Scanning at high resolutions locks computer

[Stubb]

The problem was that my iBook simply couldn't handle high-resolution scans of large-format images. I picked up a 2.0 GHz MacBook Pro last week, immediately added another GB of memory, and it's happy to scan 4x5s at 48-bit resolution and 4800 dpi with ICE. The scans take a few hours, but it remains responsive throughput the process.

Cheers,

Andreas

[RAG]

Hey,

What scale factor are you using for these scans? If it is more than 100% then you might be forcing image interpolation, which I have found to slow things down. Multiplying the scale factor times your desired output resolution gives you the actual resolution your scanner will use. If I want to scale an image 200% and I want the resolution to be 300dpi/ppi my scanner will need to scan the image at 600dpi/ppi (2X300=600).

[Stubb]

Hey,

What scale factor are you using for these scans? If it is more than 100% then you might be forcing image interpolation, which I have found to slow things down. Multiplying the scale factor times your desired output resolution gives you the actual resolution your scanner will use. If I want to scale an image 200% and I want the resolution to be 300dpi/ppi my scanner will need to scan the image at 600dpi/ppi (2X300=600).

I had been leaving the Q-Factor at 1.5 and setting the resolution to 2400 DPI. This seems sufficient for gallery prints from 4x5s given the 300 DPI resolution of the target output device. I thought that the scanner scans the image at the resolution indicated in the DPI field and that the Q-Factor and LPI setting are used for scans intended for halftone dot output. Am I looking at this the wrong way?


Thanks,

Andreas

[RAG]

Well,

Here is a quote from "SilverFast: The Official Guide" page 11.

To add even more confusion, many applications use different terminologies to refer to resolution. Photoshop uses (correctly) ppi, many scanner software programs use (confusingly) dpi, and SilverFast uses lpi and quality factor (Q-Factor) as well as dpi to represent input resolution.

SilverFast uses printing resolution (lpi) and a quality factor to determine the final input resolution. So an lpi of 150 and a quality factor of 2 will yield a final scanned image resolution of 300 lpi x 2 = 300 ppi.

Assuming we are working with the parameters from the second quote, if you then change the scale to 200% the scanner will scan the image at 600 in order to produce an image twice the size of the original at 300.

[Stubb]

Well,

Here is a quote from "SilverFast: The Official Guide" page 11.

Thanks for the reference. I was trying to figure out things from page 55 of the guide

Cheers,

Andreas