Savageduck
On 2014-09-19 22:57:34 +0000, floyd@apaflo.com (Floyd L. Davidson) said:

Floyd L. Davidson
Savageduck <savageduck1@{REMOVESPAM}me.com>wrote:

Savageduck
On 2014-09-19 20:05:56 +0000, floyd@apaflo.com (Floyd L. Davidson) said:

Floyd L. Davidson
Savageduck <savageduck1@{REMOVESPAM}me.com>wrote:

Savageduck
On 2014-09-19 19:02:24 +0000, Sandman <mr@sandman.net>said:

Sandman
In article <87vbojttf4.fld@barrow.com>, Floyd L. Davidson wrote:

nospam
In article <bc792678-99f5-4416-8002-0d75afbeadf2@googlegroups.com>,

Whisky-dave
Do you happen to know whether or not this preview file is a copy of the original file but 'rendered' at 72DPI rather than the final copy which is mostly likely to be 300+ DPI for printing ?

nospam
there is no dpi or more accurately ppi until you print. everything is always done to the original image.

Floyd L. Davidson
Until you print... or display an image on a monitor screen. Same thing, and a different value for DPI/PPI.

Sandman
Now Floyd thinks the DPI information saved for an image file is in any way related to the physical PPI of the screen. Isn't he adorable?

Savageduck
Hell! 72 ppi, or 360 ppi makes no difference on a display, but try that with a printer and the result is going to be quite obvious.

Floyd L. Davidson
Not any more or less than it will be with your monitor. The printer is either 300 PPI or 360 PPI, and your monitor is probably something between 96 and 104 PPI.

Savageduck
Yup! I use 360 ppi on my printer.

Floyd L. Davidson
Fine, assuming you have an Epson printer...

Savageduck
I do.

I usually open all my RAW images from ACR @ 360 ppi, and

Floyd L. Davidson
You don't open anything at 360 PPI.

Savageduck
Well since you don't use ACR, Photoshop, or Lightroom, you aren't exactly in a position to tell me what I can and cannot do with that software. <https://dl.dropbox.com/u/1295663/FileChute/screenshot_915.jpg> <https://dl.dropbox.com/u/1295663/FileChute/screenshot_917.jpg>

Floyd L. Davidson
Since you cannot "open anything at 360 PPI", I clearly can tell you what you cannot do with software. If you didn't know that before, now you do. Your screen shots are wonderful, but you don't understand what they are telling you. The fact is that if you change the PPI tag to 72, 720, or 7200 and then open the file the image being viewed will have exactly the same data that it did when it was tagged at 360 PPI. There is no difference relative to the opened image.

Savageduck
if I am making a round trip from LR to PS they take that trip at 360 ppi. If I am saving, or exporting for display/web sharing they usually go out at 72 ppi, but mostly I don't bother, and they end up out there at 360 ppi.

Floyd L. Davidson
That's all just nonsense. The values you are setting are just an Exif tag and has no effect at all on the image.

Savageduck
Certainly not on a display. That said, I leave that resolution setting at 360 ppi.

Floyd L. Davidson
Absolutely the same on a monitor screen as it is on a printer. If you don't change the pixel dimensions, the display/print driver will not adjust to the PPI tag, but will resample the image pixel dimensions to the physical device's PPI rate to have whatever physical size you've specified.

What affects the image is the PPI of the device used to display the image, not the tag.

Savageduck
Agreed. The display is the limiting factor for display/web viewing. However, I am working with a 360 ppi setting for adjusting dimensions, including making size constrained crops, it is not an issue with aspect ratio crops. When it comes to printing I am starting with that 360 ppi for the printer.

Floyd L. Davidson
You aren't changing anything in the image by simply changing that PPI tag. If you make calculations based on the PPI and a physical size and _then_ use the calculated size to resample the image pixel dimensions, the image changes... not the PPI.

Savageduck
That too.