Snapseed and Ambience

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tomczak
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Snapseed and Ambience

Post by tomczak »

The Android app Snapseed has an adjustment called Ambience. There is short description here: https://support.google.com/snapseed/ans ... 1600?hl=en

Would anybody know what it actually does?
Maciej Tomczak
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jsachs
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Re: Snapseed and Ambience

Post by jsachs »

I was able to achieve similar results using Brightness Curve and Multipass Sharpen. It looks like they may be trying to crudely partition the image into light and dark parts and applying different curves and local contrast enhancement to each part. You can create this kind of partition using a mask based on brightness and then blurring it heavily. Their algorithm is apparently proprietary so no way to know for sure since ambiance is not a technical term.

Also see:

https://graphicdesign.stackexchange.com ... -photoshop
http://www.photocritic.org/articles/unp ... nce-slider
Jonathan Sachs
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tomczak
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Re: Snapseed and Ambience

Post by tomczak »

Out of curiosity, I tried to replicate what the Ambience does. With Brightness Curve in Advanced mode, with masks, it all can be done but requires a bit of determination. The Two Zone Adjustment is far easier, but it lacks the local contrast enhancements ability of the Brightness Curve.

p.s. Is there a way of saving the Two Zone Adjustment masks as masks?
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jsachs
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Re: Snapseed and Ambience

Post by jsachs »

There is no way to save the 2-zone masks, but you can easily re-create them using the Mask Brightness Curve tool.
Jonathan Sachs
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tomczak
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Re: Snapseed and Ambience

Post by tomczak »

I just rediscovered the Two Zone transformation. It's pretty pleasant to use and powerful in what it can do in one go.

I was thinking that some kind of local contrast enhancement for each zone, perhaps as an advanced option similar to Brightness Curve, could be quite useful, but I'm not sure if it would justify the effort - something similar can be already done by creating a similar mask, then using the Multipass Sharpen or the Brightness Curve in Advanced mode for each zone separately, but it's a lot of work...

p.s. I just want to make sure that I understand what the Two Zone does: in the Blend tab, if the Transition Amount slider is 100%, the Transition Zone displays the original input image there, and at 0% blend of the adjustments from the Highlight and Shadow Zones?
Maciej Tomczak
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jsachs
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Re: Snapseed and Ambience

Post by jsachs »

What I currently use instead of Two-Zone is Brightness Curve as it gives you much more control. When you create a mask (which I normally do using the freehand mask tool followed by the mask blur tool), you can apply one curve to the masked area and a different curve to the unmasked area. More importantly, you can display the histograms for the masked and unmasked areas which is a big help in adjusting the curve for each one. Briefly, the technique is:

1) load the image

2) bring up Brightness Curve and create a mask. To simulate Two-Zone, create the mask using the mask brightness curve tool which lets you mask different parts of the tonal range and blur it a little. Or, use the freehand outline tool and then blur the mask to simulate dodging and burning in the darkroom.

3) click the "Base Histogram on Masked Area Only" button

4) click the White button to adjust the curve for the masked areas -- this sets the histogram to reflect the masked areas

5) click the Black button to adjust the curve for the unmasked areas -- this sets the histogram to reflect the unmasked areas

6) fine tune if desired using the black and white Amount sliders

You can also adjust the color balance and saturation of the masked and unmasked areas with this same transformation. If you use the Advanced option, you can also add some sharpening. As an additional benefit, the mask you created remains available for further transformations such as selective sharpening or selective color correction.

If you need to adjust more than two areas, just use Brightness Curve again on the result, with a different mask.
Jonathan Sachs
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tomczak
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Re: Snapseed and Ambience

Post by tomczak »

The more I play with the Two Zone, the more it feels that the Transition Amount slider in the Blend tab would be more intuitive and consistent with other Amout controls if reversed: 100% being the full strength of the effect of the combination of Highlight + Shadow amounts, determined by the other two sliders, applied to transition mask.

p.s. I just wonder if this is correct. There are 3 sliders that apply to the transition mask: the Highlight Amount, the Shadow Amount, and the Transition Amount. Would having just two sliders: Highlight/Shadow Balance + Transition Amount be equivalent and cover all the combinations of the current three?

p.s.s. Or perhaps a single double slider...
Maciej Tomczak
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Re: Snapseed and Ambience

Post by tomczak »

On the other hand, even if limiting the number of control sliders in the Two Zone would make sense, that may not translate too well to the Three Zone, making the two fundamentally similar transformations more dissimilar to control...

I think I still stand by reversing the Transition Amount slider though... :⁠-⁠)
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jsachs
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Re: Snapseed and Ambience

Post by jsachs »

I reversed the sliders for the next release.
Jonathan Sachs
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tomczak
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Re: Snapseed and Ambience

Post by tomczak »

Many thanks for that! - it's a little thing, but it makes it much more intuitive for me.

While I'm a fan of the Brightness Curve in Advanced mode (with masks) and its ability to display separate histograms for different halves of the masks, I still like the Two and Three Zone transformations for their simplicity and 'coherence' and thus the speed of adjustments. Even if adding something akin to Advanced mode from the Brightness Curve to include some LCE doesn't make sense, perhaps adding a colour balance control could make the 2/3 Zones transformations even more flexible? Just an idea...
Maciej Tomczak
Phototramp.com
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