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A Simple Colour Graduated Filter using Photoshop - by Chris Maddock


Following on from my Neutral Density Graduated filter article, this uses the same technique to apply a graduated colour filter.

Here I have an image that I shot at Bedruthan Steps where Murphy's Law prevailed and the sun disappeared behind a cloud bank before giving me any colour in the sky. I'm going to use this as the example and add a simulated warmup grad filter.

 


Now, I only want to warm up the sky (and a little of the distant sea) but a grad filter will give a horizontal transition across the whole image - including the rocks, which I don't want.

So the first thing I need to do is to select the area which I want to exclude. The quick and dirty way to do this is to use the Magic Wand. As it happened, with a tolerance of 32 one click selected all I wanted, so I don't need to alter the selection at all.

Further detailed adjustements to the selection can be made but this is outside the scope of this article.



I now save this selection for use later, by choosing Select->Save Selection. I left the destination as the current file and the Channel as New, just entered something in the Name - I've used "rocks"

Finally, I clear the selection, using Select->Deselect


Now I duplicate the layer (Layer->Duplicate) and leave it as the offered name, before adding a new layer (Layer->New->Layer).

I haven't renamed this layer but I have altered the trancparency to 25%, the reason for which will become clear later.



A quick glance in the Layers Palette shows that I now have three layers - the original "Background" image, a duplicate "Background Copy" and the new "Layer 1"

I now add some colour to Layer 1, to start creating the simulated filter. First I click on the colour picker foreground colour and type in the colours I require. In this case I am simulating a Wratten 85 warmup filter so I use R 228, G 137, B 0.

Other values for different filters are given at the end of the article.

Having selected the colour, I now use the Floodfill tool to apply it to the whole of Layer 1



I now combine the layers Layer 1 and Background copy so that the whole of Background Copy is warmed up. This is done in the Layers Palette by clicking on the arrow at the head of the tab to open the menu and choosing "Merge Down".

This merges just the selected layer and the layer below it in the list, leaving us with two layers - the original image "Background" and the warmed-up duplicate "Background Copy".

Now, as with the ND Grad article, I add a Layer Mask to the "Background Copy" layer.

Now I apply the gradient to the masked "Background Copy" layer. I set the colour picker foreground colour to White, select the Gradient Fill tool and draw a vertical line on the area that I want the graduation to cover.

Voila! one gradient warm-up filter


However, if you look closely at the previous image you'll see that the gradient has also covered the rocks. Not what I wanted.

Never mind, I'd already planned for that - remember the selection I created and saved?

I now load that selection onto the Layer Mask that included the gradient fill, by going to Select->Load Selection, pulling down the Channel list and choosing the entry "rocks".

Once the selection is loaded, I can use it to add that area to the Layer Mask so that the grad fill doesn't cover the rocks.

I switch the Colour Picker foreground to Black (to add to the mask), select the Floodfill tool and click inside the selection.

Now the rocks have been excluded from the grad fill.


Having removed the selection (Select->Deselect) I now want to adjust the amout of the warm-up as it's a bit more than I wanted.

In the Layers Palette I select the Background Layer by clicking on its thumbnail - the image thumbnail, not the mask - before adjusting tthe Opacity slider. 76% is about right so I'll leave it there.

I'm now happy with the result so I flatten the image (Layer->Flatten Image) and it's ready for finishing off.

 


The RGB values I used above were for a Wratten 85 and are those used in Photoshop CS's Photo Filter tool. Other filter values that CS offers are as follows and can be used in the same way when setting the colour of the filter in this technique;

#85: R=228 G=137 B=000
#81: R=235 G=177 B=019
#80: R=000 G=066 B=255
#82: R=000 G=158 B=255

All of the above have an indicated density (transparency) of 25%.


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All text and photos are copyright © Chris Maddock, 2007