Pixels Low But Image Large

[Talanath]

Hi,

I'm trying to reduce the size of a file image (Large format shot) I'm a little confused by the settings in image resize. Now, I had to do some major ppi reductions just to get the filters working (photoshop wouldn't even load the original 2.7 tiff - had to make a 1.5 tiff.  Then had to do ppi reductions down from 4800 to 300). 

I've then exported a couple of times to jpeg, reducing the size each time.  This is because I don't want to send the full file to the print house, as I'm only looking for a 5x7 image for now (just to check colours, etc)

I'm now left with an image withe an image which is 2856 pixels wide, and 2104 high, with a ppi of 72. However, if I change this to inches, it reads as 40 by 30 inches.  This is really confusing me.  If I was looking at those pixel dimensions from my digital 12mpx camera, then those same pixel dimensions would probably mean an image of about 10 inches. 

What am I missing here?  I'm pretty new to photoshop, so please excuse my ignorance!

[melissapiccone · Accepted solution]

You are missing the ppi - set it to 300 without resizing. You want to print at 300, 72 is for viewing on screen.

[Talanath]

Okay.  So my original PSB is 300ppi.  But when I export to Jpeg, and then open up the exported file, the resolution is set down to 72.  Why is this?  Would I just reset to 300ppi through imagesize after this, or does it not make a difference?  I guess I'm wondering what the best way is to go about reducing file sizes prior to sending to the print house, as I'm guessing the printers would need to make some sort of reduction themselves if you don't...

[Derek Cross]

Use Save As rather than Export.

[D Fosse]

Talanath  wrote

Okay.  So my original PSB is 300ppi.  But when I export to Jpeg, and then open up the exported file, the resolution is set down to 72.  Why is this?

Export and Save For Web strip resolution metadata completely from the file. The exported file doesn't have a ppi at all - not 72, not 300, not anything.

The 72 figure appears when the file is reopened into Photoshop, which for various reasons has to assign something. 72 is as good as anything else. If you need some other figure, just change it.

It's important you understand that the file is just pixels. Resolution is not a property of the file - it is just an instruction to the printer: How big do you want those pixels printed out on paper?

​ppi = pixels per inch. ​That expression means exactly what it says.

The reason this information is left out from Export is because exported files are only intended for screen. A resolution figure is irrelevant on screen, where it falls into the screen's native pixel grid, with its own resolution.

If you want a certain ppi figure preserved, use Save As, not Export.

[Talanath]

Okay, thanks to you both.  I guess Melissa's answer is strictly the correct one, as I deviated a bit, but your answer helps me too Derek, as I have been exporting each time so far.