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One of the powers of
digital output of photographic images is the ability to tailor
the scene to better represent what was originally seen or to
modify the scene to reflect artistic aims. Here is a scanned image which has been color profiled and thus represents almost exactly what is on the film. (The same issues discussed here will also apply to digital originals). As can be seen this was taken on a very foggy day and the image is quite blue and low in contrast. The scene did not appear
this blue or flat when the scene was photographed, but the film
is more sensitive to blue and ultraviolet than we are. |
![]() Original Image |
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The first step is to
improve the contrast somewhat. To do this we create a curves
adjustment layer. Here is the RGB curves
dialog. We have moved in the black and white points to increase
the contrast. |
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At the same time we want
to compensate for the overly blue cast. This is the blue curve
with the middle lowered in value. |
Blue Curve |
| Even
these small adjustments have made a dramatic change in the
appearance. The scene is much closer to what was viewed
originally. The blue is neutralized and the increase in contrast
makes the tree stand out better. Using conventional photographic techniques we could have used color filters to neutralize the blue, but there is almost nothing we could have done to improve the contrast. |
![]() Image after Curves |
| We can
probably do better with some additional adjustment. We reopen the curves adjustment layer and modify the green curve as well. We lower the mid tones to make the red tree stand out a little better, but fix the highlights so as not to shift the color of the sky towards magenta. At this point, photographic filters have reached their limits. We cannot selectively adjust color balance with them. |
![]() Green Curve |
| This
is the image after this adjustment. We see that the leaves of the
tree are more vivid. There is a little less green in the foliage,
but it still looks realistic. This is the version that I used for my final printed image. Because this is being viewed on screen it is not quite the same as the printed version. We will compensate for this later when we show a larger version. |
![]() After
Green Curve
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| The
tools provided have many short cuts. Let's see what happens if
we, instead, choose the auto adjust feature in curves. Here is the red curve that is created. Notice how much the shadow and highlight levels have been moved. We also used the balance gray tones option so there is a point added in the middle. |
![]() Red
Auto Curve
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| Here
is the green curve. It appears similar with slight differences
in all three points. The software is trying to maximize the
contrast in each color separately. You can use other options, if
you wish. |
![]() Green Auto Curve |
| Finally here is the blue curve. The auto adjust
feature is quick and easy, but let's look at the results. |
![]() Blue Auto Curve |
| The
sky has lost all its color, the leaves are drab and the
atmosphere of the picture has been radically changed. For some
purposes this may be what is desired. The point is you have the
flexibility to treat the image as you wish. The skill and art is
developing the eye to express what you wish and not settling for
just a recognizable image or "good enough". If it's worth doing, don't compromise. |
![]() Image with Auto Adjust Curves |
| Finally, to try and make the image look more like
that taken with the latest generation of supersaturated films we
show this variation. Starting with the original image, we adjusted the rgb curve to make the sky have a zero density and the shadows in the lower right read 100%. We then added a saturation layer and raised the saturation on the reds and the greens. We also lowered the blue saturation so the sky remained white. With digital processing the choice is yours. Click here for the image we chose as best satisfying our goals at a larger size. We made some adjustments to the saturation and lightness so that it will display correctly online. |
![]() Saturation and Contrast Raised |
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© 2004 Robert D Feinman