Batch process DPI?

[Arty]

I'm looking to batch process dpi. I've got PS 7 & Elements 2. I don't mind trying new programmes for this if they're not too expensive.
Also, for printing would you see a difference between 180 dpi & 300 dpi?

[Arty]

To answer myself: :D
FastStone image viewer. Does this easily - and it's free! :)

[Arty]

Hmmmmm...maybe not :( Seems a bit cranky

[Pekka]

Usually you set print DPI by setting image size and print resolution in printer driver dialog. What is embedded in image is not important except as a suggested default value.

[etaf]

Also, for printing would you see a difference between 180 dpi & 300 dpi?
yes maybe, but it depends on the size of print you intend to produce and how far away it will be viewed
300 and 240 are typical resolutions quoted for printing.
http://www.scantips.com/basics2c.html

[Arty]

To explain properly: I will be uploading to a photographers site for printing, so want to get the dpi right quality wise. I've noticed that all my shots (300D & 20D) seem to be 72dpi by default. I would like to batch process them to 300dpi.

[etaf]

well that dpi is only used when printing

so say you have a 3000 x 300 pixel image which is showing as 72PPI
then that will print out at
3000 / 72 = 41.6"
300 / 72 = 4.16"

so the print size is 41.6" x 4.16"

now if you change the PPI to 300 on the same image
all it will do is print a different size print

so

3000 /300 = 10
300 / 300 = 1

so the print will be 10" x 1"

you have not actually done anything to the image.
I don't think you will need to change anything for sending the file BUT I HAVE NOT DONE THIS MYSELF - SO MAY BE WRONG

hope I have not confused you

[robertwgross]

Some RAW converters will allow you to make the DPI adjustment at the time of the RAW conversion so that the TIF file has it the way you want.

You are shooting RAW, aren't you?

---Bob Gross---

[tim]

Don't worry about the DPI, it's usually irrelevant. Send them the file you have, and tell them the printing size, they'll worry about the rest. RAW isn't necessary like Bob suggests, though it does have many advantages, it also has some disadvantages, mainly in the processing workflow.

[Arty]

Thanks for the replies. Must admit this dpi thing is a tad baffling! I took some pic files to a printer once who told me that they were 'low res' so don't expect too much. These were 300D files that had been adjusted & saved in Photo Deluxe :o I use PS now ;) What did he mean then if nothing to do with dpi?

[Arty]

Well I've cracked the batch processing for dpi at least. It was at my fingertips all along :o
'Digital photo pro' software that came with the cam!

[etaf]

well what was the pixel size of those files and what size did you expect to have printed.
and what was "printer" remember some of these guys may get huge files very high resolution proffesionally scanned from 35mm or even medium format.
so its again it depends on the context of his statement.

[badrotation]

When printing, you want to set the image to the native dpi of the photo machine.


I actually did a test with this.

I took the same picture, one sampled to 300DPI, and one was the standard 72DPI output of the 20D.
I got both printed on the same machine (a fuji frontier with a max. 300 dpi resolution) and the 300 DPI version of the photo actually looks sharper.


Printing at 72dpi wont hurt it though, just 300 dpi seems to be a tad sharper for some reason. I am guessing the machine doesnt do as good of a job as photoshop does when resampling or something.

[etaf]

badrotation
that example would have printed out at different sizes, as i pointed out above
so unless the printer changed the way it used the file, i dont understand you point

not quite true as printers print in rgb
but if you only have 72 pixels per inch then it will not be as sharp a if you have 300 pixels per inch - of course the printer lays down CYMK colours or 6 colours

think of a newspaper made up of dots

Image Size & Resolution for printing and screen viewing:
http://www.blaha.net/Main%20Picture%20Resolution.htm

explanation of DPI and PPI
http://www.ltlimagery.com/resolution.html

[cmM]

To answer your batch process question, you can do it in photoshop. Just make an action that does what you want it to do (change DPI) and batch process