RAW dpi preset at 240

[spargett]

Guys,

I was wondering why Photoshop presets my image dpi at 240 in its RAW processor instead of the more logical 300 dpi?

Any thoughts or reasons why I shouldn't pop it up to 300 dpi? Thanks!

-Scott-

[maderito]

If you're printing, it makes a difference.

For an 8MP image - max print size (approx.)
@240 DPI - 11" x 14"
@300 DPI - 8" x 10"

You don't gain or lose pixels as viewed on the monitor image based on the DPI setting. But the setting does affect how many pixels are printed per unit of paper size. The higher the DPI, the denser the printed pixels, the smaller the printed image.

240 DPI is one standard minimum setting for acceptable print quality. Some go as low as 180 DPI.

If you can tell the difference in print quality between a 240 and 300 DPI printed image, then you have an answer to your question.

DPI set at the time of raw conversion can be changed later. Most likely, you already know this. If you use 300 DPI for all your printing, than save yourself an extra step and change the setting to 300 DPI for RAW output.

[spargett]

If you're printing, it makes a difference.

For an 8MP image - max print size (approx.)
@240 DPI - 11" x 14"
@300 DPI - 8" x 10"

You don't gain or lose pixels as viewed on the monitor image based on the DPI setting. But the setting does affect how many pixels are printed per unit of paper size. The higher the DPI, the denser the printed pixels, the smaller the printed image.

240 DPI is one standard minimum setting for acceptable print quality. Some go as low as 180 DPI.

If you can tell the difference in print quality between a 240 and 300 DPI printed image, then you have an answer to your question.

DPI set at the time of raw conversion can be changed later. Most likely, you already know this. If you use 300 DPI for all your printing, than save yourself an extra step and change the setting to 300 DPI for RAW output.
Why does 240 dpi give me a large print and the 300 dpi give me a smaller? That seems backwards...

[tim]

3000 pixels at 240ppi = 12.5"
3000 pixels at 300ppi = 10"

Really, unless your lab requires you to submit file sized exactly, you can ignore the ppi. You can send a 3000 pixel image that's 1ppi and ask them to print it 6x4 and they will, it'll look fine, because they ignore the ppi. One of my labs requires you to have the image sized exactly at 250dpi - so for a 6x4 you have to open it in photoshop and make sure it's 1500x1000px, the size is set at 6", and the dpi is 250. The crop tool is a quicker way to do it.

[maderito]

Why does 240 dpi give me a large print and the 300 dpi give me a smaller? That seems backwards... For the purposes of this discussion, PPI (pixels per inch) = DPI (dots per inch)

print dimension in inches = pixel dimension/DPI = pixel dimension/PPI

Yes, the relationship is inverse (or "backwards") - the higher the DPI the smaller the resulting print dimension. The parameter DPI or PPI refers to the number of image pixels needed to create one inch of print.

[Picture North Carolina]

For the purposes of this discussion, PPI (pixels per inch) = DPI (dots per inch)

print dimension in inches = pixel dimension/DPI = pixel dimension/PPI

Yes, the relationship is inverse (or "backwards") - the higher the DPI the smaller the resulting print dimension. The parameter DPI or PPI refers to the number of image pixels needed to create one inch of print.

You obviously know what you are talking about and I have much to learn. I have just begin to learn proper printing to an Epson R2400. Can you recommend a tutorial on how to maximize printing quality on standard print sizes such as 4x6, 8x10, 11x14, 13x19, etc? What you said about the larger print (11x14) benefitting from the lower (240) dpi screwed up my brain and everything I had been taught, namely print everything at 300 dpi.

thanks,
-Dan

[maderito]

This article (http://www.adobepress.com/articles/article.asp?p=433754&seqNum=4&rl=1) by Bruce Fraser gives some of the details. Be careful not to confuse the 2 uses of DPI which can refer to printer dots per inch OR to pixels per inch (PPI), which is what we are talking about here:


There are all sorts of theories as to the "best" resolution for inkjet printing, some more grounded in reality than others. We'll spare you the more esoteric details and simply tell you that we've obtained good results using resolutions between 180 ppi for very large prints and 480 ppi for small prints. Most of the time we print at somewhere between 240 and 360 ppi, depending on the print size and the available resolution in the image. We've yet to find a reason to send more than 480 ppi to any inkjet printer. -- Bruce Fraser
In practice, it's straightforward. Your printer driver will take care of the details of how to transform your pixels into printed dots. You just need to give the printer a minimum of 240 pixels per inch (or whatever you decide) to work with.

If you're working in Photoshop, go to Image > Image Size to see and/or change the relationship between image size and resolution (PPI). See this article (http://www.espressographics.com/text/imagesize.html) for details.

This subject is also covered extensively here on POTN in prior posts.

[jj1987]

Guys,

I was wondering why Photoshop presets my image dpi at 240 in its RAW processor instead of the more logical 300 dpi?

Any thoughts or reasons why I shouldn't pop it up to 300 dpi? Thanks!

-Scott-
First off, its PPI. Does it really matter? Nope, but several people here seem to have a hard on for correcting people about that, I dont really understand why the need to correct people, but I'm warning you. :lol:

Secondly, lets use round numbers for examples.

lets say I have a .1 megapixel camera.

That is 1000pixels total.

And for math sake, it shoots in a square format.

so
1x1in @ 1000ppi
2x2in @ 500ppi
10x10in @ 100ppi

and so on.

As you can see if you multiply length x width x ppi, all of the sizes I gave you come out to 1000 pixels, which is the exact same size file, no difference in quality.

hope that helps.

[tzalman]

You obviously know what you are talking about and I have much to learn. I have just begin to learn proper printing to an Epson R2400. Can you recommend a tutorial on how to maximize printing quality on standard print sizes such as 4x6, 8x10, 11x14, 13x19, etc? What you said about the larger print (11x14) benefitting from the lower (240) dpi screwed up my brain and everything I had been taught, namely print everything at 300 dpi.

thanks,
-Dan

I highly reccomend this series of tutorials by Mike Chaney, the author of Qimage:
http://www.steves-digicams.com/techcorner/tc_index.html
and especially the following:
http://www.steves-digicams.com/techcorner/January_2005.html
http://www.steves-digicams.com/techcorner/May_2005.html
Elie

[Picture North Carolina]

Thanks to both Maderito and Tzalman. Very good tutorials, read some last night.

I have a question. I personally have yet to print a very large print. In the general thinking, apparently the general comfort range is 240 ppi, however as Bruce Frazer says when scaling up in size, he still gets good results at 180. So the question I have is when you are viewing large prints that were printed at 240 and 180 at a normal viewing distance of say 6 feet, can you see a difference?

[René Damkot]

lets say I have a .1 megapixel camera.

That is 1000pixels total.

And for math sake, it shoots in a square format.

so
1x1in @ 1000ppi
2x2in @ 500ppi
10x10in @ 100ppi

and so on.

As you can see if you multiply length x width x ppi, all of the sizes I gave you come out to 1000 pixels, which is the exact same size file, no difference in quality.

Sorry for correcting :lol:, but I suppose you mean a 1megapixel camera, so an image of 1000x1000 pixels. That way a 10*10inch*100ppi = 1000000