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Author Topic: A7RII initial thoughts and images  (Read 201381 times)

ErikKaffehr

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Re: A7RII initial thoughts and images
« Reply #140 on: August 08, 2015, 09:00:10 pm »

Edmund,

err, I have googled both many times, but that doesn't turn me into a colour scientist.

Best regards
Erik

err, have either of you thought a minute about why it is called the "green channel" or the "red channel"? I think you would do well to google "Cie observer functions" and "Luther Ives condition".

Edmund
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holyhikaru

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Re: A7RII initial thoughts and images
« Reply #141 on: August 08, 2015, 09:18:44 pm »

I've been using this camera for 3 days. Here are some RAW files that I took;

- Sony a7rii + Leica APO-Summicron-M 50mm (Voigtlander VM-E Close Focus Adapter)
https://www.dropbox.com/s/emmclez8mrs6uwh/DSC00016.ARW?dl=0
https://www.dropbox.com/s/1ptfrncddkpjuib/DSC00023.ARW?dl=0
https://www.dropbox.com/s/u6zodgu5yir9wlg/DSC00025.ARW?dl=0

- Sony a7rii + Zeiss Otus 85mm (Novoflex Adapter)
https://www.dropbox.com/s/vqhn0ldkevxuczy/DSC00053.ARW?dl=0
https://www.dropbox.com/s/mser630094hv9dj/DSC00072.ARW?dl=0

I also have Zeiss Otus 55mm and waiting for Leica WATE and Sony FE 90mm macro to arrive. will take more photos once I have more time to explore this camera.

Personal thought;
I think it is very great camera. I heard there is some overheat issue with long video recording but I don't mind as I bought this for photo taking and some short video record for my baby.
Form factor is comparable to my Leica M-P240. I can fit a7rii with Leica 50mm lens in my small shoulder bag and, to my eye, the image quality from Sony A7rii is better than the Leica especially in high ISO. A7rii with close focus adapter also solved minimal focus distance issue from Leica as I like to do food photography when I go to restaurant.
At this point, I am thinking of using a7rii as my main camera and Leica M-P240 as a backup.

« Last Edit: August 08, 2015, 09:23:06 pm by holyhikaru »
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Norm Nicholson

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Re: A7RII initial thoughts and images
« Reply #142 on: August 08, 2015, 10:51:39 pm »

Quentin,

I know that style. I've used it myself with the A7 and other cameras. But I didn't have to use it with the Merrill or Fujis. And I use it very sparingly with the G3, all in one.

Must not buy PRECIOUS.... Must not buy Precious.

Maybe I'll be successful this time.

Norm
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eronald

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Re: A7RII initial thoughts and images
« Reply #143 on: August 09, 2015, 12:12:19 am »

Edmund,

err, I have googled both many times, but that doesn't turn me into a colour scientist.

Best regards
Erik


Erik,

 Yeah, the standard colorimetric x, y and z are rgb  observer functions which are obtained by passing light through a (spectral) filter which basically corresponds (after various neural encoding issues) to the cone pigments in the average eye - 3 types of cones.

 So some illuminant spectrum bounces off some object, into your 'standard observer'  eye, gets filtered through say the "r" cone pigment, then the power of the remaining light gets integrated. Hey now you have 'x'.

 A camera needs to somehow recreate these integrals if it wants to recreate the observer perceptions. With 3 filters that means having filters which need to basically be independent linear combinations of the cone pigment spectra, I guess.  This is called the Luther-Ives condition.

A camera which does not satisfy Luther Ives will suffer from so-called metameric failure, ie. it will differentiate colors seen as identical by a human observer, or fail to differentiate colors perceived as different. Of course no camera satisifies the Luther Ives condition, but high-end colorimeters try to, and so do  the computations in spectroradiometers. I believe a standard research technique is to aim a teleradiometer at a scene and a camera and compare the two. Such experiments where discussed at ICC meetings when talking about formats for camera data.

 Anyway my comment to your comment :) is that in my opinion with a 3 filter CFA array the ideal "slopes" of all the CFA spectral functions satisfying Luther-Ives here are in some way known - there is little tolerance for variation because they are determined by the cone functions which are physiological - if the standard observer were to donate his body to science, we could cut his eye open, extract some cones and measure the pigment transmisittivity.

 What happens a lot with real cameras  -I believe-  is that the  x'y'z' in the camera are not "orthogonal" enough, and then the determination of the xyz becomes imprecise. I don't really understand this part, but I see it happen a lot, and I've talked to people like the ex-CEO of Hasselblad who told me this is the problem they faced *in practice*. Or rather, he told me this is the problem his competitors with dLSRs faced in practice :) My feeling is that the A7IIR is facing this type of issue. Or quite possibly I'm wrong.


Edmund

« Last Edit: August 09, 2015, 12:24:44 am by eronald »
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Quentin

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Re: A7RII initial thoughts and images
« Reply #144 on: August 09, 2015, 04:49:31 am »

Edmund,

You seem to follow a different path, one more critical of the A7RII.  That's actually very useful; it helps the rest of us keep our feet on the ground, otherwise its easy to get carried away with new stuff. Different opinions are always valuable- so long as I can understand them!

I'm used to trying to extract the best from oddball cameras like the Sigma DP merrill series ( as Norm and others here have done, I think).  I get the feeling I will still still be using them at times in the future, because the rendition of the A7R II is fundamentally different- smoother, low contrast v the Merrril's high contrast, etc.  It's a more complex decision as to whether the A7R II is a possible replacement for MF digital, which I also use (CCD based).  That will take a lot more time and effort to work through.

Ray, I will try to find time to post a few 100% crops sometime later this weekend.

« Last Edit: August 09, 2015, 04:57:29 am by Quentin »
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Quentin

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Re: A7RII initial thoughts and images
« Reply #145 on: August 09, 2015, 06:30:10 am »

A7RII. 90mm F/2.8 Macro G OSS



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ErikKaffehr

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Re: A7RII initial thoughts and images
« Reply #146 on: August 09, 2015, 11:13:52 am »

Hi Edmund,

What you write corresponds pretty well to my understanding of Luther Ives and metameristic matches. Still I have observed that spectral plots representing the "R" pixels have a very steep sensivity gradients at around 560 nanometers, so I would assume that the steepness of the gradient and the exact position of the gradient may matter a lot. But, I cannot convert this into goodness of "linear combination".

Best regards
Erik



Erik,

 Yeah, the standard colorimetric x, y and z are rgb  observer functions which are obtained by passing light through a (spectral) filter which basically corresponds (after various neural encoding issues) to the cone pigments in the average eye - 3 types of cones.

 So some illuminant spectrum bounces off some object, into your 'standard observer'  eye, gets filtered through say the "r" cone pigment, then the power of the remaining light gets integrated. Hey now you have 'x'.

 A camera needs to somehow recreate these integrals if it wants to recreate the observer perceptions. With 3 filters that means having filters which need to basically be independent linear combinations of the cone pigment spectra, I guess.  This is called the Luther-Ives condition.

A camera which does not satisfy Luther Ives will suffer from so-called metameric failure, ie. it will differentiate colors seen as identical by a human observer, or fail to differentiate colors perceived as different. Of course no camera satisifies the Luther Ives condition, but high-end colorimeters try to, and so do  the computations in spectroradiometers. I believe a standard research technique is to aim a teleradiometer at a scene and a camera and compare the two. Such experiments where discussed at ICC meetings when talking about formats for camera data.

 Anyway my comment to your comment :) is that in my opinion with a 3 filter CFA array the ideal "slopes" of all the CFA spectral functions satisfying Luther-Ives here are in some way known - there is little tolerance for variation because they are determined by the cone functions which are physiological - if the standard observer were to donate his body to science, we could cut his eye open, extract some cones and measure the pigment transmisittivity.

 What happens a lot with real cameras  -I believe-  is that the  x'y'z' in the camera are not "orthogonal" enough, and then the determination of the xyz becomes imprecise. I don't really understand this part, but I see it happen a lot, and I've talked to people like the ex-CEO of Hasselblad who told me this is the problem they faced *in practice*. Or rather, he told me this is the problem his competitors with dLSRs faced in practice :) My feeling is that the A7IIR is facing this type of issue. Or quite possibly I'm wrong.


Edmund


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Erik Kaffehr
 

ErikKaffehr

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Re: A7RII initial thoughts and images
« Reply #147 on: August 09, 2015, 11:26:17 am »

Hi Quentin,

Nice observation, you don't happen to be a legal expert?

It is easy to get overly optimistic about a new system. There may be some limitation in the system we miss. The A7rII is young, colour profiles and stuff is first generation. We may see modfications/change or shift with time.

I also feel that we claim different things. Lloyd Chambers blames "Sony 11+7 bit raw compression" for pretty much everything, BC blames CMOS for everything. Anders Torger says it is mostly about profiles and I talk about gradients of the "red" channel at around 560 nm. We all have some favourite pony. I would side with Anders a bit, as he has done a lot of work in colour rendition recently.

Best regards
Erik

Edmund,

You seem to follow a different path, one more critical of the A7RII.  That's actually very useful; it helps the rest of us keep our feet on the ground, otherwise its easy to get carried away with new stuff. Different opinions are always valuable- so long as I can understand them!

I'm used to trying to extract the best from oddball cameras like the Sigma DP merrill series ( as Norm and others here have done, I think).  I get the feeling I will still still be using them at times in the future, because the rendition of the A7R II is fundamentally different- smoother, low contrast v the Merrril's high contrast, etc.  It's a more complex decision as to whether the A7R II is a possible replacement for MF digital, which I also use (CCD based).  That will take a lot more time and effort to work through.

Ray, I will try to find time to post a few 100% crops sometime later this weekend.


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Bart_van_der_Wolf

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Re: A7RII initial thoughts and images
« Reply #148 on: August 09, 2015, 12:33:26 pm »

I also feel that we claim different things. Lloyd Chambers blames "Sony 11+7 bit raw compression" for pretty much everything, BC blames CMOS for everything. Anders Torger says it is mostly about profiles and I talk about gradients of the "red" channel at around 560 nm. We all have some favourite pony. I would side with Anders a bit, as he has done a lot of work in colour rendition recently.

Erik, it's almost always about the profiles. The Raw compresssion, if done intelligently, should not make a big difference. CMOS versus CCD is virtually never the issue (except for required LCCs to correct off-center image-circle colors). The color filter array makes (small) differences (but more important are the peak transmissions), but then the profiles change everything again. Profiles rule everything, and they remain to be compromises (given the mismatch with the eye sensitivity curves).

The steepness of the transition zones between CFA color filters (and the resulting overlap of the pass-bands) only affects the magnitude of the multipliers needed in the transformation matrix, and thus has some effect on noise, which mostly affects color demosaicing in very subtle transitions and low signal levels.

IMHO, of course.

Cheers,
Bart
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rdonson

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Re: A7RII initial thoughts and images
« Reply #149 on: August 09, 2015, 12:38:15 pm »

Excellent observations, Erik.  

For me I'm going to withhold judgement a few months on the a7r II.  I'd like the shine to wear off and for a LOT more real world and lab observations.  I do think that Sony has pushed the technology a bunch but how that works in the real world is the question.  Also, it will be interesting to see if Sony responds to bugs and shortcomings like the lossy compression with firmware updates.    

The only thing I know for certain at this point is that I'm tired of hauling my heavy Canon gear around.  I find myself shooting with my Fuji X-T1 a lot more and loving it.
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Ron

adias

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Re: A7RII initial thoughts and images
« Reply #150 on: August 09, 2015, 01:33:14 pm »

Reading user observations it appears that the real issues are:

1 - Non-trivial RAW compression artifacts - http://www.dpreview.com/forums/thread/3885375?page=1

2 - Sensor heat both in filming and long time exposures. Using long time exposure NR changes to 12-bit encoding - http://www.dpreview.com/forums/thread/3885355
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eronald

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Re: A7RII initial thoughts and images
« Reply #151 on: August 09, 2015, 03:32:04 pm »

Hi Quentin,

Nice observation, you don't happen to be a legal expert?

It is easy to get overly optimistic about a new system. There may be some limitation in the system we miss. The A7rII is young, colour profiles and stuff is first generation. We may see modfications/change or shift with time.

I also feel that we claim different things. Lloyd Chambers blames "Sony 11+7 bit raw compression" for pretty much everything, BC blames CMOS for everything. Anders Torger says it is mostly about profiles and I talk about gradients of the "red" channel at around 560 nm. We all have some favourite pony. I would side with Anders a bit, as he has done a lot of work in colour rendition recently.

Best regards
Erik


I claim it's always the photographer's fault :)

Let's all chant louder "MUST NOT BUY PRECIOUS" and see how well that works :)

Edmund
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the_marshall_101

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Re: A7RII initial thoughts and images
« Reply #152 on: August 09, 2015, 04:42:25 pm »

Quentin,

Really nice work, love these shots.  Is the image review speed any better then the general Sony standard (i.e. slow!)?

Nathan
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Quentin

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Re: A7RII initial thoughts and images
« Reply #153 on: August 09, 2015, 05:57:06 pm »

Nathan,

Thanks!

I find it pretty quick.

Edd, my middle son, puffs on a stogie after dinner on our terrace.  A7RII, 90mm macro G OSS, ISO 6400 F/2.8, 1/50 sec. Edit - link fixed.

« Last Edit: August 10, 2015, 03:55:00 am by Quentin »
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eronald

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Re: A7RII initial thoughts and images
« Reply #154 on: August 09, 2015, 07:02:09 pm »

Nathan,

Thanks!

I find it pretty quick.

Edd, my middle son, puffs on a stogie after dinner on our terrace.  A7RII, 90mm macro G OSS, ISO 6400 F/2.8, 1/50 sec.



 Fix the link?
 Must not buy precious. Must not buy. Must not. Must ...

Edmund
« Last Edit: August 10, 2015, 11:26:40 am by eronald »
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jduncan

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Re: A7RII initial thoughts and images
« Reply #155 on: August 10, 2015, 10:33:46 am »

Hi,

Tony and Chelsea, tested the camera:

https://www.youtube.com/watch?v=C1kI4NacaUw

More positive news
Best regards,
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Chris Livsey

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Re: A7RII initial thoughts and images
« Reply #156 on: August 10, 2015, 11:15:02 am »

More positive news
Best regards,

The comments would seem to be more mixed than that.

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eronald

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Re: A7RII initial thoughts and images
« Reply #157 on: August 10, 2015, 03:38:10 pm »

The comments would seem to be more mixed than that.



 It's a camera, not the solution to all of the world's problems.

 The video is *really* not so good as the GH4 at base ISO, see their imagery.

 My impression is "jack of all trades". AKA the universal backup. Canon AF lenses seem to work iff they are after 2006.

Edmund
« Last Edit: August 10, 2015, 04:50:46 pm by eronald »
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BernardLanguillier

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Re: A7RII initial thoughts and images
« Reply #158 on: August 10, 2015, 05:49:46 pm »

Has anyone here been able to perform long exposures?

Reports about excessive noise are starting to pop up.

Cheers,
Bernard

eronald

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Re: A7RII initial thoughts and images
« Reply #159 on: August 10, 2015, 06:32:00 pm »

Has anyone here been able to perform long exposures?

Reports about excessive noise are starting to pop up.

Cheers,
Bernard


Look on fm. It seems Nikon have historically done better than Sony with NR on Sony's sensors.

Edmund
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