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View Full Version : Is there a point to printing at higher than 300dpi?


jimbobuk
06-01-2006, 17:25
Hi guys,

Kind of linked to my other post about sharpness to apply to the files.. I'm just wondering a little bit about resolution. I know the human eye has its limits, I don't think my eyes are particularly great anymore for stellar resolution, and most prints i've gotten look good when held at arms length, or a bit shorter.. however I do sometimes think, ahh there's a bit of detail there and instinctively bring it closer to my eyes to look closer.. there is a point where this no longer reveals any extra information where its still quite a way from being uncomfortably close to my eyes.

I'm just wondering say you do have a file that has the resolution to go higher than 300dpi, why NOT use this extra resolution and say print at 600dpi to allow for a bit of close up scrutiny should you want to.

The only reason i get confused is in a similar fashion to how manufacturers pimp up their quoted scanner specs with inflated maximum resolutions, printers also seem to not be immune.. for example

http://www.epson.co.uk/products/inkjet_printers/Stylus_Photo_R800.htm

Outstanding photos, reprints and enlargements from a resolution up to 5760 x 1440 optimised dpi on suitable media

or

http://www.epson.co.uk/products/inkjet_printers/Stylus_Photo_R300.htm

Produce premium quality photos at up to 5760 optimised dpi*

What the hell are they talking about? its a higher resolution in dpi than even the inflated scanner resolutions of most affordable flatbed scanners, what would be the point of being able to print something with more density than a piece of film? I also question if its indeed even possible to print anywhere near this limit?

Hence my conservative 600dpi instead of 300dpi.. surely most printers can easily do this?

Or is this bizarre dpi thats quoted (including the 2D one for the r800 with significantly more resolution in 1 direction than the other) meant to me something else, such as an ability to do subtle tonal changes with effective dots of this 5000dpi being the tools that can be used to create the variations in colour?

As you can see i'm a bit confused, anyone shed any light on this madness? And would there be any slight benefits for close scrutiny at printing at slightly higher 600dpi, is this something printers can do?

Cheers

keoj
06-01-2006, 19:03
I'll try to clear this up but I'm sure there are others that could explain it better than I can. Inkjets basically deposit "splotches" of ink that don't have clean edges to them. Think about line-pairs and concept of gettting a good contrasting edge (no run off) of black, next to a line-pair of white (or any other color). The more DPI of a printer, the better quality (generally), the finer resolution (with no run-off) of the edge. Thus, there are many, many printers which have 1200 or higher DPI.

Now, onto the next concept. The optical limit (normal eyes) is around 300 DPI. If I have a perfect 4000 ppi scanner (and I mean theoretically perfect), and I scan a 1 inch slide, then the theoretical maximum of a print size that I can achieve is 4000/300 or 13.33" wide. If I print larger than that, I will have to interpolate data. If I print smaller than that, I have excess data.

The reality is that no 4000 ppi scanner can scan accurately on a pixel to pixel basis and some resolution is lost.

Hope this helps.

amateriat
06-01-2006, 20:26
Hey, after all these years using the things, sometimes it still confuses me. I have a few of my facts straight tonight, but I'll need help where I screw up. :-)

The thing to remember is that there's a difference between input resolution and output resolution. There's also an upper limit to what printer drivers will accept in the first place.

For example, my Minolta DiMage Scan Elite 5400 (first version) has a maximum input resolution of, yes, 5400 dpi optical resolution (as opposed to interpolated resolution, which is "cheating" in the same way as using Bicubic Interpolation in Photoshop, which is essentially spinning out additional data that wasn't originally there to begin with) Output resolution is, in fact, a tad lower, but you'd never feed that to a printer. The big deal about this scanner's resolution is that you can output a file that can print at, say, 17x22" at 300dpi without interpolation via Photoshop, Genuine Fractals etc.. (If I have one overriding rule for my digital darkroom, it's this: the less unnecessary monkeying-around with the image file, the better). 300dpi (or ppi, to be a bit more precise) is still the target goal for resolution (some would say 360 is optimum and a few have stated that they've seen a difference when feeding 720ppi files to print, but I won't get into that here); what a high-/ultra-high-resolution scanner allows you is the luxury of printing very big without using "hamburger helper" solutions to get to that magic number before clicking Print.

(The stated resolution of a given film scanner is based on the original size of the media. In other words, my scanner can give you, roughly, a 5000-5400dpi/ppi scan at 24x36mm. Resize that file in PS up to 16x20" without interpolation and watch what happens in terms of dpi/ppi.)

Printer output specs get a little hairier. These specs are partly controlled by the the droplet size the printer lays down: a printer that can lay down a 2-picoliter droplet will have a higher numeric spec than a printer with a 4-picoliter droplet spec. Does this mean the former is automatically superior to the latter? Not necessarily (as I learned the hard way). There are a bunch of variables such as dye vs. pigment inks, number of inks used by the printer, and how well (or badly)-designed the print driver is (which goes some way to explain why some photographers go to the expense of buying third-party print-driver solutions like ImagePrint).

The most seaoned pros are feeding 300-360dpi/ppi files to their printer because, much of the time, that's about the maximum resolution that's usable even in large-ish prints, although there's no hard rule that says you can;t get slightly better results printing a bit higher; it depends on how critical your faculties are, or at least how critical you think they are.

One other critical factor is the amount of raw horsepower your computer is packing: it takes a whopping amoung of RAM, HD space and processing power to make relatively quick work or a properly-worked image file intended to be made into a fine 16x20"print (or 13x19" for that matter). Past a certain point, "more information" does little more than bog down your PC and doesn't result in a better-looking print, even on the grain-sniffing scale. One needs to find that nexus of quality and smooth, efficient production; more isn't always more.

Two sources of info, from people who've forgotten 100 times more about the subject than I've yet to absorb:

- Martin Evening, who puts out the fine Photoshop (6, 7, CS, etc.) for Photographers
books;

- Andrew Darlow, a fairly well-known Photoshop svengali who frequents the Epson and Digital black-and-white printing Yahoo! Groups, is another fantastic source of info. I've attended a few of his seminars; when you get past the intimidating speed at which he works he's sort of the Dale Earnhardt of digital imaging you can pick up quit a bit in terms of imortant fundamentals.


- Barrett

sf
06-01-2006, 21:18
I'll try to clear this up but I'm sure there are others that could explain it better than I can. Inkjets basically deposit "splotches" of ink that don't have clean edges to them. Think about line-pairs and concept of gettting a good contrasting edge (no run off) of black, next to a line-pair of white (or any other color). The more DPI of a printer, the better quality (generally), the finer resolution (with no run-off) of the edge. Thus, there are many, many printers which have 1200 or higher DPI.

Now, onto the next concept. The optical limit (normal eyes) is around 300 DPI. If I have a perfect 4000 ppi scanner (and I mean theoretically perfect), and I scan a 1 inch slide, then the theoretical maximum of a print size that I can achieve is 4000/300 or 13.33" wide. If I print larger than that, I will have to interpolate data. If I print smaller than that, I have excess data.

The reality is that no 4000 ppi scanner can scan accurately on a pixel to pixel basis and some resolution is lost.

Hope this helps.

I notice that my scanner hits the same grains no matter how many times I scan a neg. It seems 100% consistent, and reaches down to 1 pixel details. But I don't really know what I'm talking about.

Only thing that matters to me, with a printer, is that it prints without streaks or lines or bands, doesn't hide my grain with its own inkdrops, and doesn't ahve any trouble with subtle and extreme tonality. The Canon IP5000 prints at much higher than 300 dpi, and its prints are noticeably higher resolution than those with lower dpi counts.

You also have to consider the size of those droplets. 1 pl or 4 pl? At 300 or 3000 dpi, that measurement makes a big difference.

back alley
06-01-2006, 21:45
i have no answers but this...my lab wants all files at 300 and no more.

easy for me as i don't really understand it all but i have this built in parameter.

joe

wdenies
06-02-2006, 00:38
On the luminous landscape site there should be an article dealing with print/scanner resolution.
The starting point is the max. printsize and resulotion (300/360)
Applying the calculation method gives the scanner resol. to apply.
Results for a 30x45cm (12x18"?)
35mm: >4000 dpi
MF: >3000 dpi

Of course you could use the formulas the other way around:
For a given scan resol. what is my max. printsize?

Wim