Output File Sizing Problem

[pknouf]

I have SilverFast Ai Studio and am scanning a 4x5 Velvia transparency. The input size in 4.7x3.6. I want to be able to print a 30x24 print at 300 dpi so I set my output to 30x24 and set the dpi to 300. The Q-Factor is 1.0 and the Screen is 300. This give me a file size of 362 megs. Pressing the F5 key shows me that the actual scan resolution is 2400 dpi. Then I tried setting the output dimensions to the same as the input, that is, 4.7x3.6. I then set the output scan resolution to 2400, the Q-Factor to 1.0 and the Screen to 300. Using this method produces a file size of 545 megs, a whopping 183 megs larger!! What gives? Shouldn't the output file size be the same if you use the same scanner resolution? Please help!

[LSI_Morales]

Dear Pknouf,

When you press the key F5 in SilverFast Ai Studio (windows version) or Alt+Ctrl (Mac version), SilverFast will display the optical resolution it uses to scan, in the first case you describe, you are telling SilverFast to do a very precise job with exact output, which in reality needs 1950 dpi. However SilverFast only scans using the real optical resolution of the scanner in this case the next optical level is 2400 dpi, then it will downscale internally to 1950 for the output file.

In the second case you mention, you are simply telling SilverFast to use the full 2400 dpi for the output file, hence the difference in size of both files, because the second file is actually bigger.

If you want to see the real output file in your SilverFast use the key F6 instead of F5 (windows) or the combination Alt+Shift+Ctrl (Mac).

Cheers

[pknouf]

"When you press the key F5 in SilverFast Ai Studio (windows version) or Alt+Ctrl (Mac version), SilverFast will display the optical resolution it uses to scan, in the first case you describe, you are telling SilverFast to do a very precise job with exact output, which in reality needs 1950 dpi. However SilverFast only scans using the real optical resolution of the scanner in this case the next optical level is 2400 dpi, then it will downscale internally to 1950 for the output file."

When SilverFast goes through the downscale process, is there any quality loss?

Can I get the same pixel depth by entering in the file size that Photoshop's new file dialog indicates, i.e., 370 Mb for a 24 x 30 image at 300 dpi?

[LSI_Morales]

Dear pknouf,

I believe what you want to know is whether there is a quality loss by downscaling in SilverFast as oposed to photoshop?

When it comes to downscaling there is always a quality loss (yes, even in photoshop), it is all a question of different mathematical algorithms (that is a very complex topic beyond the scope of this thread).

SilverFast produces a "better" downscaling than photoshop (although this a very relative and sometimes subjective assertion).

If you have your doubts, I recommend you to make a test, producing two images, one with the optical resolution and one downscaled, you can then make the downscaling of the first picture in postproduction and print both, in the end what counts is what works for you.

You can then remain true to the method of your liking.

Cheers