Photoshop - Some professionals say dot gain20%, others gamma 2.2 ??????

"Cum grano salis" does NOT translate into "don't believe anyone"!

It only means that you take the information, test its validity for yourself, and then you can rave about it if it works and toss it if it doesn't.

It means "be patient" and "take the time to try things out."

"I think every reply so far has agreed there is absolutely
no effect on colour printing."

Really ?
If we convert sRGB to Grayscale by G=2.2 we get one set of
numbers (image1). If we convert RGB to Grayscale by G=1.8
we get a different set (image2). Now let's assume that no
profile is embedded, or not input profile can be defined.
Then the printer assumes probably G=2.2 and the print of
image2 would be wrong.

Bad as well for press printing as PDF/X-1a. One conversion
for dot gain 28% (or so) because of G=2.2. The other for
dot gain 20% or by using a more accurate gray profile:
the first print would be very wrong on coated paper.

Using a qualified RIP, Grayscales are printed correctly
for three cases:
a) the profile is embedded and honoured by the RIP.
b) the profile is not embedded but chosen explicitly as
required.
c) G=2.2 was chosen and the RIP assumes this always (bad).

Best regards --Gernot Hoffmann

>Really ?

Well, yes, up to that point, I didn't see any disagreement. Didn't say
there couldn't be.

>If we convert sRGB to Grayscale by G=2.2 we get one set of
>numbers (image1). If we convert RGB to Grayscale by G=1.8
>we get a different set (image2). Now let's assume that no
>profile is embedded, or not input profile can be defined.
>Then the printer assumes probably G=2.2 and the print of
>image2 would be wrong.

But why would the colour printer be converting sRGB to greyscale at
all, if it's a colour image and a colour printer?

Aandi Inston

I may have missed something along the thread, but I thought this discussion was about the effect of the default greyscale profile in Photoshop's Color Settings on the viewing of a file's individual channels -- not about converting a color image to greyscale.

Am I incorrect about that? If I am correct, I fail to see the relevance of Gernot's comment.

> I thought this discussion was about the effect of the default greyscale profile in Photoshop's Color Settings on the viewing of a file's individual channels

Not really. The discussion was about the general recommendation, in
some places, to choose a particular greyscale profile so a color image
prints properly.

We've been all over the place, but all we've been able to come up with
on why this advice is any use is if you might be viewing the channels,
or converting to greyscale.

Aandi Inston

Not really. The discussion was about the general recommendation, in some
places, to choose a particular greyscale profile so a color image prints
properly.





I fail to see the connection...

We've been all over the place, but all we've been able to come up with
on why this advice is any use is if you might be viewing the channels,
or converting to greyscale.





Yes, which is another way of saying, although in a roundabout way, that the choice of greyscale profile (in the Color Settings, I assume) has nothing to do with the way a color image will print.

Sorry, only a communication test.
Login didn't work reliably.
G.H.