What exactly is black point compensation?

Yes I 've Googled this and still can't work out what it does when printing
from Photoshop.
A simple explanation would be great.
regards
PeterH

My View

Re: What exactly is black point compensation?

Hi Mike,
You mean this is done after adjusting the levels of the image, right?
Hi OP,
BlacK has always been a real problem as it is not a synthesised ray of
any color. Rather, we can call it a "blackout" when RGB space is
involved, ie, the most beautiful black on screen is the black that
emits no light and only screen's black background shall represent it
(upon proper monitor calibration).
Black point compensation issue can only be of real essence when
printing (or CMYK space) is involved. In Photoshop there is an
excellent control over black generation which can be adjusted according
to the required purpose.
Mohamed Al-Dabbagh
Senior Graphic Designer

Mohamed Al-Dabbagh

Re: What exactly is black point compensation?

That is correct.
BPC is a proprietary color management addition to the ICC
color-management. It can be (but not always is) useful when profiles
that conform with v.2 ICC spec are being used since the blackpoint is
not properly managed in them. The v.4 ICC spec does specify device the
device blackpoint unambiguously so the effect of the BPC could be
(usually is) different when v.4 profiles are in use.
Also the v.2 ICC profiles can affect to the conversion of the device
blackpoint but this goes by approximation (where the v.4 profiles
provides the accurate blackpoint tag). Some/many profilers (that output
v.2 profiles) do such approximation, some do not. Therefore it is a very
good idea to check behavior of a new printing path, in respect to the
BPC, using a suitable test chart.
The problem with v.4 ICC profiling is that most of the
spectrophotometers are not good enough to measure the blackpoint
accurately, only the most expensive laboratory grade spectros have good
enough dynamic range.
Timo Autiokari
http://www.aim-dtp.net

Timo Autiokari

Re: What exactly is black point compensation?

That time of the month Dave? I hope I spelt that correctly.
Thanks anyway Dave for pointing that out. I'm sure your heart is in the
right place.
My apologies Mike for quickly replying with your surname - honest mistake.
Don't you hate it when people are human and make honest mistakes.
Mike, your reply was exactly what I wanted to know as I tried Googling it
and all I got was a list of sites that explained how to print from PS with
"Black Point Compensation" selected. They did not state what BPC was - now I
know. I get all my prints done at professional labs and have never used the
PS print option. Simple printing at home is done using the printer software.
Hence my lack of knowledge on this particular subject.
I've received many great replies from you and always take your replies as an
excellent source to learn the finer points of PS.
I once again appreciate you realising that the main reason people use
newsgroups is because firstly they don't know or cannot find the exact
answer to a simple or complex question and secondly because they are looking
toward people like yourself to progressively improve their
knowledge in the use of this great package.
Mike once again keep up the great work - I always look for your name in
replies to this newsgroup as a source of good and reliable knowledge on
these subjects. Your website is on my favourites as well.
I hope you will continue to reply to "stupid fools" like myself so one day
we will all be as proficient in PS as Dave is.
Dave, I will also be looking out for your replies in the future so I can
make my own judgement as to whether or not you are also worth following like
Mike.
regards
Peter

My View

Re: What exactly is black point compensation?

No offense taken for thanks of any kind. At least he spelled it with two
l's! :-)
--
Mike Russell
www.curvemeister.com/forum/

Mike Russell

Re: What exactly is black point compensation?

On Sat, 22 Jul 2006 02:33:57 GMT, "My View" <no spam ple@se.com>
wrote:
Pity you answered this stupid fool, Mike.
Maybe we should have a kind of houserule here
like only reacting to calls placed by people with names.
Sorry for this explosion, but you carry this kind of weight here,
that it irritates when a *nobody* does not even have the decency
of saying thanks to you by your name but calling you by the surname.
Dave
Here are the links to those much-talked-about
Crime Reporting Websites :
http://www.crimexposouthafrica.co.za
http://www.southafricaiscrap.blogspot.com
http://deathofjohannesburg.blogspot.com
http://www.wea.co.za/

Dave

Re: What exactly is black point compensation?

Thanks Russell

My View

Re: What exactly is black point compensation?

It means that black in the source image's color space will be mapped to
black in the destination color space.
For example, because of paper reflectivity, a printed black is typically
brighter than black
on a monitor. Instead of converting printed black to something like
RGB(10,10,10) value, black will be converted to the black of the destination
color space, RGB(0,0,0).
--
Mike Russell
www.curvemeister.com/forum/