LaserSoft Imaging

Hi Everyone, I am new to the forum and to scanning but I have a project to convert several 35mm slides to large digital prints.

The end product will be ~30x40 inch digital prints.

I assume that when I choose the output size i should enter 30 x 40...

But for such large prints where quality is the over-riding concern what is the recommendation for the Q setting (Quality) and the screen?

Dear smerth,
for digital print ( as opposed to offset printing i hope ) you should use a Q-Factor of 1.0 as this is only needed for Offset...

And --> RIGHT you should simply use the Output SIze in Silverfast --> 30"x40" !

The Question is:
What to use in the "screen" field...


You are trying to enlargen the image approximately 30 times ( roughly ).
I wonder what scanner you are using for this, but anyways don't expect miracles !!

i'd recommend to use an Output resolution ( lpi ) of no more then 150 lpi.

This would mean your scanner has to scan in 30 x 150 = 4500 dpi.

While this doen't seem much judging from the flashy prints on most scanners packaging ( 14400 dpi !!!! ), this is more then even a dedicated Film Scanner offers and way beyond the "effective" ( not optical ) resolution of a flatbed scanner...

So: if you are not using a high end scanner 150 dpi is probably too much already but its not THAT bad.
If you are using a flatbed scanner << $1000 USD you can just select 100 lpi Output resolution and probably won't see a difference...


I hope that helps your task !!!

Greetings & best regards,

Nils Heidorn

I would approach the problem by scanning as high a quality as possible at a lower size and then re-sizing the image in Lightroom (or Photoshop). My opinion is that you will get a better interpolation for a large print by using software specifically built to interpolate rather than Silverfast.

Dear all,
while stlbob's recommendation was perfectly true years ago, nowadays you can trust SilverFast to scan at the perfect Resolution and do the downsampling.

This saves time & hassle :-)

Greetings,

Nils Heidorn

Hi Nils,

What algorithm is Silverfast using these days to create pixels during upsampling ?

Best regards,

Frank

Dear Frank,
as you know, upsampling is something that we avoid like vampires avoid garlic :-)

But for the others who read this:
95% of all scanners have some Hardware Resolutions they "like best" for scanning, mostly those are integer dividers of their Optical resolution.

e.g. a 4000 dpi scanner can also scan just fine in 2000, 1000, 500, 250, 125 dpi ... ( /2, /4, /8, /16, /32 ).

Whenever a User Input results in a Resolution that is somewhere in-between, SilverFast chooses to scan in the next HIGHER Resolution and does a downsamling afterwards.
e.g. the User chooses 3000 dpi, so SF scans in 4000 dpi then samples it down.

So upsampling like mentioned from Frank will only occur if a User goes beyond the optical resolution which won't result in much good anyways...

In that case we also use bicubic sampling or bicubic antialiased interpolation ( selectable in the options )

But again, we probably could also use bilinear because data will be very unsharp at those situations anyways :-(

We did not like the more fancy ones like stair or lanczos as they can interfere ( resulting in artifacts ) with our beloved USM sharpening.


Greetings,

Nils Heidorn