[brodie_geers]

Could I see what the aliased section of your test looks like compared to mine?

-Brodie

[tom]

Could I see what the aliased section of your test looks like compared to mine?

Yes, I have the same result with you.

But, please try with this pair:

[brodie_geers]

Okay, opened the files separately and changed the alpha to grayscale. Pasted it in to the render as a layer mask resulted in the first image (black halo). Applied the layer mask, remove black matte, results in second image (white halo).





What system are you using? OS and version of Photoshop? If we're using the same images and coming up with different outputs it seems like it must be a Photoshop issue so unless you have any more ideas I should probably find a photoshop forum out there somewhere.

BTW, I tried my images last night at home on Vista and CS4 with the same results as I was getting here at work.

-Brodie

[tom]

I'm on XP x64 with PS CS5 12.0.1 but it works with any version on any platform. Could you please post the screenshot of your color management settings in PS?

Please check with this PSD:
http://www.fileden.com/files/2009/5/30/ ... //test.psd

If this PSD works, it means there's something wrong with your layer mask. It could be due to bad conversion to greyscale or another obscure setting.

[brodie_geers]

Opened your .psd and saved as .jpg. Definite black halo.



I just downloaded Gimp on an XP 32bit machine I have downstairs and ran a test on that as well. I'm not seeing any difference there either. (sorry about the compression).



Color settings



-Brodie

[tom]

Opened your .psd and saved as .jpg. Definite black halo.

Sorry, maybe I was not clear. I'm talking about opening my PSD but opening it, applying the mask and removing black matte. Does it work? Btw, your greyscale profile is Dot Gain 20% which is strictly incorrect for video work. Dot Gain 20% is a screening profile for offset printing. So, as you convert RGB image into greyscale it becomes damaged and not suitable as alpha anymore and it explains your white halo. Instead, you should do the conversion from Edit / Convert to Profile... / Destination Space / Grey Profile: sGray

[brodie_geers]

ahh, happy days! Converting it to sGray worked wonderfully! Thanks for the diligent help Tom!

So in Working Spaces I should change the profile from Dot Grain 20% to sGray? Are there any other settings in there that stick out to you? Should I change the Spot profile to sGray as well?




Yay!

-Brodie

[brodie_geers]

Oh ya, also about removing the black matte. Is that something you always have to do or is that a result of the alpha/gamma bug you mentioned earlier?

-Brodie

[tom]

ahh, happy days! Converting it to sGray worked wonderfully! Thanks for the diligent help Tom!

Thanks for your patience.

So in Working Spaces I should change the profile from Dot Grain 20% to sGray? Are there any other settings in there that stick out to you? Should I change the Spot profile to sGray as well?

You can. But, this is not essential as long as you do the conversion like I pointed out. The color management usually targets proofing the print work so you may like to keep it at Dot Gain 20%. Spot color is totally related to printing so, better don't make changes to it.

Oh ya, also about removing the black matte. Is that something you always have to do or is that a result of the alpha/gamma bug you mentioned earlier?

No, it's the standard way of doing this (I mean using images premultipled with black). The gamma compensation trick was something we've done to PS plugin as PS cannot convert RGB clipboard to greyscale properly when pasting into a layer mask. But later, we saw it's not helping perfectly so, we will remove this in the next update. PS SDK also doesn't allow pasting the alpha to its own channel so it remains as a user responsibility to take the alpha out and convert it before to use.

[jc4d]

Sorry for the little hijack, but I´m using gimp and photoshop elements and at least in photoshop elements I can´t install new colors profiles, but in gimp I can, there is a way to download or something sGray profile?

Cheers
JC

[tom]

Somebody has uploaded here (googled)
http://www.mediafire.com/?jxlwfyjzjzj

[brodie_geers]

When I was routing around looking for sGray, I also noticed that there was a Gray 2.2 (and 1., which I found to be recommended elsewhere. Are you familiar with the difference between sGray and Gray 2.2?

-Brodie

[tom]

Are you familiar with the difference between sGray and Gray 2.2?

Sure. At first sight they may look very similar or even equal, but they are not. Although, practically you can still pick one of them and it won't be a big mistake. The proof lies in a more straightforward explanation and it is; we're after fetching the per-channel (one of the Red, Green or Blue) pixel value as gray. This means, you don't even need to convert it to any greyscale profile. You can directly go to the channels palette and copy one of them (R,G or B) and use in layer mask. But, if you're going to use greyscale conversion, I'd suggest sGray as it's not making any change to the pixel values in sRGB channels. Actually, Gray Gamma 2.2 is doing the same with slightly affecting these values and I guess it's a small error with the conversion accuracy. Up to you