Size change?

[Huggy-photo]

Why have document sizes appeared to have got smaller?!! 

I've used Photoshop for 20years plus and i know my photo sizes but they seem to have suddenly got smaller in the 2024 version! I've checked every setting and all seems normal but where I might have made an image thats 20 x 16 at 72ppi for example an works out to be less than 1MB! What's that all about? This has only happened recently.

Please could some help.

Thanks

Nick  

[Trevor.Dennis]

Hi Nick.  If your 20 x 16 is referring to inches, then at 72 PPI that is only 1440 x 1152 pixels.

You mention the files size as being less than 1Mb, but don't tell us the format and quality setting used.

An all white image saves out at 117kb even with quality set to maximum.  Fill that canvas with coloured noise, (the most difficult conditions for JPG compression) and it becomes close to 6Mb.  That's a factor of almost 50, so you can see how much difference content can make.

Does that make any sense?

[Conrad_C]

The Image Size dialog box shows a file size at the top, and for a 20 x 16 inch image at 72 ppi, that file size is 4.75 megabytes. This is the pure, uncompressed file size, so it is not necessarily what you see on the desktop. But for the uncompressed image data, 4.75 megabytes is what it has been and always will be, even outside of Photoshop, because that’s how the math of pixel bits works out (there’s a formula) for the current pixel dimensions, bit depth, and number of channels.

20 x 16 at 72ppi for example an works out to be less than 1MB!

By @Huggy-photo

It is very likely that you see a different file size when looking at it on the desktop. It might be larger if the file includes elements such as layers and imported graphics, and it might be smaller if file size compression was applied or if the content isn’t complicated, because content can affect file size as Trevor demonstrated. The document for my screen shot actually saves to just 725KB, and that’s probably because it’s just a big gray rectangle…no variety to store, plus Photoshop applies its own lossless compression that is on by default. The screen shot below is from Photoshop Preferences / File Handling.

It can be smaller still, very small, if lossy compression was used, which is what happens with JPEG. So one way a desktop file size could look unusually small is if it was exported from Photoshop format to JPEG format using different compression settings than you usually use.

Because otherwise, the basics of file size for an image have not changed since Photoshop was at version 1.0. They didn’t change before then either.

[Huggy-photo]

Thank you all for your help, that's very helpful and kind of you.

However, one problem still persists - please see this screen shot! The image - in old money - 18x 1.45 inches displayed at 100 is this big! Really? Theyve never been this small, not even at 72ppi. What on earth is going on?

[Per Berntsen]

Digital images don't have physical dimensions, they only have pixel dimensions.

So the physical size of the image on the monitor depend on the pixel dimensions of the image, and the size of the screen pixels. At 100% view, one image pixel is displayed using one screen pixel.

If you have a high resolution monitor (4k or more), the image will appear at approximately half the size compared to a standard resolution monitor (like 1920 x 1080). To fit all these extra pixels on the screen, they have to much smaller.

Web browsers and image viewers enlarge images to 200% when they detect a high resolution monitor, but Photoshop cannot do this, it has to display accurately.

PPI (pixels per inch) is optional metadata used by printer drivers to calculate the printed dimensions of an image.

Pixel dimensions divided by PPI = Printed dimension in inches.

At 72 PPI, the printer will use 72 image pixels to print one inch on paper.

PPI has no effect on screen viewing, the image will display the same with a PPI value of 72 or 600, or with no PPI value at all.

[Huggy-photo]

I never knew that. Thank you Per for enlightening me, as i do indeed have a 4K monitor

[Trevor.Dennis]

When my old camera club agreed — kicking and screaming — that we'd allow digital image entries to the monthly competitions, nothing caused the members more confusion than the whole DPI/PPI thing, and we see it on this forum constantly.  Conrad and Per have explained it for you, but I just wanted to let you know how contentious the concept is.   I have even seen International Salons and Exhibitions that asked for digital image entries to be something like 1620 x 1080 and 72PPI. 

[Conrad_C · Accepted solution]

What Per Bentsen is bringing up is “big” and “small” in terms of how large it appears on the screen. Earlier you were talking about “big” and “small” in terms of file size. For this image, are you talking about a small file size, or small apparent size on screen? If it’s the latter, then Per is right. If it’s still about file size, the earlier answer still applies.

And if it is about images appearing unexpectedly small on screen, the next question is: Did you start noticing this after upgrading to a newer screen (specifically Retina) after using a much older screen (specifically non-Retina)?