I'm trying to understand why Lightroom by default is set to 240dpi for saving a Tiff or Jpeg from a Raw file.Isn't better to set it to 300dpi for printing ? What's the difference ? Thank you very much !
Until you pick a print size it is a completely arbitrary and irrelevant number it can be set at anything. There is no difference in the file just the projected print size and sense you don't know that yet ignore it.
You can change that default if you want. It will remember a change from session to session.
By the way, PPI (pixels per inch) is usually the better term. DPI (dots per inch) usually refers to printing from something like an inkjet and there can be more dots than pixels.
PPI is usually not that important unless you are talking specifically about printing. In the case of printing, 240 PPI is a pretty good place to start in terms of having sufficient detail in a print. You can adjust up or down from there depending on how big a print you are making, expected viewing distance, how much detail is in the image to begin with, and your own personal preferences.
Just to give you an idea, here are the PPIs recommended by the late Bruce Fraser based on viewing distance and a viewer with 20/20 vision:
Thank you ,Eyeball, your post have been very helpful; so if you look at a print from a smaller distance, the image it should be printed at a higher resolution (300 ppi or higher ) !!
That's the idea, yes, but if your image does not have much fine detail (like a portrait, for example), you can usually get away with less. Most people are not looking at prints from 8 inches away. At my age, I can't even focus at that distance without glasses.
Going the other direction though, a common example is a billboard. Equivalent PPI for a billboard can be less than 20, since no one is looking at it close-up except the guy who pasted it up there.
I wouldn't say it is "better". I think Adobe just needed to have a default and 240 seemed like a reasonable resolution for normal printing.
Using a higher resolution will normally be "better" although you may not appreciate that it is better with normal viewing.
There is not much downside in printing a higher-resolution file unless the printer or printing service has a particular limitation or there is some type of constraint on file size.
I usually use 300 PPI for printing on my HP inkjet or when I have images printed at a lab. I suspect you would have a difficult time telling the difference between 240 and 300 PPI without a side-by-side comparison and it might require a loupe even then.
If you have a print where you think resolution is going to be critical, the best thing to do would be to run some test prints or swatches.
The PPI only matters if you are sizing an image to a particular print size. Say if you want an 8x10, and want it really high quality, then setting it to 300 PPI will produce a 2400x3000 pixel JPEG.
However, if you exporting a 12megapixel image as a 3000x4000 pixel JPG from Lightroom or Photoshop (or any other editor) then the PPI is irrelevant because you've already specified the output pixel dimensions. A pixel is a pixel is a pixel, it in itself has no PPI setting. You can do a test and see for yourself. Export an image as a JPG at particular resolution (say 800x1000 pixels) with a PPI of 10 (yes "ten") and with a PPI of 300. You'll see that the resulting file size is the same. A binary compare of them will only show a byte or two difference. The PPI at that point is just a piece of metadata which most online printers (Costco, Mpix, etc.) ignore as they only look at number of pixels. Each of those companies have their minimum resolution requirements for prints. In other words, a 800x1000 image with a PPI setting of 10 (ten) does not mean you can get a 80-inch by 100-inch print, you don't have enough pixels.
Slightly different from what the OP is asking but the PPI setting in LR behaves differently when exporting from the Library vs "Printing to file" from the print module.
When exporting from Library, LR just sets the metadata variable for PPI. As explained above, it has no effect on the image of any kind. In the print module when printing to file, it will up or down res the image so that the resulting file will have enough pixels to print at the specified PPI on the paper size specified when "printing to file". I just did a quick test and exporting at 72 ppi gave a 433 kb file. changing only PPI to 300 gave a 5.3 MB file
So the resolution was changed, more pixels bigger file size so the resulting files are different sizes both in resolution and file size. This is a surprise to you?
Not to me . But people new to LR are often not aware the PPI behavior in print module is different from LR export. I do not think it is clear to everyone that setting ppi in export does nothing but setting it in "print to file" changes the number of pixels (careful using "resolution" in this context )
!!
. But people new to LR are often not aware the PPI behavior in print module is different from LR export. I do not think it is clear to everyone that setting ppi in export does nothing but setting it in "print to file" changes the number of pixels (careful using "resolution" in this context