-------- Original Message --------
Subject:        Re: scanning specifications
Date:   Tue, 05 May 2009 10:11:44 +0100
From:   Nicholas Verge <[log in to unmask]>
To:     [log in to unmask]
References:     <[log in to unmask]>



Richard,

I dont see the justification for 48-bit scanning, unless a colour
photograph is being scanned (and it would have to be a very high quality
transparency to justify this). 24-bit colour scans are sufficient for
maps. 48-bit colour images cannot be diplayed by all but very high-end
display devices (GPU + screens). The huiman eye cannot discern the number
of colours possible in 48-bit images. 48-bit images are only needed in
order to perform image processing to avoid artifcat creation.

However, it would have been better and i urge you to scan maps at a
minimum of 400dpi. 300dpi is too low.

Cheers

On Mon, 04 May 2009 21:04:42 +0100, Maps-L Moderator <[log in to unmask]> wrote:

> -------- Original Message --------
> Subject:        scanning specifications
> Date:   Mon, 4 May 2009 15:54:46 -0400
> From:   Boardman, Richard <[log in to unmask]>
> To:     <[log in to unmask]>
>
>
>
> Hello,
>
> We’re having a conversation here about scanning color maps from our
> collection of Philadelphia real estate atlases. Each plate is usually a
> two-page spread, measuring about 20” x 28”. They have been scanned at
> 300dpi, 24-bit color but some are now advocating going to 48-bit color.
> Others maintain that this would produce a huge, almost unusable file.
>
> What are the pros and cons of 24 vs 48-bit color scanning? Is anyone
> doing anything at that level? How is it working out?
>
> Thanks.
>
> Rich Boardman
>
> Map Collection
>
> Free Library of Philadelphia



--
----------------------------------------------------------------------
Nicholas J. Verge BSc. FGS
Geologist and geological remote sensing/GIS consultant


Henley-on-Thames, Oxfordshire, UK.

Voice: ++ 44 (0)1491 572022 (office hours 0900-2200UTC, Monday - Saturday)
Email: [log in to unmask]