Help with resolution and file size.

[castelino33]

This question was given to me by my design teacher. we have our own opinion, but I would like to know what would be your answer. 

Keeping width and height same, if we increase or decrease the resolution of the image file, do you think the file size will change?

[SuperMerlin]

Yes, because you are resampling the image. If you just change the PPI then no change whatsoever

[Derek Cross]

As a student you should check this yourself and experiment. Have a look at: Image > File Size and experiment to see what happens when you change the  Resolution and you tick and untick the Resample box.

[castelino33]

Yes! I have done my share of experiments. I just wanted to know the opinions other people have over this question.

Thanks you for your reply.

[Conrad C · Accepted solution]

castelino33  wrote

Keeping width and height same, if we increase or decrease the resolution of the image file, do you think the file size will change?

Uh oh. The question doesn't include enough information to provide a good answer. That's why, when you search for this topic on the Web, you see all kinds of confusion and arguments about the correct answer.

The correct answer depends on what the question means by "width and height."

• If the width and height are in pixels, and the real world measurement (e.g. inches) is not fixed, then changing resolution will not change the file size. (This is like using the Photoshop Image Size command with the Resample option off.)
• If the width and height are in a real world measurement (e.g., inches), then changing resolution will change the file size, because the number of pixels has to change in order to keep the width and height constant. (This is like using the Photoshop Image Size command with the Resample option on.)

Because the question doesn't say what width and height really mean, the question either needs to be more specific to get a good answer, or it's a trick question designed to provoke discussion and learning.

[gener7]

The only way to keep Image Pixel dimensions the same is to uncheck "Resample" so that you do not alter that, and that means the file size in Megabytes or Gigabytes will stay the same.

Resolution basically applies to Print and it is "metadata" or file information. It just tells the printer how many pixels to pack in an inch or centimeter. By turning off Resample, you can see how the Document size on paper changes when you change resolution.

You could even take out that Print metadata and it would not have any effect on the Image Size (pixel with and height). All it is, is instructions for the printer.

Image Size is the size of the digital image in pixels

Document Size refers to the size in inches or cm as printed on paper or any other material the printer uses

So is your instructor asking about the Image or the Document?