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Author Topic: A7RII initial thoughts and images  (Read 196027 times)

eronald

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Re: A7RII initial thoughts and images
« Reply #120 on: August 06, 2015, 04:23:49 pm »

Interesting posts Edmund, though  I am not sure I understand what you mean by 'green discrimination' and I don't have anything to compare your negatives to.  Can you explain a bit more, a bit more quantitatively?  Do you mean that the color filters are less selective than in other sensors in order to gain a little extra sensitivity?  If so that should be easy enough to quantify for people like Jim Kasson.

Jack

Jack,

I think the simple quantitative stuff which interests you is all here.

http://www.dxomark.com/About/In-depth-measurements/Measurements/Color-sensitivity

As for "easy to quantify", things are not so simple. Color like sound is a percept. So one's quantification always relies on judgements. This is why there are "color consultants", who look at stuff and bridge the quantitative and the aesthetic. In fact there is a "color community" and people hold meetings and commission studies to figure out what metrics to use, and how to measure them, and what sort of values are acceptable. Then the various firms like DxO, Imatest and Image Engineering implement those metrics, as they are written into some standard.

For instance, a year or so ago I happened to be at a phone-camera quality meeting in Paris, physically hosted with great generosity by DxO, and at one people were discussing image noise. Somebody had commissioned a first study, and it seemed to demonstrate that consumers who now view everything on a screen prefer images with chroma noise to luma noise.

This seemed counterintuitive to just about every person in the room,  because as you know we photographers hate chroma noise, and so a second study had been undertaken, and it had confirmed those results.

And so in the future, cellphone camera designs (and probably consumer and then pro cameras) will be optimised to prioritise filtering luma noise when possible, over chroma noise which consumers appear to tolerate better, although old-gen experts hate it.

I'm not a particular expert on anything, but as you know I used to be an ICC member and so I know the process. Andrew Rodney, a color consultant who used to be a regular on these forums was also an ICC member, way back. A lot of the color geeks in companies and and the color consultants and image consultants sort of know each other, have corresponded with each other etc.

Digital color is very much a collaborative process as images are captured under some commercial illuminant manufactured to standards issued by the CIE, move to a raw file, are converted to a colorimetric space defined by the ICC, get displayed on a monitor that needs to be calibrated and also placed in acceptable working viewing conditions in which a retoucher can work  and then printed using profile formats and conversions described by the ICC. We move all the way from real-life spectral color in an on-site perceptual context, all the way to viewing a flat reflective print. Across these steps, there is a basically a collective assessment of color in which the whole community continually participates, as measurement methods, color conversion algorithms and assessment criteria get accepted across the industry and rolled out so that each device can talk to the next, and the consumer sees an image that reminds her of the dress she wore on her sister's wedding day.

Edmund

PS. I still stand by my personal and subjective opinion that the A7RII is not very good at discriminating greens  ;D
« Last Edit: August 06, 2015, 05:04:13 pm by eronald »
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Jack Hogan

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Re: A7RII initial thoughts and images
« Reply #121 on: August 07, 2015, 03:26:16 am »

Ok, thanks Edmund.  Hopefully Jim will do some testing to corroborate your feeling.

Jack
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Chris Livsey

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Re: A7RII initial thoughts and images
« Reply #122 on: August 07, 2015, 03:38:12 am »

http://www.bbc.co.uk/programmes/b01mxxz6

Fake or Fortune?

A BBC series on now I think its second run currently is worth looking at (if you are allowed access). Some of the science on authentication is shown, IR shot on a Canon 35mm last week, but the real work is in the provenance trail.
One of the first in this series was on L S Lowry. He famously used a very restricted range of pigments, all well known. A disputed work was shown to have a different white, immediate red flag. A still frame from a contemporary BBC documentary showed a box of paint labelled with the suspect pigment in his home studio, strangely gripping if you have any interest in this area.

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shadowblade

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Re: A7RII initial thoughts and images
« Reply #123 on: August 07, 2015, 04:13:43 am »

How does the AF with third-party lenses compare with the AF using those same lenses on a Canon body? Faster than the 6D? Anywhere near as fast as the 5D3? Better than the 5D2 at least? What about in continuous focus/tracking mode?
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pegelli

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Re: A7RII initial thoughts and images
« Reply #124 on: August 07, 2015, 04:43:06 am »

How does the AF with third-party lenses compare with the AF using those same lenses on a Canon body? Faster than the 6D? Anywhere near as fast as the 5D3? Better than the 5D2 at least? What about in continuous focus/tracking mode?
http://www.getdpi.com/forum/sony/55651-a7rii-canon-af-database-reference.html]
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rdonson

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Ron

NancyP

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Re: A7RII initial thoughts and images
« Reply #126 on: August 07, 2015, 11:06:24 am »

I am a pathologist, spend my days at the microscope and the tissue dissection bench and doing real-time operating room pathology consults. There's lots of pattern recognition, mental 3D reconstruction from 2D tissue slices on glass slides, some need for decent color discrimination, so it's a very visual job, in addition to the medical and scientific thinking involved. Surgeon removes a piece of tissue - is the mass cancer? is it benign inflammation? if cancer, what type? relationship of cancer to resection margin (did surgeon cut all of the tumor out)? Basically, it's geeky scientific work where I get to use visual skills. Also, in the past, I had an active basic science research program going, had to abandon it when clinical duties got very heavy (basically, everyone in department left but me).
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NancyP

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Re: A7RII initial thoughts and images
« Reply #127 on: August 07, 2015, 11:09:32 am »

eronald, do you know Larry Warter, recently retired from Fuji NA, their in-house color geek and now a consultant, was involved in ICC. He's my cousin's husband.
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eronald

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Re: A7RII initial thoughts and images
« Reply #128 on: August 07, 2015, 06:30:04 pm »

eronald, do you know Larry Warter, recently retired from Fuji NA, their in-house color geek and now a consultant, was involved in ICC. He's my cousin's husband.

No, I used to know a guy from Fuji Japan who I met several times at ICC and ISO meetings, but I cannot remember his name, even at the time he was already semi-retired.

Edmund
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ErikKaffehr

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Re: A7RII initial thoughts and images
« Reply #129 on: August 07, 2015, 06:51:17 pm »

Hi,

My personal and subjective opinion is that discrimination of greens is dependent of the steepness of the red channel and the overlap between green and red channel, combined with the colour profile. I would also suggest that colour profiles are a very major component of colour reproduction.

It has been suggested that CFA design may have been compromised to yield higher quantum efficiency and thus allowing higher ISO ratings. That may be the case.

Another factor that should not be ignored is the IR filter on the sensor. Chlorophyll for instance has a high IR-content and with a weak IR filter it may affect the red channel.

As I have not yet received my A7rII I cannot say anything about it's colour reproduction.

Best regards
Erik


PS. I still stand by my personal and subjective opinion that the A7RII is not very good at discriminating greens  ;D

« Last Edit: August 07, 2015, 06:53:54 pm by ErikKaffehr »
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Jack Hogan

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Re: A7RII initial thoughts and images
« Reply #130 on: August 08, 2015, 05:47:50 am »

My personal and subjective opinion is that discrimination of greens is dependent of the steepness of the red channel and the overlap between green and red channel, combined with the colour profile. I would also suggest that colour profiles are a very major component of colour reproduction.

Makes sense, Erik.
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Kevin Raber

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Re: A7RII initial thoughts and images
« Reply #131 on: August 08, 2015, 09:44:44 am »

Michael and I are in the Palouse.  Both of have been shooting with the a7r II for days.  It's been  long time since I have been so impressed by a camera.  We'll do a report and review on this camera as soon as possible.  I shot image last night at sunset with the Tamron 150-600mm at 600mm and it focuses great and fast.  I have with us a full compliment of lenses including Batis lenses and we will do some comparison tests and we'll try to offer some sort of downloadable files (JPEGs at 100%) so you can look at things yourself.  Bottom line impressive, responsive and some super captures so far.

Kevin Raber
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Dshelly

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Re: A7RII initial thoughts and images
« Reply #132 on: August 08, 2015, 11:32:39 am »

Very much look forward to a review. I hope you're able to test Canon lenses with this camera body.
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eronald

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Re: A7RII initial thoughts and images
« Reply #133 on: August 08, 2015, 03:01:59 pm »

Makes sense, 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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Quentin

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Re: A7RII initial thoughts and images
« Reply #134 on: August 08, 2015, 04:19:22 pm »

A few mono conversion from near Tower Bridge, London today, all taken with the excellent 16-35mm F/4





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Re: A7RII initial thoughts and images
« Reply #135 on: August 08, 2015, 04:30:07 pm »

ISO 5000, at Butler's Wharf, London.

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Jack Hogan

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Re: A7RII initial thoughts and images
« Reply #136 on: August 08, 2015, 05:09:42 pm »

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".

Just curious to see whether Sony has changed its CFA recipes,  Edmund. Shouldn't be too difficult to figure out for someone with both A7rx's.

Jack
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Ray

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Re: A7RII initial thoughts and images
« Reply #137 on: August 08, 2015, 08:24:46 pm »

Quentin,
Your images are very nice and very professional-looking. It's such a pity you don't do 100% crops so that pixel-peepers can appreciate the wonderful resolution of the A7RII with 16-35mm lens.  ;)
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uaiomex

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Re: A7RII initial thoughts and images
« Reply #138 on: August 08, 2015, 08:31:39 pm »

+1


Quentin,
Your images are very nice and very professional-looking. It's such a pity you don't do 100% crops so that pixel-peepers can appreciate the wonderful resolution of the A7RII with 16-35mm lens.  ;)
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eronald

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Re: A7RII initial thoughts and images
« Reply #139 on: August 08, 2015, 08:51:00 pm »

ISO 5000, at Butler's Wharf, London.



I think you are developing an interesting style with this camera.
I fear I don't think much of the equipment itself, but you are doing well with it - good buy!

Edmund
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