alpha channels

[mk3]

Hello,

I am new to Photo while have been working with Photoshop many years. I have problems with alpha channels in Photo. My rendered 3D images usually have alpha channel already for backgrounds. Opening them in Photo will show the background 100% transparent. I tried to get the background back by selecting the whole image, creating a spare channel and load this into the alpha channel. This brings my background back but creates white pixels at the borders of my foreground (where alpha isn´t 100% black or white?).

 

[GarryP]

Welcome to the forums.
If you just want to put a background behind your isolated image then you can create a rectangle behind the image layer and apply a gradient to that rectangle. Saves messing around with alpha.

Or have I not understood the issue? If not (often happens), is it possible for you to attach the original image?

[firstdefence]

By selecting the whole image do you mean the object?

It would help if we could download the file and or see the layers panel.

Also which 3D app are you rendering from and in what format PNG? TIF? etc

[mk3]

This doesn´t solve my problem. The white pixels are still there. But I need the original background anyway. I attached my original file and a flat (without the alpha) jpg copy of it.

 

19-12-06_EPC_DL-T2_05.tif

[mk3]

It seems to me like the ability to edit channels is very limited in Photo. I cannot edit the alpha channel with anything other than white. This might be part of the problem.

[R C-R]

29 minutes ago, mk3 said:

This doesn´t solve my problem. The white pixels are still there. But I need the original background anyway.

I don't understand. If you need the background, can't you just export it from the 3D app?

[firstdefence]

Photoshop renders this perfectly, so when you turn the alpha mask off you get a nice transition from background to product the same thing in Photo gives the effect of a white line but its actually semi transparent pixels.

This is from Photoshop

Affinity Photo

There are obviously inherent differences in how Alpha channels are handled, i.e. you can't just turn the Alpha channel off and on you have to fill it, invert it, etc so maybe this action is creating the edge.

The other thing to note is in Photoshop the pixels on the Alpha channel are 100% opaque regardless of the shade but in Affinity there are levels of transparency between shades on the edge.

[lacerto]

(...)

[firstdefence]

You didn't say which App you are using for the 3D render so until then I'll go with Cinema 4D.

In C4D you can add a compositing tag to the object and in the render settings select multipass and add an object buffer. In the save options you can export a mask which masks the background better than using an alpha channel in Affinity Photo.

[mk3]

Thank you all for your help. Photoshop does this job perfectly and of course there are workarounds with the help of the 3D software. But to be honest: A Photo editing software that cannot handle alpha channel transparency correctly and lacks of alpha channel editing options, does not seem to be an alternative for professional photo editing. At least not for me. Too bad, I would have liked to give Photo a chance. Maybe with a future version.

 

[firstdefence]

Would this not do?

Test render.afphoto

This was done with the method mentioned earlier.

[firstdefence]

These are the files used.

Untitled.tif

[lacerto]

(...)

[firstdefence]

Excellent info @Lagarto and makes sense from what I've seen. 

It's this kind of information that should be in the help files or an "advanced" help file with this level of technical information.

[lacerto]

(...)

[Roger C]

1 hour ago, firstdefence said:

It's this kind of information that should be in the help files or an "advanced" help file with this level of technical information. 

Absolutely!

39 minutes ago, Lagarto said:

Yes, it would be very useful to have details of things like color management and image manipulation (algorithms / alpha channels) documented to some extent. I suppose they are discussed in video tutorials, but often there is no time to watch long videos simply to find out more about technicalities.

Absolutely again!

For numpties like me using Affinity, the only way to glean extra information when using these apps is to spend hours each week sifting the forum for hopefully relevant nuggets.

Sure it has by necessity become my new hobby , but it's not an efficient use of work time.

[firstdefence]

1 hour ago, Lagarto said:

As for alternative methods, was the version you provided above (alpha transparency used as a mask) directly exported from a 3D app (Cinema 4D?), or did you manually create the mask?

Created in C4D using a render tag: composite on the object and then specifying an object buffer under render settings.

[lacerto]

(...)

[firstdefence]

Yes, C4D is up there with the best of them, I tried blender but just couldn't get along with it, but for a freebie it's off the chart awesome.

[lacerto]

(...)

[R C-R]

1 hour ago, Roger C said:

For numpties like me using Affinity, the only way to glean extra information when using these apps is to spend hours each week sifting the forum for hopefully relevant nuggets.

Or you could just start a new topic in the appropriate sub-forum with a descriptive title & a clear explanation of what info you are looking for.

[firstdefence]

What about a Tips & Tricks sub-forum?

[walt.farrell]

23 minutes ago, firstdefence said:

What about a Tips & Tricks sub-forum?

Tutorials?

[firstdefence]

19 minutes ago, walt.farrell said:

Tutorials?

Already got them: https://forum.affinity.serif.com/index.php?/forum/9-tutorials-serif-and-customer-created-tutorials/

[walt.farrell]

1 minute ago, firstdefence said:

Already got them: https://forum.affinity.serif.com/index.php?/forum/9-tutorials-serif-and-customer-created-tutorials/

That's what I pointed to, firstdefence

I was suggesting that it is already a sub-forum for Tips & Tricks.