Brightness/Contrast/Gamma Controls-Unwanted linkage

AAProds wrote on 12/15/2022, 7:31 PM

Movie Studio 2023 v167

In the Brightness/Contrast effect, I note that the three Gamma controls, Lows/Mids/Highs seem to be linked. This defeats the purpose of having separate controls. For example, in the attached video, I set the Lows to 32, the Mids to 100 and the Highs to 100. But when I go back to Lows, it is way overbrightened because the control stays at 100, the High setting. If I reduce the Lows value back to 32, the others reduce as well.

The manual says:

Gamma: Set the mean gray value that can be calculated from the various color ranges. In the preset list, you can select different areas to edit only the dark, median, or brightest areas of the image.

Which doesn't indicate that only one of the three can be set.

In another program I use, Virtual Dub, it has similar controls but each band, Low/Med/High, is completely independent and therefore much more practical.

I think VPX does the same.

Am I missing something about how the effect is supposed to work in relation to the three bands? What are other's thoughts on the operation of the effect and would it be better if each band was truly independent?

https://drive.google.com/file/d/1aEdjk4pkSLj62yg8jRpaP674d57mJUyc/view?usp=share_link

Comments

browj2 wrote on 12/15/2022, 9:00 PM

@AAProds

Hi Al,

This is where you need VPX and the meters.

As far as I can tell, the Gamma settings are one or the other. There is another line in the manual:

Using the fader, you can also set the level of brightening or darkening.

It would be nice to have more clarity on this.

If you watch the meters, you can see what is happening as you change the values.

And, it would help if I could upload images but they are being refused with the Error uploading.

Of all that I did using your video, without touching the curves (in VPX), here is what I would say is close to the best:

Gamma 70, HDR Gamma 60, HDR Blur 80.

Gamma itself adjust the overall values but is not like Brightness - it brightens with contrast.

Gamma Low affects the lows mostly, with the effect gradually diminishing as the areas get brighter. I don't mean as you make it brighter, I mean in the already brighter areas.

Gamma Mid affects mostly the mid area with the effect gradually diminishing as the areas get into brighter and darker.

Gamma High affects mostly the highs (brighter areas) diminishing as the areas get darker.

Using the HDR Gamma raises the lows but also decreases brighter areas.

Using the HDR Gamma in combination with Gamma allows you to raise the lows, but it also raise the brighter areas that decreased due to the HDR Gamma effect.

Or something like that.

You really have to watch the meters as the values change to better understand. I'll try to make a video.

John CB

CubeAce wrote on 12/15/2022, 10:00 PM

@AAProds @browj2

Hi Al.

You are correct as far as I can tell and have had similar problems myself in the past.

My favorite method is to use one of the third party effects. The HitFilm Shadows and highlights as opposed to the New Blue version, along with just the slightest amount of use of the MS tonal control.

Personally I find adding too much HDR gamma often leads to a brightness 'shine' around clouds or skylines or similar.

In your example the female has very dark clothing anyway.

These were my settings and result. It may help to reduce the colour saturation as well.

AAProds wrote on 12/15/2022, 10:36 PM

@browj2

Thanks John, understand all that, my concern is the three are linked. As you point out, just using the main Gamma slider does the best job. It's annoying having these apparently great features (Low/Mid/High controls) that, to me, are completely dysfunctional.

@CubeAce

Thanks Ray, that video's pretty good, probably just a bit bright in my eyes.

CubeAce wrote on 12/16/2022, 4:05 AM

@AAProds

Hi Al.

It just needs a touch of colour de-saturation. Set to about 30% for all RGB values should do it.

Ray.

browj2 wrote on 12/16/2022, 6:46 AM

@AAProds

Hi Al,

The Gamma selections are not linked. They are just variations that allow you to tweak the lows, midtones or highs. Gamma is the main one to select for your image. I looked in the Paintshop Pro manual:

Gamma

If the overall image is too dark or too light, adjust the gamma, which is a standard measure of change in an image’s contrast. To lighten the image, increase the gamma by 142 PaintShop Pro dragging the Gamma slider (the gray triangle) to the right. To darken the image, decrease the gamma by dragging the Gamma slider to the left.

Adjust the Midtones slider.

Note: If the graph has peaks on the left and right sides and contains low points in the center, the midtones need to be compressed. Shadows and highlights must be expanded to reveal the information they contain. Photography subjects that are too close to the camera appear brightly illuminated against a dark background. To compress the midtones, drag the Midtones slider up. If the graph peaks in the center and has a low number of pixels at the left and right sides, expand the midtones by dragging the Midtones slider down.

So even Paintshop Pro has just a main gamma slider, but the Midtones seem to do what Gamma Mid would do.

If the Gamma selections were linked, they would just be fighting with each other.

Here is the video showing the meters and what happens when using different sliders. The dialogue is not very erudite.

John CB

AAProds wrote on 12/16/2022, 6:41 PM

@browj2 @CubeAce

John, thanks for the video, but I disagree, they are linked. You move the mid and the low is changed. As you say:

If the Gamma selections were linked, they would just be fighting with each other.

That is exactly what is happening in Magix. Set the Low on -80, the other two go there. Slide the mid to 100, the low goes there, from -80, and the whole thing becomes a blowout, but when you go back to the "gamma" in the dropdown, the image returns to somewhere near what I want. The whole system is illogical, with no info on how it is supposed to work.

The reason I think this isn't working properly is because the same controls in Virtual Dub (Colormill filter) work completely independently (they can be locked together though). Quite often, only the one needs to be adjusted, and the other two don't move.

And yes, I agree, we may as well just use the Main Gamma slider because the lo/mid/hi is dysfunctional, IMO.

I've slept on this, had another play, and still can't see any logic in what's happening.

PS You got me on your voiceover; it is quite quiet, so I had my volume full up. Then I played the clip and that zit at the start almost blew my head off! 😃

browj2 wrote on 12/16/2022, 9:25 PM

@AAProds

Hi Al,

I can't see anything that would lead me to see that the settings are linked. It's one or the other.

Below shows the meters with reset, then Gamma Mid = 100

Below, reset, Gamma Low = -80, then switched to Mid which keeps the same value but it's for Mid, nothing to do with Low, raised the value to +100.

Can you see any difference in the images? I can't.

Here is Gamma Low = -80

Here is switching from Gamma Low = -80 to Mid = -80

Here is reset, Gamma Mid = -80

Can you see any difference in the last two images? I can't. There is no influence by first setting Low to -80 then switching to Mid which is automatically -80, than there is just setting Mid to -80.

Sorry about the sound on the video. I should have normalized it less1db. The volume would have been about 8db higher.

BTW, did you notice this? I just noticed it the other day.

John CB