Archived from groups: comp.periphs.printers (
More info?)
Hello, these replies are very interesting but they tell me only what should
be happening; I am actually after some sort of method of verifying these
claims, perhaps by counting dots, if that is possible (I have a microscope),
maybe there are test pictures available on the internet which make this
easy. All this is probably pie in the sky.
Ivan.
"Kennedy McEwen" <rkm@nospam.demon.co.uk> wrote in message
news:qP006Ml98acBFw6M@kennedym.demon.co.uk...
> In article <cqYbd.71003$ay5.13039@fe1.news.blueyonder.co.uk>, ivan
> danicic <ivan@goaway.spam> writes
> >Hello All, Do you know how I might find out at what resolution (DPI) an
> >ink-jet printer (epson 860) is *actually* printing? Any replies
gratefully
> >received.
>
> In common with all Epson desktop inkjet printers, your Epson Stylus
> Color 860 printer will always print at 720ppi, irrespective of what you
> send it. The first step in the printer rendering process is to resample
> everything to 720ppi if necessary.
>
> The Epson driver is capable of resolving the full resolution if it is
> present in the image with sufficient contrast. However it will
> dynamically adjust the actual resolution to achieve the best tonal
> quality with the inks available. So, if the exact colour you want in a
> certain pixel cannot be achieved, the error between what is required and
> what is available from the inks will be distributed to the 4 of the 8
> nearest neighbouring pixels that have not yet been printed. Thus, if
> high contrast detail is present, it will be printed at full resolution,
> but if it is low contrast then the error of any given pixel will be
> spread over several pixels, in effect trading resolution for exact
> colour rendition.
>
> Being limited to 4 colours with the SC860 means that this occurs more
> than it would with 6, 7, or 8 colour printers, so more resolution must
> be traded for colour precision, but it is impossible to say with
> accuracy what the actual resolution on any part of the image *actually*
> is - so there is no fixed answer to your question. You can, of course,
> limit the actual resolution in the image you send the printer, thus
> giving the printer more tonal precision in individual pixels. For
> example 360pp gives 4 times as many ink potential drops, and thus 4x as
> many reproducible colours, per pixel than 720ppi, whilst 240ppi will
> produce 9 times as many. An unaided human eye can only resolve about
> 250ppi on a printed page, so limiting the resolution in this way is
> almost imperceptible on the best quality paper and even more can be
> traded on poorer paper. If you have the resolution in the original
> image, it is generally better to let the printer driver trade the
> resolution than restrict it yourself in this way, because the driver
> will do it dynamically across the image - yielding best resolution where
> it exists, which means your prints can stand closer examination.
>
> However, because the printer driver always resamples to 720ppi in the
> first place, you should always use an integer division of 720ppi to
> avoid aliasing, which can become obvious depending on the content of
> your image. For example, some text strokes can appear thicker than
> others or, in images, bricks or windows in buildings or paving can
> appear uneven or have a coarse pattern running through them even though
> the original image is perfectly regular. For Epson printers this means
> that the magic numbers are 720ppi, 360ppi, 240ppi and 180ppi. For
> resolutions below 240ppi it is recommended to select the
> --
> Kennedy
> Yes, Socrates himself is particularly missed;
> A lovely little thinker, but a ah heck when he's pissed.
> Python Philosophers (replace 'nospam' with 'kennedym' when
replying)
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