bert bigelow

In another thread, I have been engaged in an ongoing discussion regarding inkjet printer technology, optimum resolution for printing, and related subjects.
New printers on the market are capable of resolutions approaching 6000 dpi. Some knowledgeable people claim that the conventional wisdom advocating 300 ppi as the "optimum" resolution for a Photoshop image to be printed is nonsense. They claim that the new generation of inkjet printers is capable of generating printed images with resolutions much higher than 300 dpi. In fact, some have made the statement that "more is better" without limit.
I would like you all to address the following questions:
1. Is 300 ppi still the optimum resolution value for the "new" generation of printers?
2. If higher resolution is preferable, can the human eye see it?
There are more questions we could raise on this subject, but let's start with these. Please feel free to raise related issues that you think are relevant. Okay...ready...set...go!!!
Bert

chuck snyder

Bert, I'm not going to participate in this one any more than to say that the
confusion between image resolution in ppi (pixels per inch) and printer
resolution (dpi) continues to be a real problem for me. The two resolutions
can't be the same because it takes more than one dot (which is cyan,
magenta, yellow or black) to make up a pixel (which can be any one of 16.7
million colors). So....the best bet is probably (I say with trepidation) to
deliver the best real image resolution possible to your printer, and
independently set your printer to its base (uninterpolated) resolution.
When you read that a printer is 2880x720, that means its base resolution is
720; anything higher than that is interpolation - just like adding pixels
via upsampling on the image side. I don't know....you'll probably hear that
the interpolated printer resolution is better, and maybe it is - otherwise,
why would it be a feature? But the concept of maximum pure ppi and maximum
pure dpi appeals to me....

OK...I've already said more than I know...again.

:-)

Chuck

yrbkmgr

Chuck touches on an important point that we, as this thread continues, need to make sure is abundantly clear. DPI and PPI are two different measurements. For those who are unclear as to their relationship and definintions, a visit to ScanTips <http://www.scantips.com> should clear it up.

Having said that, and more to your point Bert, if we use the human eye as the measurement tool, then there are indeed limits beyond which more resolution makes no sense.

The ****ogy is 16 bit color depth for images as well as 32 bit color displays. The common wisdom, as it relates to bit depth for images (8-bit v. 16 bit) is that the human eye cannot see the all the colors that are in a 16 bit image. There are no displays that can accurately represent those colors, and there are certainly no output devices that can reproduce those colors.

There is considerable value however, to some cognescenti, that certain edits done at 16 bit depth, results in a "cleaner" histogram when the image is converted to 8 bit depth for the final edits/printing. It is generally agreed that a higher bit depth is more "pure" data, and thus on some images, in some cir***stances, there may be some subtle benefits to using 16-bit images. But let's not mince words - there are no inkjets that can output 16-bit images. Photoshop "proper" converts the image to 8-bit for printing behind the scenes, because otherwise, you wouldn't be able to print the image.

The point is, just as there is more data in the image that we can see, there is more data in the image than we can print (and see in a print).

As it relates specifically to Inkjet printing, consider this. As Chuck was quick to point out,

When you read that a printer is 2880x720, that means its base resolution
is 720


But not quite for the reason that he states. Inkjet printers with 4 colors, rated at 2880 produce a 720 dot per inch output. The issue is that 2880 divided by all 4 colors (albeit in varying amounts) is 720 dot per inch since 4 colors are used to make a single dot. Technically, this is not 100% accurate, 100% of the time, but this is the way that inkjet manufacturers rate printer output. There is no real way to gauge output in dots per inch since there are so many factors that affect the image output - like dot gain (or spread), and different implementations of nanoliter dispensing of ink.

So the question you pose, technically goes to defining the relationship between pixels per inch and dots per inch. Is there one? Maybe - but no one has really defined it yet.

Rather, we determine the appropriate pixels per inch to send to a printer based on empirical data - that is through trial and error. Usually the measurement tool is the human eye. Some people have a "better eye" than others, true, but there are limits (just like the number of colors in a 16 bit image).

So the next question is, really, this: If my printer cannot functionally print more than a certain density, and there is no defined relationship between pixels per inch and dots per inch, can we say that there must be a limit to the resolution of an image that can be represented on an inkjet? Or is it unlimited?

Can I keep piling more and more data to a printer and expect better and better output? Or is there some "saturation" point at which any more pixels per inch cannot be represented on an inkjet?

Surely this latter must be true.

Using this reasoning, the statement that:

In fact, some have made the statement that "more is better" without limit.


Is certainly an uninformed one.

Specifically to your question, "Is 300 ppi the 'new' upper limit?" based on advances in inkjet technology, the answer is, really, "maybe, but certainly no more".

The inkjets are still only putting out a density of 720 dots per inch. That's the max density. The old 1440 dpi printers have a functional output 360 dpi, and the 2880 printers are twice that (720 dpi). So it may stand to reason that you should be able to send twice the data and get better output.

That may be true theoretically, but there is no data that concludes that point decisively. Most "purests" have been sending way too much data to the old printers (1440 dpi) and have arrived, empirically, at an image resolution of 150-300 ppi as being the optimum.

In my own tests, with my images (I output about 6,000 images per month via inkjet, although, they are really only 300 different images, just multiple copies), I have seen absolutely NO difference in sending images to a 2880 (720 dpi) at resolutions greater than 200 ppi. Will some see better output at higher resolutions? Maybe. But it would be image composition dependant, and there certainly is a limit.

I was going to give my two cents, but I gave a buck - keep the change <grin>.

Peace,
Tony

bert bigelow

Here is a link to another thread on the same subject. I would like your comments on Peter's very detailed comments. Go to Post #1.
Peter Duniho "Resolution ?????!!!!!" 9/24/03 11:41pm </cgi-bin/webx?14@@.2ccd881b/0>
Bert

yrbkmgr

Bert,

I had a biology instructor in college who was invited to debate a fundamentalist Christian in a national college symposium on the subject of Evolution. I asked him if he planned to engage - he said "Are you kidding? It doesn't whether you're right or not, it only matters if you can sell the audience that you're right - I'm a biologist without an agenda, not a salesman with and agenda."

With that general idea in mind, I'm not comfortable voicing my comments on Peters remarks in the Elements forum. I view myself as a visitor here and the regular Photoshop forum is where I hail.

That is a polite way to say, that while Peters argument doesn't hold water, I am not comfortable debating it here. Sorry I can't be of more help, maybe some of the other "old pro's" would be willing to comment.

I will say, though, that if the topic were being discussed in the regular photoshop forum where the audience is more seasoned (in general) there would be many folks able to clarify the mysteries of dpi and ppi and dispel the urban legends.

I think, as I said in my earlier post, that anyone who is interested in the subject should spend some time at scantips.

Peace,
Tony

bert bigelow

When you read that a printer is 2880x720, that means its base resolution
is 720; anything higher than that is interpolation - just like adding
pixels
via upsampling on the image side. I don't know....you'll probably hear
that
the interpolated printer resolution is better, and maybe it is - otherwise,
why would it be a feature? But the concept of maximum pure ppi and maximum
pure dpi appeals to me

Chuck,
That's exactly what I thought. But I'm hearing different from people who are smarter than I. Hopefully we'll both learn from the discussion here.
Bert

bert bigelow

Tony,

For those who are unclear as to their relationship and definintions, a
visit to ScanTips should clear it up.


I am also a disciple of Wayne Fulton and his book. That's sorta what prompted me to start this thread, because I'm hearing different opinions on resolution and its ramifications, and I'm getting confused, because they seem to be contradicting his dogma, and admit I am brainwashed by Wayne. He is a very convincing teacher.
So, I'm hoping we get lots of input here. I would particularly like Peter Duniho to chime in. I hope we'll all learn from the interchange.
Bert

peter duniho

No, it does not. It means the printer is capable of positioning a dot to
within 1/2880th of an inch in one direction, and to within 1/720th of an
inch in the other direction. It has nothing to do with interpolation or
upsampling.

Pete

peter duniho

I feel my previous posts have conveyed just about as much information as I
can. I have done my best to combat the urban legends that appear rampant
here, and frankly, I'm done. However, given that I appear to be the "some
people" referenced in your message, I want to clear up one
mischaracterization of my statements that you've made:


limit.

The only place I've made any statement that could reasonably be interpreted
to that effect, the context was in a message where I was trying to keep
things as simple as possible. Even in that message, a more detailed
explanation followed.

Clearly, for any printer, there is an image resolution beyond which that
printer is incapable of producing. It is unfair of you to imply that I said
otherwise.

Pete

peter duniho

I have no more a right to a comment in this forum than you do.

Please, I would love to hear why you claim my statements "don't hold water".
Without any further explanation, your claim to that effect is pointless,
holding no water itself.

Pete