Thank you Kaml!!!
May I ask, does your iPad uses white LED or miniatures fluorescent tubes?
500 patches? It takes about more than one hour to measure 500 patches?
/ Roger
From: argyllcms-bounce@xxxxxxxxxxxxx [mailto:argyllcms-bounce@xxxxxxxxxxxxx] On ;
Behalf Of Kamil Tresnak
Sent: Saturday, December 2, 2017 1:53 PM
To: argyllcms@xxxxxxxxxxxxx
Subject: [argyllcms] Re: Profiling backlit film (with Monitor?)
Hi Roger,
I have done few profiles with very satisfying results (common large format
print, no hi quality requirements) with CMYK targets around 500 patches. I am
using somewhat bigger patches for easy device (i1pro) positioning.
I never succeed with strip reading, always i have to use patch reading. I am
using chartread -t, exactly as Alexey suggested.
I was experimenting with few LED strips, but some of this having spectrum with
unpleasant peaks. IPad is excellent tip, thank you Alex!
Regards!
Kamil
On Sat, Dec 2, 2017 at 5:35 PM, Roger Breton <graxx@xxxxxxxxxxxx
<mailto:graxx@xxxxxxxxxxxx> > wrote:
How many patches do you read, Alex? And how big do you make the patch?
Could you write what instruction you type to generate the target?
/ Roger
-----Original Message-----
From: argyllcms-bounce@xxxxxxxxxxxxx <mailto:argyllcms-bounce@xxxxxxxxxxxxx>
[mailto:argyllcms-bounce@xxxxxxxxxxxxx ;<mailto:argyllcms-bounce@xxxxxxxxxxxxx>
] On Behalf Of Alexey Gribunin
Sent: Friday, December 1, 2017 12:07 PM
To: argyllcms@xxxxxxxxxxxxx <mailto:argyllcms@xxxxxxxxxxxxx>
Subject: [argyllcms] Re: Profiling backlit film (with Monitor?)
Hello Roger!
1. Chartread. I'm measuring with Chartread –t. I prefer it because the i1Pro
calibration is performing relative to lightbox+clear backlit. So the testform's
paper patch (CMYK 0000) is L=100, a=0, b=0, i.e. perfect white and it's not
necessary to recalculate it afterwords.
2. Strip mode vs Patch mode. Theoretically Strip mode is possible but in my
practice it's very unstable because the light intensity of lightbox is not
enough. Maybe it's possible to do with higher intensity lightbox, but it seems
to me that then another problem will arise - i1Pro drift due to overheating.
So I'm using patch mode. It's slow but it's stable.
3. lightbox. Theoretically an incandescent light source with 80A (or
similar) blue filter would be very good choice. I tried to construct lightspot
for patch measurements with incandescent light source and 80A filter. CRI of
such construction is very good, the spectra is similar to real D50. But I found
that overheating also is an issue. The spectra of such construction still has
quite high amount of IR. So it's better to add an IR filter also. But I didn't
find it and left this idea for simpler light sources...
In my practice iPad (i.e. LED source) showed himself better than fluorescent
light source. It's more stable and it's also much more usable because I always
have it in my bag :))))
So I would suggest you to try LED first to develop the complete workflow and
then to think about another types of lightboxes.
Best regards,
Alexey Gribunin, UNIT Color Technologies, Moscow, Russia.
On 01/12/2017 19:32, Roger Breton wrote:
All of a sudden, I need to come up with an ICC profile for backlit
media – small world!
Many questions…
First, suppose I use Chartread –e. Can I read in strips with the i1pro?
Or do I need to read in Patch mode?
Second, choice of lightbox. Is it “better” to measure with the media
sitting on a fluorescent light source? Or is it better to measure with
an incandescent light source? Why not LED light source?
I was thinking of using this kind of lightbox:
https://www.ebay.com/itm/1x-JUST-Normlicht-Color-Smart-Light-5000-Tran
sparency-Flat-Viewer-15-x-10/361307134398?hash=item541f9559be:g:LtkAAO
SwNSxVZhQt
I remember reading that the issue of light source “color temperature”
was not important. How is that?
Best / Roger
*From:*argyllcms-bounce@xxxxxxxxxxxxx <mailto:argyllcms-bounce@xxxxxxxxxxxxx>
[mailto:argyllcms-bounce@xxxxxxxxxxxxx ;
<mailto:argyllcms-bounce@xxxxxxxxxxxxx> ] *On Behalf Of *Kamil Tresnak
*Sent:* Thursday, November 23, 2017 5:22 PM
*To:* argyllcms@xxxxxxxxxxxxx <mailto:argyllcms@xxxxxxxxxxxxx>
*Subject:* [argyllcms] Re: Profiling backlit film with Monitor
Thanks for sharing, Alexey!
Regards,
Kamil Tresnak
In the past I used LCD monitor without matrix (it was damaged, but
lamp itself was good, so I just remove the matrix and used it as a
light table). But the uniformity and stability is not very good, so
it was necessary to calibrate i1Pro every few patches.
Now I'm using iPad (!) and found it much more stable
(auto-brightness=off).
But calibration every 10-15 patches is also highly desirable. It's
necessary to get really repeatable and reliable values.
I'm calibrating device during measurements in two different ways:
1. I'm making ArgyllCMS native calibration every 75 patches.
2. I'm measuring white patch every 15 patches and making linear
spectral correction afterwords in EXCEL.
Best regards,
Alexey Gribunin, UNIT Color Technologies, Moscow, Russia.
