Best way to resize for high quality?

[LosFelizGirl]

I am submitting an image to a digital exhibition.

The instructions it says to "Size each image 1200 pixels on the long side at 72 dpi"

My original image is 5280 X  3096 pixels at 240 resolution.

What is the best way to resize this to maintain the best quality?  

Do I save as 72 DPI first, then go in and change pixel diminsion?

What about the resample box, do i leave unchecked?

I'm not a professional photographer, I need your help.

Thanks!

[Trevor.Dennis]

No subject seems to cause as much confusion among camera club members, Exhibition entrants, _and_ organisers, as image size, resolution and pixels-per-inch.

This is how Photoshop defaulted when I created a document your original size.

If I turn off Resample and change the resolution to 72PPI, the image is _exactly_ the same.  It is still 5280 x 3096 pixels.  The only difference is that if you sent the file to a printer, it would print at a different size.

But to save the receiver of your entry having a melt down, keep Resample checked, and put 12 in the width field.

OK that and open Image Size again.

Uncheck Resample, and type 72 in the resolution field.

Good luck with your entry.  Would you care to show us?

[Conrad C · Accepted solution]

The simplest way to do this is to leave the original unchanged, and use one of the export commands to export a copy that’s resized to the required pixel dimensions and file format.

These are the steps In the demo below:

1. Choose File > Export > Export As.

2. Select the Format (file format). Most art competitions require JPEG, but verify that for the one you’re applying to.

3. Set the long side to 1200 px. When you apply that by clicking in the short side field or pressing Tab, you’ll find that the short side is automatically calculated (to maintain the image’s original proportions).

That’s it, you’re done with resizing. The rest of the steps are optional.

4. You might want to select Copyright and Contact Info if that metadata is already entered in the image and you want that info to be included with the exported copy.

5. To help ensure that the original colors are reproduced as closely as possible on whatever computer or device the judges are using, select Embed Color Profile.

There is no resolution option because it won’t matter, because with these settings the long side of the exported copy becomes 1200 px regardless of the original resolution.

Now, if for some reason you do want to use Image > Image Size, first make sure it’s on a duplicate of the original, because saving the original after reducing it to 1200 px would permanently reduce the resolution of the original, and you don’t want that.

Do I save as 72 DPI first, then go in and change pixel diminsion?

By @LosFelizGirl

In Image > Image Size, the steps are more confusing than in Export As, so it is good that you ask those questions.

If you still want to use Image Size, then these would be the steps:

1. You must enable the Resample option, for two reasons. One, you want 1200 px on the long side, and the only way photo software can change 5280 px to 1200 px is to downsample, which means resampling down. If Resample is not selected, the image must stay at 5280 px. The second reason is related to that: If Resample is not selected, there is no way to set it directly to 1200 px because the Pixels option is not available in the unit of measure menu; enabling Resample makes the Pixels unit available.

2. In the unit of measure menu for the long side (in your case, Width), choose Pixels.

3. Change Resolution to 72 ppi.

4. Change Width to 1200 pixels.

So the tricky thing with Image Size is that the way you fulfill the competition requirements is not by simply setting the options from top to bottom; it’s a different order.

If you do it correctly then when you finish, the numbers and menus should look like this picture:

After you click OK, now you still have to remember to save the copy in the file format and color settings that are appropriate for the competition requirements. If you had use Export As, all of that could have been set in one place and you’d already be done.

[D Fosse]

...and you also have to remember to check the "Embed Color Profile"-box ... 😉

I can't imagine that the ppi number matters in the slightest here. They're just going to see this on screen or a projector.

[LosFelizGirl]

I did the image size version (only because it wasn't clear to me if the Export As would have given me a 72 dpi version. 

THank you Conrad.  
This is what I did.

1) Image > Image Size,

2) changed the resolution to 72. (this also resulted in the pixel dimension changing to 1584 X 929).  

3) Entered 1200 into the width (resample was checked off for both moves)

Check out my attachments.  I'm pretty sure I did it correctly!

[D Fosse]

@LosFelizGirl 

The ppi requirement is utterly pointless, and, frankly, just shows they don't understand what ppi is. We see this quite often. It really is completely irrelevant for this.

But, just to make them happy, you can change the ppi number to anything you like in the Image Size dialog. It doesn't change anything in the file as long as you keep "resample" unchecked.

The important thing is the pixel size, 1200 pixels long size in this case. That's the real image size. The image is just pixels.

There's no problem changing both in one go.

Ppi, pixels per inch, is just that. It's a way to translate pixels into a physical size when needed. For screen and display it's not needed.

[gener7]

Ever wonder where the 72 ppi standard came from?

https://www.photoshopessentials.com/essentials/the-72-ppi-web-resolution-myth

TLDR: 1980s Mac 9 inch monitor resolution designed to work with their 144 ppi Imagewriter printer.

[Trevor.Dennis]

Gene I bet you have been waiting ages for a chance to share that wee gem. 🙂

[gener7]

If a quick lookup from yesterday counts as "ages" 😉