

Fig. 6.4 .... and WB after. Image © Christian Hough.

TEMPERATURE VS TINT

Remember: Adjusting the Temperature slider will make the photograph warmer or cooler, whereas the Tint slider compensates for the green or magenta tint.

Fig. 6.5 Exposure slider, underexposed. Image © Christian Hough. Model: Carmen Bellacassa.

Fig. 6.6 Exposure corrected. Image © Christian Hough. Model: Carmen Bellacassa.

Exposure Slider

It is always preferable to use a light meter and expose your images properly at the time of shooting. No amount of processing can beat a properly exposed photograph. However, there are of course times when exposure may not be as accurate as we had hoped for. It is common, even in studio photography and can be affected by subjects moving in and out of the light source or even by variances in power from cheaper flash heads. As you would expect, there are a few processing tweaks we can do when working with RAW files, but like everything, there is a caveat.

The Exposure slider essentially elongates the histogram and increases the clipping point of the highlights. Moving the slider to the right will lighten the image and moving it to the left will darken the image. The Exposure slider basically ascertains where the highlight data will clip, and then converts the clipped highlight value to 255. The remaining darker tones are lightened, and the histogram elongated and smoothed out.

All of this flexibility with exposure sounds great, but it is limited and its flexibility will depend entirely on the camera system you are using and the quality and bit depth of the image it produces. For the most part, increases above +1.00 can begin to introduce noise and artefacts into your photograph. You may also find that it causes shadow detail to break up and posterize. The higher the ISO used, the more noticeable these artefacts can become. Higher-end 35mm systems and medium-format digital can be pushed further without necessarily experiencing any degradation of image quality.

Recovery Slider

Traditionally, it is the highlight information in digital photography that is the most susceptible to being blown. This is in contrast to film, where there is less latitude within the shadows. The studio, for the most part, is a controlled environment, where lighting can be adjusted to ensure that photographers achieve a properly exposed photograph without blowing the highlights; yet there are occasions when highlights are clipped, due to reflective surfaces, lighting and positioning constraints or even movement. The Recovery slider can help you retrieve some or all of the lost highlight data, and this is one of the huge benefits of shooting RAW.

Fig. 6.7 Normal exposure. Image © Christian Hough. Model: Carmen Bellacassa.

Fig. 6.8 Effects of increasing highlight recovery slider. Image © Christian Hough. Model: Carmen Bellacassa.

You will find that moving the Recovery slider to the right will begin to slowly recover the highlights and as you move it, you will notice the highlight information on the histogram moving to the left and slowly bunching with the mid-tones. It is important to keep a close eye on the rest of the image, as pushing the slider too far will slowly begin to affect all of the lighter tones and can on some occasions make some highlights appear grey. Using the Recovery slider in conjunction with the Exposure slider will increase the rate of highlight recovery and retrieve most highlight data without the introduction of artefacts. It is an extremely useful and capable facility and it is possible to retrieve up to two ƒ stops of information, but don’t expect it to perform miracles!

Fill Slider

The Fill slider behaves like an artificial fill light. As you move the slider to the right you will see from the histogram how it will lift the shadow and mid-tone detail in the image, whilst the highlight detail remains stationary. It is particularly useful when you want to lift a small amount of shadow detail. Moving the slider too far to the right will begin to produce some unusual effects and will begin to make a photograph looks as if it is solarized. Despite being a useful tool, it is no replacement for a properly positioned and metered fill light and is best when used sparingly.

Fig. 6.9 No adjustments. Image © Christian Hough. Model: Carmen Bellacassa.

Fig. 6.10 Effect of increasing the fill slider. Image © Christian Hough. Model: Carmen Bellacassa.

Blacks Slider

True to its name, this slider adjusts the darkest or blackest parts of the image, by setting a new clipping point for the shadows. It is a useful tool for tackling slight overexposure or mild haze as it elongates the histogram, pulling it down to the left whilst leaving the highlights intact and increasing the contrast within the shadows. The Blacks slider can be used to complement adjustments with the Fill slider if the image begins to look a little flat and lifeless.

It is worth remembering, though, that you are basically clipping the shadow detail out of the image before you export it into your editing software, so it is worth considering what further post-processing will be done and whether you could utilize some of that shadow detail later on.

Fig. 6.11 Blacks at normal level. Image © Christian Hough. Model: Carmen Bellacassa.

Fig. 6.12 Effect of increasing the Blacks slider. Image © Christian Hough. Model: Carmen Bellacassa.

Brightness Slider

Brightness should not be confused with the Exposure slider as they perform different tasks. Whereas the Exposure slider concentrates on the highlights, pushing the histogram to the right, the Brightness slider tends to concentrate on expanding the mid-tones whilst compressing the highlights. As you adjust the Brightness slider, the mid-tones push to the right, lightening the image.

Many photographers neglect the Brightness tool in favour of adding a tone curve during post-processing. Yet it remains very useful when used in conjunction with the Blacks and Exposure slider as a way of making those final adjustments to the equally important mid-tones. Like any adjustment, it needs to be done in moderation as too much can begin to make an image appear washed-out and lacking in contrast.

Fig. 6.13 Effects of decreased brightness. Image © Christian Hough. Model: Carmen Bellacassa.

Fig. 6.14 Effects of increased brightness. Image © Christian Hough. Model: Carmen Bellacassa.

Contrast Slider

Every photograph needs contrast; otherwise it would look flat and lifeless. The task is to strike the right balance between the shadows and highlights, whilst keeping enough detail in the mid-tones. The Contrast slider is one of the tools I rarely use as there are many other more precise ways to add contrast. Even when processing RAW files, it is possible to increase contrast using a combination of the Blacks and Exposure sliders, before editing a parametric or point-based tone curve. The Contrast slider basically elongates the histogram, stretching the mid-tones whilst compressing both the shadows and the highlights. It reality, it is the layperson’s way of adding contrast and is best left for those quick fixes or batch processing contact sheets.

Fig. 6.15 Effects of reduced contrast. Image © Christian Hough. Model: Carmen Bellacassa.

Fig. 6.16 Effects of increased contrast. Image © Christian Hough. Model: Carmen Bellacassa.

Clarity, Vibrance and Saturation

These three sliders are located under the Contrast slider in Adobe Camera Raw, and they are for the professional studio photographer, as more precise adjustments can be made later on during post-processing.

Clarity

The Clarity slider increases or decreases the contrast around the edges, which gives the impression that the image looks sharper. If you are processing high-contrast black and white street photography or environmental portraits with lots of texture, then the Clarity slider when pushed to the right may prove to be very useful. If you are working with models or even family portraits, however, then it is definitely one to avoid, as it has a tendency to pick out every imperfection – definitely not what most people want, and it will double the amount of healing and cloning during post-processing!

Vibrance

The Vibrance slider makes the image look more vibrant by way of increasing the saturation of the colours without clipping the already well-saturated areas. When pushed too far, it can make an image look rather false, as all the colours look too even, so less is definitely more. For studio work the use of the Vibrance control is limited, unless you are batch processing contact sheets, as more precise adjustments can be made during the later stages of post-processing.

Saturation

When increased, the Saturation slider increases the colour throughout an image, causing the colours that were already strong to be clipped. It can of course also decrease the colour, but tends to produce a rather flat and uninteresting black and white image. Unless you are batch processing, the Saturation slider is better left untouched, and instead an adjustment layer made in the latter stages of post-processing.

DETAIL TAB

By moving along the tabs located under the histogram, you will come across the Detail Tab. By selecting this tab, you open up the options to vary the sharpening and add an element of noise reduction if necessary. Both the Sharpening and Noise Reduction sliders are very useful tools, but care needs to be taken when using them as they can introduce unwanted artefacts into the image. It is important to remember that once the RAW image has been processed and exported into your editing software it has the ability to become more destructive the more you edit. Your use of the Sharpening and Noise Reduction sliders will of course depend entirely on your given market. So if you are photographing a hundred portraits a day and then batch processing the lot, the detail tab will be ideal for your workflow. However, if you are shooting commercially and will be editing a small number of photographs, you may wish to leave much of the sharpening to the later stages of post-production, where parts of the image can be masked and the layers peeled back if necessary or adjusted to the output size and medium.

Sharpening

Amount

As it suggests, moving the slider adjusts the strength of the sharpening. Moving the slider to the right increases the sharpening and moving it to the left decreases it. It is worth watching the image as you increase the sharpening, as too much has a tendency to produce halos and pixilation around contrasting edges. Default value is 25.

TOGGLE VIEW

When adjusting the Radius, Detail and Mask sliders, you can press and hold the <ALT> key to toggle between a greyscale mask to assist in visualizing the effects of the sharpening.

Fig. 6.17 Close-up of unsharpened photograph. Image © Christian Hough. Model: Gavin Randle.

Fig. 6.18 Close-up of sharpened photograph. Image © Christian Hough. Model: Gavin Randle.

Radius

This is the area around or within a pixel where the sharpening will take effect i.e. the width of the halos. Increasing the radius basically increases the area that is sharpened, or, adjusts the size of the details that sharpening is applied to. Using a smaller radius will allow you to sharpen smaller and more subtle parts of the image, whereas a larger radius may assist you in correcting minor motion blur. A larger radius setting will also emphasize the finer edges and at the same time enhance the softer edges. Default value is 1.0.

Detail

The Detail slider suppresses the halo effects whilst allowing you to increase the Amount of sharpening without unwanted artefacts. When the Amount and Radius sliders are at their default values, the effect of the Detail slider is fairly subtle and is useful for bringing the fine edges of hair and fabric, even when pushed to the maximum value of 100. However, multiply this with a sharp increase with the Amount slider and the effect is immediate and unpleasant, producing unwanted noise and artefacts. For studio portraits, lower detail settings are recommended.

Masking

The Masking slider affords you some control over the overall sharpening effect. The more you increase the Masking slider, the more you begin to protect the flatter tones within the image from the effects of the sharpening. Utilizing the greyscale edge mask by holding down the key will help you visualize your adjustments more clearly.

Noise Reduction

Noise is caused by several factors within the camera. This can be anything from the heat generated by the sensor, in-camera processing or even exposure times. Noise reduction (NR) is a very useful way of removing unwanted noise from images. As a rule, noise isn’t a common issue with studio photography, given that most images will be taken between 100 and 200 ISO and be correctly exposed. However, there may be occasions when you find that you need to increase your ISO to compensate for depth of field or lack of power. It is occasions such as this when underexposure is a risk and where noise can begin to creep into the shadow areas. Applying noise reduction during RAW processing and post-processing is for the most part better than doing it in-camera, simply because you have greater control over the whole process and will avoid introducing unwanted artefacts at the early stages. Noise reduction is destructive and if applied during RAW processing it becomes permanent. For this reason, it is advisable to leave noise reduction until the later stages of editing, so that it may be applied selectively and peeled back when necessary.

Fig. 6.19 Image at 400 per cent without noise reduction. Image © Christian Hough. Model: Gavin Randle.

Fig. 6.20 Image at 400 per cent. Increasing exposure can increase noise. Noise reduction can reduce ‘grain’, but will introduce artefacts. Image © Christian Hough. Model: Gavin Randle.

Luminance

The Luminance slider controls the type of noise we most commonly know as grain, also known as greyscale noise. The default value in ACR is ‘0’, so moving the slider to the right will increase the noise reduction and decrease the film grain. It is important not to increase this too much as it will begin to remove the detail. Grain is rarely an issue, adds character to an image and is even less noticeable when printing.

Luminance Detail and Luminance Contrast

Unless you are shooting at very high ISO or pushing the exposure on a very underexposed image you are unlikely to benefit too much from using these sliders. The Luminance Detail slider controls the luminance noise threshold. On the face of it, the higher the value the more detail and noise it will return to the image, although the detail is more apparent on the edges, leaving the flatter tones looking smooth. The Luminance Contrast slider is useful for very noisy images. When used at higher values, it will assist in preserving the contrast, but will also introduce blotches of noise and mottling.

Colour

The Colour slider default is set at 25. It is not unusual in studio photography for the default setting to be zeroed in order to preserve the original colour. If you have noise in your image, moving this slider to the right will begin to remove the coloured speckles that you can see in noisy images, which are normally red, purple and green, know as chroma. Increase the Colour noise reduction too much and the image will become blotchy.

Colour Detail

The Colour Detail slider controls the colour noise threshold. It is there to assist in reclaiming some of the detail removed by Colour noise reduction. Pushing the slider to the right will protect finer, detailed colour edges, but increase colour speckling. Decreasing the amount of Colour Detail will remove coloured speckles at the risk of introducing colour bleed.

LENS CORRECTIONS TAB

The Lens Corrections tab offers a range of lens profiles to fit a range of common lenses from different lens manufacturers. The lens corrections compensate for the three most common lens aberrations, namely vignetting, geometric distortion and lateral chromatic aberration. By selecting the lens manufacturer and the lens used to take the photograph, ACR will then make a series of adjustments based on the lens calibration data available.

Correction Amount

Once your chosen lens has been selected, the three greyed-out adjustment sliders under the Correction Amount heading will become available.

Distortion and Chromatic Aberration

The Distortion slider will allow you to fine-tune bends in parallel and horizontal edges/lines, such as barrel or pincushion distortion. The Chromatic Aberration slider will help remove colour fringing along high-contrast edges. You will find that overuse of these sliders can frequently correct some areas of the photograph, whilst causing issues in others.

Vignetting

Vignetting is basically the gradual light fall-off that can be experienced towards the corners of a photograph. It is more prolific when using wide lenses, very long zooms and wide apertures. For studio work that is shot on standard lenses at apertures between ƒ8.0 and ƒ16 it is rarely a major issue. In fact it can actually prove to be fairly useful for portrait photographers as the gradual light fall-off assists in reducing the plainness of paper backgrounds, whilst making the viewer focus on the subject in the middle. Portrait and wedding photographers frequently add vignetting to their images.

Ultimately, how you use this RAW process will depend entirely on your workflow and intended results. It may be easier to remove a vignette globally that to add one. It should be applied in the same way as many other corrections and effects prior to post-processing. If it is possible to leave it until later on in post-processing, then this would afford you more flexibility over the finished image. On the other hand, if you are batch processing hundreds of images, it may be worth applying it globally to many images at the same time.

There are two common types of vignetting:

PHYSICAL VIGNETTING

This is usually apparent in the extreme corners of the lens and usually caused by a physical object intruding on the lens, such as a lens hood or lens filters. This will usually require cloning or cropping.

INTERNAL VIGNETTING

This is most often caused by the optical elements inside the lens and is easily correctable using software or by stopping down. If you are using a full-frame DSLR then you may suffer from the effects of vignetting more often than with a system utilizing a cropped sensor.

EFFECTS TAB

Post-Crop Vignetting

As opposed to a lens correction, the Post-Crop Vignetting tool under the Effects tab is intended to be used artistically, rather than as a lens correction.

Style

The Style has a drop down menu offering you three choices: Highlight Priority, Colour Priority and Paint Overlay. Highlight Priority will apply a vignette whilst protecting the contrast within the highlights, but may cause colour shifts within the shadow areas. Colour Priority preserves colour hues but can reduce the detail within the highlights. Paint Overlay will blend the colours within the image with a black or white vignette, with a possibility of reducing the contrast within the highlights.

Amount

Moving the slider to the right will lighten the corners of the image, whereas moving the slider to the left will darken them.

Midpoint

An increase in the Midpoint slider will restrict the area of adjustment near the corners, whereas a decrease will apply the adjustment to a larger area from the corners.

Roundness

Increasing the values by pushing the slider to the right will make the effect more circular, where moving the slider to the left will begin to make the effect more oval.

Fig. 6.21 Standard image. Image © Christian Hough.

Fig. 6.22 Image with white vignette applied. Image © Christian Hough.

Feather

Higher values will begin to increase the feathering between effect and the surround pixels. Reducing the values will perform the opposite.

Highlights (Highlight Priority and Colour Priority)

This controls the punchiness of the highlights, such as the glow from various continuous light sources.

Fig. 6.23 Standard image. Image © Christian Hough.

Fig. 6.24 Image with dark vignette applied. Image © Christian Hough.