Lessons

Lesson Info

Creating Masks with Channels

normally when we talk about doing things like making selections and so on we have a variety of selection techniques I'm gonna talk a little bit more again about that tomorrow with compositing but if you think for a second when we make a layer mask really what's happening is safer in the sake in this example if I wanted to replace the sky in this photograph in just the sky my mask ultimate looked like a black silhouette of the boat house the trees everything else and the sky would be white that's what would be a perfect mask the problem is it's got all that fine little detail in the leaves and everything and trying to use any selection method could be quite challenging you could try it but it's going to be tough so one of things that we have to think about is when we create a mask uh just do a quickie here so there's my laywer mask and it's black on white whenever you have a layer mask it's temporarily in the channels panel just as black and white information so ultimately that's what I...

'm asking is is different shades of gray so if we think about that a little bit that means we might be able to use this information in an interesting way rather than trying to build a mass based on some selection and trying to I don't know I don't know how you even do it color range maybe magic one maybe I mean it would be a lot of effort instead we do something called a channel based selection now when I'm making selections a lot of the time I'm taking photographs of people on a plain background with the express purpose of taking them off that background so I can use standard selection methods but a case like this where later on to look at and say yeah I think I might want to try this that would be an awful lot of effort so that's when I go to this channel based selection method and the way that it works going toe look att each of these channels and try and find the one that gives you the most the best start towards a black silhouette and a white sky and right now it looks like the blue is the best but I'm thinking I could give myself and even better start by doing something else and that something else is one of two things either add an adjustment layer and we'll use black and white I don't want a black and white photo but I'm doing it as an adjustment layer which means I can go in and I can try to really darken up everything in this photograph so I get it looking the way that I want so it's already closer to what I want let's do one morals do eh the level's adjustment lair dark and that leyton this a little bit like that so that's already starting toe look kind of towards a mask so this point now I could go back to the channels panel and now when I look at the red and the green in the blue they're all pretty much the same because of the adjustments I've made now the next part of this operation is crucially important so we don't do this part you will wreck your photograph we don't want to actually work on the red green or blue we want to make a copy of one of those so I'm gonna take the blue channel and drag it down on top of the new channel icon and it says blue copy it's extremely important that from now every step forward I'm working on a thing that's called something copy either red green or blue copy if I'm working directly on the red green or blue channel I will wreck my photograph in ways that will not make anyone happy so once I've done that now I can get rid of these adjustment layers because they've served their purpose was very important I use adjustment layers rather than something under the image adjustment menu because those I can't just throw away so the nature of adjust mirrors of their temporary now I mentioned could have done this in two ways the other way is since this is a camera raw smart object I could have double couldn't gone camera raw and move sliders around to try and make it more black and white so we'll talk about that tomorrow as well but that would be another option so at this point I go back to my channel that blue copy I made and now my goal is to make this as black and white as possible now in a real world scenario if I was being really clever I would probably want the lake to reflect the sky a little bit but for our purposes I'm just going to not do that just take it ease so at this point I'm going to try to continue making this black and white no shades of gray so I do that in several ways I can use levels again on here and try and say let's take everything grey and make it darker and let's take everything that's great in the sky make it lighter now the only word of caution here is when I first tried this I was like moving sliders like way really far really quickly when I in this zoomed out view it looked fine when I zoomed in actual size I noticed fine little details were getting lost so use this sparingly don't go too far or else you'll notice the little leaves suddenly disappear completely in fact this is already probably a bit much for what I want to do at a certain point the likelihood is like in this case it's going to be easier for me to say this whole part down here needs to be filled with black so I just make a big selection say let's just get that into black okay because at a certain point I just need to do that let's get a little closer we can see some areas here for example that part of the roof is gray it needs to be black and there's some other similar areas like that but you can see how most of the details least I think I went a little too far because you can't see some of them quite as much so one of the things that is your best friend when it comes to working on masks like this like let's look at this part over here see that bit of gray and the sky that really needs to be white not gray but if I took my paintbrush and simply painted with white I would be in danger by mistake hitting the tops so these trees which actually looked pretty good so I press b for brush and then I use a wonderful option which is to change the blend mode of the brush to overlay so I pressed command option she's me options shift ofer overlay organise change it up here I usually lowered the opacity a bit too and overlay is a mysterious mode that someone adobe probably could explain better than me because this this whole engineering thing but the benefit of playing an overlay of painting and overly mode is look where my brushes I'm right on top of those black bushes there if I attempt to paint right now with white nothing's happening because an overlay white cannot change the color of black it only change the color of light grey so this way I can go right over here not even have to worry about it without I'm not being really careful about staying within the lines because overlay mode is doing it for me over here where I have medium gray that's supposed to be black I'm still in overlay modes which my color to black and now it just lets me paint away all those gray areas without worrying about getting into the white by mistake so someone years ago discovered this and share it with the rest of this and they should get the nobel peace prize for photo shop if there was such a thing because this has made life so much simpler eyes to be zooming in being very careful with my paintbrush and undoing now just kind of go yeah that's good works well one tip that I suggest is I find if I've been staring at something for too long like in this case black with a white sky I'm worried I might miss something because I'm my eyes are just so attuned to it so even though I wanted to end up this way black silhouette with white sky temporarily I might press commander control I for invert and this way I can look at it the opposite and sometimes I'll notice something oh I missed that part there because now your eyes spot something different that you might not have seen before so that's always a choice you can make and eventually you end up with some thing that looks the way you want but it's a channel not a mask so if I command of control click on any time you hold down commander control and click on something like this wherever it is whether it's in the layers panel channels panel it'll turn into a selection so now after doing all that I could go back to my layers panel and click on the ad layer mass button and now I have a cut out ready to go or fine since I'm doing a new sky here's another interesting option if I take this sky select all copy but this case is that of choosing paste I don't want to paste on the mask I want a paste it into this area there actually is a function that's called paste into when you have an active selection and you choose paste into a couple of important things happen it makes a mask but also the mask and the layer unlinked normally when you add a layer mask it's linked with the layer so if you gotta move the layer the maskell moved with it in this case that doesn't make a lot of sense so I'd much rather have them unlinked like this and that happens automatically so now I can do this anyone gonna flip this the other ways the clouds over here now clearly it still needs some work and the edge still needs to be a little better and we'll talk about that again in more detail tomorrow but it's at least want to show you that when you have what appears to be a very challenging selection using this channel based method to make a selection as often going to give you a pretty good result quite quickly at this point I could once again go back to this mask edge and see if I can't tweet the results a little further using this and again we'll get into all that more detail to morrow but since we're talking about masks this is one nice way to make a mass is use the channel based information that's already there one other possibility I don't like this quite as much but it's another interesting option is a function called calculations and this will let you have a dialog box and this is extremely important to have the preview button turned on and you can say what happens if I took the green channel and the blue channel and I had them set to multiply or overlay and sometimes you'll do that kind of go oh that's kind of a good start and then you can use that to make a new channel so instead of just duplicating the red green or blue this gets you closer start and it's there's no formula I found that says I always use green and blue or red would it varies with the document usually it's either overlay or multiply but that's another way that we can at least get a good start another way we can take advantage of the information's already in the channels and this is a little bit different is there's a mode in photo shop called l a b mode and this is different than than our normal way of working in photo shop and it gives us a very specific instance where we khun change something normally if I'm taking a photograph of someone with the intent of extracting them off the background there's not a huge advantage to using a green screen or a blue screen with one exception and that is if you've got one hundred fifty kids and you want to automate it because I'd figured out a way why can automate extractions off of a green screen potentially a blue screen that's quicker than we have to do each one by hand and involves this thing called l a b mode and one of the reasons we can do it is because you'll see norman we create an action to automate something there are certain things you can't record in action like make a selection is not something that would make sense to record because every person is a different shape so recording that shape wouldn't work so I want to do it based on wherever there's green use that to create the mask and the only challenging part in this case is he has a little bit of green in his eyes jersey which could present a bit of a problem but well we'll see so normally when we look at a document course it looks like this rgb red green blue and each channel is just a slight variation but you can see none of these would give me really that great a start toward take a lot of effort for me to turn this into a nice mask so instead I changed the mod to this thing called l a be color which describes our document still visually looks exactly the same but in the channels panel now we see three channels lightness which is kind of the grayscale information and the color is contained an a and b and we look at the a channel to me there's pretty good contrast there even though there's still gray in there I can see enough difference between these two that that should give me a good start so again crucial that I duplicate the channel and work on something called a copy now rather than use levels and moved triangles and things that I want to be able do this so that for every single photograph I'll do it the same way because I know people recorded as an action so the way that I do this is I use phil and this is always gonna be an overlay mode so it use that same functionality showed he was going to go where overlay on ly affect certain things so if I start off by saying fill with white in overlay mode it means white will on ly affect the things that are slightly darker than it which in this case would be all these sort of medium grade not the dark ray so I click okay see how it got pretty white and the background is still different enough now I go back to jews fill this time with black and click okay black again and then one more white got a mask I didn't have to any painting I don't do any selecting it's just change the mode to l a be copy that channel very important and then do those steps and it occurred to me that because I'm not doing any select painting those steps could easily be recorded in action because always the same then at this point I change the mode backto rg because that was just a temporary mode to get me working but now aikens a load that is a selection go back to the layers panel this is where I would typically do refine ad just to see but you can see overall looks pretty good already and then make a layer mask so if I had I didn't in this case because I want to talk about it but if I know this works now then I wouldn't need to go to my actions panel a new action start recording to exactly those same steps I just did l a b mode b channel copy or sees me a channel copy fill in overlay which I happen to have done previously I'm sure I have one that must that's a c m pretty sure I have one in here that's called something about green extract there it is so this ipod recorded previously now for any green screen photograph I just had play and it goes all to this point and it pauses at refined edge for me to tweak it so all remains for me to do is go okay I'm done so that I have yet to see any method that that could be done with anything other than green because every other cop is like a white background there's no automated function of you to say select all the white it would be way too hard so I've done this with a siri's of photographs where I wanted to get to this point now is it perfect no and if I did a hundred kids of football players there might be ten or twelve that need some work because now they have green eyes now they have little holes where their eyes were but at least it's a mask so I can go on edited in this case that happened that this kid was a day when this is for a project I was doing as a demonstration he showed up in the first day I saw he had green on his uniform was like great but it happened that the green was just different enough than the green backdrop that it was still partially there so when you look at the mass you can see there really is is just a tiny seed on there I can see it better in mind there's the hair a very light gray which means it's got just enough of that green but I can't really see it but if you compare the alternative if I had two on one hundred photographs manlio make a selection refine edge make a mask I'd go with this every day because I would go batch folder walk away from my computer come back and see a hundred psd files with a mask waiting to be tweet now there is a little bit of green notice about his hair and we're not going to fix it now we're going to fix it tomorrow so I have a version of this where you can see what what do you do when you have a problem where there is a little bit of colored fringe which happens around someone here we'll look at some examples of that during our compositing thing so I've always been using that for green screen but then I thought what what about blue because in l a b mode you can work with blue now so I brought this line into my studio in front of a blue backdrop no no I did I was looking through stock photos and went oh look there's a line in front of a really blue sky and there's like no clouds right and I thought that might work as well so I tried it and I was very happy to see it were pretty much the same with one little difference and that is when you go to l a b mode in this case it would be the b channel not the a channel a channel doesn't have enough contrast the bee does so then the rest of his the same duplicate fill with white fill with black fill with black I can see why I don't want to automate this fill with white pretty good mask just have to make it into one now do you use either the air there be for and is very specific a works with green be works with blue great so it's one of the other ok now you can see in this case it worked pretty well but there's a lot of blue fringy stuff going on here so I'll give you a little foreshadowing of what we're going to talk about this is where I would try a couple different things the first one I would try his mask edge and in here there's a function called decontaminate colors and sometimes if you pull that up it'll get rid of some of it it's not bad sometimes you can just get away with applying levels to the mask and as you push it now it's actually kind of compressing or contracting the masses a bit so I would do as much as I can and then finish it off this is to force people to come back and watch tomorrow you see howto really fix it tomorrow but even now I I I got ahead of myself because I really shouldn't make a decision yet as to whether it looks good until I really tell because I don't think I just want extract the lion and have transparency behind them I'd like to have you know another photograph so let's put another photograph in there and see what it looks like cats better I can still see a bit of that fringing but one of things we will talk about in our compositing segment tomorrow is you want to everything in context there's no point in just extracting a lion onto a lair by itself without thinking but what is the back room gonna look like is then colors might actually look better than you think they are or if you know he was up here that blue doesn't look as bad anymore because other blue so that it really you have to think about context before we go too far doing all that kind of stuff