Digital BW, The Print

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, Howard Shaw 
<glassman@...> wrote:
>
> Joost Horsten wrote:
> > --- In DigitalBlackandWhiteThePrint@yahoogroups.com, "Kevin Bradford" 
> > <bradford@> wrote:
> >>
> >> --- In DigitalBlackandWhiteThePrint@yahoogroups.com, Howard Shaw
> >> <glassman@> wrote:
> >> > I'd be interested to know if you also see this banding with ABW for 
> >> > example or does it only occur with QTR?
> >> > 
> >> > Howard
> >> >
> >> 
> >> The ABW print did not show any banding, it was very smooth. 
> >> 
> >> Kevin
> >>
> > 
> > 
> > Howard,
> > 
> > This seems to support your theory we discussed off-line. Perhaps you 
> > could elaborate here?
> > 
> 
> Joost
> 
> I mentioned to you that, at least at 2880dpi, the QTR 100% ink limit 
> calibration test produced an anomalous result at the 50% step with the 
> density being less than at 45%. It was therefore necessary to 
> interpolate this density. As you surmised this appeared to be a specific 
> dithering problem that only occurred at this step.
> 
> If you then chose an ink limit of 70% say and reprinted the 21-step you 
> wouldn't notice it because none of the steps would be at 71.4% (50/70).
> 
> The theory was therefore that the series of bands in Graham's test image 
> were caused by each ink (for which you had different ink limits) going 
> across it's own 50% mark.
> 
> If it is caused by this you should be able to work out where each band 
> will occur by looking at each ink's limit and calculating where it 
> crosses the 50% mark.
> 
> There is contrary evidence to this. For example, at 2880dpi my ink 
> limits are often beneath 50% yet when I printed the test image I also 
> saw banding. Also you would think that the phenomenon would have been 
> frequently noticed in images with gentle gradations at which these ink 
> limit boundaries are crossed. On the other hand these bands are 
> particularly noticeable in Graham's test but not on a linear ramp so 
> maybe we wouldn't notice them anyway.
> 
> So, inconclusive but I'd be interested to hear if any other QTR users 
> have noticed these odd readings during the calibration test.
> 
> Howard
>

Howard,

I'm not sure what printer you are using.  The one thing that gives anomalies
is too much ink. I can't imagine much else especially at 2880dpi.  But if you 
have some other than that I'd like to see what it is.

Roy