As a side note... Vignette Correction is apparently not available in the Studio Version?

Just rubbing this in a bit....
A quick tutorial or description on how to shoot what for vignette compensation
and if any post-processing (normalization or the like) is needed would be very welcome.

Cheers & all the best.

Eric.

So, apparently Axy sort of 'knows' what it's doing when compensating for a Vignette.
Some questions though...

When capturing an evenly lit gray card with open aperture and medium exposure through Axy's 'Capture Vignette',
Axy does something to the image in terms of pushing the brightest pixels to 100% and (apparently) reducing color saturation to 0%.

I tried to recreate that behaviour in Fusion and I'm wondering what's the difference between the manual workflow and Axy's automagic approach.
So here's the waveform of the gray card captured manually:

Pushing the values towards white should be a gain (multiplier) operation, which looks like this:

However, Axy's automagic capture gives a slightly different waveform which seems to be more 'spread out',
as if some sort gamma correction or linearization was applied:

Not that it matters in terms of quality, it's more the technical aspect I'm interested in...

Cheers & all the best.

Eric.

Another note on this...

When applying the Vignette Correction (VC), Axy also brightens up the center of the image
(which in fact is already bright enough since we've already set the exposure of scene correctly)
So with VC applied we have to lower the exposure on the camera by about 1 stop.

Am I doing something wrong here?
I would expect the VC to only influence areas of the image that are darker than the brightest spot...?

Cheers.

Eric.

Hi Eric,

Don't use a gray card. And don't modify the reference image.
Vignette Correction is available in the Studio version and in every version. If you don't find it, it is probably because the common studio libraries haven't been updated.

You can check how the color values are pushed towards white inside the camera compound's Flow logic. It is not an over-complicated system.

Warmest regards,

Hi,

This is a simple tutorial on the Vignette Compensation.

The vignette compensation removes the darkening towards the borders of your camera's picture. This vignette is caused by the characteristics of the camera and lens.

Currently, for Vignette Compensation you need to make one picture with your camera. This might change in the future...

This one picture should be fully filled out with one flat homogeneous (uniform) white surface. And the camera must not overexpose!
The flat surface should face your camera and should be at the same level as your camera:

For the best quality, you would use a led wall as the white surface.
If you don't have a led wall, we suggest using a tv, monitor, or even a laptop's screen. In these cases, you will probably have to move your monitor up to the level of your camera and quite close to your camera.
By the way, you can easily put out a white screen on a monitor with Aximmetry, just use the Solid Color module:

If you don't have any homogeneous white light source like a monitor, then you can try using white cardboard. The white cardboard should be well-lit with diffuse white lighting.

To get the best results, your camera's picture should be close to overexposure. But, any part of the picture being overexposed will significantly reduce the quality of the Vignette Compensation.
To determine if the camera is overexposed or not, we suggest turning on the zebra ( https://en.wikipedia.org/wiki/Zebra_patterning ) in your camera.
When the zebra is turned on, you should increase the exposure until the zebra appears, and then turn the exposure just a little bit down until all of the zebra disappears.
Also, while the zebra is visible, it can give a good idea if your white surface is homogeneously white and evenly lit. As the zebra should only appear in the middle of the picture where there is no vignette. If the zebra pattern is more numerous in one direction, then your white surface is probably not evenly lit.

Warmest regards,

Hi @Eifert.

Thanks again for another brilliant tutorial!
Lots of valuable information in there since it would have never occured to me to shoot on white.

Funny enough the modification of the reference image (pushing the medium-exposed gray towards white) was done by Axy automagically... :-)

Hi Eric,

Yes, it gets pushed to white. But pushing it will make it lose accuracy, that's why it is suggested to use white in the first place with as high of exposure as possible without overexposing.

Also, different zoom levels, exposure, or lighting will change the vignette. So if any of these changes, you might need to make a new vignette or adjust the current one. The current method of vignette compensation will probably change in the future to better deal with these challenges.

Warmest regards,