Digital BW, The Print

Peter De Smidt wrote:
> I've finally gotten around to scanning some of my 4x5 negatives, and I 
> wonder what ppi I should send to the printer. Given the large size of my 
> files, I could send a 720 ppi file without resizing, but some think that 
> this leads to a drop in quality.  For example, In Real World Photoshop 
> CS2, Bruce Fraser and David Blatner say, "It's certainly possible to 
> send too much data to an inkjet printer, not only increasing print times 
> unconsciously but also degrading the image. You do not want to send a 
> 1440-ppi image to a 1440 dpi inkjet." (p843.)  I seem to remember them 
> saying that 720 ppi is too much as well.  They recommend 480 ppi for 
> small prints, and 360 or 240 for large one.  To meet this requirement, 
> I'd have to significanly down-sample my files, at least with my R2400. 
> Anyone have any thoughts on this?


Peter,

This has been discussed before on several lists. Bruce could 
be right in some cases, more in the past than now. It is a 
pity that he didn't explain what happens.

The Qimage list usually gives the best explanations for what 
happens and the tools to get best quality.

Native resolution is the key in this discussion. The recent 
Epson desktop models have 720 PPI as their native resolution 
for almost all settings (Qimage shows the native resolution 
above the preview window, it gets that information from 
Windows API where the printer/driver puts that request). The 
recent Epson wide formats have 360 PPI most of the time and 
720 PPI when fine detail is selected (if allowed for that 
paper etc). Older models have 360 PPI. The Fuji Frontier has 
300 PPI and there are other numbers around.

If the printer you select has a 300 PPI native resolution then 
either the software you print from or the driver has to do up- 
or down-sampling to get the right resolution for input if it 
wasn't 300 PPI right away. The up- and down-sampling routines 
in the software differ from one another. Early Epson drivers 
had at best a nearest neighbour algorithm. Today a crude 
bicubic. We all understand that up-sampling can be done with 
different results due to the quality of the algorithms. It is 
an issue with down-sampling too. Anti-aliasing is one of the 
things often missing in the drivers. So the quality can 
decrease in down-sampling by the driver if compared to a good 
down-sampling done in image editing software.

It is hard to predict what happens in the workflow you use. If 
your printer uses 720 PPI native resolution then sending 720 
PPI doesn't harm. Whether it will show better quality than 
sending a 360 PPI file that has been carefully down-sampled in 
editing software and carefully up-sampled by good driver 
software again is hard to predict. If the native resolution of 
the printer is 360 PPI or an odd number then I would send that 
data after careful down-sampling. I use Qimage and that does 
the job automatically and good 90% of the time.

Bart de Wolf has a nice page on the subject:

http://www.xs4all.nl/~bvdwolf/main/foto/down_sample/example1.htm

Ernst


                    --
           Ernst Dinkla


www.pigment-print.com
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