03-22-2016 12:59 PM
"Look, we agree here. I agree that you cannot *set* the dpi in the camera. But the fact is the EXIF info straight from the camera contains dpi info set to 72. Have you ever examined the EXIF straight from the camera?"
Who's arguing? I merely explained why 72 is used as a standard DPI for images displayed by computer monitors, and why is it's use has persisted for so many years, and years to come.
03-22-2016 01:17 PM
"You CAN NOT set DPI in camera. You are simply being fed useless info by your software program"
And here is the data from EXIFTool:
ExifTool Version Number : 10.13
File Name : IMG_6452.jpg
Make : Canon
Camera Model Name : Canon EOS DIGITAL REBEL XS
Orientation : Horizontal (normal)
X Resolution : 72
Y Resolution : 72
Resolution Unit : inches
Software : QuickTime 7.6.6
Strangely, my S100 sets it to 180 dpi.
03-22-2016 01:25 PM
"Strangely, my S100 sets it to 180 dpi."
Do you have the ability to change the setting from 180 to something different, though?
03-22-2016 02:06 PM
I'm argueing & I'm RIGHT. Software produced your screen capture, not your camera. I don't know what software nor how to use it but that is USELESS information. The PIXEL Dimensions shown are TRUE & USEFUL information. IF you send that file to a photo grade printer it will set the DPI to it's maximum setting IF you print at a common setting (* X 10 or smaller) & then lower the DPI setting if you can print large enough. UNTIL you either crop deep into a photo OR request it be printed VERY large your printer will default to 300 DPI or greater. 300 DPI is considered the LOWEST rsetting to use for photos that will be viewed at arm's length. 72 DPI can be used for wall posters & larger, BUT unless you have the ability to print that big you will NOT be printing your full frame at 72 DPI even though you think you will.
03-22-2016 02:21 PM - edited 03-22-2016 02:23 PM
I agree that dpi is useless. That "software"* is simply reporting the information in the image file. Are you saying that there is no dpi info in the EXIF in the image file? Because that is plainly wrong. Look for yourself.
(Just because it is useless does not mean that Canon did not put it there! So we have deal with it.)
*Actually 3 different sofware programs on two OS's: Windows Photo Viewer, Photos and the gold standard EXIFTool.
03-24-2016 10:14 AM
I was attending google university about this and found something interesting, which makes a lot of sense. EXIF data applies to scanned images as well as camera images. The dpi info in the file is there so the scanner can tell you how big the original was.
As we have *ahem* discussed, this information means nothing to a camera image, but rather than deleting it or setting it to a value to tell the software to ignore it - like 0 or -1 - it is to be set to 72 for cameras as a sort of default. I don't know why I have cameras that set it to 180!
03-24-2016 11:44 AM
Until the file is sent to a printer (the machine, not a printing company) there isn't any actual DPI. It's the printing device that creates those dots and frankly as someone who has been using digital photo printers since 1998 none of them could even be set to print at such a wide dot spacing. I'd have to crop soo deep into a file to make the printer print it that poorly that I'm sure I'd get some kind of warning from my software that things weren't right. If you shop (just to see how fine modern printers actually print in DPI) you'll find the specs are huge relative to even 300 DPI, which is considered OK for a print.
Now this isn't actual DPI info but it's close enough to help understand the relationship. I used Photoshop to re set the pixel dimensions to the same size that the camera used for the screenshot produced, then changed the PIXELS per inch figure to some other numbers & you can see how that affected the size of print that would then be created at those numbers.
03-24-2016 11:50 AM
Here's a larger view of two of those.
03-24-2016 12:18 PM - edited 03-24-2016 12:21 PM
Like I said, the Batch Processing Tool in DPP 3/4 allows you to dial in whatever DPI that you want the output file to have. There is no need to use an application as fancy as Photoshop. Most Image Editors can change the DPI/PPi, too.
That is from the freeware application Paint Dot Net.