More gray inks equal less sharpness than fewer?

[Some Guy]

Have a white circle on a black wall.  Printing it with a printer with 7-8 shades of black inks never seems as sharp as one with 3 blacks/grays and colors.

Zooming in 400% in Photoshop on the white-black edge I can see about 6 pixels of light-to-dark density which I am guessing the multiple gray ink printers attempt to fill in and hence it appears less sharp over the printer with less black inks that might not be able to dither that area so the white to black transition is more distinct with more apparent sharpness. i.e.  More tonality = Less sharpness?  I can sharpen to get rid of many of the extra gray pixels, but then it looks jagged too.

Anyone know if this unsharpness can be due to having more shades of gray?

SG

[aaronchan]

I used to use K7 back in the day with both Matt and Glossy.
Never had a problem of what you were mentioning in the final out put.
The prints from both Matt and Glossy are always as sharp as they were supposed to be.
Even better than my Canon iPF8300 back in that time.

aaron

[Jager]

My experience is that K7 inksets are much more accurate than, for example, Epson ABW.  Accurate in the sense that each pixel in your file will much more precisely reflect the correct ink tone it is mapped to.

It is a higher fidelity system that provides greater resolution and sharpness, if that's what you're aiming for.

In your example, if you have a pixel mapped to 0 adjacent to a pixel mapped to 255, you should see that pure white and pure black exactly printed.  If you're seeing tones of gray when you zoom in, that would suggest that the file is not as precisely white/black as it appears when not zoomed in.

It's certainly true that Epson's ABW can sometimes give the appearance of being sharper/contrastier than K7, because it is unable to render all the tones in the file, going full-black before 0, and full-white before 255.  

The beauty of K7 is you get exactly what's in your file, nothing more, nothing less.

[mkihne]

Antialiasing printed accurately?

[Ernst Dinkla]

Have a white circle on a black wall.  Printing it with a printer with 7-8 shades of black inks never seems as sharp as one with 3 blacks/grays and colors.

Zooming in 400% in Photoshop on the white-black edge I can see about 6 pixels of light-to-dark density which I am guessing the multiple gray ink printers attempt to fill in and hence it appears less sharp over the printer with less black inks that might not be able to dither that area so the white to black transition is more distinct with more apparent sharpness. i.e.  More tonality = Less sharpness?  I can sharpen to get rid of many of the extra gray pixels, but then it looks jagged too.

Anyone know if this unsharpness can be due to having more shades of gray?

SG

Let us skip the fact that many viewers describe a high contrast image/edge as sharp while it may not represent more detail/information/resolution compared to a smoother B&W print.

There are however some factors that could influence the information quality of quad and beyond inkset B&W prints compared to Black Only B&W prints. Laying down 10x the ink medium with an LLK ink to create the same density a single droplet of black can achieve, asks more of an inkjet coating. Not all coatings can handle that. Ink limitation in Black Only B&W is done at 100% density, with quad and beyond partitioned ink channels there are more spots on the tone range where bleeding/dotgain can happen. Proper partitioning and the right dilutions are the way to go. Calibration, profiling is a must and maybe additional sharpening can help too. The alignment of the print heads for precise droplet addressing plays more a role with several ink channels at work on the image than with just one or two ink channels. No sharpening etc in the workflow helps then, a proper head alignment is needed. It is not different to a color print and its color channel mixing on the paper but the flaw is more disguised in the quad print.

On the other hand the overlap of several partitioned ink channels smooths head banding but in the black areas. Some custom B&W configurations use two black channels to suppress banding in black areas as well, a solution more often needed on consumer desktop models with very small droplet sizes and low nozzles per channel heads, the droplet addressing is better in pro models with somewhat larger droplets. Minuscule banding in black areas also has quite an effect in spectrometer/densitometer readings, Dmax drops while it may not be so different visually.

Met vriendelijke groet, Ernst

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