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How to change canvas dimensions but keep pixel dimensions without losing quality?

Forum|Forum|1 year ago
April 30, 2024
3 replies
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Hello. I’ve been working on a project that I initially set up as 2500 px X 3750 px, a width to height ratio of 8.3 in : 12.5 in, and a resolution of 300ppi. I want to convert the width to height ratio to 6 in : 9 in for printing while keeping the pixel dimensions and resolution the same. Is there a way to do this without losing any detail in the image? Is it as simple as changing the width and height values in the image size dialogue box, or will this discard some data from the original image? I'm fairly new to Photoshop, and I don't understand how downsizing dimensions affects the pixels that are kept or discarded in this case. Thank you very much to anyone who can answer!

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Correct answer Lumigraphics

Don't resample. Just change the assigned dimensions, keep the pixels the same.

Trevor.Dennis

Community Expert

I was introduced to the Topaz Labs Photo Ai and Gigapixel plugins today, and their upresing capability is beyond impressive. Scroll down to the Grand Canyon image, click on Compare, and drag the bar left and right to see the difference. They are claiming being able to increase pixel size by 600% ! Upresing plugins have been around for years and years, but always performed as if they were snake oil. I think this might be the real deal. Gigapixel is $99, but the person who told us about it was using a similar upsize tool in their Photo Ai plugin, which does way more, but is $199. I am definitely tempted, but I don't do a lot of photography nowadays.

https://www.topazlabs.com/gigapixel

It seems that it is not just the Adobe apps that are getting inordinately more powerful — which does stand to reason.

D Fosse

Community Expert

They are claiming being able to increase pixel size by 600%

By @Trevor.Dennis

Pardon me, but that's obviously not possible.

As we just discussed in another thread, this isn't upsampling. This is an AI-generated new image that just uses the old image as an input prompt. Those aren't real details. They're made up.

In fact, this is a great example of why I think AI is a very dangerous technology inviting misuse and fraud.

Bojan Živković11378569

Community Expert

If I understand correctly, for future projects, the answer is no. You cannot convert an image with dimensions of 3500 by 1800 pixels to a 3:2 ratio while retaining the original dimensions, as it is neither logical nor feasible.

J

Jess393Author

Participant

Thanks very much for taking the time to answer, @Bojan Živković11378569! I think I didn't word my question very well. To clarify, the pixel dimensions are 2500px by 3750px, and I want to keep them the same. What I want to change is the area they are distributed over. Currently, the printed product dimensions are 8.333in by 12.5 in. I want it to be 6in by 9in, which is almost exactly the same ratio (.66664 vs. .66667). I wondered what happens to the pixel data when we downsize the print like this while keeping the same pixel dimensions.

L

Lumigraphics

Legend

2500:3750 = 2:3

6:9 = 2:3

So there is no change in aspect ratio.

Just change the dimensions in Image Size with the resample checkbox OFF. There is no need to worry about resolution at this scale. 300ppi isn't magical, its just a common setting for print.

J

Jess393Author

Participant

Thank you very much, @Lumigraphics! This is what I wanted to understand -- if I keep the aspect ratio the same and don't select resample, then the exact same arrangment of pixels (2500:3750) will just redistribute over the printed area without any loss in downsizing from 8.3in : 12.5in to 6in : 9in?

By contrast, if I create a new project with the dimensions I want (6in : 9in and 2500px : 3750 px), then resize the current image (8.3in : 12.5 in and 2500px : 3750 px) within it by scaling down with the transform command to fit the canvas, would the image lose detail?

I apologize if this is a tedious question. When I try to google my way to an answer, everything about loss of resolution discusses upsizing instead of downsizing. But I know that downsizing without converting to a smart object within a project discards pixels, so I wondered if the same would happen if I downsize the dimensions of an entire project. For context, I designed an ebook cover where only the pixel dimensions mattered. Now I want to convert it to a print book cover where the physical dimensions do matter and detail preservation is crucial.

Thank you again for your time!

D Fosse

Community Expert

@Jess393

An image is just pixels. It doesn't have a size.

You give it a size by assigning a pixels per inch number. That translates from pixels to size. Pixels per inch.

As long as the pixels don't change, the image file doesn't change.

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