On 13/1/09 05:29, "aussieshepsrock" <[email protected]> wrote:
>
> "The optical
>> resolution of your scanner - say 600x600ppi for this purpose - is the limit
>> for original capture - higher resolutions like 9600x9600ppi can only be
>> provided by interpolation ... "
>
> Your input is greatly appreciated, but I'm fully up on the Optical vs
> Interpolated with Scanners.....
<snip>
>> done selectively per image in Pshop if you have it as ramping the edges to
>> provide a sharper image can produce artifacts."
>
> You are quite right about the Unsharp Masking in Photoshop being an
> incredibly better tool than the ones in scanning software itself.
> However,......
<snip>
All I'm pointing out about unsharp masking is the most important part of
image capture via any device - originals vary enormously and some will
benefit more than others from varying amounts of sharpening. Judging your
originals used to be the byword of prepress scanning but that's my
background - when drum scanners were the size of an estate car.
>
> "> Levels is a destructive process which affects the entire image
> - if you
>> move the black point or white point by 10% you are not only disposing of 25
>> channel levels from each colour - you are creating 25 new ones for each
>> colour as each channel must have 256 levels. I use the non destructive
>> curves if at all possible and reserve level adjustment for very poor low key
>> originals."
>
> I only have personal experience to draw upon because authoritative
> information about this has been difficult to find, but I have doubts
> as to your statement's......
<snip>
Any adjustment of the levels is destructive - as is the brightness and
contrast settings. Even if there is no data in the levels you are clipping
the image editor must generate new levels to compensate for those lost as
there must be 256. In generating new levels there is inevitably error as
they must be whole numbers between 0 and 255 - the algorithm used generates
new levels with partial values which are rounded up or down or the error
carried over. An adjustment layer for levels could be used non destructively
but the file size would reflect this.
<http://www.developertutorials.com/tutorials/photoshop/5-tips-for-photoshop
-efficiency-8-03-26/page4.html>
>
> "> Highest resolution? I would say around the 200/300ppi mark
> unless they
>> are earmarked for substantial enlargement. The human eye can only resolve
>> around 180 levels, b/w newspapers print photos at around 80 lines of dots
>> per inch (the cheap paper limits the res) and we see them well as images.
>> Glossy colour mags 133/150/175 lines of dots per inch and they look very
>> acceptable even though the CMYK space is smaller than RGB. Computer monitors
>> are limited by dot pitch and can only manage hardware res around 90ppi so
>> any res above this is a software representation - tv's are worse with poorer
>> dot pitch."
>
> This information is extremely valid, but I have a sense my thoughts on
> resolution and your's aren't entirely describing the same things.
"The Myth of DPI" is worth a read...
<http://www.rideau-info.com/photos/mythdpi.html>
>
> "> My archive of high res images is stored at 360ppi, medium res
> at 180ppi"
>
> I think there is also the disconnect between the 'historical image
> archive' I'm contemplating and the 'working' image archive you seem to
> be describing because the ppi's are based upon the capabilities of
> your output source. I'm most concerned with archiving the maximum
> image capability of my source materials. The connection my project has
> to output methodologies is indirect at best. It will be a resource of
> source materials that on screen viewing, printing, or publishing, can
> then be derived from.
The ppi's are corrected higher for output source - normally they would
be 300ppi and 150ppi but many of these are A4 borderless so storage space is
a vast issue - the 360's would be 400MB each at 1200ppi. Output of images is
everything - without it we cannot see them - monitors, all printers and all
publishing is output.
>
>
>
> "> Finally I would add the fact that re-resing is always possible
> with a
>> good image editor - a 200/300ppi digital image can be easily upped to
>> 1200ppi without problems. The image editor is simply doing what the scanner
>> does over and above it's optical resolution - interpolation - but probably
>> doing it much better in the case of Pshop."
>
> Accurate info, but not directly applicable to my methods and goals.
> Yes, photoshop is the best image upscaler around and is quite usable
> when wielded judiciously. I have most assuredly used it, especially
> when making 8x10's from 4x6 originals I need bigger prints off of.
> However, If I scan an image at 1200dpi and someone in the background
> turns out to be important to someone years down the road, there will
> be lots of pixels to fish out the best image that's possible. If I
> scanned it at 300dpi, there is no way to interpolate the missing
> 900dpi of information, the result would just be a really big high
> resolution file describing low resolution information. The intention
> of this scanning archive is to stand in for missing originals should
> they be lost or destroyed and to secondarily give a lot of people
> access to the photos that sitting in storage somewhere would not give
> them.
That's earmarking for enlargement in the future....all my archive is for
reproduction at that size (s/s) though in working on archives for others I
have scanned at very high res to enlarge a portion of an image to be used as
an accompaniment to the original like a face picked from a crowd etc.
>
>>
>> Pete
>
> I sincerely and dearly appreciate your input pete. I also would
> appreciate whatever input on Levels and such you might have or point
> me to. At no point do I force harsh adjustments, cause color oddities
> or saturation issues, and I definitely don't place a slider so it cuts
> off any part of the actual values the scanner picked up. (except for
> whites in dusts or scratches). Archive and Museum sources have noted
> the dangers of excessive level and curves adjustments to the integrity
> of the scan itself and to the actual usability of images edited in
> such a manner when it comes to differently calibrated monitors,
> various current or future OS's, and especially when outputting the
> file to hardcopy. The resulting edits as applied to the image might
> make it visually quite wonderful and compelling, but at the expense of
> the integrity of the image file and it's 'true' linkage to the source
> material and it's visual content.
I've not really kept up with developments in the field of digital
imaging since my postgrad masters course on it some years ago but two
learned facts have certainly stuck with me. One is that we have light
sensitive cells at the back of our knees - strange eh? And the other is that
our eyes - being single lenses - reflect what we see upside down and our
brains put it the right way up - amazing.....
Pete
> >
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