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

Hallo, I print only to my inkjet at home, canon 4 ink epson 8 ink. In the colour management policy for photoshop cs3 within creative suite 3 I have set the Grey dot gain to gamma 2.2 instead of the default 20%. There seems to be about a 50/50 on this issue. the botom dot gain (Spot dot gain) this is not important for me.

Could someone clarify this situation because I have found no definitive explanations on the web about this issue. Even colour management tutorils seem always to avoid these issues.

Tankyou, Chris.

Do you ever convert your photos to greyscale? If not, I don't think
the grey profile is ever relevant (but I'm ready to be surprised).

Aandi Inston

Chris,

What you do depends on a number of factors. Dot Gain is usually used when outputting to a press, since it is more likely to reflect press behavior than a gamma curve. If you had the 'average' actual dot gain for a given press, it would probably give you a closer match to a properly calibrated monitor.

If most of your work is either displayed on web, emailed or printed on an inkjet, gamma 2.2 is probably a better overall choice. The web and email are based on sRGB, which also has a gamma of 2.2, so your grascales will display more accurately online if you use gamma 2.2. As long as you use the correct printer profiles for printing (for your paper/ink/printer), your files will be converted so they look correct on your inkjet. The more accurate your profiles, the better the result.

Photoshop will take either your gamma 2.2 or 20% dot gain encoded file and convert the numbers to your printer profile.

Dot gain curves and gamma curves are not quite the same. You can see the effect if you wish as follows: convert a color original to gamma 2.2. Then, ASSIGN a 20% dot gain curve. Your overall image will look lighter than the gamma 2.2 original. Try assigning 25% and 30% dot gain curves, and as the dot gain increases, your file will appear darker. Although not all parts of a dot gain curve mirror a gamma curve precisely, it appears to me that a gamma 2.2 curve is fairly close to a dot gain of approximately 27% or so.

Probably more theory than you wanted. If you aren't going to a press, gamma 2.2 is a good bet and fairly flexible. But you can get good prints both ways.

Lou

Hi Aandi, thanks for your reply, Are you Dutch? Double 'a' is a dutch dipthong, tot zo!. Lou, I appreciate your time in this, and no, it was not too technical. I need details in order to fully grasp a concept, so Thankyou.

Chris.

Whatever you have loaded as your grayscale working space will affect how your individual channels of a color document are displayed, so that may have an impact if you do any amount of channel work.

No, not Dutch, sorry.

From what Peter says it has occasional effects on display, but still,
it's not a very relevant setting. Chris, what are you sort of
expecting it to effect? It isn't really anything to do with dot gain
in a general sense; it's a greyscale profile which compensates for a
particular dot gain WHEN WORKING IN GREYSCALE.

Aandi Inston

No idea Aandi. But a video podcast and a web site suggested that if you are not sending work to a printer then set this to gamma2.2 because that is the RGB space of your monitor and printer. If youare using PROPHOTO then set this setting to 1.8? Since I was used to keeping it at the default I was somewhat confused as to what to do here.

Chris.

Hi Peter. thanks that is an interesting point. I often use and load and manipulate individual channels, especially for sharpening. But maybe the difference are not so apparant and maybe miniscule. But thanks for that tip though.

> But a video podcast and a web site suggested that if you are not sending work to a printer then set this to gamma2.2 because that is the RGB space of your monitor and printer.

I have to tentitively say this sounds like one of those bits of
mythology which has no basis in real facts, but sounds convincing
enough that it gets repeated. It's certainly wrong in detail, because
it isn't an RGB space at all, and won't affect the normal display or
printing of RGB.

Aandi Inston

But...it seems irrelevant to me whether or not you use a greyscale space as default that has the same gamma as your working RGB space. That has no bearing whatsoever on how the composite RGB image appears onscreen or prints or separates to a CMYK space. None at all.

Why would it be important to see the individual channels in the same gamma as that used by your working RGB space? What would be gained by that?