Lambda 400 or 200 dpi

[tlitody]

Is there a noticeable difference between printing at 200 ppi verses 400 ppi on a lambda?

i.e. if I took an image file and printed at 400 ppi and then downsized by half its linear pixel dimension and printed it at 200 ppi. Could I tell the difference without sniffing the print?

[bob carnie]

If there is small type in the image you will see the difference.
We run all work at 400ppi, unless we are given small file size or high run commercial jobs then we will run at 200ppi.

Text would be one of the main reasons.

[tlitody]

thanks

[Matus Kalisky]

I did this test once (not with Lambda, but with inject) for myself and printing at less then 240 dpi was obviously less sharp with less detail than 360 dpi.

[tlitody]

I did this test once (not with Lambda, but with inject) for myself and printing at less then 240 dpi was obviously less sharp with less detail than 360 dpi.

I don't think you can compare to a lambda because inkjet suffers ink bleed even though small, whereas a lambda doesn't. But then you may get a tad of light scatter from a laser but I doubt it. And that makes me curious as to whether a lambda uses a larger aperture at 200 dpi. i.e. does it use a larger dot size or just spread them thinner than at 400 dpi

[bob carnie]

Your question is a good one.
Here is how I see it.
one- the lambda runs 1ft per min at 400ppi, 1ft per 30 secs at 200ppi.
two - the lambda has an internal rip unit, I believe ours is a cheeta rip.
therefore when setting ppi , we can send the files over at any ppi and then choose 200 or 400ppi depending on the type of job.
A 21 step tablet is exposed and calibrated with an onboard densitiometer to aim end aim points supplied by the paper manufacturer and the roll of the calculater is to make each greyscale step equal in the R, G and B curves.
Once the paper is calibrated you can then proceed with your files and much like a computer driven enlarger you set the ppi, paper, size of image and so on.
Colour correction is onboard and curve shaping is onboard for adjustments to files, though I prefer to adjust contrast in PS and for colour and density would use the onboard controls.
By sizing the print with an selected ppi and paper setting, the rip unit will uprez or down rez the file to fit.

I have done tests of sending over 200ppi files and letting the lambda uprez VS sending over a 400ppi file from PS .. I could not tell the difference.

so I believe what happens is the slower speed allows the more concentrated information form at 400ppi.
All the laser devices are 8bit, Lambda , Chromira and Lightjet and I believe they operate the same.

I have tested our inkjet printer with the Harmon AR gloss paper against the lambda fuji flex and they both exhibit the same amount of sharpness/clarity etc.
When you move to a more porus paper like photorag, enhanced matt or watercolour you do experience the inks spreading and one must adjust the inkflows to lay down a bit less to reduce the spreading.
Some here who only print on inkjet are experts in ink balancing and it is something that I am aware of and try to keep in mind when swithcing papers but it is quite a process to test all the papers available to us.

I understand this is not the final answer to your question but I hope it helps.

I don't think you can compare to a lambda because inkjet suffers ink bleed even though small, whereas a lambda doesn't. But then you may get a tad of light scatter from a laser but I doubt it. And that makes me curious as to whether a lambda uses a larger aperture at 200 dpi. i.e. does it use a larger dot size or just spread them thinner than at 400 dpi

[tlitody]

thinking about it, I rekon that if the dot size remained the same then 50% of the paper would remain white. So does the calibration compensate for that? I doubt it.
So maybe the paper moves while a pixel is being exposed so the dot becomes bigger at the increased paper speed for 200ppi? That's a possibility. Inspection with a loupe might show a difference but it would depend on the exposure time for a pixel for the "dot drag" to be visible under magnification. Otherwise the lambda would need to make the dot size bigger for 200ppi.
Only the man on the spot (pun intended) can know via Durst support.

[tlitody]

infact going from 400 to 200 ppi 75% of the paper would be white if the dot size remained the same. But as you say, what the lamda rip actually puts down on the paper may not correspond directly to 200ppi.

[bob carnie]

I will try over the next week to get a more detailed response for you. I will have to talk to a couple of other operators and the mechanic.
From my understanding you would consider the speed as the most important factor and I am sure there are those here who could give a more logical explanation than I on the exact nature of how ppi is changed within a file.
The slow speed is to allow for the more detailed information to lay down when running at ppi, I do not think there is any laser change.
As I know the three lasers fire into a collecting mirror that then sends a single beam of light/energy/information to the paper. The settings for 400 and 200 are the same except for the speed of the transport.
When calibrating we are advised to run at 200ppi first , then when it is in calibration we then run a 400ppi calibration, which is in most cases bang on.

Interesting side points..

RA4 papers like flex , dura , lustre, can all run at both speeds.
Fibre Paper and Cibachrome paper do not work at 200ppi or at least a lots of futzing with the laser outputs would be required. I believe this is due to the slower ISO of the Ciba and Fibre paper.
I am now testing real black and white film and so far I only use 400ppi , but due to the faster ISO of the film it should run at both settings.( I will have to test that one)
Therefore you will see labs that do run Cibachrome and Wet Fibre**gallarie G4 use either Lambda or Lightjet, or Theta which use laser exposure and not Chromira which uses LED exposure.
I understand that Harmon is trying to make sure the next rounds of fibre papers for digital exposure will work on Chromira's as there seems to be more of them around and Harmon would like the added client list.
I do not run Cibachrome any more on my Lambda and it is a shame, but we could not find the clients willing to pay for the product, or better said we could not find enough of them . Keeping the plots, and machine online and in control was costing us more cash than the actual ammount of work going through most months.

[bob carnie]

Here is some reading on the Lambda, I have a 76plus which is a 32inch version of the 130 which is 50inch.