Pixels per dot...a printing question

Hi Guys,
I am trying to get an understanding of the different view between the screen and a printed image, particularly relating to noise.

I was wondering how fine a printer can drop ink in relation to pixel size.
Say an A4 print with a K-5 ...How many dots of ink per pixel ( or the other way round ?)

Tried a search but couldn't frame the question usefully
cheers
Pete

You can work this out. If you have a print where the printer is laying down 300 pixels per inch (dpi) and you know how many pixels long the image is....it gives you a rough idea.

But it's not only the number of drops of ink per pixel that gives us the photographic quality in a print, there's dithering where the printer shakes each drop slightly to make them merge better.

All images for print need sharpening before printing to crisp up the dilution of sharpness that the printer causes.

It will depend on the printer so you'll need to look up the resolution for yours in the manual, however, here's an example of how you can calculate it:

Let's say you're printing a photo that contains 300 pixels per inch (fairly standard stuff) and you're using an inkjet printer with a resolution of 1440 dots per inch (again, fairly standard). To calculate the number of dots the printer lays down to represent each pixel you divide the second number by the first, so:

1440/300 = 4.8

That will tell you the number dots in one direction (horizontal or vertical) so to get the whole picture you need to square it:

4.8 x 4.8 = 23.04

So in this example the printer is laying down 23.04 dots of ink to represent each pixel that makes up your photo. The printer needs to lay down multiple ink dots (compared to the number of pixels) because it has to replicate the RGB colours using only a limited palette (CMYK and possibly LC/LM/etc depending on the printer) and so resorts to mixing them.

Hope that helps

http://www.ehow.com/about_5315274_explanation-megapixels-print-sizes.html

http://www.dpiphoto.eu/dpi.htm

http://www.design215.com/toolbox/print_guide.php

This is probably not precisely on topic but some might find it interesting.

The default printing resolution that's usually quoted is 300 dpi, so an 8x10 would be 2400 x 3000 pixels. However, 300 dpi is what used to be requested by publishing houses for magazine reproduction. I always understood, and I haven't tested this, that it is better to have the printing resolution a divisor of the printer resolution. 300 doesn't go into 1440 but 360 does and that is why I've always used 360 when doing prints, with great success over the years.

Fantastic thanks Guys
very helpful links thanks Frogfish

cheers
Pete

That is quite interesting actually, I might give that a go.

It's 360 dpi for Epson printers and 300 dpi for HP if I remember correctly?

My elderly Epson prints at 1440dpi so 360ppi makes good sense.

just a little bit more info for the larger prints you don't need 300 dpi because the viewdistance is larger so you're unable to see such fine details.
Just look closely to those big commercial signs on the street, they have quite a low DPI.

Does someone has a way to calculate this, i know there is but have no idea how and where to find it....

It used to be said with film that if you could make a 10inch x 8inch print that looked sharp..... It was sharp enough to enlarge to any size, because holding a 10x8 print in your hand was far more critical than standing back looking at a large print on a wall.

Any calculations would involve the circle of confusion.

Just found this link which would appear to answer all of the questions about print resolution.

link

Yes thanks that was the one.

North-light has great articles about colour management as well.

Since the topic seems to be on prints, here's my latest large format printer: https://picasaweb.google.com/lh/photo/x95Ownk0qtdlkBzpdWOjwNmpfYh8sk_zEiORYDw27p...

[quote:3496ace15f="pentaxian450"]Since the topic seems to be on prints, here's my latest large format printer: ]https://picasaweb.google.com/lh/photo/x95Ownk0qtdlkBzpdWOjwNmpfYh8sk_zEiORYDw27p...

I don't think that would quite fit on my desktop