dot size?

[Kevin]

In my research of these printers I've found that the Epson has a 'dot size' of 6 picoliters (sp) for the 750 and 1200 (both of which are 6 color printers) and the Epson 900 has a dot sizze of 3 picoliters.

The HP1000 uses 'layering' technology - but I don't know how that translates into dot size in picoliters...

It would seem that smaller dot size leads to better prints. And can even allow 3 color printers (plus black) to meet or exceed the 6 color printers with bigger dot size.

Takers on this?

 

[Dave Schambach]

In my research of these printers I've found that the Epson has a 'dot
size' of 6 picoliters (sp) for the 750 and 1200 (both of which are 6
color printers) and the Epson 900 has a dot sizze of 3 picoliters.

The HP1000 uses 'layering' technology - but I don't know how that
translates into dot size in picoliters...

It would seem that smaller dot size leads to better prints. And can even
allow 3 color printers (plus black) to meet or exceed the 6 color
printers with bigger dot size.

Takers on this?

I think that small dot size can lead to better prints. However, picoliter is
a measure of volume (drop size) not diameter (dot size). Although I'm
sure the two are pretty closely related, I'm not sure that there is a
a direct conversion between "drop size" and dpi.

Takers?

 

[paul-ny]

I don't know what "layering technology" is or does, but dot size is worth knowing about. There was an interesting comparison of various Epson dots somewhere on Digital Darkroom @ Singapore several months ago, but I don't know if it's still there.

The smaller the minimum dot size, the better the picture will look in the highlight areas. A pale tone can fade to absolute white in a (film) photograph; digitally printed, the image will consist of smaller and smaller dots that eventually drop away entirely. If the dots can't get very small, you will easily see a blotchy edge where the color drops off and white begins. As the dots approach invisibility, the image will approach the smooth gradation of a film photograph.The volume of each dot is what an Epson printer can actually guarantee; the diameter of the dot is a function of how the ink sits on or soaks into the paper once it lands on it. I don't suppose that halving the inkdot's volume (and printing on photo paper) will exactly cut the dot diameter in half, but there's some kind of relationship there, and small minimum dot size is a desirable thing.

Six color printers achieve light colors by printing with two additional light-colored inks. The same phenomenon of blotchy fade-to-white will occur with these inks, but the difference is that they can print pale colors such as pink and light blue with a great deal more intensity than four color printers. Six colors and tiny dots are both good features; they're not equivalent.

Dots per inch is a measure of how far apart the printer places dots on the paper. It's the resolution of the printed image. The 1400 dpi setting on the Epson printers makes an image with very sharp lines and smooth edges. It's only appropriate for certain very smooth, non-absorbent papers, though, because normal paper will absorb the ink dots and spread them out to a size where they will run into each other. And the picture will lose definition in color and values that would be evident at a lower dpi setting. Drop size and dpi are really not related, except in that you couldn't print 1400 dpi without being able to produce dots that are pretty small.

In my research of these printers I've found that the Epson has a 'dot
size' of 6 picoliters (sp) for the 750 and 1200 (both of which are 6
color printers) and the Epson 900 has a dot sizze of 3 picoliters.

The HP1000 uses 'layering' technology - but I don't know how that
translates into dot size in picoliters...

It would seem that smaller dot size leads to better prints. And can even
allow 3 color printers (plus black) to meet or exceed the 6 color
printers with bigger dot size.

Takers on this?

I think that small dot size can lead to better prints. However,
picoliter is
a measure of volume (drop size) not diameter (dot size). Although I'm
sure the two are pretty closely related, I'm not sure that there is a
a direct conversion between "drop size" and dpi.

Takers?

 

[Leon Wittwer]

Assuming coated paper and little or no blooming, the linear size of a dot goes as the cube root of the volume. Thus a factor of two decrease in picoliters per dot will result in a 26 percent decrease in linear size. Not as big a deal as some would have you believe. I've tested both an Epson 700 and a 1200 for resolution. Both came out about 150 lines per inch. As mentioned elsewhere, the droplet volume probable has more to do with tonal smoothness than resolution.

 

[David E. Scott]

Leon,

If all inkjet printers printed non-overlapping ink dots, your evaluation would be absolutely correct! However... although only HP advertises multi color dot layering, virtually all inkjet printers use a form of ink dot overlapping to achieve what the manufacturers consider virtual dpi patterning.

In other words, the ink dot may not be as small as the number of ink dots which are fitted into a given inch, hence the dpi specification for different printer resolutions. This does not mean the printer manufacturers are giving out false advertisement, merely that their printers are capable of putting so many ink dots in a printhead travelled inch.

I think you may be confusing the commercial art form of half-toning with consumer ink jet print dithering at various dpi settings. I am not really familiar with how images are printed in magazines and books, but I do know that the ink droplets do not overlap as they do with higher resolution consumer inkjet printouts.

It follows that the smaller the size of the ink dot, the finer and sharper the edge definition will be, no matter how much each ink dot overlaps with its neighbor. Logically, the inkjet printer with the smallest ink dot will have the sharpest printout, and the inkjet printer with the highest dpi specification, even though overlapped, will achieve print quality closest to continous tone gradation by the process of dithering overlapping dots of ink.

All of this, of course, is highly dependent on how accurately the printhead can deposit the dot of ink in a specific location. Consider the splatter created by heating soup on a stove as opposed to the controlled movement of the soup by spoons to a cup and you will have the analogy of thermal dot deposition compared to piezoelectric dot deposition, as is used by Epson!

Once you can control where the dot where go and how many of those dots you can place per given linear distance, even though they will need to be overlapped, you will have the finest registration of lines and dithered colors available for that specific printer.

This is why the print quality of Epson printers is so high, not because of the size of the ink dot alone, but rather because of where and how many of the ink dots are placed accurately on the paper! If Epson and all the other inkjet printer manufacturers only printed their ink dots side by side, as in half-toned prints, then they would, indeed, be limited in resolution by the size of the ink dot.

But this, thank goodness and some obscure team of ingenious researchers, is not the case with inkjet printer dot pitches and rated resolutions!

I would hope I have given an adeqate explanation for print quality as opposed to physical specifications of ink droplets, and how they are both related and unrelated.

Enjoy Your Printers Everyone!

David E. Scott

-----------------------///----------------------------

Assuming coated paper and little or no blooming, the linear size of a dot
goes as the cube root of the volume. Thus a factor of two decrease in
picoliters per dot will result in a 26 percent decrease in linear size.
Not as big a deal as some would have you believe. I've tested both an
Epson 700 and a 1200 for resolution. Both came out about 150 lines per
inch. As mentioned elsewhere, the droplet volume probable has more to do
with tonal smoothness than resolution.

 

[Jay]

In my research of these printers I've found that the Epson has a 'dot
size' of 6 picoliters (sp) for the 750 and 1200 (both of which are 6
color printers) and the Epson 900 has a dot sizze of 3 picoliters.

The HP1000 uses 'layering' technology - but I don't know how that
translates into dot size in picoliters...

It would seem that smaller dot size leads to better prints. And can even
allow 3 color printers (plus black) to meet or exceed the 6 color
printers with bigger dot size.

Takers on this?

Kevin,

I did some research for a new printer in the past couple of months as well. I wanted a good all around printer. I do not need professional quality as I take and print digital photos just for fun. I read about picoliters and color layering. I don't think it really matters. What I did was take a picture and demoed a few printers with the same paper. The HP 970 had very good pictures but I thought the Epson was nicer. I bought the Stylus 900 and couldn't be happier for what I use it for. Certainly I'm no expert but the photo quality output on photo paper is outstanding. Not quite as good as the Epson or HP dedicated Photoprinters (or so I'm told) but for a novice it is very difficult to tell the difference.

Find the printers that fits your needs and demo all of them and judge for yourself. Other people's opinions are only that, and the debate of HP versus Epson seems to create a lot of emotionally charged issues.

Hope this helps

jay

 

[paul-ny]

Leon,

If all inkjet printers printed non-overlapping ink dots, your evaluation
would be absolutely correct! However... although only HP advertises
multi color dot layering, virtually all inkjet printers use a form of ink
dot overlapping to achieve what the manufacturers consider virtual dpi
patterning.

In other words, the ink dot may not be as small as the number of ink dots
which are fitted into a given inch, hence the dpi specification for
different printer resolutions. This does not mean the printer
manufacturers are giving out false advertisement, merely that their
printers are capable of putting so many ink dots in a printhead travelled
inch.

I think you may be confusing the commercial art form of half-toning with
consumer ink jet print dithering at various dpi settings. I am not
really familiar with how images are printed in magazines and books, but I
do know that the ink droplets do not overlap as they do with higher
resolution consumer inkjet printouts.

It follows that the smaller the size of the ink dot, the finer and
sharper the edge definition will be, no matter how much each ink dot
overlaps with its neighbor. Logically, the inkjet printer with the
smallest ink dot will have the sharpest printout, and the inkjet printer
with the highest dpi specification, even though overlapped, will achieve
print quality closest to continous tone gradation by the process of
dithering overlapping dots of ink.

All of this, of course, is highly dependent on how accurately the
printhead can deposit the dot of ink in a specific location. Consider
the splatter created by heating soup on a stove as opposed to the
controlled movement of the soup by spoons to a cup and you will have the
analogy of thermal dot deposition compared to piezoelectric dot
deposition, as is used by Epson!

Once you can control where the dot where go and how many of those dots
you can place per given linear distance, even though they will need to be
overlapped, you will have the finest registration of lines and dithered
colors available for that specific printer.

This is why the print quality of Epson printers is so high, not because
of the size of the ink dot alone, but rather because of where and how
many of the ink dots are placed accurately on the paper! If Epson and
all the other inkjet printer manufacturers only printed their ink dots
side by side, as in half-toned prints, then they would, indeed, be
limited in resolution by the size of the ink dot.

But this, thank goodness and some obscure team of ingenious researchers,
is not the case with inkjet printer dot pitches and rated resolutions!

I would hope I have given an adeqate explanation for print quality as
opposed to physical specifications of ink droplets, and how they are both
related and unrelated.

Enjoy Your Printers Everyone!

David E. Scott

This is very interesting. It makes me want to know one thing: Don't Epson printers make darker colors through an increased dot size, or is it by laying down a greater density of uniform dots? If it's the latter, I see your point about sharp edges being a result of small dot size. If dark colors are made by large dots, I would have thought that an edge where a dark color breaks sharply to white, say, would be created by dots (on the colored side) of a larger size, in which case the dot size might be the same on a 3 picoliter printer as on a 10 picoliter printer, and the sharpness of the edge would be determined by the dpi of the printer and not really related to the (minimum) dot size. What do you say?

Also, to get extremely nitpicky about what Leon was saying, it seems to me that the size of a dot would vary not with the cube root of the drop's volume, which is what the drop's diameter does, because the dot is a squashed form of the spherical drop, still three dimensional but shaped more like a disk, assuming no soaking into the paper. If, theoretically, the thickness of the ink layer is the same for all sizes of dot, then doubling the volume of the ink drop will double the area of the dot-- and it is the area of coverage that determines the darkening effect of printed dots. That would mean that dot volume makes more of a theoretical difference than Leon says, but what he observed was the most important test.