Re: perceptual differences in Lab deltaE
Re: perceptual differences in Lab deltaE
- Subject: Re: perceptual differences in Lab deltaE
- From: simon--- via colorsync-users <email@hidden>
- Date: Tue, 7 Jan 2020 20:48:28 +0000
Hi Roger,
I did this some time ago (2005 or 2006 if I remember correctly), and since then
have migrated to Apple from Windows. I cannot find the files that created the
patches, but it would certainly have used Photoshop and printed them on my
Epson 3880, as that workflow was the only reliable/controllable one available
to me at the time. The actual Lab values were measured with my EyeOne Pro
(and, unsurprisingly did not follow exactly the intended values due to the
limitations of the colour profiling for the printer). The intent of the files
was to produce a deltaE of 0.5 on the a and b axes, but the 0.3 resulted from
the errors in printing workflow. I have done a quick search for the files I
used, but suspect that they are still on an old Windows PC. If I can locate
them I will send you a copy.
At the time I was seeking to persuade some of my engineers that they needed to
use the evidence of their eyes (using my test samples) rather than blindly
believe what the colorimeter salesman used as his pitch!
Simon
> On 7 Jan 2020, at 12:14, Roger Breton via colorsync-users
> <email@hidden> wrote:
>
> Hi Simon,
>
> Interesting observations. Your findings corroborates my very own, humble
> experience. If I understood you correctly, you and your students found that
> our color vision is "less forgiving" of color differences in neutral colors
> and "more forgiving" in saturated colors?
>
> I agree intuitively that observing color side by side does not "forgive" much
> 😊
>
> I'm curious how were you able to print chart patches with as little as 0.3
> deltaE (which flavor?) color differences... Suppose I was to replicate your
> findings with my students?
>
> Best / Roger
>
> -----Original Message-----
> From: colorsync-users
> <colorsync-users-bounces+graxx=email@hidden> On Behalf Of
> simon--- via colorsync-users
> Sent: Tuesday, January 7, 2020 5:48 AM
> To: Roger Breton via colorsync-users <email@hidden>
> Subject: perceptual differences in Lab deltaE
>
> Hi Andrew,
>
> I did some tests a few years ago by printing charts patches to exhibit small
> deltaE variations. My conclusion at the time was that the limit of deltaE of
> ≤ 1 was fine for colours with values of a or b > ±10 but as the colour
> approached the neutral (L) axis in the range 40 ≤ L ≤ 70 smaller values of
> deltaE were clearly visible. Most of my test subjects could detect
> differences of about 0.3 when the patches were compared side-by-side, and
> (almost a neutral grey).
> My conclusion from this was not surprising - for all my test subjects the Lab
> space was not perfectly perceptually uniform, and detecting differences in
> deltaE was significantly easier for values of -3 ≤ (a or b) ≤ 3 when
> comparing patches side-by-side.
>
> Simon
>
> email@hidden
>
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