Recommendations on size

[smerth]

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?

[LSI_Heidorn]

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

[stlbob]

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.

[LSI_Heidorn]

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

[degrub]

Hi Nils,

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

Best regards,

Frank

[LSI_Heidorn]

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