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Canon LiDe50 Calibration

Last response: in Computer Peripherals
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July 30, 2004 5:44:56 PM

Archived from groups: alt.comp.periphs.scanner (More info?)

In order to test the accuracy of my new LiDe 50 I scanned a Pantone color
card which included their Hexachrome D swatches for yellow, magenta and
cyan. The color mode setting was color photo. Then using Photoshop Elements
I eyedroppered the swatches to get their RGB readings. The yellow swatch was
correct (R:255, G:255). The magenta and cyan readings were off - I'll only
mention the magenta which read R : 255 G: 0, B: 102. I repeated the
experiment only this time I pressed the scanner driver's calibration button
and let it calibrate before making the scan. The results were a small
improvement for each magenta and cyan, but the yellow swatch was now R: 255,
G: 255, B: 151. My question is do I need to return the scanner?




The scanner driver software for this scanner has a calibration button on the
Setting menu which causes the scanner to do something for about 45 second
Anonymous
August 3, 2004 1:57:09 AM

Archived from groups: alt.comp.periphs.scanner (More info?)

In article <shsOc.85932$fv.24650@fe2.columbus.rr.com>, josqb@cinci.rr.com
says...
>
>
>In order to test the accuracy of my new LiDe 50 I scanned a Pantone color
>card which included their Hexachrome D swatches for yellow, magenta and
>cyan. The color mode setting was color photo. Then using Photoshop Elements
>I eyedroppered the swatches to get their RGB readings. The yellow swatch was
>correct (R:255, G:255). The magenta and cyan readings were off - I'll only
>mention the magenta which read R : 255 G: 0, B: 102. I repeated the
>experiment only this time I pressed the scanner driver's calibration button
>and let it calibrate before making the scan. The results were a small
>improvement for each magenta and cyan, but the yellow swatch was now R: 255,
>G: 255, B: 151. My question is do I need to return the scanner?


I sure dont think this is any reason to do that. I think you're probably
doing fine, except that your expectaions of color accuracy are frankly not
realistic. I'd say stop testing, and just enjoy your scanner and photos.

RGB is device dependent, and by definition, RGB is NOT an absolute color
value. R255 will be pretty red, but it is not an absolute color value. It
is a RGB value. 255 just happens to be the maximum (brightest) value
possible in the device (at current automatic settings), but 255 does not
represent any specific absolute bright shade of red. It is probably 255
because of automatic White Point clipping. The same 255 will appear as a
different result in the scanner, and in the video monitor, and in the
printer, the best the device can interpret that 255 brightness level. RGB is
device dependent, not an absolute color by any stretch of the imagination.

I wouldnt expect any other scanner to do any better (not in any absolute
measurement sense). Your best hope is enjoyable "pleasing" results, and I'd
guess the scanner will do that if you would stop trying to measure the color
samples, which is doomed. Scanners are not precision color measurment
devices. For sure, a $100 consumer scanner is not a million dollar prepress
color calibration system (and it's a plenty tough job for them too).

--
Wayne
http://www.scantips.com "A few scanning tips"
August 17, 2004 5:28:29 PM

Archived from groups: alt.comp.periphs.scanner (More info?)

Thanks Wayne. I guess I'll have to lower my expectations. I'd be curious to
know what the scanner is doing when you click the calibration button.

Josh
"Wayne Fulton" <nospam@invalid.com> wrote in message
news:ELWdndsz6vGaYpPcRVn-uA@august.net...
> In article <shsOc.85932$fv.24650@fe2.columbus.rr.com>, josqb@cinci.rr.com
> says...
> >
> >
> >In order to test the accuracy of my new LiDe 50 I scanned a Pantone color
> >card which included their Hexachrome D swatches for yellow, magenta and
> >cyan. The color mode setting was color photo. Then using Photoshop
Elements
> >I eyedroppered the swatches to get their RGB readings. The yellow swatch
was
> >correct (R:255, G:255). The magenta and cyan readings were off - I'll
only
> >mention the magenta which read R : 255 G: 0, B: 102. I repeated the
> >experiment only this time I pressed the scanner driver's calibration
button
> >and let it calibrate before making the scan. The results were a small
> >improvement for each magenta and cyan, but the yellow swatch was now R:
255,
> >G: 255, B: 151. My question is do I need to return the scanner?
>
>
> I sure dont think this is any reason to do that. I think you're probably
> doing fine, except that your expectaions of color accuracy are frankly not
> realistic. I'd say stop testing, and just enjoy your scanner and photos.
>
> RGB is device dependent, and by definition, RGB is NOT an absolute color
> value. R255 will be pretty red, but it is not an absolute color value.
It
> is a RGB value. 255 just happens to be the maximum (brightest) value
> possible in the device (at current automatic settings), but 255 does not
> represent any specific absolute bright shade of red. It is probably 255
> because of automatic White Point clipping. The same 255 will appear as a
> different result in the scanner, and in the video monitor, and in the
> printer, the best the device can interpret that 255 brightness level. RGB
is
> device dependent, not an absolute color by any stretch of the imagination.
>
> I wouldnt expect any other scanner to do any better (not in any absolute
> measurement sense). Your best hope is enjoyable "pleasing" results, and
I'd
> guess the scanner will do that if you would stop trying to measure the
color
> samples, which is doomed. Scanners are not precision color measurment
> devices. For sure, a $100 consumer scanner is not a million dollar
prepress
> color calibration system (and it's a plenty tough job for them too).
>
> --
> Wayne
> http://www.scantips.com "A few scanning tips"
>
Anonymous
August 17, 2004 5:28:30 PM

Archived from groups: alt.comp.periphs.scanner (More info?)

In article <1KnUc.23145$cT6.1254@fe2.columbus.rr.com>, josqb@cinci.rr.com
says...
>
>
>Thanks Wayne. I guess I'll have to lower my expectations. I'd be curious to
>know what the scanner is doing when you click the calibration button.

I am not familiar with that scanner, but I have never seen one that had a
calibrate button. But all scanners do an automatic calibration initially,
and often every few minutes thereafter (when next used). That calibration
sets overall gains, specifically it matches all RGB sensors to the same
maximum from a white reference strip under the cover, so this becomes a
balanced white without color cast. This affects and helps colors, but it is
not a color calibration in that sense. Less than the maximum bright colors
fall where they may, but the sensor is a rather linear device. Regardless,
RGB is device dependent, there is no sense of absolute color accuracy.

A button doesnt seem necessary, but perhaps you have a button to redo that
automatic calibrate manually? Where is it mentioned in the manual? I found
no mention of the button in your online manual.

Your manual says the standard thing:

[Preview] Button

Use this button to perform a trial scan of an item.

When you click the Preview button, the image is automatically cropped (auto
crop) to the selected paper size.

* The scanner driver will automatically calibrate the scanner the first time
it is used. Then the scanner will start the preview scan. Please wait until
this process concludes.

------------

Preview and cropping are essential to best results, dont skip it for best
results. It is how the scanner discovers what is on the bed to be scanned,
and what it should do about it.

--
Wayne
http://www.scantips.com "A few scanning tips"
!