May 26, 2018, 01:53:30 PM

Author Topic: Want to Increase The Dynamic Range of Your EOS 5D Mark IV Raw Files?  (Read 13115 times)

Sporgon

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Re: Want to Increase The Dynamic Range of Your EOS 5D Mark IV Raw Files?
« Reply #45 on: February 14, 2018, 08:38:52 AM »
So the (sub)photosites have some headroom in well capacity, being able to represent higher values before saturating than the ADC and post-ADC digital electronics. Basically the sensor has a ”native” ISO lower than 100.

No, they have half the well capacity, it is a maths issue.

If a 14 bit ADC had a range from 0-10, 10 being clipped, then if each half is below 5 the highlight will have detail in the main frame. If both sub pixels register 8 then in the main frame the value would be >10 so blown, but the value from the sub frame is 8, so it retains highlight detail.

The point is the main frame has the FWC of two sub pixels added together to make the output value limited at 14 bits, this means if the value of the sub frames pixel is less than 1/2 the 14 bit ceiling you will get additional highlight detail out of the sub frame. As we all know 1/2 or x2 is equal to 1 stop, so in theory there is a possible 1 stop improvement in highlight detail using this technique.

So could canon have given the sensor an extra stop of DR by using a 16 bit ADC?  Edit: removed a dumb question

Yes. 14 bit files are holding Canon sensor capabilities back nowadays, more bit depth would realize more DR even with todays dual pixel sensors.

But would 16 bit really make any practical difference ?

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Re: Want to Increase The Dynamic Range of Your EOS 5D Mark IV Raw Files?
« Reply #45 on: February 14, 2018, 08:38:52 AM »

privatebydesign

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Re: Want to Increase The Dynamic Range of Your EOS 5D Mark IV Raw Files?
« Reply #46 on: February 14, 2018, 08:58:33 AM »
So the (sub)photosites have some headroom in well capacity, being able to represent higher values before saturating than the ADC and post-ADC digital electronics. Basically the sensor has a ”native” ISO lower than 100.

No, they have half the well capacity, it is a maths issue.

If a 14 bit ADC had a range from 0-10, 10 being clipped, then if each half is below 5 the highlight will have detail in the main frame. If both sub pixels register 8 then in the main frame the value would be >10 so blown, but the value from the sub frame is 8, so it retains highlight detail.

The point is the main frame has the FWC of two sub pixels added together to make the output value limited at 14 bits, this means if the value of the sub frames pixel is less than 1/2 the 14 bit ceiling you will get additional highlight detail out of the sub frame. As we all know 1/2 or x2 is equal to 1 stop, so in theory there is a possible 1 stop improvement in highlight detail using this technique.

So could canon have given the sensor an extra stop of DR by using a 16 bit ADC?  Edit: removed a dumb question

Yes. 14 bit files are holding Canon sensor capabilities back nowadays, more bit depth would realize more DR even with todays dual pixel sensors.

But would 16 bit really make any practical difference ?

If you look at the difference between some of the example images where there are clipped highlights, yes. Those of us that know how to wring out the very best from Canon sensors know we have to ETTR, having another stop of headroom is exactly how we can utilize that extra DR on a practical level on scenes that do have that DR range.

Do we need that extra stop most of the time? No we absolutely don't as many scenes simply don't have the DR to use it, but that doesn't mean we couldn't use it on the scenes that could need it.

My cameras, although being dual pixel, don't have the option of saving the dual format, but if I did I would shoot it in situations where the scene could use it.
Too often we lose sight of the fact that photography is about capturing light, if we have the ability to take control of that light then we grow exponentially as photographers. More often than not the image is not about lens speed, sensor size, DR, MP's or AF, it is about the light.

Sporgon

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Re: Want to Increase The Dynamic Range of Your EOS 5D Mark IV Raw Files?
« Reply #47 on: February 14, 2018, 09:09:54 AM »
So the (sub)photosites have some headroom in well capacity, being able to represent higher values before saturating than the ADC and post-ADC digital electronics. Basically the sensor has a ”native” ISO lower than 100.

No, they have half the well capacity, it is a maths issue.

If a 14 bit ADC had a range from 0-10, 10 being clipped, then if each half is below 5 the highlight will have detail in the main frame. If both sub pixels register 8 then in the main frame the value would be >10 so blown, but the value from the sub frame is 8, so it retains highlight detail.

The point is the main frame has the FWC of two sub pixels added together to make the output value limited at 14 bits, this means if the value of the sub frames pixel is less than 1/2 the 14 bit ceiling you will get additional highlight detail out of the sub frame. As we all know 1/2 or x2 is equal to 1 stop, so in theory there is a possible 1 stop improvement in highlight detail using this technique.

So could canon have given the sensor an extra stop of DR by using a 16 bit ADC?  Edit: removed a dumb question

Yes. 14 bit files are holding Canon sensor capabilities back nowadays, more bit depth would realize more DR even with todays dual pixel sensors.

But would 16 bit really make any practical difference ?

If you look at the difference between some of the example images where there are clipped highlights, yes. Those of us that know how to wring out the very best from Canon sensors know we have to ETTR, having another stop of headroom is exactly how we can utilize that extra DR on a practical level on scenes that do have that DR range.

Do we need that extra stop most of the time? No we absolutely don't as many scenes simply don't have the DR to use it, but that doesn't mean we couldn't use it on the scenes that could need it.

My cameras, although being dual pixel, don't have the option of saving the dual format, but if I did I would shoot it in situations where the scene could use it.

I wasn't referring to the practical use of the theoretical one stop extra, but rather given current tech will 16 bit really realise that extra full stop ? Going from 14 bit to 16 bit is such a tiny fraction of an increase.

snoke

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Re: Want to Increase The Dynamic Range of Your EOS 5D Mark IV Raw Files?
« Reply #48 on: February 14, 2018, 09:16:05 AM »
I wasn't referring to the practical use of the theoretical one stop extra, but rather given current tech will 16 bit really realise that extra full stop ? Going from 14 bit to 16 bit is such a tiny fraction of an increase.

16/14 = 1.14 - 14% increase
14% tiny?

This not real problem.
Real problem is more stops always highlight.
More stops never more shadow or dark.

Sporgon

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Re: Want to Increase The Dynamic Range of Your EOS 5D Mark IV Raw Files?
« Reply #49 on: February 14, 2018, 09:27:25 AM »
I wasn't referring to the practical use of the theoretical one stop extra, but rather given current tech will 16 bit really realise that extra full stop ? Going from 14 bit to 16 bit is such a tiny fraction of an increase.

16/14 = 1.14 - 14% increase
14% tiny?

If you research bit depth you'll see why the move from 14 to 16 is very slight, just as 12 to 14 was. 8 to 12 was significant.

BeenThere

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Re: Want to Increase The Dynamic Range of Your EOS 5D Mark IV Raw Files?
« Reply #50 on: February 14, 2018, 10:24:59 AM »
I wasn't referring to the practical use of the theoretical one stop extra, but rather given current tech will 16 bit really realise that extra full stop ? Going from 14 bit to 16 bit is such a tiny fraction of an increase.

16/14 = 1.14 - 14% increase
14% tiny?

This not real problem.
Real problem is more stops always highlight.
More stops never more shadow or dark.
I probably would not do it, but if you can add a stop of exposure to what you would normally use, then you have boosted the shadows by a stop.

IglooEater

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Re: Want to Increase The Dynamic Range of Your EOS 5D Mark IV Raw Files?
« Reply #51 on: February 14, 2018, 11:17:58 AM »
I wasn't referring to the practical use of the theoretical one stop extra, but rather given current tech will 16 bit really realise that extra full stop ? Going from 14 bit to 16 bit is such a tiny fraction of an increase.

16/14 = 1.14 - 14% increase
14% tiny?

This not real problem.
Real problem is more stops always highlight.
More stops never more shadow or dark.
I probably would not do it, but if you can add a stop of exposure to what you would normally use, then you have boosted the shadows by a stop.

Well, not exactly.  Practically yes, in that you can expose brighter and then pull from deeper in the shadows than before.  Technically, your shadows stay the same relative to the brightness of the scene. It would be closer to having an iso 64 with better dr than iso 100. So you do have to expose brighter to get that extra shadow detail.

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Re: Want to Increase The Dynamic Range of Your EOS 5D Mark IV Raw Files?
« Reply #51 on: February 14, 2018, 11:17:58 AM »

IglooEater

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Re: Want to Increase The Dynamic Range of Your EOS 5D Mark IV Raw Files?
« Reply #52 on: February 14, 2018, 11:18:45 AM »

So could canon have given the sensor an extra stop of DR by using a 16 bit ADC?  Edit: removed a dumb question

Yes. 14 bit files are holding Canon sensor capabilities back nowadays, more bit depth would realize more DR even with todays dual pixel sensors.

Thanks :)

While I’m asking, could Canon have resolved our parallax issue by writing both subframes instead of one subframe and the combine frames?  I understand DPRAW was not built with that in mind, I’m just curious.  Might one convert to 16 bit depth and average the two subframes?

sebasan

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Re: Want to Increase The Dynamic Range of Your EOS 5D Mark IV Raw Files?
« Reply #53 on: February 16, 2018, 11:47:23 AM »
Maybe is a silly question, but, for the use of this feature, you have to take an exposure which blows the highlights of the picture by one stop, am I right?
Thanks.

IglooEater

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Re: Want to Increase The Dynamic Range of Your EOS 5D Mark IV Raw Files?
« Reply #54 on: February 16, 2018, 11:52:46 AM »
Maybe is a silly question, but, for the use of this feature, you have to take an exposure which blows the highlights of the picture by one stop, am I right?
Thanks.
  Yes. The goal here is achieving an extra stop of DR.  That is achieved even without blowing the highlight.  To actually use that extra DR one needs to blow the highlights 99% of a stop.   It’s just the same as ETTR’ing, but actually going almost a stop too far deliberately.

sebasan

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Re: Want to Increase The Dynamic Range of Your EOS 5D Mark IV Raw Files?
« Reply #55 on: February 16, 2018, 12:02:05 PM »
Maybe is a silly question, but, for the use of this feature, you have to take an exposure which blows the highlights of the picture by one stop, am I right?
Thanks.
  Yes. The goal here is achieving an extra stop of DR.  That is achieved even without blowing the highlight.  To actually use that extra DR one needs to blow the highlights 99% of a stop.   It’s just the same as ETTR’ing, but actually going almost a stop too far deliberately.

Thanks for the answer.

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Re: Want to Increase The Dynamic Range of Your EOS 5D Mark IV Raw Files?
« Reply #55 on: February 16, 2018, 12:02:05 PM »