The clue about Apply Image is in the name. You can only apply something to the image you have open on the screen.
It’s fair to say that Adobe does not really give you much information about Apply Image.
Apply Image has been around for many years. In many ways, it’s a legacy tool that Adobe hardly ever mentions.
Some Photoshop experts will show you some wild and wonderful image edits using Apply Image. To be honest, some edits with Apply Image are more interesting than useful – and can be easily done without resorting to Apply Image.
Anyway, let’s get started.
Apply Image applies a Blend Mode to the Target (the image you are seeing on screen), using a Source.
The Source is normally the image you have open. But it can another image, of the same pixel dimensions.
From within the Source you can choose:
- An individual layer
- All the layers (Merged)
- An individual channel Red, Green, or Blue or the RGB Composite Channel.
- The Transparency, i.e. the overall transparency of the image.
- You can also choose to Invert the channel/s. As channels are greyscale images. With invert you are turning white to black, and black to white and inverting all pixel luminosity values in between.
Within the target you can be on:
- A blank layer.
- A layer with pixel data.
- An individual channel.
- RGB composite channel.
- A blank Alpha Channel.
- An Alpha Channel.
Are you still here?
By now you should realise there are just too many permutations to predict what results you are going to get in advance.
Unless you stick to tried and tested methods like Frequency Separation you are just stabbing in the dark.
If you are using another image as the source it has to have the same pixel dimensions as the Target.
Apply Image is confusing
I don’t think there’s anyone on this planet who could tell me what result you are going get for all the permutations you can have.
So, don’t worry if you don’t understand it. Just try and stick to one or two methods using Apply Image.
Apply Image is useful for
- Frequency Separation (used for skin retouching).
- Creating simple luminosity masks.
- Refining or creating Alpha Channels for use as masks.
Apply Image Workflow
- Target Image is always the image you have open.
- Using the Target image, select either a Pixel Layer, Layer Mask, individual Channel, RGB composite Channel, or blank layer you want to apply (the clue is in the name) the effect to. This now becomes the Target.
- Go to: Image/Apply Image… Make sure Preview is ticked. With Preview ticked you can see the results in the Document Window in real-time if you are on a blank layer.
- Set the Source Document, which defaults to the image you are working on. So in normal use, the Target image and Source image are the same. You can pick another Source image, only if the image is open, and of the same Pixel Dimensions.
- Then choose the Layer, Channel, or Transparency. Then Invert if necessary. Please note Merged (merged layers) will be an option if you have more than one Layer.
- Pick the Blending you want. There are two Blend Modes called Subtract, and Add which have additional controls of Scale, and Offset. All other Blend Modes behave in the same way as normal Layer Blend Modes.
- You can change the Opacity, Preserve Transparency, or output the result via a Mask.
- Source = Usually the same image. It can be another open image with same Pixel Dimensions.
- Layer = Any Layer within the source. Including all the layers combined which are called Merged.
- Channel = Any channel including, Alpha Channels, Colour Channels, the Composite Channel (RGB) or Layer Transparency.
- Target = Channel, Layer or, Layer Mask, you have selected in advance.
- Blending = Any Blend Mode. Add, and Subtract give you access to Scale and, Offset.
- Opacity = You can make the effect of the blending less opaque if you wish.
- Scale = Only available with Add, and Subtract. Scale divides the result of the Add, and Subtract blends. A scale of One (1) has no effect, two (2) has the maximum effect. Any number above one, to three decimal places, will make the result darker, i.e. 1.578.
- Offset = Only available with Add, and Subtract. The result of the Scale is passed to Offset. Offset has a range of 255 to +255, to darken, or brighten.
- Preserve Transparency = Only the opaque pixels will be affected.
- Mask = Output the result of the blending via a mask.
The two Blend Modes Subtract, and Add is the most flexible because they give you access to Scale, and Offset.
In the scenario above we subtracting the luminosity of the Source, Composite Channel (RGB), from the Target.
Simply put we are subtracting the overall luminosity of the “Target” using the Source Layer’s overall luminosity, or grey value.
It helps to think of Target’s pixel grid laying on top of the Source’s pixel Grid in the same way as the subtraction in maths.
I am not entirely sure what numbering system is used in Apply Image, as Adobe does not divulge this type of information. For all, we know it could be a mixture of integer methods.
But, using the 0-255 system works well to explain with this scenario, where zero is black, and 255 is white, even if it’s not the Integer system Adobe actually uses.
Subtract Blend Mode
Let’s say we have a number of 200 luminosity Pixel Value on the Target layer’s pixel grid. And, the Source pixel has the value of 100 in the same place as the Target on the pixel grid. So the Target is brighter than the source as 200 is brighter than 100 on the 0 – 255 scale.
200 minus 100 = 100 (Target minus Source)
The result is now darker.
Subtract will always Darken, and Add will always lighten.
The scale runs between 1 to 2, and any value between up to three decimal places.
The Scale divides the result from the Subtraction.
A scale of One has no effect for instance 100/1 = 100.
A scale of two has the maximum effect
Let’s assume a Scale of two:
100 divided 2 = 50 – making the image darker.
Note: As dividing any number by one, changes nothing. Any scale number above one will result in a darker result with softer transitions.
The final stage is the Offset, ranging from -255 to +255. The reason for such a wide range is that it’s entirely possible to have a number below zero. For instance minus (-200) luminance. We will only see black on our screen, but the 200 number is stored and passed on to the Scale.
You are effectively using Offset to bring the result back to the visible range of 0 – 255.
Offset to brighten or darken
In this scenario, a positive Offset of 128 would make it brighter.
50 + 128 = 178
Opacity can be useful sometimes if you want to lessen the effect of the blending.
Mask… looks complex, it isn’t. Mask simply outputs the result of the blending via the luminosity of a channel, or area of a selection. By the way, a selection is seen as an Alpha Channel by Photoshop, but you will just see the marching ants.
Let’s say you use one of the colour channels. Anything that is white on that channel reveals. Anything that is black will conceal. And grey will allow results to show depending on how near to white it is.
A little-known method is to select an area on an image first. Then run Apply Image, and everything will be output via the selection. The confusion might come if you want a selection as a Mask, which as in the example above. which is really counterproductive.
You might find it useful to learn verbatim Frequency Separation for portrait retouching.
There’s a link below to an article I’ve done Frequency Separation.
Play around with Apply Image as part of your Photoshop learning curve. To be honest, don’t waste too much time on Apply Image.