dpi Question

[pixie09]

I took my 35 mm film in to be developed, ordering 4x6 prints & a cd. I then downloaded the pictures from the cd to my computer. When opened one of the tifs up in Photoshop CS4 and went to "image size" it came out as the following:

width: 25 in
Height: 16.875
Resolution: 72


Why are they coming out this way, as opposed to 300 dpi in 4x6 size?

Thanks in advance for any clues!

 

[lbridges]

If you change just the DPI in CS4, the image size will drop down to something like you were expecting. I suspect (but haven't actually checked) the 72 DPI is some sort of Photoshop default - it will not adversely affect your photo - reiterating - change just the DPI to 300, and watch the image size change,

 

[pixie09]

Thank you very much! I will give that a try.

Have a great day!!

 

[Big Mike]

It's not DPI (dots per inch)...it's PPI (pixels per inch) and it doesn't mean anything. It's just telling the computer how large to display the image on a computer screen.
72 PPI is the typical resolution of a computer monitor...which is why it's often the default setting for digital images.

In the 'Image Size' box, you can simply change it.
First, uncheck the 'resample image' box...then change the PPI to 300 (or whatever)....then recheck the 'resample Image' box. You image will now have a different PPI...but will otherwise be exactly the same.
The 'document size' will change...but that's just how large it is (at 100% zoom) on your computer screen. The actual pixel dimensions won't change.

 

[apertureman]

If you change just the DPI in CS4, the image size will drop down to something like you were expecting. I suspect (but haven't actually checked) the 72 DPI is some sort of Photoshop default - it will not adversely affect your photo - reiterating - change just the DPI to 300, and watch the image size change,

Just make sure you have "Resample Image" check box UNCHECKED when you change the image resolution.

25" at 72 dpi = 6" at 300 dpi
16.875" at 72 dpi = 4.05" at 300 dpi

You're still good.

...then recheck the 'resample Image' box...

There's no need to recheck the box, just hit OK.

 

[Dwig]

... I suspect (but haven't actually checked) the 72 DPI is some sort of Photoshop default - ...

Correct. PS will default to 72ppi when it encounters a file that has no PPI value set in its header. This is the common choice from most apps that deal with PPI. You would have to read through the EXIF data in the header to see whether the lab's software specified 72ppi (which I doubt) or whether it left the field blank.