Resolution

It's not a "hobby horse", it is fact. What you have bought are the emporer's new clothes!

The K-5 is very convenient if, like us, you happen to print at A3. It's already sized at about A3 and 300ppi. Perfect.

In the case of other cameras, that might have native 72 or 180ppi, for printing resizing should be done. That would apply to anything for optimum results. Letting the printer or print service sort it out is not the best route. This applies to web images in this forum as well. Resizing properly before uploading to a web hosting service is much better than letting it happen automatically.

Photoshop or equivalent is an excellent route to take.

Anyone using an Epson printer should use 360dpi instead of
300dpi it should be slightly sharper.

Don't be confused with ppi and dpi.

The image we handle on the computer is measured in ppi (pixels per inch) and the printer prints these pixels with dpi (dots per inch).

We need a lot more than 360dpi at the printer, otherwise we'd have one pixel represented by one dot of ink. I work at 2880dpi, which does give excellent quality prints.

When we use a lab to print, they will usually specify their ideal ppi. In the case of peak this is 240ppi. In practice 300ppi also works well with their printers.

Many thanks for all the helpful replies. I've just got in from work so will have a closer look when I've eaten !
From a quick look at the replies, it looks as if I've been fretting for nothing.
By the way, it's not an old Mac - well, it's 18 months old

Sorry John you've got that wrong They are both identical
Different names for the same thing


See the previous link. The screen completely ignores ppi/dpi. It just prints pixels. A screen grab/copy contains no dpi information.

One pixel is one dot What you getting confused with here is that a printer doesn't have 16 million colors of ink it has only 3-6 and no white so it has to use all sort of tricks to make that one dot look right. Sometimes scattered dots and sometimes mixing together several drops of ink to make up one pixel.

The 2880dpi refers to how fine a printer can print printer ink dots to make up the required colours of each pixel.

This page explains things a bit better:

http://www.scantips.com/basics3b.html

There's a handy PDF Chart on that page:

http://www.scantips.com/p86.pdf

Sorry, Algi, but the link you provided earlier to a Wikipedia article included:
"The DPI measurement of a printer often needs to be considerably higher than the pixels per inch (PPI) measurement of a video display in order to produce similar-quality output."

If you take a fairly hi-res monitor, with a dot-pitch of 0.25mm, then that monitor has a native dot-pitch of close to 102/inch. What happens to the individual pixels which that screen can display is a matter for the setting on the graphics card. On our hypothetical 0.25 mm monitor, if the graphics card will not go beyond 800x600 pixels then that is it. What the printer prints out is a matter for the printer driver - which is quite happy to convert RGB into CMYK. Of course printers work in CMYK - if I open up my Canon i560 (so a few years old now) I will find 4 (count them, 4) ink cartridges inside Cyan Yellow Magenta and black.

If I take a memory stick to a printer and say "Print me this image" he will print it at the size (in inches, or mm, or cm)I have made the image. If I mail it to a printer he will ask for a size at a resolution (often pixels x pixels).

Geoff

The Scantips site is probably more reliable than the Wikipedia article.

Perhaps this paragraph from the Scantips page will help you understand just what a printer does. i.e. it uses it's extra printer ink dots to try to match the colours only.... nothing to do with resolution. That's why B&W Lasers which are the sharpest general purpose printers use a maximum of 600dpi (sufficient for most purposes) or 1200dpi (used by the pros).

Line art mode is the exception, being 1-bit 2-color B&W with no gray, no halftones, no dithering. In line art mode, the printer CAN use its full resolution, because pixels and ink dots can be the same spacing then. Every line art image pixel is either Black or White, and the printer can make black dots without dithering colors. You may want to print 600 dpi line art images, since line art is the exception, the one mode when the printer can use an image resolution equal to the ink dot resolution of the printer.

In the above case all 2880 printer ink dots would just be black or nothing (white). Close examination of the print would show 600dpi.

If you print an image with the printer set to 1440 it should print the same size as a setting of 2880..... the extra printer ink dots are just used for a better colour match (in theory) or marketing

I was told by a Adobe trainer about 20 years ago that "ppi" on inkjet printers was irrelevant, inspite of claims by Epson and Canon etc. None of them exceeded 144 Lines Per Inch so to get the best quality you needed to double this figure for the actual file (DPI) 300 being more than enough.

I can assure Algi that I do not have this wrong. The confusion between ppi and dpi even crops up from time to time in magazines.

It's almost the digital equivalent of the age old confusion between depth of field and depth of focus.

300 DPI from the K-5 gives 16.43 inch x 10.88 inch prints which
fit on A3 paper.

Printed at 4800 DPI it would probably fit on a postage stamp
Actual size would be 1.03 in. x 0.6 in.

Canon claim up to 9600 ..... Behave!

No Algi, it's a 300ppi file. The number of pixels is defined. The size is defined.

The printer dpi has nothing whatsoever to do with this. It only changes the quality at which the 300ppi file is printed.

I really think you are confused about this.

It does seem that everyone sees this differently There is also the problem rarely picked up that pixels do not have a space between them..... printer dots do have white space, although modern ones might not

I can't see how you can work at 2880dpi? = 1.7 x 1.13inch prints?

This is only a different way of saying the same thing? The K-5 output is fixed at 4928 pixels wide. Software exists that can enlarge this, but there is a quality loss even with the very best software and a modest enlargement in other words it can't really be done

The software in a printer can't do it either 2880/300 is a 9.6x enlargement. In any case that wouldn't be any use to the printer because it has to resolve the problem of printing 16M colours with only 4 inks, so it basically keeps the 4928 pixels and prints over them along with a bit of dithering on either side of each pixel sometimes spilling over to adjacent pixels. That's why B&W lasers, even the top ones don't go beyond 1200dpi = 4 inch x 3 inch print off a K-5.

Then why resize to match the paper size and mess about with the PPI for printing? I am bamboozled by this. Not overly concerned, since I don't think it actually makes a huge amount of difference, but would like to finally get to grips with the logic behind it.