RE: Any use for the D65 filter on the Spectrolino?
RE: Any use for the D65 filter on the Spectrolino?
- Subject: RE: Any use for the D65 filter on the Spectrolino?
- From: "Hirsch, Steve" <email@hidden>
- Date: Mon, 11 Apr 2005 14:11:27 -0400
- Thread-topic: Any use for the D65 filter on the Spectrolino?
Title: RE: Any use for the D65 filter on the Spectrolino?
Hi Robin,
This issue peaked my interest so I ran some tests on my own with the D65 filter on my Spectroscan, re-profiling my new Popular Photography mag target so I could compare the D65 filtered results to my original unfiltered results. I compared the two profiles (D65 and Unfiltered) via my test images and also compared white point adjusted versions. Both myself and my top color gal, reviewed the results and we found that the D65 filtered profile did indeed give us better results than the non-filtered version, i.e., there was a significant amount of shape and contrast improvement overall as well as gradient transition improvement in both the Cyan and Magenta channels especially. The D65 filtered results appeared to "eat up" a great deal of the Yellow cast throughout the range which usually required a yellow curve tweak in the forward tag to reduce cast contamination in my softproofing profile. We had far less of a distance to travel when tweaking the softproofing profile when starting with the D65 filtered profile. I suspect that this filter would be far more useful to us when profiling very yellowish publication proofing stocks than it would be when profiling whiter sheets but I will be experimenting with those whiter sheets as well as those with FWAs to see if this D65 filter helps them as well as you described. Thanks for starting this thread and bringing this to my attention.
I had asked Brian Ashe from GMB about this issue and referred this thread to him for his comment. His response is below FYI.
Steve
Steven Hirsch, Systems Manager
Hachette Filipacchi Media, U. S.
212-767-6536
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From: Brian Ashe
Sent: Friday, April 8, 2005 8:02 PM
To: Hirsch, Steve
Subject: Re: Hi Brian
Hi Steve,
I know Robin pretty well and respect his opinion, but I must say this is news to me. We really only use the D65 filter in respect to our Ink Formulation software. I do not think it would make a better ICC profile. Yes we use Tungsten Light source (it is cheap, reliable, and lasts a long, long time) but the data is converted to D50 light source. If Robin thinks D65 is a better choice you can change this in the software set up and convert to D65 rather than D50 (people in Europe do this) but I see no advantage in using the physical filter on the Spectrolino.
Thanks,
Brian
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From: colorsync-users-bounces+shirsch=email@hidden on behalf of Robin Myers
Sent: Thursday, April 7, 2005 9:34 PM
To: email@hidden
Subject: Re: Any use for the D65 filter on the Spectrolino?
On 7 Apr 2005, at 16:53, Roger Breton wrote:
>> The D65 filter shapes the spectrum of the tungsten halogen
>> illumination
>> in the SpectroScan to be close to the D65 spectrum. This increases the
>> amount of blue in illumination. This will improve the signal to noise
>> ratio in the green/blue/violet region of the spectrum. Additionally,
>> it
>> does a better job of activating fluorescent whitening agents in the
>> paper, if you are into measuring such things.
>>
>> I use the D65 filter on most of my measurements because it does a
>> better job of simulating real world lighting than tungsten halogen.
>>
>> Robin Myers
> Are you saying that the D65 filter absolutely increases the light
> output in
> shorter wavelengths? Or does it not simply attenuate the light energy
> in
> longer wavelength by partially absorbing light from, say, 580 to 750
> nm,
> like the Solux 4700K lamp does?
I should have said it increases the "relative amount of blue in the
illumination". Of course, if you put any filter into a light path there
is some absorption, so the total amount of light decreases. In this
case, the D65 filter is a blue filter, which decreases the amount of
longer wavelength light. To compensate for the lower amount of total
illumination, the SpectroScan increases the integration time to get
back to a good signal to noise ratio.
Robin Myers
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