Understanding Luminosity selections

In short, Luminosity masks are masks created from luminosity selections. These are selections based on brightness of pixels. The most basic luminosity selections would be then:

• Bright – This selection selects every white pixel by 100%, every black pixel by 0%, and everything in between based on their brightness. So the brighter a pixel is, the more it is selected. So 25% grey pixel would be selected by 75%, 50% grey pixel would be selected by 50% and 75% grey pixel would be selected by 25%.
• Dark – This is the inverse selection to the bright one. A white pixel is selected by 0% and a black pixel by 100%. Everything in between is selected based on how dark it is. So 25% grey pixel would be selected by 25%, 50% grey pixel would be selected by 50% and 75% grey pixel would be selected by 75%

These two selections split an image into two parts. The part that is mostly dark and the part that is mostly bright. A pixel with a 50% grey color, would be right in the middle, selected by 50% in both. I know it’s a bit hard to get the understanding of this, so let’s look at a very basic image, that illustrates this. This is a just a gradient from black to white.

If we do the Bright and Dark selections here, there results would looks like this (this is already shown as a mask, as you can’t display opacity graduation in a selection, white means 100% selected, black means 0% selected).

Bright selection

Dark selection

As you can see on the Bright one, everywhere where it was bright in the original image, there is a shade of grey up to white. On the Dark one, you get the inverse, and it affects the areas that were dark. Let’s looks at one more example, this one with a regular photo.

Original photo

Bright selection

Dark selection

You see the same effect. The Bright selection selects only the bright areas (clouds, snow), the Dark selection only the dark ones (mostly mountains).

There are also Midtone selections, which are created by subtracting Bright and Dark selections from a photo, but I will get to those in a separate article.

Refined Luminosity selections

You often here these selection being referred to as Bright 1, Bright 2, Bright 3 … Dark 1, Dark 2, Dark 3… and so on. In this context, the Bright selection I mentioned would be equal to Bright 1, the Dark to Dark 1. All others are refinement of these selection. By creating an intersection of a selection with itself, you create a new, more restrictive selection. So the higher the number here, the less is selected. On the gradient image I shown you earlier, the restricted masks would looks like this:

Bright 1

Bright 2

Bright 3

Bright 4

Creating Luminosity selections and masks in Photoshop

Ok, now that you hopefully at least have an idea on how luminosity selections look, let’s go into Photoshop and create some.

Open you image in Photoshop, and go into the Channels window. Here you will see 4 layers. The RGB, Red, Green and Blue. We want to work with the RGB one. Hold down Ctrl and click on it. This will create the Bright selection. Click on the Save selection as channel button in the bottom right (white square with black circle in the middle) and this will create a new channel. Let’s rename it to Bright 1.

We will now work with this one. You should still have your selection active. Hold down Ctrl+Alt+Shift (a small X should be next to your cursor) and click on this new Bright 1 channel. The selection will change. Save it again as a new channel. Name the new channel Bright 2.

You can now continue like this and create further, more restrictive selections, Bright 3, Bright 4, … and so on. If you ever loose your selection, just Ctrl+click on the one you want to restrict further, and the Ctrl+Alt+Shift+click on the same one again. Doing so on Bright 1 will create Bright 2, on Bright 2 will create Bright 3 and so on.

Now onto the Dark selection. Go back to the RGB channel and Ctrl+click on it. This will create a Bright 1 selection. Now hit Ctrl+Shift+I on your keyboard (or select Select/Inverse from the menu). This will change the selection to the Dark 1 selection. You can create a new channel from this selection and call it Dark 1. To create all the other ones, just follow the same steps as when creating the Bright selections.

If you want to avoid having to do this all the time, you can make it easier on yourself. Create actions that makes these masks, or buy Raya Pro or TK actions. Both of them create all the masks for you in one button press.

Once you have these channels, just choose one you want to work it and create a selection of it with Ctrl+click. If you want to make it into a layer mask, go back to layers with the selection active, choose the layer you want to use and click on Add layer mask (button looks the same as the one we used to create channels, in the bottom right of the layers window)

Higher ISO or bigger aperture?

So which one? Both approaches have their problems. When you use a bigger aperture (smaller F number), you loose the depth of field and sometimes also sharpness. When you use higher ISO, you are getting more noise and sometimes, when you go too high, you may loose small details completely.

I look at it this way. You can remove noise in post-processing, you can’t change a blurred area into a sharp one (OK, Topaz Sharpen AI can partially do it, but the results are not the same). As cameras are getting better and better and have less noise in higher ISO, the approach here is quite obvious.

Try different ISO settings on your camera, to determine the highest one you are still comfortable to use. I prefer not to go more than 400 to 800 ISO on my camera. I know that a higher one would still give a nice result, but I prefer to stay a bit lower. So once you can no longer use ISO 100 or lower, stick to the F stop you want to use first. Then raise your ISO until the ceiling you determined for your camera, and only after that start going to bigger apertures.

Different solutions

• Manual focusing. If you focus manually on exactly what you want, you can get away with using a bigger aperture, without loosing the depth of field you want. Having a look at focusing using Hyperfocal distance will also help you to maximize it.
• Underexposing a photo. A way to get over the 30s limit, is just to underexpose the photo. When you shoot in RAW, you can get few exposure stops from it. So you can take a photo that is 2 stops underexposed and then just overexpose it in post-processing. Can save you a lot of time in the field.
• Bulb timer. You can stick to your ISO and aperture, and just use a very long exposure. Some cameras have bulb timer build in, for some you need a remote. Bulb timer is a great solution if you have a lot of time to spare. But that’s often not the case. For instance, taking photos during a short blue hour. It’s just over so quickly. If every photo you take takes you 5 minutes, you take only very few.
• Focus blending. Depending on the scene you are capturing, you can try doing focus blending. Instead of one long exposure, do multiple shorter ones, with bigger aperture and different focus points. Then blend them into one in post-processing.
• Tilt-shift lens. One of the ways one can use a tilt-shift lens, is to tilt the focus plane. It’s mostly used to get a shallow depth of field, but you can also go the other way. You can use it to get a bigger depth of field, while still using a bigger aperture. Like that you can use a shorter shutter speed and lower ISO.
• Magic Lantern firmware. If you have an older Canon camera, you can use the Magic Lantern firmware on it and so remove some of the camera’s limitations. It provides a build in bulb timer and also allows for longer than 30s shots when doing bracketing. Overall, it gives so many features, that’s it’s worth a try.

Paul Couturier bridge in Lyon

After the rainy photos, here is one from a very sunny day in Lyon. It was so hot and sunny that day, I was not able to stand for 5 minutes in the sun. I was getting dizzy from the dry hot air. Really not my kind of weather.

This was taken on the red Paul Couturier bridge in Lyon, few years back. I managed to find a flat for rent like 10 min walk from this bridge, so I returned here every day to get my photo. And while waiting for nice clouds or a sunset, I never got one. The whole week I was there, the sky was clear or with only a bit of hazy clouds, like on this photo. I also tried the same photo in the evening, but since there are light that shine through the sides of the bridge, I got a crazy amount of flares. Will have to try that again next time.

This is a three shot blend, done in Photoshop. For my suggesting for photography spots in Lyon, check out the list here.

Photoshop shortcuts for photo editing

• Ctrl+Z – undo. I’m only including this, as recently the undo behavior changed in Photoshop. Ctrl+Z is now a regular undo and you can press it multiple times to go back in editing history. Previously it toggled the last state instead.
• Shift – restrict movement. Holding down Shift with most other tools in Photoshop will restrict what you do to only horizontal or vertical movement. So for instance when you are using a brush and want to do a straight line, hold down Shift and draw your line. It will be straight. You can use the same with Clone stamp tool, Gradient and other tools in Photoshop
• Space – pan. The most basic shortcut. When you hold down space, you cursor will change into a hand and you can drag around your image. Using scroll bars or zooming in/out is just not as effective.
• Ctrl+Space – zoom in. After moving around, zooming is the second most common thing you will do in Photoshop. When you hold down the keys, the cursor changes to a magnifying glass and you can zoom in by clicking. You can also hold Alt+Space for zoom out, but I never use that. The shortcut is not as comfortable to use. Instead, while holding down Ctrl+Space I right click, and from the menu choose Fit to screen. This makes for a very fast navigation overall
• Ctrl – move. By holding down Ctrl, you will temporary switch to the move tool. It’s just for the time you holding it. So you can for instance be painting, and you notice you want to move something. Hold it down, move what you need, and just let it go and return to what you were doing.
• B – brush. When masking photos, you will use the brush a lot. Not needing to go back to the tools panel will save you a lot of time
• Alt+RMB+move mouse – change hardness/size. One needs to change the hardness and especially the size of a brush very often. To avoid having to go to the toolbar all the time, there is a simpler way. This works of course only when the brush tool is selected. What you do is to hold down the Alt key together with the right mouse button. A circle will shot up. Now move you mouse left to decrease the size of the brush, right to increase. Move down to increase the hardness, up to decrease it.
• D – default colors. Hitting D on your keyboard will set the foreground color to black, with the background to white. Especially in masking you will use these two colors a lot, so this makes for a great and easy way to reset them. (btw. when you have a mask selected, it defaults to the opposite, so black foreground with white background)
• X – switch colors. Using the X key will switch the foreground and the background colors. Again, really useful with masking, where you switch between white and black all the time.
• Ctrl+T – free transform. Another one you will do all the time. This will let you transform your selection. Don’t forget, that you can change the way you transform by just right clicking the selection and choosing from the menu. Perspective, distort and warp are really useful in photo editing.
• Ctrl+I – invert. Pressing this combination will create a negative of you photo. Not really that useful there, but much more with layer masks. For instance when you have a mask that selects all the light parts of a photo, just press it and you have a mask that selects all the dark areas of a photo.
• Ctrl+D – deselect. Everybody knows Ctrl+A is select all. But you will not use that that often in Photoshop. Instead, especially if you work a lot with selections, you will need to deselect quite a lot. And going through the menu all the time is just too much of a hassle.
• Ctrl+H – show/hide extras. Things like marching ants, guidelines and grids are very helpful when editing. But sometime there are just in the way. You need to see what you are doing without any distractions. In this case, just hit Ctrl+H to hide them all. But when you can’t find them afterwards, don’t forget to turn them back on :)
• Ctrl+Alt+Shift+E – merge visible. Often during the editing, you need to merge all the layers you already worked on, into one. For instance when you are using a plugin and you want it to work on more than just the last layer. Pressing this combination will merge them all and create a new layer on top.
• Shift + Backspace – fill dialog. Another one that you will use all the time. This shortcut opens the fill dialog, where you can fill a selection with a specific color. But the more important use is that you can choose content aware as the fill option here. Like this you can use Photoshop to quickly fill in missing parts of a photo, or to remove objects or people from it. Just do the selection around them, open the dialog, choose content aware and confirm.
• Ctrl+click on layer – select layer content. Another useful shortcut when working with layers and layer masks. If you hold down Ctrl and click on a layer in the layer window, the whole content will be selected (which with photo is mostly the whole image). But when you click on a layer mask, everything that is white is selected. This is very important in editing and the creating of luminance masks. You want to restrict your selection, and this is how it’s done.

Let’s end here so this does not end up like a Photoshop manual :) There are many other shortcuts and the ones you use will mostly depend what you do there. But in photo editing, I think these are the ones you will use all the time. After a while, you will even stop thinking about them and just use them automatically.

Sphere in Nursultan

Still raining today, so let’s continue with another photo from a rainy evening. Even if again you will not see the rain in the photo.

This one is from the Expo Sphere building in Astana, or better said Nur-sultan. This is because the name of the Kazakhstan capital city Astana was changed about 3 weeks ago. So now it’s Nur-sultan (I seen it being written as Nursultan and Nur-sultan, so not sure which one is right). Probably the first time I ever been in a city which changed it’s name. Does not happen that often.

This is a three shot blend, all done in Photoshop.