Advanced question about printing and resolution?

[paulr]

I disagree with the suggestion to use no sharpening. I find sharpening to be critical in any kind of digital printing; sharpness gets lost both in the scanning process and in the raw mosaicing process, and needs to be restored. Print drivers also reduce sharpness slightly. I'd suggest a look at the most recent book in the Blatner / Frasier Real World Photoshop series for a tutorial on sharpening workflows. It's a subject by itself.

As to your original question, with many current inkjet print drivers, I see zero difference between interpolating in photoshop and just letting the driver do it. I'm still in the habit of resing up smaller files to 720 or 360 ppi, but can't say there's a good reason to do it.

My understanding is that things are very different with some other kinds of printers, like light jet.

In the end, the only way to know for sure it to experiment. It's easy; you don't have to make a 16x20 print. Just print small portions of one. You can print four print samples on a single 8x10 sheet for comparison.

[codex0]

Peter, Do we know this for sure finally? Is it written by Epson somewhere? I have heard so many opinions on this issue.

The tooltips and manual for my 3880 state that you should send files at 360dpi (native).

Checking the box for finest detail in the driver us it to 720dpi....
"Finest detail for sharper edges on vector-based data including text, graphics, and line art. (This setting does not affect photographs and is not recommended for large files)" (page 50 of the manual)

Also see here (this page is about the 3800)

[Greg Miller]

My two cents.
Do not use any sharpening. If you think you need it then something is wrong. If you need any correction do it in 32 bits. Convert to a wide color profile like ProPhoto. Avoid jpeg, use at least tiff 16. Get a real printing application with decent interpolation like QImage.

Converting to a wide color profile like ProPhoto only helps if the color gamut of the image exceeds the range of a smaller gamut workspace. Take a foggy scene with a small gamut range. You would be fine with Adobe sRGB. Going to a wider color space will not help, and can actually hurt since both color spaces have the exact same number of total color values. And therefor the wider color space has to have bigger steps between the values to cover the larger range.

[Larry Gebhardt]

In my opinion the reason to resize to a consistent ppi is so any print sharpening will be consistent between your prints. If you sharpen first and send the image at 180dpi to the printer it will be resized to 360 or 720dpi by the printer. So any sharpening you do will also be doubled (your 1px radius will effectively be a 2px). While this will work just fine, it makes it hard to develop a sharpening system where you can look at the screen and know it will look good on the print.

So I always resize to 360ppi and sharpen right before printing. I sometimes resize to 720ppi if my scan or image has enough pixels and the fine detail matters. But then I need to experiment with the sharpening a bit.

The other reason I have heard to resize before printing is to take advantage of the better resize algorithms in Photoshop, vs what's in the print driver. Personally I have tested this, and can see no difference, but my experiment wasn't very well setup (just a few prints).

[Preston]

So I always resize to 360ppi and sharpen right before printing. I sometimes resize to 720ppi if my scan or image has enough pixels and the fine detail matters. But then I need to experiment with the sharpening a bit.

This is exactly the workflow I use. Works quite well.

--P

[James Hilton]

Peter, Do we know this for sure finally? Is it written by Epson somewhere? I have heard so many opinions on this issue.

On the 3880 "Finest Detail" mode is 720 dpi, and normal is 360 dpi. Print a grid of lines on gloss paper and you can verify this using a scanner. I have tried it and could print a grid of black lines at 720 dpi without any problems, the same goes for printing at 360 dpi with Finest Detail off.

Printing grids of lines at various resolutions and looking at the ugly results of driver scaling is a great advert for always sending at 360 dpi for photos!