What is a Canvas?

[SEASONS283724216wp2]

(1)

Is the Canvas in Photoshop a physical or virtual concept? For example, if I create a new A4-sized document with a white background, is the white part the physical canvas itself or the image on the (virtual) canvas?

In other words, is the Canvas an imaginary concept (space) that shows the maximum size of the image that can be visually displayed on it?

(2)

If I create a new A4-sized document and make the background transparent, the Image Size dialog box shows a number equal to the Canvas Size, but why does it show a dimension even though there is no image?

As a Photoshop beginner, I can understand what is being explained in various materials or lectures, but I'm not sure I understand the concept of a Canvas.

[Bojan Živković]

"In other words, is the Canvas an imaginary concept (space) that shows the maximum size of the image that can be visually displayed on it?"

Well, yes. The canvas is an area that can be displayed when an image is exported or saved. It can be larger than an individual component of the composition and can be expanded without affecting any composition component. In other words, the canvas can be manipulated without altering pixels of existing composition elements, which is why it is useful.

[D Fosse]

Yes, as Bojan says. But you can't think "physical" vs. "virtual". Nothing is physical here; it's all virtual.

The Canvas defines the available area, defined as pixels wide by pixels high.

It doesn't have a physical size, nothing in Photoshop does, only an array of pixels. A physical size is a derived property, defined by the pixels per inch (ppi) number that you set.

The canvas can be expanded or contracted, thus expanding or contracting the number of pixels it contains. The pixel grid itself is always fixed in the canvas.

Image Size determines pixel density; the resolution. This is where you decide how many pixels you decide to fill your available area with.

Don't know if that makes sense. It always seemed very intuitive and logical to me, so maybe I'm assuming it makes sense when it really doesn't 😉 😄

[c.pfaffenbichler]

If I create a new A4-sized document and make the background transparent, the Image Size dialog box shows a number equal to the Canvas Size, but why does it show a dimension even though there is no image?

The image may be »empty«, it is still an image and X times Y pixels at three Channels (in the case of RGB) at 8bit (in the case of 8bit images) still results in a certain number. 

The actual saved file may be smaller or larger than the indicated »Image Size« depending on the actual image content, how well that compresses, the file format and compression settings, … 

[SEASONS283724216wp2]

Thank you for your kind reply.

[Stephen_A_Marsh]

@SEASONS283724216wp2 

I was going to point you to the following related discussion:

https://community.adobe.com/t5/photoshop-ecosystem-discussions/what-exactly-does-the-size-of-a-layer...

And then realised that was you too!

Sometmes metaphors are helpful, but not always, especially when it comes to software.

[SEASONS283724216wp2]

Thank you for answering my trivial questions.

[Stephen_A_Marsh]

Thank you for answering my trivial questions.

By @SEASONS283724216wp2

Understanding canvas size and layer size will serve you well, even more so when you discover artboards.

[SEASONS283724216wp2]

Many resources for artboards describe the artboard as a canvas(1-1); however, some resources describe the dark area that the artboard sits on (the Pasteboard area in Indesign) as the canvas, and say that the canvas that the artboard sits on is infinite in size(1-2).

(1-1)

“Artboards in Photoshop are a powerful feature that allows designers to work on multiple canvases within a single document.” (https://proedu.com/blogs/photoshop-skills/what-is-an-artboard-in-photoshop)

(1-2)

“An artboard is an individual workspace in a Photoshop or Illustrator file. It can be thought of as a virtual piece of paper on a larger canvas. Multiple artboards can be added to a canvas.” (https://www.computerhope.com/jargon/a/artboard.htm)

At the 1:30 in the video below

(https://www.youtube.com/watch?v=YFjZgZ6_sDA&ab_channel=AdobePhotoshop)

In Adobe Manual, It seems to be a bit ambiguous.

“You can think of an artboard as a special type of layer group. Visually, artboards serve as individual canvases within a document.” (https://helpx.adobe.com/photoshop/using/artboards.html) (Personally, because of  the word "Visually", I understood it to be something like 1-2.)

As I was learning Artboard, I wondered if the concept of a canvas was different in the case of artboards than it is in general, and which of the two conflicting descriptions was correct, which led me to ask the question about Canvas.

Every time I ask a question, I wonder if I'm annoying people with a low-level question. As always, thanks for the great answers.

[Stephen_A_Marsh]

@SEASONS283724216wp2 

I can't agree with the 1-1 quote, as there is only 1 canvas in Photoshop. Multiple areas of the single document canvas is the correct description.

1-2 is better, however, I would say that the canvas expands to include each new artboard. Semantics?

The Adobe manual is correct:

Technically, it is a type of layer group, that is similar to having a hidden "mask" or "window" that reveals part of the overall canvas.

Start with a canvas of say 500x500px with a single pixel layer.

Convert the pixel layer to an artboard. The artboard properties should state 500x500px. Double-check the canvas size, it should still be 500x500px.

Add a second artboard that is 500x500px, if there is no space/gap between the artboards, then the canvas should now be 1000x500px (or 500x1000px). If there is a space/gap between the artboards, then the canvas would match the size of the 2 artboards plus the space of the gap.

[SEASONS283724216wp2]

Thanks for the answer. I think that should be cleaned up.

But if I have two artboards that are 500px X 500px and I paste them horizontally, they show up in the Properties panel as exactly 500px X 500px each, but the Canvas Size is 1500px X 1000px, which is 500px more horizontally and 500px more vertically.

(1-1) Convert the pixel layer to an artboard.

(1-2) Add a second artboard that is 500x500px.

(1-3) There is no space/gap between the artboards.

[Stephen_A_Marsh]

@SEASONS283724216wp2 

You are correct, I was answering from (poor) memory, I was, of course, describing how I believe the feature should work – not how it actually works!  :]

The artboard tool has an option to "shrinkwrap canvas on save" which restores sanity to the canvas.

[SEASONS283724216wp2]

Thank you for your kind answer. Thanks to you, my understanding of artboard is a bit clearer.