EXR transparency issue (Updated)

[holmes1977]

Hi
I normally use a programme called "Image convertor Plus" to convert EXR images to PNG (Alpha channel)
This has worked really well. Untill I tried to convert any EXR file over 400mb. The progamme just crashes.

So I downloaded the openEXR pluggin for PS CS3. I havent been able to get the alpha channel to come through.
So I end up with no transparent background or transparency through glassed areas. I get a white ghost out line aswell.

I see you have to play around with the exposure and gamma settings. It was really easy using "Image convertor Plus"
It would just convert the EXR to PNG (Alpha channel) with out changing anything. No ghosting no changing settings.
But it just crashes if the file is to big.

What do other people use. Or am I missing something?

PROBLEM WITH GHOSTING (WHITE OUTLINE) SOLVED
When I was importing the EXR into PS I was ticking the Un-Premultiply option in EXR Import settings.

Attached is a screen shot

[thomthom]

Re: EXR transparency issue

I use Photoshop.

Though I am a little bit confused in regard to the correct procedure. The image looks fine when I set Photoshop to proof the colours. But when I convert the 32bit image to 8bit I get a previwe, that looks fine as I would expect the results, but when I press OK, it is overexposed.
The only way I found to work was to add a 0.4545 gamma to the 32bit image before converting to 8bit.

[holmes1977]

Re: EXR transparency issue

Thanks for the tips thom

The image rendered in Vray has an VFB alph channel
This seems to disappear when I convert it in PS
But I do get a white line on the edges between the rendered image and the alpha channel (background)

Did you get a transparent background (Alpha channel)?

So not to confuse people. The image that is in the galley area is done straight from Vray to a PNG then touched up in PS.
The image Im referring to is 7400x5550 so had to save to file (VRimage then convert to EXR)

PROBLEM SOLVED
There was a Alpha it was under the channels, not cut out on the layer.

[holmes1977]

Re: EXR transparency issue

As normal Im the one to confuse myself.

Im used to opening PNG (Vray output) in PS and having the Alpha channel cut out (transparent) on the same layer

The EXR when opened in PS has an Alpha channel.

Can somebody point me to a good tutorial on how to use the Alhpa channel to cut out or make transparent the background
Like a PNG exported from Vray with a VFB Alpha

Hope the picture explains it better

[frip51]

Re: EXR transparency issue (Updated)

Holmes,
it's a simple thing after converting the file to 8bit:
- Duplicate layer (since OpenEXR comes out flattened)
- CTRL-click Alpha Channel in list (selects visible parts)
- Add layer mask (reveal selection)

Job done.


Cheers,
Matt