Layer Masking - Its Black & White


McGregNi

Link Posted 16/11/2014 - 20:29
I want to share some thoughts on Photoshop Layers, in particular layer masking concepts. It seems to me there a good number of quite incomprehensable processes in Photoshop, and many unintuitive methods and terms ... 'burning, dodging, unsharp mask?'

Layer masking has its own peculiar working approach which I want to focus on here ... I like to think things through in a unique way, and share that when I have found a good approach to understanding something - thats why I like doing guides to things.

I'm going to restrict this thread to the use of black and white 'painting' on layer masks. This is really a rather unusual, and not at all obvious method of working I found - certainly I struggled to 'get it' when I started out with Photoshop. Now its automatic, but I realise I had to come to understand it in a different way to the designers of the software!

Firstly, its important to understand that there is a total difference between painting onto an actual 'image' layer, such as the main background layer or a duplicate of that, and 'painting' onto a layer mask. On an image layer, that contains actual pixels, it can be thought of as representing real painting - you choose a brush and colour and the paint goes on top of the image and covers it as you go.

Now on a layer mask this is not the same at all. It should not be thought of as 'painting' paint onto the layer ... but what is it actually then, and why does it still use brushes and colours?

I see it like this .... on a layer mask the process we are applying is actually targeted and controlled opacity settings. Now, the layer with the mask has its own Master Opacity setting, that fades it in and out, and fades its effect on the image below it. But we don't always want the effect to apply to the whole image, and that is the point of the mask ... to allow us to apply the effect to controlled areas of the image and in controlled 'amounts of fade' also.

Say we used a Saturation/Hue adjustment layer, and increased the reds using that ... but we only wanted the reds to be increased on some boats in a harbour ... we didn't want the reds to increase on the sandy beach, because what was good for the boats was too strong for the sand. So the mask is to allow us to fade out, or block completely, the increased red effect over the beach area, but allow it to apply to the boats.

Now this is where masking comes into it. How do we mask? Well, you paint on some black with a brush! What? No, that can't be right! Well, on the surface it is right - but really, no - we're not painting black paint onto the mask. The black and white paint is just a way the software designers have decided to use the available tools to apply selective and controlled opactity settings on the mask ... and its not a very eloquent solution in terms of the concept, but it does work.

So what the paint is actually doing is using a colour range (black through to white) to represent mentally actual percentage amounts of layer opacity settings ... so, black represents 0% opacity, meaning that nothing from the masked layer will come through ... and white represents 100% opacity, meaning that all of the applied effect on the masked layer will come through.

So, take our red sandy beach ... after applying the saturation adjustment layer the beach has gone bright red ... now 'painting' on the layer mask with a 'brush' in black over the beach area tells the software you want to reduce the opacity of the layer to 0% on the parts that you move the mouse over . Thats a more accurate description of what is actually happening. Therefore the beach will go back to its colour before you applied the extra red.

Likewise, using a white 'brush' and 'painting' back over the beach again, tells the software that you now want to increase the opacity of the layer to 100% on the parts that you move the mouse over. Therefore the beach will go back to bright red as the increased red from the layer is now allowed to be applied fully to that area.

So how do we make an effect partly apply, like 75% of its strength? What colour do we have to use then? Well, this is where the whole painting with colours thing falls down - we don't pick some colour that is 75% of black (although we can use 50% grey), but rather we simply adjust the fade strength (also known as opacity) of the brush effect - like applying less pressure on a real brush. This is done on the tool setting itself, not the layer. So its still black to set 0% layer opacity over the area, but then the brush too is made weaker by its opacity setting (eg 75%, in which case it will actually create a layer opacity setting of 25% over the area). Thats the actual computational process going on - its not about black & white at all!

Hope I've kept you with me on this! And I hope its been on interest and a help .. if anything I hope it will stimulate more thinking and discussion right here about layer masking
My Guides to the Pentax Digital Camera Flash Lighting System : Download here from the PentaxForums Homepage Article .... link
Pentax K7 with BG-4 Grip / Samyang 14mm f2.8 ED AS IF UMC / DA18-55mm f3.5-5.6 AL WR / SMC A28mm f2.8 / D FA 28-105mm / SMC F35-70 f3.5-4.5 / SMC A50mm f1.7 / Tamron AF70-300mm f4-5.6 Di LD macro / SMC M75-150mm f4.0 / Tamron Adaptall (CT-135) 135mm f2.8 / Asahi Takumar-A 2X tele-converter / Pentax AF-540FGZ (I & II) Flashes / Cactus RF60/X Flashes & V6/V6II Transceiver
Last Edited by McGregNi on 16/11/2014 - 20:48

johnriley

Link Posted 16/11/2014 - 20:37
Quote:
and many unintuitive methods and terms ... 'burning, dodging, unsharp mask?'

For anyone who has ever done any film darkroom work, these are very intuitive terms. Burning is giving more light to an area to make it darker, dodging is holding back light to make an area lighter, unsharp mask is a film process for giving an illusion of sharpness. The earliest mention of this last term that I have found is in the early 1930s, but it may predate that.
Best regards, John

McGregNi

Link Posted 16/11/2014 - 20:53
johnriley wrote:
Quote:
and many unintuitive methods and terms ... 'burning, dodging, unsharp mask?'

For anyone who has ever done any film darkroom work, these are very intuitive terms.

No doubt John, but that is part of my point .... we are not talking about darkrooms ... we are talking about a computer software image manipulation effect - this is about the user of a computer programme, and how that user interacts with the process through the 'man machine interface'. From this perspective then physical darkroom practices are 'unintuitive'.
My Guides to the Pentax Digital Camera Flash Lighting System : Download here from the PentaxForums Homepage Article .... link
Pentax K7 with BG-4 Grip / Samyang 14mm f2.8 ED AS IF UMC / DA18-55mm f3.5-5.6 AL WR / SMC A28mm f2.8 / D FA 28-105mm / SMC F35-70 f3.5-4.5 / SMC A50mm f1.7 / Tamron AF70-300mm f4-5.6 Di LD macro / SMC M75-150mm f4.0 / Tamron Adaptall (CT-135) 135mm f2.8 / Asahi Takumar-A 2X tele-converter / Pentax AF-540FGZ (I & II) Flashes / Cactus RF60/X Flashes & V6/V6II Transceiver

johnriley

Link Posted 16/11/2014 - 22:09
Where I disagree with you Nigel is that I think we are photographers, not computer program users. Just in the same way as we were once photographers and not darkroom users. Yes, we use computer programs just as we used darkrooms, but that wasn't and isn't the primary focus.

Of course it's possible that someone could indeed be more interested in the computer than the photography, or making darkroom prints as opposed to the photography, but the nomenclature is still the same and needs to be understood.
Best regards, John

McGregNi

Link Posted 16/11/2014 - 22:16
Perhaps its better to keep to the matter I was really addressing, which was layer masking. I do accept that older photographic processes, and their termonologies, can be understood and used when their effects are being reproduced on a computer.

As far as layer masking is concerned, what I am interested in is the pedagogy ... and how the concept is disguised and becomes more difficult to understand, because the practical tools and terms used are not logical in how they directly control the actual digital process.

In any case, was there ever an actual photographic technique where black paint was used to obscure an image on a layer above another, or indeed then white paint splashed back on top to reveal that layer again? My point here is that the computer programmers have simply grabbed a convenient tool and method to allow control over layer masks .. but the tool and method chosen are not related in any directly applicable way to the actual digital process.
My Guides to the Pentax Digital Camera Flash Lighting System : Download here from the PentaxForums Homepage Article .... link
Pentax K7 with BG-4 Grip / Samyang 14mm f2.8 ED AS IF UMC / DA18-55mm f3.5-5.6 AL WR / SMC A28mm f2.8 / D FA 28-105mm / SMC F35-70 f3.5-4.5 / SMC A50mm f1.7 / Tamron AF70-300mm f4-5.6 Di LD macro / SMC M75-150mm f4.0 / Tamron Adaptall (CT-135) 135mm f2.8 / Asahi Takumar-A 2X tele-converter / Pentax AF-540FGZ (I & II) Flashes / Cactus RF60/X Flashes & V6/V6II Transceiver
Last Edited by McGregNi on 16/11/2014 - 22:20

richandfleur

Link Posted 17/11/2014 - 04:42
These types of write ups really need pictures attached, or to be talk through video demos. A lot of text soon loses people if anything is even slightly unclear/ambiguous, and it requires a certain level of knowledge to even begin with.

The process you describe is really useful. There is a function to align layers which can be handy too. Layer masks should actually be common place for anyone looking to mask out areas of a layer/image, as if for no other reason, it allows you to fix stuff you go over too far etc, by simply painting back the opposite colour. Pressing X to switch between black and white certainly helped there Nigel.

From my perspective there is a lot of uncertainty around photoshop, and quite rightly so as it seems overwhelming initially. Guides are awesome for conveying small bits and I'm all for them, just text only is a pretty dry medium these days is all.

Link Posted 17/11/2014 - 08:22
Thanks for this Nigel. I think that layer masking is one of the most important skills to learn in Photoshop but for me it's the most difficult concept to get my head around. It's so simple but I always need to run a tutorial before attempting it. Bookmarking this post for sure.
As for me, all I know is that I know nothing.

johnriley

Link Posted 17/11/2014 - 08:31
Think of layers as a pile of acetates, just like we used on overhead projectors in lecture theatres. Each layer can be removed or adjusted as required, and when we've finished they can all be combined at the end with Flatten Image. Adding or removing a layer doesn't mess with the pixels of the original image, so is a much better way of doing many adjustments without destroying or degradind the original.
Best regards, John

Link Posted 17/11/2014 - 08:39
Cheers John.
As for me, all I know is that I know nothing.

McGregNi

Link Posted 17/11/2014 - 17:13
Lü wrote:
Thanks for this Nigel. I think that layer masking is one of the most important skills to learn in Photoshop but for me it's the most difficult concept to get my head around. It's so simple but I always need to run a tutorial before attempting it. Bookmarking this post for sure.

Hi Lu, please feed back your thoughts here when you've had a further chance to look at it. It seems to me that one cause of issues that people often have is the illogical application of physical processes to a digital manipulation technique ... as John's example of acetate shows us ... yes, the idea of transparent sheets on top of one another is sound ... but then we start to paint in black onto them ? and then paint in white onto that again?

Here I've tried to explore the actual digital effect that is occurring, as I feel an understanding of that is the best way to improve the interface between user and programme.

Richard, it may be that you didn't have the time to read my post fully ... its not a 'write up' on how to use masks .. rather its an exploration of the concepts and user interface aspects of masking. This sort of thing, for me, needs to be delivered in a detailed written form ... I do believe the written word ultimately will offer the best rewards for absorbing complex ideas, and for the exploration of ideas. I'm afraid if you expect to be provided with pictures and YouTube videos for this sort of thing then you will simply miss out.
My Guides to the Pentax Digital Camera Flash Lighting System : Download here from the PentaxForums Homepage Article .... link
Pentax K7 with BG-4 Grip / Samyang 14mm f2.8 ED AS IF UMC / DA18-55mm f3.5-5.6 AL WR / SMC A28mm f2.8 / D FA 28-105mm / SMC F35-70 f3.5-4.5 / SMC A50mm f1.7 / Tamron AF70-300mm f4-5.6 Di LD macro / SMC M75-150mm f4.0 / Tamron Adaptall (CT-135) 135mm f2.8 / Asahi Takumar-A 2X tele-converter / Pentax AF-540FGZ (I & II) Flashes / Cactus RF60/X Flashes & V6/V6II Transceiver
Last Edited by McGregNi on 17/11/2014 - 17:15
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