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[stevebrot]

Hmmmm...150 Mpixels as source document --> 8x10" !!!

Too bad it is not possible to show how much sharper the high dpi prints were.

I wonder what can be done with a 36Mpixel source? For a K-1 image that would provide 4912 pixels across the 6" of the short side of the print for a maximum X-axis (at the printer) resolution of 819 dpi if printing the full 3:2 ratio frame to 8x10 with minimum 1/2" margin.

Of course, conventional wisdom is that Canon printers have native resolution of about 300 dpi with anything above that being supported by some sort of magic that I certainly would not understand. Despite conventional wisdom, Canon claims a horizontal ink droplet placement pitch of 1/4800" minimum for my Pixma Pro-100. For the 6x9" print area described above that yields support for an astounding 1.2 Gigapixel 3:2 sensor!!! We won't even think about the memory required to marshal the pixel data for printing. Woa, Trigger! Ink droplet placement pitch is not the same as pixel-driven dot pitch, particularly if printing 8 colors of ink. Moving away from the tech talk, the actual claim is up to 2400 dpi on the X axis at the printer (short side), attained by head movement. Twice that is claimed for the long axis (attained by paper movement), but I don't buy it without there being a wizard somewhere. 2400 dpi brings us down to a somewhat more reasonable 311 Mpixel capture. In case anyone is wondering, scans of large format negatives routinely touch that realm.

Assuming that Canon is not fibbing, what does that say about our K-1 capture? Is there value printing at 800 dpi with little or no data munging or even 666 dpi from my K-3? Would one be able to see the difference, even on high gloss, low-spread paper without magnification? I am disinclined to waste expensive ink and paper on such an adventure, but would be very interested if others are willing to do so in the interest of science. Actual copy photographs at a reasonable magnification might prove adequate to allow comparison.

Any takers?


Steve

[EFats]

I used to work for a printer company doing very large format inkjet printers (largest size was about 2.5 x 3.5 meters). We were a subsidiary of a very big, well-known company that starts with a "C" :-)
I was deep into the system design and print modes and I can tell you .... it's complicated. At least for the machines we designed, the horizontal and vertical DPI are "true", not marketing terms. However, it's not the same as when quoting DPI for an LCD display or camera sensor. Some of it has to do with the number of colours that are used, some with the ink drop size on paper, some with how each layer of ink is layed down.
I've printed large images from full frame DLSR and I can tell you the difference when doing it at, say 300 DPI and 600 DPI are enormous. Stepping up to 800-1200 DPI can make a difference, depending on the image. The difference isn't so much what I would call resolution, but in the image "grain" and smoothness of colour gradients/changes.


The smaller desktop printers have a bit of advantage as they have finer dot pitch and also much smaller drop sizes as well, but then of course they can't print as big. The 2400 DPI on the x-axis is not unreasonable. There's no magic there (unless you count the engineering required to reliably position ink droplets accurately time after time).

There's way too much to talk about in the forum, I could have enough to fill a series of articles...

[biz-engineer]

Given the scale at which printer technology works, it is almost certain that digital cameras are the limit to the quality of the print quality output, not the printers.

[TonyW]

I am sure the author means well but there seems to be flaws in his thinking and conclusions

Seems to be confusing DPI with PPI. "decided to make 8x10 prints from 150MP file at 150 dpi, 200, 300 -900+dpi etc,"

AFAIK there is no way to set Canon (or for that matter Epson or HP) printers to the dpi mentioned. The print driver will not allow it and generally the driver will allow you to specify custom settings which may be a series of numbers from Draft to Fine e.g. 5 - 1 with 1 being finest, typical for Canon drivers. Espson similar with Level 5 being their maximum quality at 2880x1440dpi YMMV depending on printer and print driver

So my take is that he does not mean DPI but rather PPI i.e. the image resolution he is sending to the printer

It is not surprising that resolution is better the more PPI sent to the printer - up to a point and depending on capture resolution and subject matter, It should be better. Canon resolution requirements being 300/600 PPI and Espson 360/720 PPI. Also worth mentioning there is also the opportunity to go to 1200 or 1440 PPI with Canon or Epson.

What has not been taken into account is the fact that at less than 300 ppi or more than 600 ppi that any image data sent to the printer will be interpolated by the print driver to the printers requirements (and you may also need to set the driver for higher resolution quality manually). The print drivers resampling algorithms will use Nearest Neighbour for speed, whereas if you resample first to 300 or 600 in PS, LR etc then you will generally get a superior result.

Subject matter (assuming a tack sharp capture!) is also key in seeing 'improvements' in resolution. Going from 300 to 600 ppi for instance (assuming possible with native file resolution) may only yield marginal improvement, possibly only visible in circles and angled straight line. These improvments may be irrelevant when taking into account viewing distance for a larger print

I believe the advice to send the printer all the PPI (not DPI) you have is flawed as already mentioned the file will be interpolated by the driver to either 300 or 600 ppi regardless of what you think you are printing at - so for optimal results best to resample yourself to the printers required resolution using superior algorithms available in LR or PS.

DPI does have an effect on print quality it controls how much liquid to squirt on the paper and in turn will be calculated by paper type absorption and spread of liquid sitting on top of paper. Most print drivers will stop you from setting high/maximum DPI for example to plain paper as this would just soak and buckle the paper.

[Alex645]

The point the video is making is that in his tests, which concur from my own experience, avoid automatically using any common standard such as 300 ppi to resample an image. In the offset printing of books, usually done at 150 lpi or higher, quality artifacts become visible when the source image is below 240 ppi for color and below 200 ppi for monochrome. So to ensure quality, 300 ppi is usually the default to try to keep the masses out of trouble.

As a teacher and yearbook advisor, I am guilty of preaching 300 resolution as the standard, because I am trying to prevent students from using low res jpegs. But in truth, if we want the best IQ possible, ideally don't downsize the RAW file image size or resolution.

With Epson inkjet printers, I usually set the printer to 1440 dpi, because I've yet to find a paper that can handle the 2880 dpi option and although I can see increased quality with 600 ppi images, for most applications, 300 ppi images is the compromise for reasonably sized images and the printed results. What the video is saying is if you want the max resolution, simply don't downsize.

[stevebrot]

AFAIK there is no way to set Canon (or for that matter Epson or HP) printers to the dpi mentioned. The print driver will not allow it and generally the driver will allow you to specify custom settings which may be a series of numbers from Draft to Fine e.g. 5 - 1 with 1 being finest, typical for Canon drivers.

There is more than one way to drive a printer. I use Lightroom's print module, which does allow setting a numeric dpi number Correction: more correctly, "numeric ppi number". See continuing discussion below.

But in truth, if we want the best IQ possible, ideally don't downsize the RAW file image size or resolution.

Yep...though matching print size to pixel dimensions allows the best of both worlds, assuming reasonable viewing distance. Printing big (say 16x20) at 2400 dpi from a 36 Mpixel source is just so much interpolation. Printing small (8x10) from a 150 Mpixel source is an entirely different matter.


Steve

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Last edited by stevebrot; 02-22-2019 at 01:42 PM.

[TonyW]

There is more than one way to drive a printer. I use Lightroom's print module, which does allow setting a numeric dpi number.
.............

Steve

No LR does not allow setting up a numeric dpi number. It does not drive a printer but allows you to send the correct amount of PPI to a particular printer. It does not understand dpi none of the Adobe products do it works in PPI which is image resolution as opposed to printer stepper motor movement and squirting liquid

It really does not matter what you think you are sending relating to data to the print driver it will upsample/downsample and produce a bitmap equating to its requirement as declared to OS that being 300/360 or 600/720 Canon Epson. Send jyour Canon printer a file at 80 ppi the driver will upsample to 300 and if your native file size allows more the print resolution will be improved (up to the limits of your image acquisition)

300 ppi is the correct resolution to send to a Canon printer or if your native file falls above then 600 ppi may show improvement
360 ppi is the correct resolution to send to an Epson printer or 720 ppi if native resolution above.

If you use an application for printing like Qimage you will find that the ultimate ppii doubled for your printer i.e. 1200 or 1440 ppi

---------- Post added 02-22-19 at 09:53 AM ----------

With Epson inkjet printers, I usually set the printer to 1440 dpi, because I've yet to find a paper that can handle the 2880 dpi option and although I can see increased quality with 600 ppi images, for most applications, 300 ppi images is the compromise for reasonably sized images and the printed results. What the video is saying is if you want the max resolution, simply don't downsize.

Usually(?) for the Epson printers the driver will set the quality which is highly dependent on the paper surface . So for level 5 highest quality the driver will set 2880/1440 dpi for photo papers, 1440 dpi is the really relevant number as that is the stepper motor minimum step in the x direction.
300 ppii is not an optimal resolution figure for and Epson printer the figure is actually 360 ppi and is derived from the number of print nozzles (some Epson print head have 180 nozzles). For those images that exceed 360 ppi at print size then 720 ppi is normally optimal

[stevebrot]

No LR does not allow setting up a numeric dpi number.

I must be special...




Steve

[TonyW]

I must be special...




Steve

Not special just repeating what seems to be the majority of people misunderstandings (including the subject of the OP) the concepts of PPI vs DPI...

Look again at your image and you will see that the measure is actually PPI a measure of file resolution which will be sent to the printer. Again Adobe does not deal in or understand the concepts of printer DPI.

What you set for PPI here is the amount of pixel data the application sends to the print driver - it does not control the driver in any way but if the PPI is at the 'correct resolution' for the printer then the print driver does not do anything other than produce a bitmap (spooling) prior to sending to print. If on the other hand you just send it the data as is then it will have to interpolate prior to producing the bitmap for print. In the case you show your 111 ppi would be resampled by the print driver (sub optimal!!) to either 300 ppi for Canon printer or 360 ppi for Epson

[stevebrot]

Not special just repeating what seems to be the majority of people misunderstandings (including the subject of the OP) the concepts of PPI vs DPI...

Look again at your image and you will see that the measure is actually PPI a measure of file resolution which will be sent to the printer. Again Adobe does not deal in or understand the concepts of printer DPI.

I configured per advice from Martin Evening. His books on Lightroom are considered to be the definitive reference for the software. Apparently he is not so bright either.


Steve

(...mulling the matter of printing pixels...thought printers worked from bitmaps...)

[stevebrot]

Look again at your image and you will see that the measure is actually PPI a measure of file resolution which will be sent to the printer.

That is true and while it is a bit strange, I can assure you that it has nothing to do with files, even temporary ones. I take it to be a bit of "Adobe Speech" where words don't always mean what we think they mean. The intent of the "Print Resolution" box is to allow an override of Lightroom's automatic scaling. Doing so is not without hazard since there is risk of upsampling to make up for a lack of pixels in the source. OTOH, perhaps the setting does nothing and I am in need of better glasses.

BTW...you are quite correct regarding the difference between ppi and dpi. In some circumstances, they are synonymous. At other times they are not. Where things get interesting is when there are multiple dots per pixel, each applied with different color than specified by the pixel so as to create a gradient or enhance an edge where such is not present in the source data.


Steve

[TonyW]

That is true and while it is a bit strange, I can assure you that it has nothing to do with files, even temporary ones. I take it to be a bit of "Adobe Speech" where words don't always mean what we think they mean. The intent of the "Print Resolution" box is to allow an override of Lightroom's automatic scaling. Doing so is not without hazard since there is risk of upsampling to make up for a lack of pixels in the source. OTOH, perhaps the setting does nothing and I am in need of better glasses.


Steve

Adobe means exactly what it says on the tin this is PPI not as you seem to want to quote DPI - a totally different kettle of fish

I can assure you that the intent of the Print Resolution box is to allow those that understand their printer resolution needs to adjust accordingly. If left alone the print will be scaled to size and default PPI will be applied the image then passed to the print driver to interpolate.


Selecting the sampling yourself to the correct level will give the optimal result - should you go too far (in LR opinion) you will get a warning indicator. In any case you should check what PPI LR is sending first as default before changing.

Attached is an example from someone who knows printing very well - Mike Chaney application Qimage. You will see that this particular image 16x20 on Epson P800. Note the printing resolution quoted is again PPI not DPI. You will also see that the printing resolution chosen is 720 ppi (because the native file size warrants it). Now look when set to 360 PPI the red warning dot signifying less than optimal resolution being sent to the printer. One could argue that the difference may be negligible (for most!) but the fact remains that less than 720 ppi is less than optimal

---------- Post added 02-22-19 at 01:12 PM ----------

I configured per advice from Martin Evening. His books on Lightroom are considered to be the definitive reference for the software. Apparently he is not so bright either.


Steve

(...mulling the matter of printing pixels...thought printers worked from bitmaps...)

Would you kindly quote/reference from Martin Evening books his words on PPI and DPI. I configured per advice from Jeff Schewe, Martin Evenings mentor

[stevebrot]

I can assure you that the intent of the Print Resolution box is to allow those that understand their printer resolution needs to adjust accordingly. If left alone the print will be scaled to size and default PPI will be applied the image then passed to the print driver to interpolate.

My understanding as well. In case it is not clear, I am shifting into learning mode now and fully appreciate your comments. I may not have done a good job of explaining my practice nor have I been clear (even in my own mind) regarding the subtleties in the relationship of dpi and ppi. Part of that is driven by my practice when scanning negatives. In that realm, I always do a direct mapping of a scanned "dot" to saved pixel and leave the scaling to smarter software than the scanner driver.

FWIW...I am reading through Schewe's comments on the subject in a DPR thread as well as an article linked from there. He's good.


Steve

[TonyW]

My understanding as well. In case it is not clear, I am shifting into learning mode now and fully appreciate your comments. I may not have done a good job of explaining my practice nor have I been clear (even in my own mind) regarding the subtleties in the relationship of dpi and ppi. Part of that is driven by my practice when scanning negatives. In that realm, I always do a direct mapping of a scanned "dot" to saved pixel and leave the scaling to smarter software than the scanner driver.

FWIW...I am reading through Schewe's comments on the subject in a DPR thread as well as an article linked from there. He's good.


Steve

Thanks for that Steve. I am sure you will find Schewes words to be wise on these matters.

I know that I can be a pedant on the subject of DPI, PPI, SPI and LPI (and probably many more 'i's' ) but it was part of my photograpphic training over very many years and beaten into me by my mentors and a necessary thing to understand when dealing with customer education - quoting or substituting wrong figures could lead to problems down the line so the i's must always be dotted and the T's must always be crossed. Unfortunately over time DPI has crept into our photographic language as a catchall for all types of resolution