Joel Tjintjelaar

Creating 16-bit luminosity masks

Creating 16 bits luminosity masks and half masks

A tutorial on the creation of the normal (integer) and half luminosity masks in 16 bits for Photoshop using the Calculation and Levels method combined without loading selections.

In one of my older blog posts from 2014 I explained in detail how to create luminosity masks, using a simple method. That article describes the basic way of creating luminosity masks by loading and intersecting selections.

The downside of this method is that it only allows you to create a limited set of luminosity masks: luminosity masks in between the integer values, what I call half value luminosity masks, cannot be created using this method. Another downside, more theoretically than practically, is that since selections are used to create the luminosity masks in this method, they will always be 8-bit masks instead of 16-bit masks, as a selection is hard-wired in Photoshop to be 8 bits.

The method I’m describing here is a 16-bit method of creating masks that allows you to create any value between the luminosity masks with integer numbers, without loading selections during the creation of the masks, so the 16-bit depth of the channel masks will be preserved. It’s a method that has been described earlier by, of course, Tony Kuyper and several other photographers. I’m trying to put variations on this method with the Levels tool together in one article and at the same time describe how to create the in-between values when applying this slight variation to the 16-bit method as described earlier by Tony Kuyper and others.

A 16-BIT METHOD FOR ‘NORMAL LUMINOSITY’ MASKS WITH INTEGER ‘FULL’ VALUES

Below you will find the suggested sequence of creating 16-bit luminosity masks with integer values. There are variations on this, but they all come down to the same: start with either Lights1 or Darks1 or both, and then it’s easy to create the rest of the masks.

Lights1 Mask – Navigate to Image > Calculations. Select the layer of which you want to create the luminosity mask. Usually, you’d start off with the original file, so choose background layer. Also, at this point, you would usually have no channels yet, other than the Red, Green, Blue and Gray Channels. Choose Gray under Source 1. Do the same For Source 2. Set the blending mode to Normal and Opacity 100%. The result is New Channel. This new channel can be found under the Channels tab and will be called Alpha 1. Navigate to the Channel Tab, stand on the Alpha 1 channel and rename it to Lights1: you have your Lights1 luminosity mask in 16 bits.

Darks1 mask – After creating the Lights1 mask, I would continue with Darks1, instead of creating Lights2, 3, etc. But that’s all up to you. Navigate to Image > Calculations, choose the same settings as for the Lights1 mask, but check the ‘invert’ boxes this time. The result is again New Channel that can be found under the Channels tab and will be called Alpha 1 (or Alpha 2 if you haven’t renamed the first one yet). Navigate to the Channel Tab, stand on the Alpha 1 channel and rename it to Darks1: you have your Darks1 luminosity mask in 16 bits.

Lights2 mask – Lights2 and other subsequent masks in the light series, can only be created after you’ve created Lights1. Navigate to Image > Calculations and under Source 1 > Channel, now select Lights1. The same for Source 2. Now set the Blending mode to ‘Multiply’ instead of Normal. This has the same effect as intersecting the selections in the 8-bit method. Everything else is the same. Again the Result should be New Channel and if you look under the Channels tab you will find your newly created Alpha channel. Rename it to Lights2 and now you have your Lights2 Luminosity mask in 16 bits without loading the selections of the mask. You can now create Lights3, 4, etc. the same way as Lights2. Of course, make sure that the input channel for Lights3 under Source 1 and Source 2, are the preceding luminosity masks, in case of Lights3 that would obviously be Lights2, and so on and so forth.

Darks2 mask – Similar to creating Lights2 masks off the Lights1 Mask. Navigate to Image > Calculations. Select the preceding masks, in this case, Darks1 under Source 1 and Source 2 and Blending Mode is set to Multiply. But do not check the Invert Boxes this time! You only need to do that for Darks1 once. The rest is exactly the same as with the Lights2 masks. Don’t forget to rename the new Alpha Channel to Darks2. Creating Darks3 and higher will be exactly the same, every time choosing the preceding channel as input channels with blending mode set to ‘multiply’.

AN ALTERNATIVE 16-BIT METHOD WITH LEVELS AFTER THE INITIAL MASKS HAVE BEEN CREATED

Lights3 Mask – Levels step 1 – To be able to create the in-between luminosity masks like Lights2.5 or Darks1.5, you need to know how to create the luminosity masks using the Levels tool instead of the Calculations, after you’ve created the initial Lights1 and Darks2 masks. There’s no way, at least not to my knowledge, to create the in-between luminosity masks with the Calculation method. Since I’ve already created the Lights2 in this example, I’m going to create the Lights3 mask, now using the Levels method. First duplicate Lights2 that has already been created with the Calculation method by right-clicking on the Lights2 channel. The dialogue box will then ask you to give the duplicated channel a name. Rename it to Lights3.

Lights3 Mask – Levels step 2 – After duplicating the channel mask to a new channel called Lights3, stand on the channel. Make sure the correct channel is highlighted and the ‘eyeball’ is on. Only then you have selected it correctly. Then navigate to Image > Adjustments > Levels. You will see that the box with the value in the middle, the Gamma box, is set to 1.00. That’s the value you need to adjust. Leave the values in the boxes on the left (black point) and on the right (white point) as they are.

Lights3 Mask – Levels step 3 – Go to the Gamma box in the middle, and change the value to 0.5, then click OK. You’ve now created the Lights3 mask with the Levels tool by starting with a copy of the Lights2 mask and changing the mask one whole value to the next integer, by changing the Gamma to 0.5 while at the same time preserving the 16-bit depth of the channel.

The same procedure can now be followed to create the subsequent light luminosity masks to the next integer value, by ensuring you always use a copy of the preceding luminosity mask as the starting point for the new luminosity mask. Of course, the same procedure can be followed to create the new dark luminosity masks without the Calculation method.

CREATING ‘HALF’ LUMINOSITY MASKS IN 16 BITS

Creating half values in 16 bits
To create the luminosity masks with half values like Lights2.5, and preserve the 16-bit depth, we start out with the method to create the initial masks such as Lights1 or Darks1 described above, using calculations and then continue with the Levels method to arrive at the desired masks with half values or ‘full’ integer values. In this example, I’ve already created Lights2 and Lights3 masks using the 16-bit method, and I now also need the Lights2.5 mask as I find Lights2 too light and Lights3 too dark. All I need to do is to duplicate Lights2 and call it Lights2.5, the same way as described in the previous paragraph and then go to Image > Adjustments > Levels and instead of setting the Gamma value to 0.5 to arrive at the next Full value (Lights3), I set it to 0.75 and then click OK. By doing this I arrive at the next Half value: Lights2.5. This can be repeated for all other Half values, just by taking the preceding Full value and then adjust Gamma in levels with 0.75. Or, alternatively, to arrive at Lights3.5, you could also take Lights2.5, and then set the Gamma value in the Levels tool to 0.5 to arrive at the next Half value. Gamma value 0.75 always takes you a half value further, while Gamma value 0.5 takes you a full value further from any starting position.

MID TONE MASKS IN 16 BITS

CREATING THE MID TONE MASKS AFTER LIGHTS1 AND DARKS1 ARE CREATED

To create a mid-tone mask in 16 bits you have to create the Lights1 and Darks1 masks first foll

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