DPI: Lightjet vs Inkjet

[george_rhodes]

I have been working with someone locally, who prints my work onto

Fuji Crystal Archive paper with his Lightjet. He always operates

the Lightjet at 200 DPI and says the human eye cannot differentiate

the difference between the maximum 300 DPI capability of the

Lightjet and the 200 DPI that he prints at. My prints are very

sharp, with good tonal range. I will be working with another

person, who will use an Inkjet printer, to print some of my images

onto canvas. He prints with his Inkjet at 600 DPI. How does the

DPI translate between the two systems. Will my Imacon scans that

produced very sharp images on the Lightjet printer at 200 DPI, be

adequate for the 600 DPI pattern of the Inkjet printer? Thanks in

advance to any who reply.

[awahlster]

YES

[scott_eaton]

I think your local lab is simply scanning the images no higher than 200 dpi final print size and letting the LightJet scale them to 300dpi. As I understand it from my local LightJet labs, they can't see a difference when files are submitted at 300 vs 200 dpi because the LightJet does such a good job with *reasonable* interpolation. They don't however operate their lightJet at 200 dpi device resolution because the LightJet is around 300dpi native resolution anyways. So, they don't require files to be any higher than 300dpi raw resolution and find 200dpi is adequate. A local Lambda based shop is running at 200dpi device resolution, and the difference is obvious compared to the 300dpi LightJet.

 

You should be dumping the best possible scan to a LightJet or Ink-Jet regardless. Get the best scan for your money, and use every pixel when printing.

[andrew_rodney1]

The Lightjet is a true continuous tone printer, the Epson isn't so higher PPI values to create

higher effective DPI values to the printer are usually necessary. Anything over 360ppi to an

Epson is overkill.

[pieris_berreitter]

They may look sharper with the Lightjet because optical sharpness is defined in part by edge contrast, of which there is probably more in the photographic print than the inkjet. Especially since you're printing to canvas, which will give you a lower contrast image overall.

<P>

As to how much resolution you need to do justice to your scan,

the definition of 20/20 vision is the ability to resolve contrast features of one arc minute in size. For viewing distance L (m), the minimum resolvable feature = 0.000291*L. Spatial frequency is double this.

<P>

So, the minimum resolvable detail at 13cm viewing distance (near my close-focus ability) is 0.038 mm. Spatial frequency is 1/(2*0.038) or 13 line pairs/mm.

<P>

The minimum feature size at 300dpi (standard accepted for high resolution prints) is 0.073mm. <I>This means that at a 13cm viewing distance, a person with 20/20 vision will be able to distinguish a 600dpi print from a 300dpi print. At 25cm viewing distance, the two prints will look the same.</I>

<P>

(from a study I did posted on my <A HREF="http://www.pmb.net/darkroom/">Digital Darkroom</A> blog).

<P>

This is based on Norman Koren's math for minimum resolvable features. I haven't checked his numbers.

[pieris_berreitter]

Andrew I can visibly see 11lp/mm on my Epson inkjet, which is significantly more than 360dpi... not that it looks very appealing at that limit of resolution (due in part to the fact you pointed out, that it resorts to dithering), but there is at least a visible difference in printing at the higher dpi on (my) Epson.

[rcoda]

Forgive my silly question, but why would anyone (save portraits) want to print a fine photograph on canvas? I've seen them in galleries and I have to tell you that the texture of the canvas really bothers me.

[george_rhodes]

As an old school fine art photographer, I personally greatly prefer the look of a photograph printed on photographic paper. However, some of my patrons are asking for prints on canvas, which my competitors are providing to their clients. It is a matter of staying in business, that I provide my clients with what they want, rather than sending them to my competitors. Therefor, I will continue to print my work on photographic paper, but will also offer prints on canvas. This will help to keep me from having to get a REAL job.

[dean_erger]

Pieris, Andrew was writing about ppi, you were writing about dpi, (and never the twain shall meet).

[Spearhead]

<i>why would anyone (save portraits) want to print a fine photograph on canvas? I've seen them in galleries and I have to tell you that the texture of the canvas really bothers me.</i><p>

 

Do you think that everyone is bothered by the texture because you are?

<p>

The answer to your question lies within that.

[rcoda]

>Do you think that everyone is bothered by the texture because you are?

 

No I don't.

 

>The answer to your question lies within that.

 

Sorry, I come from an f/64 (large format) background... it's all about sharpness and detail.

[._._z]

So you knew the answer to your question already, yes?

[tom_schneider]

Lightjet printers (model 430 and later) have the option of outputing at 200 or 300 ppi. And yes, you can tell the difference. The reason a lab would output at 200 ppi is speed - 6 minutes vs 10 minutes to output 10 feet. I've worked on lightjets - this is not hearsay.

 

That being said, the lightjets do have incredible interpolation algorithms. If the Lightjet is outputting at 300 ppi, a 200ppi file would be hard to distingushe from a 300 ppi file.

 

Older model 5000 lightjets only output at 300ppi. You need to know which lightjet they are using and exactly what settings they are using. My old lab would charge less to output at 200 ppi. Generally, these were large quantity jobs, mostly POP images where quality was not of paramount importance.

[kelly_flanigan1]

Own our "600dpi class" inkjet large format printers; we manytimes print wallmaps with tiny steet names at 400 pixels per inch; since there are REAL details that folks use. The same printer when used for a photo rarely has enough real resolution; for a large 24x36 or 36x48" poster at 300 to 400 pixels per inch. Many times the image inputs from customers is just average an between a 100 to 300 ppi image is used for photos; with maybe 150 being the mean. A large file only chokes the RIP computer more; and causes a more delay. It also makes a larger file to be stored for rapid printing; a ripped file in the rip box. Our inkjets PRINT the image in the same amount of time; whether the 36x48" image is 50ppi or 400ppi. Only the rip process is longer with a higher ppi image.