Printer profiling and resolution

[timarmes]

Hi,

 

If there are any experts in colour management out there, you may be

able to help me...

 

Many sites offering a printer profiling service state that the

resolution of the printed profiling target must be the same as that

of the final prints to be made using the profile. That is, colour is

dependant upon resolution.

 

We find a convincing argument for this on the Internet: resolution

defines the final printed pixel size and since each pixel is made up

of an array of CCMMYK droplets, the bigger the pixel the more room

thre is to create the colour, and the smaller the pixel the more

compromises the driver needs to take when trying to create the colour

uusing the inks available.

 

On the other hand, the highly respected "QImage" printing software is

based around the fact that the printer driver will actually ALWAYS

resample the image to the printer's "native" resolution (often 720ppi

for Epsons and 600ppi for Canon printers). If we accept this fact

then we can assume that there will actually be no difference in

printed pixel colour for a given initial resolution, since pixels

will in fact always have the same physical size when printed (since

every image is resampled to the same resolution).

 

There are profiling sites that indeed make no mention of resolution

with respect to their service. Moreover, the Eye-One Photo

profiling software also fails to mention resolution during the

profiling process. I would have thought that if resolution choice

was important when profiling then then this highly respected product

would at lease ask at what resolution the target should be printed at.

 

So, with all this conflicting information I don't really know what to

believe. I lean heavily towards the resolution independent argument -

can anyone confirm this? Have any of your tested your prints at

different resolutions to see if the profile falls over?

 

Regards,

 

Tim

[john_houghton]

As you say, the image will end up at 720 pixels per inch on an Epson, but you may still have the options of a printer resolution of 720, 1440, 2880, 5760 dots per inch. It is quite possible that there will be slight differences in color rendition at these different resolutions. Profiling service suppliers generally state that custom profiles should be used at the same printer settings that were selected for printing the targets, even if they do not refer to printer resolution explicitly.

 

John

[david_rosenbloom]

I am not an expert profiling printers but Atkinson is and he has different profiles for 1440 and 2880.

[andrew_rodney1]

Ideally you?ll profile per output resolution (selected in the print driver, not the file itself). That

said. Some find profiling at one resolution can be used at others but this is going to be based

on the printer and driver and paper settings. You might find little difference in a matt paper

but a bigger difference in glossy paper. Your mileage may vary. Output the targets for a

profile using your preferred output resolution and paper settings in the driver. Then try other

settings on the same image using the same profile and see if it will fly or not.

 

Andrew Rodney

www.digitaldog.net

[timarmes]

I think I now understand my confusion.

 

Resolution here has two uses. The profile's accuracy is related to the printer DPI setting used, and not the image's PPI setting.

 

Does everyone agree that changing the PPI of the image will have no effect on the colours printed, since the printer driver will resample all the pixels to a specific PPI resolution before printing?

 

I can clearly see that changing the DPI setting could result in colour differences.

 

Tim

[paul_sokal___dallas__tx]

Tim, I think you've answered your own question. It is common to think of PPI and DPI as they same thing, but they are not. If you take a raw file from a D-70, 3000 by 2000 ppi, and output it for print at 300ppi, your going to wind up with a print of roughly 10 by 6.7 inches. With a printer output of 1440dpi, your going to have a lot of dots per pixel so you can see that printer resolution is going to have a lot of impact on the profile and how the print will look.