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Why does Dodge and Burn tools don't work on masks?


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59 minutes ago, R C-R said:

They can be represented as a greyscale image for editing & visualization purposes but the opacity alpha channel is not actually a greyscale image. For that matter, neither are the RGB channels. Each of them is just a set of numeric values in an RGBA color model.

Exactly as all image files are.
They are just lists of numbers.
And those lists of numbers represent colors, greyscales and opacity values.
And those opacity values are represented as greyscales.
And, since you can perform operations on these lists of numbers (painting, blurring, smudging, dodging, burning, apply filtersetc), it should all be possible in CMYK, RGB, greyscale and alphas.

Please, tell me, R C-R, what is the difference, internally and numerically, in the list of values of a greyscale image and the list of values of an alpha?

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After reading this thread I only just realised the original date of this: 2016!

So let me add my 2 Euro-Cents to this topic,I usually use every tool in my belt to adjust transparency of my layers in my compositions. By multiplying channels, locally dodging, burning, making an outline and blurring it - then expanding by gradation-curves and subtract the result from my original channel, and so on. Also, I often need to go back and dodge or burn one nasty part of this mask, AFTER I have imported it in my layout (Indesign/Publisher) 

I have not made the jump from PS yet, but I purchased Photo and looking forward to switching. I have not had the time to fully test all my workflows in it.

Disclaimer: Used Photoshop since 2.0 - that's before Layers so I learned to appreciate the use of channels, and I mean painting through selections on top of channels which I would then use as the final selection... So, yeah pixel-selections ARE alpha-channels ARE grey-scale images which you have to be able to manipulate as that. 

 

And no: Painting does not do the same to an alpha-channel as dodge or burn. In this Screen-grab of Photoshop I tried to tighten the mask with dodge or burn and remove the gaps – maybe someone can post an example with hair...

 

 
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The main reason that I don't ditch Photoshop completely is the way Affinity Photo deals with alpha channels.
It is so much more intuitive in Photoshop, since alphas are just greyscale images and you can do to them whatever you can do to a regular greyscale image.

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1 hour ago, rui_mac said:

Please, tell me, R C-R, what is the difference, internally and numerically, in the list of values of a greyscale image and the list of values of an alpha?

Surely, it is obvious that the difference is that they describe different things. While a greyscale image can be created from a color or alpha channel, that does not make them the same thing, any more than creating a rasterized image from a vector drawing makes them the same thing.

Please don't misunderstand or misrepresent what I am saying. I am not in any way objecting to improving or extending the tools that can be used on masks in Affinity Photo, including the Dodge & Burn Tools if you would find that useful. In fact, early in this discussion I said as much. My only objection is suggesting that alpha channels somehow are or are equivalent to greyscale images. They aren't, not in Photos, not in Photoshop, not in any graphics application, & they never have been.

Imagining that an alpha channel is simply an "extra" channel, or that the red, blue, & green channels are simply greyscale images "by themselves" may well be convenient for some purposes but it does not change what they are. Besides, it doesn't make much sense to try to do so if you are not working with an RGBA image to begin with -- for example, a CMYK image has none of those channels.

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CMYK images are a set of four greyscale channels, each one defining the amount of Cyan, Magenta, Yellow and Black ink.
Internally, there is no difference in the way they are stored.
So, a greyscale image is a list of values.
An RGB image is a set of three list of values.
A CMYK image is a set of four lists of values.
And an alpha is a list of values, just like a greyscale image. Exactly the same. Stored in the same way.
The way you interpret or use that set of values may be different, but they are all the same type of data, internally.
So, we should be able to use all tools in the same way in all of them.

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I just created a render in Cinema 4D and asked for an alpha to be produced.
I defined the file format as a TIFF file and asked for a separate alpha.
I got two files: an RGB TIFF file and a greyscale TIFF file.
So, alphas ARE simply greyscale images.
And the same happens in any format.
Sometime, if the alpha is stored as a separate file and the file format does not support greyscales, the alpha is even stored as an RGB image, with all channels storing the same information (three equal greyscale images, one for each of the R,G and B channels).
Of course, that is overkill, as the file gets much bigger.

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31 minutes ago, rui_mac said:

And an alpha is a list of values, just like a greyscale image. Exactly the same. Stored in the same way.

Just because they might be a list of values that might be stored the same way does not make them "just like" or "exactly the same" as greyscale images.

In fact, we don't even know how images are stored in the proprietary native Affinity file format. The developers have said that it is an "unconventional" format, but aside from a few hints about the use of serialization, mIpmaps, compaction after some threshold is reached, & maybe a few other clues like that an entire Affinity format file is not read into memory all at once, we can't even be sure that a document's channel data are stored individually or as simple lists of values ... or even that this data is stored the same way each time we save it.

Besides, it is clearly not true that this is how all file formats store images. Consider for example JPEGs, indexed color formats, WebP, HEIF, & other formats that use lossless compression, & so on. 

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13 minutes ago, >|< said:

You are falling into R C-R's trap, as I have often done. He knows what you mean, but he will pretend to be a fool in order to provoke an argument.

No, I don't know what he means when he says everything is stored exactly like greyscale images (or as if they were greyscale images or words to that effect), if for no other reason than because he must know that there are many formats where that is not true.

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I know all about storing methods. I teach my students how JPEG stores data. And how indexed colors (GIFs, for instance) or mipmaps work.
But when a file is loaded, even if there is some sort of internal storage scheme, when reading, writing or manipulating the data, all that data has to be accessed as raw data.
I know how that is because I code my own tools and deal with all types of data.

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6 minutes ago, rui_mac said:

I know all about storing methods. I teach my students how JPEG stores data. And how indexed colors (GIFs, for instance) or mipmaps work.
But when a file is loaded, even if there is some sort of internal storage scheme, when reading, writing or manipulating the data, all that data has to be accessed as raw data.
I know how that is because I code my own tools and deal with all types of data.

With all due respect for your knowledge & experience (& please believe me that I do have a great deal of respect for that), how could you possibly know exactly how the native Affinity file format stores image data internally, or how the Affinity apps access it?

The developers have made it very clear that they consider the native format to be unique, in part because of its unconventional for a 2D app use of mipmaps, together with data serialization, what seems to be a database-like file structure that enables non-sequential access during loads & saves, optimization for high memory efficiency at the expense of increased file size, & some other stuff they remain unwilling to discuss publicly.

All this strongly suggests that not everything in the file format is pure raw data, that at least some of it in addition to the mipmaps is stored in some unspecified fully or partially processed form, that it can be read from & written to the file in chunks that in some way may mimic how OS level memory managers work, or in some other way is truly unconventional, just like they claim it is.

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The native format is very structured, I know. And that means that is very compact when saved and also when in memory.
But, and this is a big but, if it is possible to paint or blur the alpha data, then it is possible to Dodge and Burn also.
If the alpha was stored in such a way that it was not possible to darken or lighten the values (in fact, dodging and burning are simply the increasing or decreasing of the values), then it would not be possible to paint on alpha too.

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  • 2 months later...
3 hours ago, Nekodificador said:

So... any solution?

An actual solution? Something like this.. or probably just the 20GB Photography plan.

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  • 2 months later...

My god! This argument has been going on for 3 years now and we still don't have a solution in APhoto. I get that they have been busy with Publisher, but this is a no brainer feature to add and it's still not there.

When I stumbled on to this issue I was sure I was just doing something wrong. Nope. Just simply can't be done in APhoto. Ridiculous.

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Alpha channels are simply greyscale images.
Even if they are not stored inside as such, they do show as such.
So, people assume that whatever can be done with greyscale images, can be done with alpha channels. Any paint or editing operations, or filters or adjustments.
I was going to say the EVEN PROFESSIONALS expect that, but in really, PROFESSIONALS IN PARTICULAR expect that.
So, any professional bitmap editing application should treat alpha channels as greyscale images and allow the user to do with alpha channels whatever it does with a simple greyscale image, the same way it does with a simple grayscale image.
And I think Affinity Photo is a professional bitmap editing application.
So, it should behave as one, when dealing with alpha channels.

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4 hours ago, rui_mac said:

Alpha channels are simply greyscale images.

That is not true. In the Affinity apps they are colorless channels that store transparency/opacity information.

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9 hours ago, R C-R said:

That is not true. In the Affinity apps they are colorless channels that store transparency/opacity information.

We can argue if grey is a colour... but anyway there is no valid reason why alphas could not be adjusted like any greyscale image. Even if a channel is just ones and zeroes it can be manipulated.

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42 minutes ago, Fixx said:

We can argue if grey is a colour... but anyway there is no valid reason why alphas could not be adjusted like any greyscale image. Even if a channel is just ones and zeroes it can be manipulated.

OK, but it would be hard to argue that opacity/transparency is a color, which is what I meant by colorless. :P

Anyway, if you want transparency alpha channels to be adjustable as if they were greyscale images, I see no reason why that could not be added, although in the CMYK color space there might be some conversion issues for the developers to work out.

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An alpha channel is just a "storage" place with information, as in... NUMBERS!!
Just like the Red channels is a "storage" place with information, as in... NUMBERS!!
The same for the Green, Blue, Cyan, Magenta, Yellow or Black channels.
The information (numbers) is used for operations (painting, blurring, dodging, burning, filtering), for storing (saved in a file) and for displaying.
So, they are all just clumps of numbers that are used in several ways.
The alpha channel numbers are used to interpret the level of transparency that is displayed in the colors defined by the color channel numbers.
So, there is no reason whatsoever not to be able to perform in the alpha channel, the same operations that can be performed on each individual color channel (or on a greyscale image).

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