Using Channels for Masks

[evtonic3]

I use channels in PS to help make a mask easier and more precise. In PS you have the option to create a duplicate channel to work inside of it to create your mask. Unfortunately, AP does not have this yet. But I think I worked something that will allow me to edit a "mask" with adjustments, painting in with blend modes (I've begged for this already) and other ways. I will say that one of the drawbacks of this is that you can't see the mask on the image in realtime if you want to make changes. I would recommend making a duplicate of the grey pixel layer before you rasterize to mask. Just to have a backup. Now this is a very crude and fast way of doing this since I'm always running out of time. But check it out! 

 

https://youtu.be/aSA__3WTr64

[rui_mac]

EXACTLY!

I have been saying and asking for this ever since AP beta started.

But it seems that lots and lots of people don't understand how useful is to be able to use channels in a more flexible way.

I don't mean Serif, as they will, eventually, improve the channels manipulation abilities.

I mean lots of regulars of the forum that simply miss the point of being able to use channels in the same way that we use a greyscale image.

 

Here are a couple of videos I made to show what is needed:

https://www.youtube.com/watch?v=uIN9HYB5Mwc

 

https://www.youtube.com/watch?v=W6H_8gjX-eI

[MEB]

Hi evtonic3,

I'm not able to see the video here due to its privacy settings.

 

[EDIT] Thanks for the updated link @evtonic3. I'm now able to see it.

My comment to see the mask was totally out of place here. Sorry. 

I agree that channels are very powerful for selections and @rui_mac have been stressing this from the beginning.

I'm sure we will get there. Thank you both for sharing the videos.  :D

[evtonic3]

I updated the link to a youtube video. Same principle applies.

[ronniemcbride]

I raise my hand for supporting this feature! This is a technique that season veterans use very regular. This technique is used heavily in compositing and is at the core of many workflows.

 

-Ronnie 

[DannyBCreative]

Need This!!!

[crabtrem]

Forgive my newbie questions. I have used this method with Photoshop, and believe I understand the need and use of this method in Photoshop. My first observation is that I have yet to have a good example in Affinity Photo where I needed this procedure. So if you have some good examples to practice with, I would be most grateful. 

Next, When isolating a procedure like this I have done the following. With my image, or copy of my image selected, I go down to the channels panel on the bottom right of my workspace. I choose the channel I prefer, maybe add some levels adjustment to that display. Then use the selection tool to select the area I want to concentrate on. Is it me, or when I choose to create a mask and new layer from this, I am making it from a specific channel? It seems to work well, but again I haven't had a situation yet where I had any real problems. I have had masks that were difficult to isolate but that usually was more of an issue with the blur in an image version the contrast. So I don't think I could of done any better, because there were no real details to isolate.

 The other method for fine tuning a selection area I picked up on another thread that talked about making a luminosity selection using the blend options panel that is available in the colour panel in the opacity and blend mode gear icon. It seems to me the blend options panel gives a more powerful selection of options that can be used to refine a selection, much easier and more effective than the duplicate channel mask mode in Photoshop. But I again emphasize that I am a newbie. So I haven't come across that image yet that has given me the problem where I really needed it either. And I may just not be proficient enough to be talking on this issue. I am just experimenting after all. With the methods I have used above and the common tools in the selection panels using refine, and going back and manually painting and modifying a mask, I just haven't found a need for the process yet. I look forward to learning more and refining those skills.

[evtonic3]

Crabtrem

 

If you don't need to do this than that means you don't have to go through this process!

[crabtrem]

Evtonic3, thank you for your response to me. Let me clarify. I like to be proficient, and knowledge of this process if needed could be valued. It seems to be popular. But, I have not encountered an image where I found it necessary to work beyond the selection and masking tools already. As an advanced member I would think you would understand the desire to be proficient on various techniques, I would have also thought that you would not do a technique that wasn't needed. Every tutorial Affinity has put out always emphasizes that experimenting is good, and will help with proficiency and comprehension of how exactly and why exactly you would use a method. As in any program, there are normally multiple methods that can be used to get the same result. You find the one that works best for you. So I am naturally curious about popular or well liked methods, but sometimes don't see the requirement as stated by others. And therefore I asked. 

Thank you again for your curt and stylized response.

[MEB]

Hi crabtrem,

While using the selection/refine tools can lead to good results, those methods rely on manual input from you to achieve their result. Its precision depends on the efficiency of the algorithms that detect selection's boundaries and on the quality/labor of your (manual) work.

Channels provide a way to create selections based on the information that's already present on the image. There's no algorithms or direct input from the user involved and so are less prone to errors, giving you a better result. The "manual labor" in this case is to manipulate the channel(s) to enhance/decrease contrast using the information already present to generate a mask from the elements of the image. This leads to much more detailed and precise selections/masks.

[evtonic3]

I would like to add if you want to practice this method, just pick a photo that needs a certain color to be a totally different color. What comes to mind is a person wearing a red pattern shirt, and lets say that your client wants to see that red, green instead. Or something like this. I used food in my video post because I am always needing food to pop with color and channels provides this for me.

[Bail]

One good example of using channels is in selecting just the sky. Please see the attached teaching point on the byThom site:

 

http://www.bythom.com

 

I have tried to follow his PS routine in Affinity Photo but am unsuccessful so far but will keep on trying particularly as I have just found the above helpful comments.

 

My inexperience with channels means I am on a steep learning curve and, even though I can use other methods to select the sky, I want to be able to use the channels method for future use. I shall also look for some videos/tutorials on channels.

 

Thanks to everyone who contributed above

 

Bail

[evtonic3]

Did you try the method I did in the first post? Your link's image (selecting a sky) is exactly how the channels method works great. Find a file similar and follow my steps. The steps are a little different, we don't have a way to duplicate a channel which is  why I had to select make greyscale layer and then make adjustments there. If you compare the video to the steps in your link you will see that they do a levels adjustment just like I did. I did add an extra step in that I was using a brush in overlay mode using black and white to fine tune even further. The last step is where you make the mask when I select rasterize to mask.