Raw Image File Output and Saving from VFB Have Different EXR File Sizes

[alienboy]

I've noticed this for a while and it confuses me, the EXR file size will be drastically different when you save from VFB (the "save all image channels to single file" option) vs. using V-Ray raw image file saved directly after rendering, all EXR files saved with multiple channels including cryptomatte. The EXR files saved from VFB will have much small file size then raw image file output, it can be over 60% smaller. I didn't use VRayOptionRE to change the EXR compression method.

Are the EXR files saved from VFB compressed/compressed more while the raw image files are not? Or do I lost certain information when saving from VFB? I didn't notice any visual/data difference when compositing.

[hermit.crab]

Most likely the image saved from the Raw Image File output has the 32-bit output option checked. Multi-channel Exrs from the VFB are saved as 16-bit. Check this thread for more information.

[alienboy]

Most likely the image saved from the Raw Image File output has the 32-bit output option checked. Multi-channel Exrs from the VFB are saved as 16-bit. Check this thread for more information.

I've checked the thread, thanks.

But I've further questions. When I was editing these EXR files from the same render, one saved through Raw Image File and the other saved through VFB, I can't really tell the difference as I fiddled with the exposure settings in Photoshop. I imported the EXR files into Photoshop through the Exr-IO plugin. Both of the files are showing (32-bit/channel) in Photoshop.

What gives? Am I missing something with my editing workflow or I misunderstood some concepts?

[hermit.crab]

Photoshop may not be accurately be showing the bit-depth of the images (some elements are always saved as 32-bit through the VFB, so PS possibly detects them). The correct way to show EXR information is through a compiled EXR header utility. Otherwise, attach the files here so we can take a look.

[^Lele^]

PS will promote *all* EXRs to work in 32BPC mode.
That happens regardless of the original files' bitness.
PS's 16 Bit mode is 16int, not 16fp, so a totally different thing.

You'll want to use fusion (free) or analogous to check on image data with HDR formats.

[gandhics]

When you save Raw Image File Output, it uses VRay's own raw image saver which supports exr multipart.
Also this means all exr settings are ocming from OptionsRE render elements.

If you use Save button in VRay framebiffer, it uses 3dsMax's builtin bitmap IO plugin which DO NOT support exr multipart.
Also this means all exr settings from the FIle save exr options.

Even tho it may looks ike same multi channel exr to users, multipart exr has totall;y dofferent data structure and Exr-IO plugin doesn't support correctly.

[alienboy]

It has been a while, but I want to thank all of you for the answers, they helped me!

Judging from what you guys were saying, I guess Photoshop + Exr-IO isn't a very good workflow for editing and compositing OpenEXR renders, is it?

What's your recommendation for single frame EXR compositing, then? I figure Nuke or After Effects may be a better software for this, but our company doesn't have Nuke, also a video compositing software is a bit overkill for single frame, you also lose some Photoshop's flexibility in image editing.

[piotrus3333]

proEXR for photoshop is opening vrimg files. should be easier I guess.

[^Lele^]

It has been a while, but I want to thank all of you for the answers, they helped me!

Judging from what you guys were saying, I guess Photoshop + Exr-IO isn't a very good workflow for editing and compositing OpenEXR renders, is it?

What's your recommendation for single frame EXR compositing, then? I figure Nuke or After Effects may be a better software for this, but our company doesn't have Nuke, also a video compositing software is a bit overkill for single frame, you also lose some Photoshop's flexibility in image editing.

There's Fusion which is free up to a certain resolution.
Granted, node based could be overkill for simple retouching, but you are free to mix and match depending from the pipeline stage you're at.
You'd want perhaps to do the image maths parts at higher bit depth inside a compositing tool, and perhaps the painting and final conform on an 8bit image in Photoshop.
Notice that most compositing application will have a fully-fledged painting section (or node, same thing.) which has little to nothing to envy to a Photoshop (take the old discreet *Paint, or Shake. Nuke and Fusion have excellent paint nodes as well. After Effects used to lag a bit behind, but it's likely these days it's as powerful as any other, i have no current experience with it.).
Perhaps you may miss some of the fanciest tech (AI this and that), but not much else.

What won't be free, nor immediate, will be the adaptation to new tools and workflows, of course.

[piotrus3333]

What's your recommendation for single frame EXR compositing, then? I figure Nuke or After Effects may be a better software for this, but our company doesn't have Nuke, also a video compositing software is a bit overkill for single frame, you also lose some Photoshop's flexibility in image editing.

what exactly your “editing and compositing OpenEXR” consist of? how does it look in PS+Exr-IO so far? what are you missing?