Do not look at inches or centimeters, not only is this meaningless in the context of this discussion, it is also misleading.
You want to look at the number of pixels in the exported photo. If the number of pixels is the same, then you can rest assured you have the same exported photo.
Thank you, that's exactly what I thought but it has confused magazine editors into thinking the exported LR file will not be sufficient for a DPS. So why does it state a longer edge when opened through ACR as opposed to LR when the pixels are the same?
So why does it state a longer edge when opened through ACR as opposed to LR when the pixels are the same?
Let me repeat what I said earlier: Do not look at inches or centimeters, not only is this meaningless in the context of this discussion, it is also misleading. That's my answer, just ignore the inches or centimeters.
I do appreciate your answer and completely understand what you are saying, I am merely trying to understand why one says different to the other? Please don't worry about repeating yourself, you have been more than helpful already.
I've encountered something strange and wondered if anyone could help? When I export from a Nikon D300 .NEF file to an 8 bit tiff it comes out with a longest edge size of 14cm yet if I open the file in ACR (CS4) and open as an 8 bit tiff file the longest edge is now 36cm. Is there something within LRs properties that I need to address?
As dj_paige said.......we've seen this so many times from other LR users I've decided to create a short tutorial.....so here's
Unless the image is being resized the Resolution value has no meaning. An image file can have any Resolution value you want...and still be exactly the same size in W pixels x H pixels.
In general Resolution is only useful when outputting an image to hardcopy (i.e. printing) and the ppi is specified dependent on the actual printer's dpi requirements. I'm quite surprised the magazine editors were confused since they are the printers....correct?
The magazine editors need to tell you what Resolution ppi they need (typ. 300 ppi) and actual size (cm/in) the pictures are to be placed inside the magazine. Lacking that you should send them full-size Exports with 'Resize to Fit' unchecked. There is no way to see an image file's actual dimensions (cm/in) at a specific Resolution inside LR, but you can inside PS or Bridge:
When you Export a image file from inside LR it uses the Resolution value in the 'Image Sizing' panel. If 'Resize to Fit' is unchecked the Resolution value is simply written into the file's EXIF metadata and that is all! The file remains exactly the same size in W pixels x H pixels. It's simple math and nothing more complicated!
Long Edge Dimension (cm) = W pixels ÷ Resolution (ppi)
Short Edge Dimension (cm) = H pixels ÷ Resolution (ppi)
When you open an image file inside PS using ACR it uses its own Resolution value, which may be different than what you have set in LR. Open an image file in ACR and then click on the COLOR SPACE, BIT DEPTH, DIMENSIONS, RESOLUTION numbers at the very bottom of the ACR window.
This where you set the Resolution used by ACR.
The most likely answer for the difference is that each app is using a different PPI resolution to calculate the print size.
That's great, thank you so much for taking the time and trouble to do this. Much appreciated.