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Author Topic: Best method to recover a completely clipped channel (LR or PS5) ?!!  (Read 2767 times)
PeterAit
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« Reply #20 on: January 05, 2013, 12:39:08 PM »
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By my understanding, a clipped channel is by definition unrecoverable.
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thierrylegros396
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« Reply #21 on: January 05, 2013, 12:43:51 PM »
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AFIAK this should only be an issue if "Softproof" is used with a monitor profile.

Ciao, Walter

I think you are right, it must come from the monitor.

So, I need to use Rawnalyse or Rawdigger, because I've taken some shots with my RX100 which are clipped according to the camera (RGB histogram and white blinking).
After loading them in LR4, I see a headroom of one full stop !!!
Strange because the contrast and saturation of the jpg is set to low.
And today it's a Scottish weather with low contrast and dull colors.
 Huh

Will compare with my G15.

Thierry



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thierrylegros396
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« Reply #22 on: January 05, 2013, 01:02:10 PM »
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Thanks for the raw. I'm not familiar with the Canon G15, but this raw shows the most bizzare Adobe profiles I've ever seen. As I guessed in my original reply, the problem with clippiing on this image is all in the profiles.

True, there is no clipping in the raw, as others have shown with a raw analyzer. Far from it, in fact. But load this raw in LR or ACR and significant clipping shows up under the default settings, which use the "Adobe Standard" profile. But shift to any other profile and the clipping goes away.

The other profiles also give major shifts in color. That's common with the Adobe profiles for most camera models, but the shifts in color AND tone curves for this G15 image are greater than anything I've ever seen. Makes me a bit suspicious about the Adobe profiles for that camera.

In fact, if you shift this image to any other Adobe profile (faithful, camera standard, neutral), you can then increase exposure by 1 to 2 full stops before any clipping occurs.

I converted the cr2 sample to DNG and loaded it in the DNG profile editor to look at the tone curves. The base tone curve for the Adobe Standard profile is huge compared to the others. So it's that tone curve that is driving all the values beyond clipping. Looks like the G15 really, really needs custom profiles.

Sorry, I forgot to say that the posted file is a S90 one !!

But lack of texture I see in the screen is certainly due to "out of Gamut" colors as Francisco says !
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jrsforums
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« Reply #23 on: January 05, 2013, 01:13:23 PM »
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By my understanding, a clipped channel is by definition unrecoverable.

I am not sure your definition of "clipped".

If you mean the actual RAW, as shown in RawDigger for example, it is possible to attempt to recover some of the info/texture by using the other unclipped channels.  This is the "magic" the LR and ACR do. 

If you mean clipping in LR 4, you are correct, because what is shown is after the attempts to recover the info.

Recovery is not necessarily perfect.  This is why it is best to keep the LR brightest tones at ~75% or below.

John
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John
Walter Schulz
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« Reply #24 on: January 05, 2013, 01:17:54 PM »
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because I've taken some shots with my RX100 which are clipped according to the camera (RGB histogram and white blinking).
After loading them in LR4, I see a headroom of one full stop !!!

I don't know how Sony computes histograms. Canon doesn't use the RAW data but the embedded JPEG to calculate those and highlight clipping warning is a mixture of all channels put together and this is called "luminosity".
You know there is a JPEG stored in each RAW file?
Because "luminosity" is a weighted function of those RGB channels you might see warnings where no clipping occurs and you may see no warning but clipped channels.
Therefore: Works as designed.

What's up with the CR you choosed? Do you have clipping problems withing LR? Go to "Develop", press "ALT" and left-click on the "Exposure" slider. Pictures will turn black and only clipped areas will be shown. Those are increased if slider is pulled to the right.

Ciao, Walter
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thierrylegros396
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« Reply #25 on: January 05, 2013, 01:35:44 PM »
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Thanks John and Walter,

If you mean clipping in LR 4, you are correct, because what is shown is after the attempts to recover the info.
Recovery is not necessarily perfect.  This is why it is best to keep the LR brightest tones at ~75% or below.
John
I completely ignore that, but always keep the brightest tone @80%, thanks for explanation Wink

I don't know how Sony computes histograms. Canon doesn't use the RAW data but the embedded JPEG to calculate those and highlight clipping warning is a mixture of all channels put together and this is called "luminosity".
You know there is a JPEG stored in each RAW file?
Because "luminosity" is a weighted function of those RGB channels you might see warnings where no clipping occurs and you may see no warning but clipped channels.
Therefore: Works as designed.

What's up with the CR you choosed? Do you have clipping problems withing LR? Go to "Develop", press "ALT" and left-click on the "Exposure" slider. Pictures will turn black and only clipped areas will be shown. Those are increased if slider is pulled to the right.

Ciao, Walter

I've texture problems, but it appears to come from "out of Gamut" colors !

So, next buy, a new screen  Wink
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Walter Schulz
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« Reply #26 on: January 05, 2013, 02:15:20 PM »
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May I ask which monitor type you are using now, type of operating system and monitor profile settings?
Why I'm asking this? Samsung (for example) is known to install horrible profiles unsuitable for photographers.

Ciao, Walter
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jrsforums
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« Reply #27 on: January 05, 2013, 03:25:08 PM »
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Thanks John and Walter,
I completely ignore that, but always keep the brightest tone @80%, thanks for explanation Wink

Just to be clear....this is on opening. This relates to the original RAW file.  After opening, for creative purposes, all bets are off....you can increase as desired.

Above 75-80% (on opening) is not "bad". Just risks some loss as recovery is not perfect....but much better than without it.

John

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thierrylegros396
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« Reply #28 on: January 06, 2013, 01:20:37 PM »
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Just to be clear....this is on opening. This relates to the original RAW file.  After opening, for creative purposes, all bets are off....you can increase as desired.

Above 75-80% (on opening) is not "bad". Just risks some loss as recovery is not perfect....but much better than without it.
John

Thanks for explanation.

May I ask which monitor type you are using now, type of operating system and monitor profile settings?
Why I'm asking this? Samsung (for example) is known to install horrible profiles unsuitable for photographers.
Ciao, Walter

You are right, Samsung (with Win7) has unsuitable profiles, but I've profiled my monitor with a Spider 2.

And I've just installed latest version of Rawdigger, and learned a lot of things !!!

Thierry
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