LaserSoft Imaging

my Epson printer prints at 2880 x 1440 dpi. I'm getting excellent output with 225 dpi images. being the amateur that I am, I find that a little confusing. the resolution of the images is much lower than the resolution of the printer.

the latest generation of Epson printers have a resolution of 5760 dpi. I therefore have to wonder if I should be using a higher output resolution for images that might be printed on these new printers. would the images look better at higher output resolutions?

any advice?

regards
Gregory

i assume you mean 225 PPI ?
i seem to remember that the native resolution for Epson printer driver is 360 PPI and the Epson software resamples from there and employs a stochastic dithering to further improve the appearance. So anything above that shouldn't change the output much, maybe the printing time though.
The way i understand it, the printer driver takes one Pixel and creates 1 dot at 360 dpi output, 2 dots and some blur at 720, etc.

Frank

hi Frank.

first, you were right to correct me. I should have said 225 ppi. however, I was just quoting SF's interface. next to the output resolution slider, it says 'dpi'. I wonder if that's a misnomer. the only case where dpi would be the correct nomenclature would be when printing to a dye-sublimation printer. right?

anyway, back to the main subject. the printer driver allows several resolution selections including Photo 720 dpi, Photo 1440 dpi and Photo 2880 dpi. I wonder what kind of grids they use at 2880 dpi. or maybe they don't use traditional grids at all.

I have asked Epson Support about this. I'll let you know when I get a reply.

the reason this question came up is because I'm archiving my film. after two years of pondering, I decided to keep one HDR full-resolution image (4000 dpi from my scanner) and one 24-bit 225 ppi image for each photo. the 225 ppi image compresses at maximum quality to just 2MB. it displays quickly on screen and prints to A4 with acceptable quality. if I need a better quality, I can run the HDR through SF HDR again.

the other day though, a friend commented that there was a lot of noise (in the cloudy sky area) of a 225 ppi A3 print I showed him.

consequently, I am now printing a sample photo at multiple ppi resolutions to see if they differ in quality. I have chosen 225, 300, 400, 600 and 800 ppi for this test. it will be interesting to see if there really are any visible differences in the quality of the printout.

Epson has made it a little harder for me though. as I mentioned above, they offer Photo 720, 1440 and 2880 dpi print resolutions. they also offer an 'Automatic' output. I wonder if the Automatic output examines the image before choosing an output resolution.


more later.

regards
Gregory

some results from my tests.

first, Epson Support replied to my question about the resolutions but made no reference to grids or lines per inch other than to multiply the resolution by .67 to get the relative lines per inch. they also said that the printer gets 2880 dpi vertically (720 dpi horizontally) by feeding the paper in smaller increments, if and only if the selected paper qualifies.


I printed my test scans. the scans were all 5" long and were scanned for output resolution from 225 ppi to 800 ppi. I printed these on the same paper using Epson's printer settings of 720 dpi, High Speed off, Finest Detail on, ColorSync.

my eyes are obviously not professional. the printed photos looked almost identical to me. however, I then scanned the photos at 800 dpi and viewed them at 400% in GraphicConverter and there were obvious differences between the 225 ppi, 600 ppi and 800 ppi photos. the 225 ppi photo was very course by comparison. the 800 ppi was slightly smoother than the 600 ppi.

I am therefore wondering if 360 or 720 dpi are the ideal resolutions to print to my 720 x 2880 printer. biased by my limited knowledge of screen printing and the way dots are combined to create colours, and biased too by your first response, I tend to think that 360 is probably the better resolution to use. the files will not be as large as 720 and the printouts should be very acceptable.

any comments?

regards
Gregory




P.S. I like the SF Official Guide book but don't agree with his wording when it comes to scanning resolution. the selected resolution is not the scanning resolution; it's the output resolution, and it's ppi rather than dpi -- although that's a moot point. as almost every experienced SF user can tell you, the scanning resolution can be viewed by pressing the Control key. the sampled-down resolution can be viewed by pressing Control-Shift.

i think it was Kennedy on comp.perips.scanners that mentioned that the native resolution required by the epson printer driver was 360 ppi and that all of the output from the printer was resampled and dithered from there. Any output to the driver above or below that would be re-sampled back to 360 and processed from there. So if you sent a 720 ppi stream to the driver it would get downsampled to 360 ppi and then output at what ever resolution specified and that the paper would support. i would ask Epson suppport about what the driver for you printer actually works best with and how it handles higher or lower resolution feeds. My amateur workflow is to sample the image at the native resolution of the device, archive, and on output use PS resampling down to the native PPI required by the printer driver.

Frank

My amateur workflow is to sample the image at the native resolution of the device, archive, and on output use PS resampling down to the native PPI required by the printer driver.

which is what I'm doing too ;-)

then I'll change my standard output resolution to 360 ppi instead of 225 ppi.

thanks.
Gregory