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ufraw -- exposure vs base curve

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ufraw -- exposure vs base curve Gary Aitken 14 Mar 05:45
  ufraw -- exposure vs base curve Rick Strong 14 Mar 18:51
   ufraw -- exposure vs base curve Gary Aitken 15 Mar 06:12
Gary Aitken
2018-03-14 05:45:00 UTC (3 months ago)

ufraw -- exposure vs base curve

Hi Folks,

Not sure where to ask this as I couldn't find a ufraw forum, but I figured a number of users here might be able to answer. Please redirect me if this is inappropriate.

Can anyone explain to me the difference between manipulating the base curve in ufraw and boosting the exposure? I'm wondering in terms of where in the processing pipeline the change takes place. i.e. If I could manipulate the base curve to make the image look exactly the same (to my eye, I know it's not perfect) as boosting the exposure, is there fundamentally a difference in the result?

Thanks,

Gary

Rick Strong
2018-03-14 18:51:09 UTC (3 months ago)

ufraw -- exposure vs base curve

Hi Gary,

If you are talking about photographs, altering the curve is not the same as boosting the exposure.

Generally speaking, boosting the exposure makes the whole picture brighter, while playing with the curve alters areas--shadows, mid-range, highlights--of the photograph. But, you may play around with one to end up with a result very similar to the other. This is best done in raw.

Rick S.

-----Original Message----- From: Gary Aitken
Sent: Wednesday, March 14, 2018 1:45 AM To: gimp-user-list@gnome.org
Subject: [Gimp-user] ufraw -- exposure vs base curve

Hi Folks,

Not sure where to ask this as I couldn't find a ufraw forum, but I figured a number of users here might be able to answer. Please redirect me if this is inappropriate.

Can anyone explain to me the difference between manipulating the base curve in ufraw and boosting the exposure? I'm wondering in terms of where in the processing pipeline the change takes place. i.e. If I could manipulate the base curve to make the image look exactly the same (to my eye, I know it's not perfect) as boosting the exposure, is there fundamentally a difference in the result?

Thanks,

Gary

Gary Aitken
2018-03-15 06:12:27 UTC (3 months ago)

ufraw -- exposure vs base curve

On 03/14/18 12:51, Rick Strong wrote:

If you are talking about photographs, altering the curve is not the same as boosting the exposure.

Generally speaking, boosting the exposure makes the whole picture brighter, while playing with the curve alters areas--shadows, mid-range, highlights--of the photograph. But, you may play around with one to end up with a result very similar to the other. This is best done in raw.

I understand altering different parts of the curve affects different aspects of the image, e.g. highlights vs midtones vs shadows. What I'm asking is if modifications to exposure and the base curve are applied to the same thing at the same place in the pipeline.

For example, I am looking at an image where with 0 exposure and the default linear (45 deg lower left to upper right) base curve, the rightmost 3/8 of the histogram is empty. It takes an increase in exposure of about 1.33 to bring the curve to the far right. I can get what appears to be the same effect by grabbing the upper right anchor of the line and dragging it left until it is about 3/8 of the way from the vertical left axis, essentially just making the slope of the line a lot steeper and leaving the origin at the lower left.

Are those equivalent operations, or are they doing something subtly different in terms of what processing is done to the image? They appear to be equivalent. But that may not be the case. For example, does boosting the exposure affect noise or bayer decoding artifacts more than adjusting the curve?

Alterations to the base curve in ufraw are applied at one point in the pipeline and alterations to the secondary curve (under "Correct luminosity, saturation") tab are applied at a different point. Changes to the secondary curve affect the image in a different manner than the exposure and the base curve.

Thanks,

Gary

Not sure where to ask this as I couldn't find a ufraw forum, but I figured a number of users here might be able to answer. Please redirect me if this is inappropriate.

Can anyone explain to me the difference between manipulating the base curve in ufraw and boosting the exposure? I'm wondering in terms of where in the processing pipeline the change takes place. i.e. If I could manipulate the base curve to make the image look exactly the same (to my eye, I know it's not perfect) as boosting the exposure, is there fundamentally a difference in the result?