Re: Epson canned profiles
Re: Epson canned profiles
- Subject: Re: Epson canned profiles
- From: Iliah Borg <email@hidden>
- Date: Tue, 17 Apr 2018 14:12:58 -0400
Yes, but here is the point I'm trying to add. If a roundtrip to RGB is added (I
entered the Lab values and switched off Lab input to allow for gamut mapping),
the dE is significantly larger, which makes comparisons on the screen based on
the predicted pure dE from Lab extremely problematic:
https://cl.ly/3m3e3p1m3o3T
On Apr 17, 2018, at 1:57 PM, Andrew Rodney wrote:
>
> On Apr 17, 2018, at 11:46 AM, Iliah Borg <email@hidden> wrote:
>>
>>> Fire up your favorite image editor.
>>>
>>> Fill half the screen with L*a*b* 6, 1, 4. Fill the other half with 7, 1, 4.
>>> Overlay a couple patches of 6, 0, 0 and 7, 0, 0.
>>>
>>> By your very own math, the two background halves differ by 0.85 dE
>>
>> I did it and measured the actual deltaE rather than calculating it. It is
>> 1.32.
>
> He's again under the wrong impression that a difference of one Lab value
> equates to 1dE which is just wrong.
> He's assuming (again) that firing up an image editor is going to somehow
> provide the dE math and allow differing formulas to give us that dE value.
> He states but can't repeat: "By your very own math, the two background halves
> differ by 0.85 dE" or he'd see his example is flat out wrong.
> Or that it's 'my math' rather than a tool color pro's use to actually provide
> dE values with many differing formulas. I used dE 2000, he of course can't.
>
>> Telling colours apart when printed ob different printers / using different
>> papers / different profiles is not the same as comparing two large patches
>> side by side.
>
> Which is why I posted the very fine and useful GUI from CT&A to visually show
> what a dE of (fill in the blank) appears like on-screen. You're not going to
> find this in a 'so called favorite image editor.' But Ben's toolset appears
> to be very limited. Which explains his ideas about color here.
>
>> deltaE is not a perfect perceptually uniform measure, but generally worrying
>> about anything below 1 dE is more like splitting hairs.
>
> Exactly!
>
>> I'm sorry that this discussion came to it.
>
> Don't be!
> _______________________________________________
--
Best regards,
Iliah Borg
LibRaw, LLC
www.libraw.org
www.rawdigger.com
www.fastrawviewer.com
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