D-range shadow correction. What does it do?

john wakefield · 08-28-2014, 07:00 AM

I can't understand what this actually does. I expected that when shooting in RAW it would make no difference whether it was on or off since I assumed that it applied some processing after the sensor was read and that the idea of RAW was to let the user apply all corrections. It does however make a difference. Therefore I'm not sure whether it changes the exposure or sensor characteristics before taking the picture or writes corrections to the RAW file. Is there any reason to ever turn it off since it appears to capture more information?

Adam · 08-28-2014, 07:28 AM - **1 Like**

Having the shadow correction setting enabled lowers the overall contrast (inherently), so I would only turn it on it when there are dark details in the image that would actually look better when brightened.

I think all the setting does is boost the highlights a bit. This is unlike highlight correction, which lowers the ISO by one stop to underexpose the image (hence limiting the minimum ISO selectable to 1 stop more than base ISO) then amplifies the rest of the image. The same results can be achieved in RAW without shadow/highlight correction if you expose in the same manner.

Na Horuk · 08-29-2014, 02:15 PM

Shadow correction and highlight correction are different.
Shadow correction, as far as I know, only affects jpegs (and the preview jpeg in the raw file). Highlight correction is as Adam explained, so it has an effect on the raw file (the ISO written will be higher than the ISO actually used)

I only enable highlight correction when in conditions where bright parts are very likely to be too bright (completely white with no detail). Shadow correction is pretty much always off, because I don't shoot jpeg. It is useful if you shoot jpeg, if you shoot around noon when the shadows are too harsh.

john wakefield · 09-05-2014, 02:09 PM

Originally posted by Na Horuk

Shadow correction and highlight correction are different.
Shadow correction, as far as I know, only affects jpegs (and the preview jpeg in the raw file). Highlight correction is as Adam explained, so it has an effect on the raw file (the ISO written will be higher than the ISO actually used)

I only enable highlight correction when in conditions where bright parts are very likely to be too bright (completely white with no detail). Shadow correction is pretty much always off, because I don't shoot jpeg. It is useful if you shoot jpeg, if you shoot around noon when the shadows are too harsh.

Shadow correction, from my experiments, affects RAW. So this seems to imply that either the sensor is used in a different way or the RAW file is not truly RAW.

asp1880 · 09-05-2014, 02:17 PM

Originally posted by john wakefield

Shadow correction, from my experiments, affects RAW. So this seems to imply that either the sensor is used in a different way or the RAW file is not truly RAW.

Well, it affects the raw file exif and embedded preview jpeg. Not the image data proper.

What observations lead you to conclude that shadow compensation affects the raw file proper data?
Be careful with your observations in lightroom etc. Cataloging software will often display the embedded (shadow corrected) jpeg from the raw file until you actually start working on a particular file.

The Pentax DCU program will even understand and respect the shadow correction tag in the raw file exif data and start up the laboratory module with shadow correction set appropriately.

Regards,
--Anders.

john wakefield · 09-06-2014, 02:36 AM

I set the camera to manual and then set the exposure in order to be sure that I was using the same exposure settings for all photos. I then told the cam to save as RAW. I took two photos, one with Shadow Correction off and another with it on full. To view RAW I used IrfanView (I've lost the original disks and IrfanView is a freeby which I think uses DcRaw as the processing engine). There was a big difference in the shadow detail. I decided to force the software to do some processing in order to hopefully force it to work with RAW data (just in case it was using the embedded JPG) so I told it to sharpen the images and then saved both as JPGs. There was still a large difference in the shadow detail. This seems to imply that shadow correction processes the RAW data; in other words it's not strictly RAW.
I've heard that highlight correction deliberately under exposes so I'm more interested in what shadow correction actually does.

asp1880 · 09-06-2014, 06:17 AM

Originally posted by john wakefield

... experiments with irfanview ...
There was still a large difference in the shadow detail. This seems to imply that shadow correction processes the RAW data; in other words it's not strictly RAW.

Interesting. It could still be either though.

If we can find just one raw development tool in the world that doesn't show the same shadow lift as irfanview, it'll prove that shadow lift is solely an exif thing.

Does anyone know? I'm not big on raw stuff myself, I only have Pentax DCU and faststone.

Regards,
--Anders.

08-28-2014, 07:00 AM	#1
john wakefield New Member Join Date: Aug 2014 Posts: 4	D-range shadow correction. What does it do? I can't understand what this actually does. I expected that when shooting in RAW it would make no difference whether it was on or off since I assumed that it applied some processing after the sensor was read and that the idea of RAW was to let the user apply all corrections. It does however make a difference. Therefore I'm not sure whether it changes the exposure or sensor characteristics before taking the picture or writes corrections to the RAW file. Is there any reason to ever turn it off since it appears to capture more information?

08-28-2014, 07:28 AM - 1 Like	#2
Adam Administrator Site Webmaster Join Date: Sep 2006 Location: Arizona Photos: Gallery \| Albums Posts: 51,595	Having the shadow correction setting enabled lowers the overall contrast (inherently), so I would only turn it on it when there are dark details in the image that would actually look better when brightened. I think all the setting does is boost the highlights a bit. This is unlike highlight correction, which lowers the ISO by one stop to underexpose the image (hence limiting the minimum ISO selectable to 1 stop more than base ISO) then amplifies the rest of the image. The same results can be achieved in RAW without shadow/highlight correction if you expose in the same manner. Adam PentaxForums.com Webmaster (Site Usage Guide \| Site Help \| My Photography) PentaxForums.com server and development costs are user-supported. You can help cover these costs by donating or purchasing one of our Pentax eBooks. Or, buy your photo gear from our affiliates, Adorama, B&H Photo, KEH, or Topaz Labs, and get FREE Marketplace access - click here to see how! Trusted Pentax retailers:

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08-29-2014, 02:15 PM	#3
Na Horuk Veteran Member Join Date: Feb 2012 Location: Slovenia, probably Photos: Gallery \| Albums Posts: 11,186	Shadow correction and highlight correction are different. Shadow correction, as far as I know, only affects jpegs (and the preview jpeg in the raw file). Highlight correction is as Adam explained, so it has an effect on the raw file (the ISO written will be higher than the ISO actually used) I only enable highlight correction when in conditions where bright parts are very likely to be too bright (completely white with no detail). Shadow correction is pretty much always off, because I don't shoot jpeg. It is useful if you shoot jpeg, if you shoot around noon when the shadows are too harsh.

09-05-2014, 02:09 PM	#4
john wakefield New Member Join Date: Aug 2014 Posts: 4 Original Poster	Originally posted by Na Horuk Shadow correction and highlight correction are different. Shadow correction, as far as I know, only affects jpegs (and the preview jpeg in the raw file). Highlight correction is as Adam explained, so it has an effect on the raw file (the ISO written will be higher than the ISO actually used) I only enable highlight correction when in conditions where bright parts are very likely to be too bright (completely white with no detail). Shadow correction is pretty much always off, because I don't shoot jpeg. It is useful if you shoot jpeg, if you shoot around noon when the shadows are too harsh. Shadow correction, from my experiments, affects RAW. So this seems to imply that either the sensor is used in a different way or the RAW file is not truly RAW.

09-05-2014, 02:17 PM	#5
asp1880 Veteran Member Join Date: Jul 2010 Location: Lyngby, Copenhagen Photos: Albums Posts: 742	Originally posted by john wakefield Shadow correction, from my experiments, affects RAW. So this seems to imply that either the sensor is used in a different way or the RAW file is not truly RAW. Well, it affects the raw file exif and embedded preview jpeg. Not the image data proper. What observations lead you to conclude that shadow compensation affects the raw file proper data? Be careful with your observations in lightroom etc. Cataloging software will often display the embedded (shadow corrected) jpeg from the raw file until you actually start working on a particular file. The Pentax DCU program will even understand and respect the shadow correction tag in the raw file exif data and start up the laboratory module with shadow correction set appropriately. Regards, --Anders.

09-06-2014, 02:36 AM	#6
john wakefield New Member Join Date: Aug 2014 Posts: 4 Original Poster	I set the camera to manual and then set the exposure in order to be sure that I was using the same exposure settings for all photos. I then told the cam to save as RAW. I took two photos, one with Shadow Correction off and another with it on full. To view RAW I used IrfanView (I've lost the original disks and IrfanView is a freeby which I think uses DcRaw as the processing engine). There was a big difference in the shadow detail. I decided to force the software to do some processing in order to hopefully force it to work with RAW data (just in case it was using the embedded JPG) so I told it to sharpen the images and then saved both as JPGs. There was still a large difference in the shadow detail. This seems to imply that shadow correction processes the RAW data; in other words it's not strictly RAW. I've heard that highlight correction deliberately under exposes so I'm more interested in what shadow correction actually does.

09-06-2014, 06:17 AM	#7
asp1880 Veteran Member Join Date: Jul 2010 Location: Lyngby, Copenhagen Photos: Albums Posts: 742	Originally posted by john wakefield ... experiments with irfanview ... There was still a large difference in the shadow detail. This seems to imply that shadow correction processes the RAW data; in other words it's not strictly RAW. Interesting. It could still be either though. If we can find just one raw development tool in the world that doesn't show the same shadow lift as irfanview, it'll prove that shadow lift is solely an exif thing. Does anyone know? I'm not big on raw stuff myself, I only have Pentax DCU and faststone. Regards, --Anders.