December 10, 2017, 07:43:03 PM

Author Topic: First impressions - A7R III preproduction unit  (Read 5767 times)

bwud

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Re: First impressions - A7R III preproduction unit
« Reply #15 on: November 04, 2017, 10:51:59 AM »
I was referring to sony’s claim of 15 stops, not Bill Claff’s measurements.

Surely they meant in DXO's terms, in which a few EXMOR sensors have been sitting around 14.5 in the past few years.

- A

If they did mean it that way, someone in marketing should be fired. Maybe the asterisk “Sony test conditions” is their attempt at absolving themselves of the CIPA requirement that Dynamic Range be determined and specified per ISO 15739, but it’s particularly weak. Maybe next they’ll start reporting ISO speeds with the electronics liquid cooled.

ISO requires that if test conditions aren’t to standard that they be listed along side the results, and further requires that lossy compression, which would include downsampling, be disabled if possible (which it is).

Full disclosure my copy of ISO 15739 is revision 2003. Maybe they’ve since added a provision for downsampling. However I can think of no instance in which electronics or electrical components of which DR is a significant parameter are permitted by standard to specify a downsamped value.

An enthusiast website like DXOmark which concerns itself with making comparisons on a normalized basis is a whole
different ballgame than a device manufacturer reporting a single spec.

I’m not convinced either way.
« Last Edit: November 04, 2017, 11:16:25 AM by bwud »

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Re: First impressions - A7R III preproduction unit
« Reply #15 on: November 04, 2017, 10:51:59 AM »

bwud

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Re: First impressions - A7R III preproduction unit
« Reply #16 on: November 04, 2017, 11:41:57 AM »
here:

http://www.photonstophotos.net/Charts/PDR.htm#Canon%20EOS%205D%20Mark%20IV,Sony%20ILCE-7RM2,Sony%20ILCE-7RM3

measured against A7RII and 5D IV. yes, in camera exposure blending ( Multi Pixel shift whatever mode) - will "extend" DR somewhat wide, of course. that is, likely,  where this 15 stop of DR claim is originated from


Either way, I would be very surprised if they would completely depart from the industry standards to which they're a member.

I was referring to sony’s claim of 15 stops, not Bill Claff’s measurements.

The problem in all this is not what it is measured, it is where you put the goal posts.

The 'industry standard' is a laughably unusable irrelevance that consigns much of that DR into noise levels that mean there is no usable image data, Bill Claff has chosen a SNR of 20%, which is a point at which he believes shadow detail is lost to noise (and I am not saying he is incorrect).

The root of the issue is we all have different ideas on what is usable, or correctable, noise levels in our images. Sometimes a SNR of 20 is perfectly OK, other times maybe not, but we have to set a baseline somewhere and to his credit he goes to lengths to explain and rationalize his methodology.

Interestingly, and I'd like to hear his reasoning, some here have argued that 14 stops in 14 bit files isn't necessarily a hard limit as a log curve could be applied to the linear sensor data in camera, his assumption is that 14 stops of DR is a limit in 14 bit files and his calculations are based on 14 stops minus the amount lost to the 20% SNR. That is beyond my expertise so an informed input on that specific would be welcome.

The goal posts should be put where the international standard specifies: SNR=1 under standard lighting and target with 18% reflectance reference, etc. 

Forget what the various websites do, I’m talking an advertised camera specification. The trade group of which Sony is a member has a meaningful standard. If they’re violating that standard they should be taken to task for it.

At the risk of posting intellectual property:
« Last Edit: November 04, 2017, 12:11:10 PM by bwud »

privatebydesign

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Re: First impressions - A7R III preproduction unit
« Reply #17 on: November 04, 2017, 12:11:41 PM »
here:

http://www.photonstophotos.net/Charts/PDR.htm#Canon%20EOS%205D%20Mark%20IV,Sony%20ILCE-7RM2,Sony%20ILCE-7RM3

measured against A7RII and 5D IV. yes, in camera exposure blending ( Multi Pixel shift whatever mode) - will "extend" DR somewhat wide, of course. that is, likely,  where this 15 stop of DR claim is originated from


Either way, I would be very surprised if they would completely depart from the industry standards to which they're a member.

I was referring to sony’s claim of 15 stops, not Bill Claff’s measurements.

The problem in all this is not what it is measured, it is where you put the goal posts.

The 'industry standard' is a laughably unusable irrelevance that consigns much of that DR into noise levels that mean there is no usable image data, Bill Claff has chosen a SNR of 20%, which is a point at which he believes shadow detail is lost to noise (and I am not saying he is incorrect).

The root of the issue is we all have different ideas on what is usable, or correctable, noise levels in our images. Sometimes a SNR of 20 is perfectly OK, other times maybe not, but we have to set a baseline somewhere and to his credit he goes to lengths to explain and rationalize his methodology.

Interestingly, and I'd like to hear his reasoning, some here have argued that 14 stops in 14 bit files isn't necessarily a hard limit as a log curve could be applied to the linear sensor data in camera, his assumption is that 14 stops of DR is a limit in 14 bit files and his calculations are based on 14 stops minus the amount lost to the 20% SNR. That is beyond my expertise so an informed input on that specific would be welcome.

The goal posts should be put where the international standard specifies: SNR=1 under standard lighting and target with 18% reflectance reference, etc.

Why? It's a meaningless number that tells you nothing about how much DR you can actually photograph in real life. Taking figures like 20% SNR get you closer to what you will actually be able to take pictures of, hence it's name, Photographic Dynamic Range, and Mr Claff gives in detail descriptions between the differences in Photographic Dynamic Range and the oft quoted and utterly irrelevant Engineering Dynamic Range.
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.

scottkinfw

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Re: First impressions - A7R III preproduction unit
« Reply #18 on: November 04, 2017, 12:25:09 PM »
@SecureGSM - We have good weed in BC.  It's like 4k HDR weed!  :)

@Jopa - I think it didn't matter to him what kind of stops they were, as long as it was more a bigger number than the Nikon D850 :P

Sony guy put a lot of emphasis on how the A7RIII was "Better than Nikon",  comparing some direct stats and also some stuff like Nikon cheats on many of its claims because they are only technically true under specific, conditions (something that Sony would never do, of course). 

Perhaps noteworthy, he barely mentioned Canon except to say that he used to shoot Canon but got tired of new cameras without great features.  If anything, the subtext was Sony A7RIII + Canon Lens = win, so please preorder an A7RIII!

In other threads people have mentioned that perhaps the true motivators for launching cameras with various feature sets is between Sony/Nikon for the #2 spot, rather than either making a run at the #1 spot. 


That 15 stops if DR claim was a one tough call.  Sony Marketing guys smoke too much wacky stuff as of late.

http://www.photonstophotos.net/Charts/PDR.htm#Canon%20EOS%205D%20Mark%20IV,Sony%20ILCE-7RM2,Sony%20ILCE-7RM3



3) Regarding 15 stops DR: Sony claims it's the same sensor but it has some new pipeline/architecture handling it.  We'll see how that pans out.


- A

I bet that's DxO stops not the real ones. And I'm pretty sure DxO can "fine tune" the DR so it will look like 15. Sony is a partner and a sensor supplier for their crappy camera.
[/quote

Thx for the review.  I remain at least curious about mirrorless, but so far, nothing resonates.
The lame excuse to switch cameras because Canon doesn't put "new" features in, is just that.  Unless you have money to burn, must have all the latest goodies, and are an expert photographer with facility with each feature AND your current camera limits your work, sit out the newest releases of cameras until something comes out that will add to your craft, not satisfy irrelevant  GAS (which I suffer from too).  If it ain't broke....

Scott

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Plus lots of stuff that just didn't work for me

bwud

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Re: First impressions - A7R III preproduction unit
« Reply #19 on: November 04, 2017, 12:25:31 PM »
Why? It's a meaningless number that tells you nothing about how much DR you can actually photograph in real life. Taking figures like 20% SNR get you closer to what you will actually be able to take pictures of, hence it's name, Photographic Dynamic Range, and Mr Claff gives in detail descriptions between the differences in Photographic Dynamic Range and the oft quoted and utterly irrelevant Engineering Dynamic Range.

There is a reasonable argument to change the standard. Standards are revised frequently (the noise measurements  standard which includes DR requirements was as recently as this year).

However if they sign up to it (and I take their membership in the trade group as evidence they do) they should follow it. “Say what you’ll do, do what you said.”

Regardless, my argument here isn’t in favor of the standard’s content, it’s with the notion they downsampled the data before computing, or computed and ratioed to approximate a downsampled value a’la DXOmark. If they did that, bad on them.


I think there is an over abundance of hype regarding DR. Most every modern camera capable of raw recording with a sizeable sensor has excellent range. But if they’re going to specify it, they should do so to the peer reviewed standard.
« Last Edit: November 04, 2017, 12:56:02 PM by bwud »

bclaff

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Re: First impressions - A7R III preproduction unit
« Reply #20 on: November 04, 2017, 10:16:14 PM »
...
... Bill Claff has chosen a SNR of 20%, ... Sometimes a SNR of 20 ... his assumption is that 14 stops of DR is a limit in 14 bit files and his calculations are based on 14 stops minus the amount lost to the 20% SNR....
It's an SNR of 20; not an SNR of 20%.
There is no assumption that 14-bit ADC limits dynamic range to 14.

bclaff

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Re: First impressions - A7R III preproduction unit
« Reply #21 on: November 04, 2017, 10:20:43 PM »
...
FWIW.
The Sony claim cites neither CIPA nor DxOMark; it has no concrete foundation.
It simply says "Sony test conditions for stills"; whatever that means.

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Re: First impressions - A7R III preproduction unit
« Reply #21 on: November 04, 2017, 10:20:43 PM »

Jopa

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Re: First impressions - A7R III preproduction unit
« Reply #22 on: November 04, 2017, 10:30:37 PM »
...
FWIW.
The Sony claim cites neither CIPA nor DxOMark; it has no concrete foundation.
It simply says "Sony test conditions for stills"; whatever that means.

That's funny. Next time they'll simply say "because we say so"  ;D

privatebydesign

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Re: First impressions - A7R III preproduction unit
« Reply #23 on: November 04, 2017, 10:43:39 PM »
There is no assumption that 14-bit ADC limits dynamic range to 14.

Then I don't understand why your explanation page runs to 14 and your figures are 14 minus the amount lost to < SNR 20.
"Here is a chart of the Photon Transfer Curve for the Nikon D300 in ADUs at all whole ISOs based on 14-bit ADUs: "

http://www.photonstophotos.net/GeneralTopics/Sensors_&_Raw/Sensor_Analysis_Primer/Engineering_and_Photographic_Dynamic_Range.htm

I understand 14 bit ADU's can represent any range of values with 16,384 steps, and that an ADC doesn't count 1:1 photons to these steps, what I don't understand is where the 14 stops of DR as a base comes from.

So, for example, a full well capacity for a pixel is 100,000 photons. The 14 bit ADC can change that 0-100,000 photons of electric charge into any one of 16,384 values, or ADU's, giving a 14 bit ADU. I understand that if it took 20 stops of DR to capture a full range of photons across the sensor then the 16,000 steps would represent 20 stops of DR, but that doesn't seem to be how it works and again I don't understand where your 14 stop start point comes from.

Would be grateful of an explanation from somebody who actually understands!  :)
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.

bwud

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Re: First impressions - A7R III preproduction unit
« Reply #24 on: November 04, 2017, 11:05:34 PM »
...
FWIW.
The Sony claim cites neither CIPA nor DxOMark; it has no concrete foundation.
It simply says "Sony test conditions for stills"; whatever that means.

I know, I’m basing my premise on their CIPA membership.

bclaff

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Re: First impressions - A7R III preproduction unit
« Reply #25 on: November 05, 2017, 10:16:26 AM »
There is no assumption that 14-bit ADC limits dynamic range to 14.

Then I don't understand why your explanation page runs to 14 and your figures are 14 minus the amount lost to < SNR 20.
"Here is a chart of the Photon Transfer Curve for the Nikon D300 in ADUs at all whole ISOs based on 14-bit ADUs: "

http://www.photonstophotos.net/GeneralTopics/Sensors_&_Raw/Sensor_Analysis_Primer/Engineering_and_Photographic_Dynamic_Range.htm

I understand 14 bit ADU's can represent any range of values with 16,384 steps, and that an ADC doesn't count 1:1 photons to these steps, what I don't understand is where the 14 stops of DR as a base comes from.

So, for example, a full well capacity for a pixel is 100,000 photons. The 14 bit ADC can change that 0-100,000 photons of electric charge into any one of 16,384 values, or ADU's, giving a 14 bit ADU. I understand that if it took 20 stops of DR to capture a full range of photons across the sensor then the 16,000 steps would represent 20 stops of DR, but that doesn't seem to be how it works and again I don't understand where your 14 stop start point comes from.

Would be grateful of an explanation from somebody who actually understands!  :)
This comes up enough that a separate article on PhotonsToPhotos is called for.

First note that the chart you make reference to has a logarithmic x-axis.
It's true it ends on the right at 14 but it also runs to minus infinity on the left even though that particular one ends at 0.

Remember, read noise is a standard deviation; so although each ADC reading is integral the standard deviation is not, and can be less than 1.
Because of quantization error in practice we can't measure below about 0.6 DN
( see http://www.photonstophotos.net/GeneralTopics/Sensors_&_Raw/Quantization_Error_in_Practice.htm )
0.6 is nearly 0.75 stops better than you might expect but to be conservative I typically say that an n-bit ADC can measure n+0.5 stops of dynamic range; 14.5 stops for a 14-bit.

I rarely test a sensor with 14-bit ADC with more than 14 stops of EDR; the Nikon D7200 is an example.
This happens more often with 12-bit ADCs; I assume these cameras don't use 14-bit due to cost considerations.
A 12-bit example is the Panasonic GX80.
Even the 10-bit ADC in the Samsung S6 phone isn't enough at ISO 50.
Attaching (note logarithmic y-axis, below 0 is below 1DN ):
http://www.photonstophotos.net/Charts/RN_ADU.htm#Nikon%20D7200_14,Panasonic%20Lumix%20DMC-GX80_12,Samsung%20Galaxy%20S6(S5K2P2)_10
« Last Edit: November 05, 2017, 10:19:00 AM by bclaff »

Mikehit

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Re: First impressions - A7R III preproduction unit
« Reply #26 on: November 05, 2017, 04:35:10 PM »
[
This comes up enough that a separate article on PhotonsToPhotos is called for.

First note that the chart you make reference to has a logarithmic x-axis.
It's true it ends on the right at 14 but it also runs to minus infinity on the left even though that particular one ends at 0.

Remember, read noise is a standard deviation; so although each ADC reading is integral the standard deviation is not, and can be less than 1.
Because of quantization error in practice we can't measure below about 0.6 DN
( see http://www.photonstophotos.net/GeneralTopics/Sensors_&_Raw/Quantization_Error_in_Practice.htm )
0.6 is nearly 0.75 stops better than you might expect but to be conservative I typically say that an n-bit ADC can measure n+0.5 stops of dynamic range; 14.5 stops for a 14-bit.

I rarely test a sensor with 14-bit ADC with more than 14 stops of EDR; the Nikon D7200 is an example.
This happens more often with 12-bit ADCs; I assume these cameras don't use 14-bit due to cost considerations.
A 12-bit example is the Panasonic GX80.
Even the 10-bit ADC in the Samsung S6 phone isn't enough at ISO 50.
Attaching (note logarithmic y-axis, below 0 is below 1DN ):
http://www.photonstophotos.net/Charts/RN_ADU.htm#Nikon%20D7200_14,Panasonic%20Lumix%20DMC-GX80_12,Samsung%20Galaxy%20S6(S5K2P2)_10

I don't know enough about the technical stuff going on here, but on first reading it is starting to sound like there is so much electronic jiggery-pokery along with each company's interpretation of the definitions that it is becoming hard to believe what any company is saying any more because there is no hard and fast definition of what constitutes acceptable noise, or dynamic range.
The MP wars have got to the point that 30MP vs 45 MP? Who really cares.   And dynamic range seems pretty much the same. Everyone is fighting over scraps at the table

privatebydesign

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Re: First impressions - A7R III preproduction unit
« Reply #27 on: November 05, 2017, 04:40:50 PM »
..... there is no hard and fast definition of what constitutes acceptable noise, or dynamic range.
The MP wars have got to the point that 30MP vs 45 MP? Who really cares.   And dynamic range seems pretty much the same. Everyone is fighting over scraps at the table

Yep, and I keep pointing that out, not that the forum DRones or measurbators care........

http://www.canonrumors.com/forum/index.php?topic=33696.msg694260#msg694260

http://www.canonrumors.com/forum/index.php?topic=33709.msg693866#msg693866
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.

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Re: First impressions - A7R III preproduction unit
« Reply #27 on: November 05, 2017, 04:40:50 PM »

bwud

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Re: First impressions - A7R III preproduction unit
« Reply #28 on: November 05, 2017, 05:25:54 PM »
... because there is no hard and fast definition of what constitutes acceptable noise, or dynamic range.

Oh yes there is. The trade group the major camera makers (including Canon, Fuji, Nikon, Sony, and Ricoh)  belong to has a (non-mandatory) guideline as to how camera specifications should be evaluated and expressed in order to "...inform consumers of product specifications fairly and accurately and to develop a sound market and digital camera business by encouraging fair competition..." That guideline includes dynamic range, in specific:
Quote
Shall comply with ISO 15739:2003 (an outline is shown below).
1. Definition
This means the ratio of the maximum level of luminance signals without saturation to the level of luminance signals where the S/N ratio to random noise is 1 (the minimum level of luminance signals)

Many people don't like that definition applied to camera products, and with good reason, but rather than petitioning ISO to change the standard, they come up the myriad hodgepodge of formulae we see in the marketplace (mostly in testing websites since few vendors publish DR).

However, there most certainly and definitively exists a hard and fast definition of what constitutes dynamic range: ISO 15739:2003 Photography -- Electronic still-picture imaging -- Noise measurements. Additionally, there is commercially available software to test per ISO, such as Imatest.

I pose a question to Bill Claff: if you defined dynamic range per the ISO standard, with the data you collected, what value would you compute?
« Last Edit: November 05, 2017, 05:36:07 PM by bwud »

privatebydesign

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Re: First impressions - A7R III preproduction unit
« Reply #29 on: November 05, 2017, 06:49:56 PM »
Many people don't like that definition applied to camera products, and with good reason, but rather than petitioning ISO to change the standard, they come up the myriad hodgepodge of formulae we see in the marketplace (mostly in testing websites since few vendors publish DR).

When Canon did that with their Cinema cameras they were absolutely hammered over it.

As for the Claff ISO standard, surely in his work that equates to the Engineering Dynamic Range.
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.

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Re: First impressions - A7R III preproduction unit
« Reply #29 on: November 05, 2017, 06:49:56 PM »