Converting and editing raw images
Raw v jpeg As we have found out, jpeg files are processed in the camera and much of the data is lost. Raw files are not.
Raw file formats: General term for a variety of proprietary file formats Canon.CRW and.cr2 Nikon.NEF Minolta.MRW Olympus.ORF Sony.SRF
Processing raw data Unprocessed raw data can be converted into usable file format using Adobe Camera Raw (ACR). Settings such as bit depth, white balance, exposure, brightness, contrast, saturation, sharpness, noise reduction and crop can be applied during the conversion process. Making changes using the full bit depth image (raw file) enables us to achieve better results. Simply double-click the file to open it into Photoshop s Adobe Camera Raw editing suite.
Processing Raw data The dialogue we are now working with has been organised so that the user starts with the top slider then works their way down to the bottom. You can also process a number of images at once, for example if they are of the same subject, using the same setting at the same time on each image. Processing steps: Step 1 Straighten, crop and size Step 2 Colour space Step 3 Choosing bit depth Step 4 White balance Step 5 Tonal adjustments Step 6 Saturation and vibrance Step 7 Noise reduction and sharpening
Basic Tools: File Histograms Basic Tools File Options Adjustment Panels
Step 1: straighten, crop, size Straighten the image with the straighten tool or by rotating a crop area. Crop the image with the crop tool. Size the image with the crop tool option menu. Set the resolution using the Workflow options at the bottom of the screen.
Step 2: Colour Space The colour space is the level of colour you have to process within in your image: Colour Match RGB - is rarely used now. srgb This offers the smallest range of colours so should be chosen for images which will be used on screen e.g. web. Adobe RGB (1998) The most common colour space used in industry for print images. ProPhoto RGB - should to be used if you have access to high end printing equipment must work in 16bit to avoid data loss.
Step 3: Bit depth Bit depth = the amount of information you have to process, the higher the bit depth, the more information you have to work on, thus a better resulting image. Working in 16 bits per channel will preserve all the information in the image. On opening the image into the standard Photoshop workspace, as long as no editing takes place the image will stay 16bits per channel. If editing takes place then 8 bits per channel will be used, compromising quality.
8 bit v 16 bit editing In 8 bit editing the channels are weaker and begin to break up. Not so with 16 bit. 8 bits per channel 256 tones per channel 16 bits per channel 32,769 tones per channel The difference is that the 8 bit edit may result in banding instead of smooth gradients from one colour/tone to another.
Step 4: White Balance White Balance option allows choice of presets including As Shot Temperature slider controls blue/yellow Tint slider controls green/magenta Both together control red/cyan balance Alternatively use the White Balance tool to select a mid grey in the image to auto balance it
Step 5: Tonal adjustments Exposure slider sets the brightest points in the image Blacks slider sets the darkest points in the image Just like Levels in Photoshop Click Auto to auto balance or Default to reset Brightness and Contrast can be used to fine tune the midtone values The Recovery slider is used to rescue highlight tone that might clip as they are adjusted. Fill Light will rescue very dark tones that may contain texture or detail
careful Tall peaks on the histogram indicate that you will lose shadow highlight or colour detail when you export to Photoshop.
Using the Tone Curve Editing the tone curve gives you the same flexibility as Curves in the normal Photoshop space. Lifting the line from the centre will generally lighten and dropping it will generally darken To lighten the light areas and darken the dark areas, add three points down the line and lift the top and drop the bottom points. You can add as many points as you require. You can select points from the image by holding down Cmd and clicking on the image.
Step 6: Saturation & Vibrance These two commands allow for the increase or reduction of colour within the image. If the image already has a high concentration of colour then it is easy to clip the image. Clipping means to lose some of the high end colours and should be avoided. Again watch the histogram for spikes at the left and right.
Editing the independent colour channels The HSL/Greyscale tab can be used to edit the individual colour channels for far more control over the process. Hue: controls the colour Saturation: controls the amount of colour Luminance: controls the light and dark in each colour The Greyscale selection converts to greyscale allowing the same control sliders to control the greys in each channel. This histogram will show a single grey channel.
Step 7: noise reduction and sharpening Zoom in to 200% and inspect the image for noise Noise can be reduced using the Luminance and Colour sliders You should only use these if noise is present as fine detail can be lost. Sharpen the image using the Amount slider Care should be taken her also, don t sharpen above 25% as it will have no effect in the actual final file editied in Photoshop.
Sensor dust, spot & blemish removal Click the Retouch tool, select a radius, click on the problem Photoshop auto selects an area to use to heal with. The green circle an be moved to select a better area if required. Clear all will reset the image.
Resetting the raw image To reset to the original raw image as it was when it game off the camera do the following: Click the menu at the top of the adjustments areas and select Camera raw defaults. To remove any crops you have applied, click and hold the crop tool then select Clear Crop.