Changing document resolution & ICC profile

[Alan9940]

A couple of editing questions:

1. To change the document resolution, is it okay to double-click Resolution on the Document panel and just enter whatever value I want, or should I use Layout>Document>Scale Document? I don't want any resampling, rather simply change from 2820dip to 300dpi.

2. To convert a document from Gray Gamma 2.2 to Abode RGB (1998), do I use Tool>Color>Convert With Color Profile? On the Document window, it appears that I can double-click ICC Profile and change to any other color profile, if the document already has a base color profile, but this method doesn't seem to allow me to go from GG 2.2 to a color profile such as aRGB.

Thank you.

[Alan9940]

Looking in the manual, I think I have an answer for question 1 above... I should use Scale Layer, set the mode to Resolution, but I'm a little fuzzy on Interpolation. Should I set interpolation to Quick for no interpolation, since all I'm doing is changing the pixel density?

[shijan]

A couple of editing questions:

1. To change the document resolution, is it okay to double-click Resolution on the Document panel and just enter whatever value I want, or should I use Layout>Document>Scale Document? I don't want any resampling, rather simply change from 2820dip to 300dpi.

Yes, you need to use Scale Layer and set dpi there. Instead of Resolution mode you can also use Normal Mode, but you need right mouse click to size field and change system to mm or inches. In this case if you change dpi setting, it will change size in pixels.

Resolution in Layer or Document attributes works unusual compare to other apps. Currently when you change dpi there, it changes size in mm, but keeps size in pixels (sort of set dpi). Normally it should keep size in mm unchanged and only change size in pixels (sort of convert to dpi). I asked about this problem long time ago but it was not changed.

[shijan]

2. To convert a document from Gray Gamma 2.2 to Abode RGB (1998), do I use Tool>Color>Convert With Color Profile? On the Document window, it appears that I can double-click ICC Profile and change to any other color profile, if the document already has a base color profile, but this method doesn't seem to allow me to go from GG 2.2 to a color profile such as aRGB.

Changing from Gray Gamma 2.2 to Abode RGB (1998) requires two steps.
1. Convert from Gray Mode to RGB
2. Convert form Gray Gamma 2.2 ICC profile to Abode RGB (1998) ICC profile.

I recommend to use Tool>Color>Convert With Color Profile, because there is a hidden confusion in Document/Layer attributes RGB/Gray mode toggle. For example if your image in some unusual profile like sRGB Gamma 1.0 and you switch Mode to Gray - it will not preserve your original gamma setting and instead of Gray Gamma 1.0 will convert image to default Gray Gamma 2.2 (or something so). Also when you change Mode from Gray to RGB or from RGB to Gray, PhotoLine don't set that default ICC profile in Layer Attributes and you see "ICC-profile: None" which brings even more confusion because user can't understand which profile now should be set manually. Technically this is not a bug because Mode toggle only changes Mode and don't designed to convert or set ICC profiles. But logically it brings confusion when user expect to convert image from Gray to RGB ICC profile and try use this toggle because it is easier to reach compare to Tool>Color>Convert With Color Profile.

So in short to convert image from Gray to RGB or from RGB to Gray:
Always use Tool>Color>Convert With Color Profile. It will preserve source and destination ICC profiles correctly.
Don't use RGB/Gray mode toggle in Layer Attributes.

[PhilM]

When the image is loaded from your camera, it has a certain number of pixels.
Example : 6000 x 4000 px.

If you decide to print the image, you set the size.
Example : 15 inches wide.

As a result, you get a dpi value of 400 (6000/15).

If you want to force print size and dpi, the software needs to resample the image to adjust the number of pixels to match (dpi = pixels/print size).

dpi is a print property ; not an image property.

[Alan9940]

Thanks for the help.