"Batch" Autocontrast

[gregglee]

Can anyone think of an approach to apply autocontrast to multiple files or an entire folder?

Presets or selective copy will not work because those copy settings vaues. Autocontrast is a one time process that calculates setting changes. It changes settings, but only for one image and one time, based on that image content and settings at that time. Settings calculated for one image would not work for another.

So this would be like a "script" or procedure that runs autocontrast for each selected image separately. I considered a keyboard script since there is a key for "next iamge", but autocontrast cannot be triggered from the keyboard.

[afx]

Put in a request for an autocontrast hotkey would be a good start....

cheers
afx

[Denis de Gannes]

Where is the "Autocontrast" button/control located in ASP?

[afx]

Where is the "Autocontrast" button/control located in ASP?

Same as in Bibble, the curves tool.

cheers
afx

[Denis de Gannes]

Will the Auto Levels button, in the Standard tab, provide a similar function.

[afx]

Will the Auto Levels button, in the Standard tab, provide a similar function.

Depends on how you define similar
Autoleves is now relatively early in the pipeline, Autocontrast happens in the curve step very late.
Autolevels re-evaluates the image every time the pipeline is run and therefore is affected by anything that happens before it in the pipeline like crop or noise reduction that changes the luminance statistics depending on the image content. Autocontrast happens only at the time you click it.
The result of Autocontrast can be adjusted via the triangles in the curves tool, Autolevels is an all or nothing toggle.

cheers
afx

[Denis de Gannes]

Will the Auto Levels button, in the Standard tab, provide a similar function.

Depends on how you define similar
Autoleves is now relatively early in the pipeline, Autocontrast happens in the curve step very late.
Autolevels re-evaluates the image every time the pipeline is run and therefore is affected by anything that happens before it in the pipeline like crop or noise reduction that changes the luminance statistics depending on the image content. Autocontrast happens only at the time you click it.
The result of Autocontrast can be adjusted via the triangles in the curves tool, Autolevels is an all or nothing toggle.

cheers
afx

Thanks for this clarification. Its not a function I normally use.

[Tadjio]

The result of Autocontrast can be adjusted via the triangles in the curves tool, Autolevels is an all or nothing toggle.
afx

I don't understand this totally. AutoLevels can be adjusted by the 'Shadow Clip Percentage' and the 'Highlight Clip Percentage' so it isn't "all or nothing". (And AutoContrast usees the same Thresholds).

My beef with AutoLevels is that I find I have to adjust the Thresholds too often (starting from 0.002) but I am hoping when the Highlights issues are resolved by Corel/Jeff that AutoLevels w ill be improved!

[afx]

I don't understand this totally. AutoLevels can be adjusted by the 'Shadow Clip Percentage' and the 'Highlight Clip Percentage' so it isn't "all or nothing". (And AutoContrast uses the same Thresholds).

It still is all or nothing, as it is either on or off. You can turn it on or off and it will work according to the thresholds you set. But it can not be fine tuned on top of that like Autocontrast which just sets the levels initially according to the thresholds and then can be tweaked further.

cheers
afx

[gregglee]

I don't understand this totally. AutoLevels can be adjusted by the 'Shadow Clip Percentage' and the 'Highlight Clip Percentage' so it isn't "all or nothing". (And AutoContrast usees the same Thresholds).

On the Bibble Forum, Colleen (Bibble staff) once said that they use the same clip percentages, but algorithm is not completely the same. (However the results in Bibble were usually similar.)

The bigger difference is continuous versus run once.
Auto level operates continuously, readjusting whenever many other tool settings are changed.
Auto contrast operates once only. Like autolevel it is affected by other tool settings at the time it runs, but does not continue to make changes. Whatever changes AC makes to curves remain fixed. (But if you make changes to other tools then run AC again, the result will be different.)

Slightly more subtle, in terms of interface AC moves the sliders on curves tool, much the same as moving them manually. AL changes the histogram, but does not reposition the sliders on the display. More like using exposure tools. So on curves tool it's as though AL repositions the startings point on the histogram for curve sliders. So adjusting sliders on top of AL is usually not the best technique. AC on top of AL is normally uselessly "of the chart." Either AL or AC, not both.

[Tadjio]

[The bigger difference is continuous versus run once.
Auto level operates continuously, readjusting whenever many other tool settings are changed.
Auto contrast operates once only. Like autolevel it is affected by other tool settings at the time it runs, but does not continue to make changes. Whatever changes AC makes to curves remain fixed. (But is you make changes to other tools then run AC again, the result will be different.)

Slightly more subtle, in terms of interface AC moves the sliders on curves tool, much the same as moving them manually. AL changes the histogram, but does not reposition the sliders on the display. More like using exposure tools. So on curves tool it's as though AL repositions the startings point on the histogram for curve sliders. So adjusting sliders on top of AL is usually not the best technique. AC on top of AL is normally uselessly "of the chart." Either AL or AC, not both.

Thanks for spelling that out. I think in practice I shall wait for the (promised) next version that will fix Highlight issues before experimenting further. It seems as though Automatic Levels in PSP is more like Auto Contrast in ASP.

[gregglee]

My beef with AutoLevels is that I find I have to adjust the Thresholds too often (starting from 0.002) but I am hoping when the Highlights issues are resolved by Corel/Jeff that AutoLevels w ill be improved!

The need to adjust is a result of being broken. Manual tool adjust is easier than clip adjust. The idea (in Bibble5 anyway) is to set default clips to your taste and your equipment, then leave alone. If they work, great, if ot turn of an go manual. Perhaps also a couple presets with different clips for special situations like bird or aircraft in flight against sky, (I in fact have this one set up.)

In Bibble5 this works well for most images because you can use limited adjustment of tools like exposure, highlight and fill over AL. AL does push back but not completely. In many image sets with AL on, I can run through using only hotkeys [, ], alt-z and alt-x. Plus selective copy instead if there are several similar. But for larger adjustments turn off AL, then use AC or manual curves and/or other manual adjustments.

Historical note: Bibble4 autolevel would almost completely offset any manual adjustments. I was one who suggested that we needed a version that would be a starting point rather than continuous, working similarly to the contemporary version of ACR auto.

Bibble 5 did just that, adding the AC tool and also changing AL to be less aggressive toward other adjustments, so that other tools could be used with it. Some may consider tools over AL an esthetically impure approach, but it worked. I was sorry to see that ASP broke both AL and AC (an unintended consequence of some other change I assume). Once fixed I hope AL and AC will work as before.

[gregglee]

But none of the above answers my original question. Can anyone think of an approach to execute AC on many images in a batch. One that doesn't depend on other changes from Corel. If Corel addresses it I would expect a complete batch tool, not an add on script. Perhaps a new tab in the left panel, hopefully for any of the once only processes like AC, increment exposure, etc. naturally with assignable hotkeys. But I doubt that would be soon. And I'd prefer the AL AC fix first.

Anyway, I previously mentioned as a thought keyboard or similar script.

I know little about plug-in capability and limitations.
Can plug-ins ever act on more than one image at once?
Can plug-ins run a process, especially an existing process like AC?.
Can plug-ins create hotkeys that are not available in ASP?


And I figure that any workaround AC batch solution for ASP will probably also work with Bibble5, so I could start using it even before ASP gets around to fixing AC.