Sunday, February 24, 2008

Adjust any Colour of the Rainbow with Blend-If type Sliders

This week's article, as you can probably guess, deals more with Advanced Photoshop Techniques.

How to select a narrow range of any color and adjust Hue, Saturation or Luminance

How to use the Replace Color function to create a tight Mask for use with other Layers

The original article was not planned to start this way, but was to examine the benefits of using the color enhancement features on a jpeg image with Adobe Camera RAW.

Camera RAW has some interesting sliders that I tend to use frequently to initially set the color attributes of the image. I thought that with the extra colours available, I would be able to produce a better image.

These are the 3 Color Camera RAW adjustments

This got me thinking about the Hue/Sat layer adjustments and remembering that you could fine tune the colours even tighter than the default adjustments provided to you when you open the Hue/Sat adjustment layer.

This image below was selected, as I wanted to do something outrageous with a Red Hibiscus. The whole process from opening the file to creating the image below only took about 3-4 minutes.

The above strip shows:
Original Image
Change Red to Blue and De-saturate remaining colours (Hue/Sat)
Another Hue Sat layer to remove any residual reddish tinge in Blue (Hue/Sat)
Create Mask to allow yellow pollen cluster to show and add to Hue/Sat Layers (Replace Color then Color Range Mask)
Create Mask from flower and add a curves layer to darken grey background (Replace Color then Color Range Mask)

The red/yellow grid below shows the actual effects achieved by using the Hue/Sat Adjustment Layer. The corresponding settings used to create the changes are beside each row. Sat (-75) remained the same for all.

The 4 colours in the top (1st) row has only a slight change in hue from each other and are representative of normal colours.

2nd Row – This is the default red channel setting with a (–75) de-saturation applied. As you can see it also affects the 2 orange colours, but the effect decreases as we move towards the yellow colour.

3rd and 4th Row – By selectively adjusting the 2 vertical bars on the colour range menu and the 2 drop-off sliders, I can control the effect of only one of the colours.

5th row - I decided to only effect the 2 orange colours.

As the graph shows, by careful adjustment of the colour range markers (start/stop drop-off) you can fine-tune the colour selection to almost any singular or joining colours of the rainbow.

Any of the other settings can be used to create the same set as that found on Adobe Camera RAW (Hue/Saturation/Luminance).

In the image below, I show 2 examples where in one I change the hue within the narrow range of cooler blues and the other I de-saturate the lemon/lime colour range. I used masks only to adjust half of the image for each change.

You will notice that on the 2 vertical colour bar sets, the top colour shows the range you wish to change and the bottom strip shows the resultant change.

Create a rainbow layer in your image editing software as test layer. By using this layer and a mask to only affect one half, you can compare the overall colour changes of the adjusting layers above in your image. If you then add another B&W gradient on the other axis set to Hard Light (70%) mode, you will get luminance affect also. Some other modes show monitor colour space clipping (bands/gradient edges) because of the larger color gamut created by mode.

In the test example above where the default is on the top and the change applied to bottom half you may notice that when I increased the green saturation it also affected the red saturation (see black circles). By clicking the effects off an on you will notice the changes better.

I have chosen an image that has complex patterns, subtle hues and a full range of colours to best show the selective effect, but it may not be the best artistic expression of this photo. I plan to turn this into a grey scale image but only leave darker reds and blues as they originally are.

Converted to B&W with only 2 narrow colour hues remaining.

There is some work to bring out these 2 different colours, as you need to create 2 separate Hue/Sat adjustment layers to handle each colour separately.

Above: The first layer, above the “Background” layer, de-saturates all the colours on the top-right portions of the image as these areas are out of focus and I did not want any colours there. The next 2 blue layers captures the blue in the image and increases lightness. The same applies for the next 2 red layers.

The image below shows these adjustments

Since each layer de-saturates, then the color set on top will de-saturate the layer below.

To overcome this effect I did 2 ‘merge visible’ to new layers, one for the red set and one for blue set (Ctrl-Alt-Shift-E).

Creating Mask with Replace Color

A mask was created for the red color in order to not affect the blue below.

By performing “Image - Adjustments – Replace Color” I selected all the red parts by using the middle eye dropper (cumulative) to several areas.

I then saved the mask to a convenient location.

To get mask for red layer you press Select – Color Layer and load the layer you just saved. I find it easier to create the mask in the first step than in the second.
To further fine-tune this mask (becomes a permanent change) you perform a curves function (Ctrl-M) and increase steepness in the curve, to create a better B&W mask.

For simplicity and ease I prefer the Camera RAW color controls, but when I need to I can fine-tune almost any colour.

If you have a chance, please let met know how this articles works for you as I find it more difficult to write detailed technical articles. I’m never quite sure if I have too much detail or I assume too much Photoshop knowledge.

Niels Henriksen

A Photographer’s Adage

Photography is like fishing. You go out in the morning with no idea of what the trip will bring. Sometimes luck is on your side and all your crab pots are full of prime Lobsters. Other times you get nothing. - Bob Croxford, From Cornwall With Love by Bob Croxford


Dan Locke said...

Thanks very much for the very well written tut on fine tuing color replacement.

Dan Locke said...

Thanks very much for the very well written tut. Can't believe you have no earlier thank yous!


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