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How to Improve a Digital Negative

Every digital camera takes a Raw file. This will capture all the information that can possible be retained by that particular camera, lens and silicon chip.
When the quality of the Raw file is as good as possible, it will require fewer adjustments and the quality of the final image is better.

Some users don't save the Raw file but save only the JPEG. The JPEG can also be improved with a couple of settings prior to taking the picture.

White Balance
Transparency film had a built-in neutral colour balance, either for Daylight colour or Tungsten colour.  As long as the light was within a certain range, the greys would be neutral and colours accurate. Digital does not have such built-in colour balance; we have to set it for each circumstance and adjust the colour balance of the image during editing.

Most cameras have a number of settings for the white balance, which aim to make the image neutral and the colours as true as possible.

One white balance setting to be avoided is 'Automatic'. It is certainly convenient to have everything set automatically, but the results can be inconsistent. The colour balance will fluctuate from subject to subject. Photograph a group of people and there will be one colour balance setting. If someone joins the group wearing a blue shirt, the colour balance will change. This can make later matching of the images more awkward.

Common alternative settings for the white balance are:

Incandescent
Flourescent
Direct sunlight
Flash
Cloudy
Shade

Sometimes there are settings for individual Color Temperatures.

If at all possible, select the most suitable setting for the conditions. The results will be more consistent and nearer to the final image.

Checking the Histogram
The second action worth taking is to look at the histogram and then adjust exposure accordingly. A histogram is a graphic display of all the tones the camera has captured in the  photograph.

When we use Levels in Photoshop, we are looking at the image's histogram. Black is on the left with a zero value, pure white is on the right with a value of 255.

The graph tells us what the tonal distribution is in the image. We can adjust and fine tune to tones with the histogram in Levels.

The histogram is just as important within a digital camera. It can tell us if the exposure is correct and if we have all the necessary detail in the image.
Certainly we can look at the preview image, but the preview is a rough JPEG processed within the camera from the real recorded image. Very often it is not a good representation of the image itself. Especially if one is shooting Raw, this preview guide can be misleading and wrong.

Most cameras, even fairly basic digital cameras, can display a histogram on its LCD screen. It can be displayed over the image it applies to.
By looking at the histogram of the photograph just taken, it's possible to get much better information about the exposure.

The histogram should show a good distribution of tones. Most cameras have a 8 stop dynamic range and we want to be sure our result is within this range.

The way a digital camera chip reacts to light is similar to the way colour transparency film works. Too much light will burn out highlights and result in a loss of detail.  Far too little light will mean there is no effective shadow detail recorded.

An 'ideal' exposure will be in the middle of the recording chip's dynamic range of 5 stops. I have put the word 'ideal' quotation marks because what is ideal can vary with circumstances. If you are concerned with recording all the subtle tones on bright clouds or white surf, you would give a little less exposure. Similarly, if photographing a very dark subject, exposure would be increased.

Although the preview can tell us the image is on the light side, the histogram tells how bad it really is. If most of the information is squashed over to the right, it means the image is seriously overexposed and a lot of the highlight detail will be burnt out. There is always a limit as to how much can be recovered in Camera Raw and Photoshop. Another shot needs to be taken of this scene with much less exposure.

A scene might have such a large tonal range that not everything can be included in one shot. Bright white clouds in the sun and shadow detail on the ground will be too wide a range for one digital capture. Two or more photographs will need to be taken and then merged later. On some occasions, fill-in flash can be used on foreground material in shadow to reduce the contrast range.

The histogram should not be followed dogmatically, however; some human interpretation is required. A lot of the curve may be over to the right and it can be justified. If there is a lot of white in the scene and the curve is not severely pushed over to the right, everything might be all right.

The same will happen on the dark side. A photograph with lots of dark will give a graph mainly over to the left. The graph will show a lot of dark but there can still be enough midtones.

It's when far too much of the curve is squashed over to the right that the histogram will indicate the image is going to be underexposed and will not produce a viable digital file with a lack of detail in the shadows and midtones.

The two simple actions

1. setting a white balance compatible with the light conditions and
2. checking the exposure by referring to the histogram will greatly improve the accuracy of the Raw file and then the final image.

 

About the Author

Duncan Wherrett is an experienced professional photographer and Photoshop instructor. More information can be found via: ---->Photoshop

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