Dpi for A4

[timk]

Hi all,hopefully someone can help.
ive just bought a canon pixma ip4500 A4 printer with a max resolution of
9600 x 2400 dpi,how do i work out the maximum dpi i can print at (what dpi do i put in the box) when printing A4.
The images are captured on a K10D (image size 3872 x 2592).
I cant get my head round how you work it out.
Thanks
Tim

[JCSullivan]

Any and all printing at 300 max so far as I know

[timk]

ah ok thanks

[Roburg]

300 dpi will give you very good quality. You can usually go down to 240 if needed. To work out the optimum size for your prints, divide the image size by 240-300 - in the case of the K10, up to 16x10 should't pose any problems, so they should look great at 300 dpi on an A4 sheet (which is about 12x8).
If you crop the photo re-do the calculation with the new image size..

[Nesster]

If you use Photoshop, you can have it do the math for you

[MrA]

Can I ask a related question I've never quite understood:

9600 x 2400 dpi

How can a resolution (dots per inch) be quoted as two figures? You see it quite often. Are the dots non-square, ergo there are more in one inch in one direction than in one inch in the perpendicular direction?

Or is it just that the printer, for an A4 at maximum resolution, will print 9600x2400 pixels (ie its not a resolution in dpi at all).

[Arjay Bee]

The maximum print area of the device for which the resolution is quoted is not square - it is rectangular so the long side is quoted first. No matter what size the file is that you send to the printer, that is the maximum that it is capable of printing. In actual fact the human eye cannot discern variation at that resolution so a lot of that data is wasted - hence printing at 300dpi is more than adequate. Screen resolution need only be 70dpi.
When it comes to scanning however it is good, but very memory hungry, to scan at the maximum sampling rate possible - 9600x2400 is about what you can get on the average consumer scanner.

[MrA]

I see, I think. I mean I get that the area is non square, but look:

A4 = 297x210mm = 11.68" x 8.26" (decimal inches) note ratio 1.41:1

9600 x 2400 pixels to an A4 page (printing) note ratio 4:1

9600/11.68 = 821.9 dots per inch (long direction)
2400/8.26 = 290.5 dots per inch (short direction)

^^^ why are they different resolutions? Mechanical limitations of the printer?

[sewebster]

Originally Posted by MrA

I see, I think. I mean I get that the area is non square, but look:

A4 = 297x210mm = 11.68" x 8.26" (decimal inches) note ratio 1.41:1

9600 x 2400 pixels to an A4 page (printing) note ratio 4:1

9600/11.68 = 821.9 dots per inch (long direction)
2400/8.26 = 290.5 dots per inch (short direction)

^^^ why are they different resolutions? Mechanical limitations of the printer?

I'm not an expert, but I have always thought that yes, this was a printer limitation. Not so difficult to believe considering how it prints.

BUT I think that your calculations are off base. It shouldn't be 9600x2400 pixels, it is 9600x2400 DPI. So the size of the A4 sheet is irrelevant. The printer just happens to have different capabilities in different directions.

AND I believe the 9600 DPI is for the horizontal direction, which is the short direction on the page (?). Also, it isn't clear to me if it overlaps different coloured ink droplets, because the 9600 number is how close together it puts droplets. If it doesn't overlap then the "true" resolution would be different (?). But probably this sort of thing isn't really important for most people as printing at only 300 dpi is pretty good.

[Arpe]

I always thought it meant it could do a greater resolution (9600) in one direction than the other (2400)? So one is parallel to the paper feed axis, and the other at right angles, no matter which way the paper is fed into it? But I was always just guessing.

[graphicgr8s]

PPI is more for monitor resolution/size. DPI is a printer resolution. Look at the size in inches/mm not ppi. Look at the resolution in DPI If going to a printer you want 300 DPI/PPI at the finished size.