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Author Topic: Sony Kicks Butt  (Read 297349 times)

MatthewCromer

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Re: Sony Kicks Butt
« Reply #40 on: June 13, 2015, 04:36:05 PM »

Thanks for that information, but I'm not sure it follows that autofocus with Canon lenses will either work perfectly or not at all, when using a Metabones adapter.

Having checked the Metabones website at http://www.metabones.com/products/details/mb-ef-e-bm3  I'm a bit alarmed to discover a long list of possible limitations when using a Canon lens with a Sony camera, as itemised below. Would all, or at least some of these limitations not apply to the A7R II?

Autofocus

"Autofocus is supported, with the following known limitations.
Autofocus speed is very slow and inadequate for most moving subjects.

That's for previous Sony bodies.

Apparently things are very different with the A7R2.
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Ray

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Re: Sony Kicks Butt
« Reply #41 on: June 13, 2015, 07:26:44 PM »

These problems have noting to do with fine tuning.  

They have to do with a lack of some sort of fine tuning. I've already accepted that the type of AF Micro-adjustment often required with DSLRs with a mirror, do not apply to the A7R2. My concern is not primarily with AF fine tuning. That was just an off-the cuff example of a possible limitation. My concern is with the full functionality of any Canon lenses that I were to use with an A7R2.

I already have sufficient Canon and Nikon lenses for my purposes. I don't want to feel pressured into buying additional lenses as a result of my Canon lenses not autofocussing adequately with the A7R2, or not  performing in other respects, as expected or hoped for.
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telyt

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Re: Sony Kicks Butt
« Reply #42 on: June 13, 2015, 07:29:48 PM »

They have to do with a lack of some sort of fine tuning. I've already accepted that the type of AF Micro-adjustment often required with DSLRs with a mirror, do not apply to the A7R2. My concern is not primarily with AF fine tuning. That was just an off-the cuff example of a possible limitation. My concern is with the full functionality of any Canon lenses that I were to use with an A7R2.

I already have sufficient Canon and Nikon lenses for my purposes. I don't want to feel pressured into buying additional lenses as a result of my Canon lenses not autofocussing adequately with the A7R2, or not  performing in other respects, as expected or hoped for.


So what you're concerned about is basic function of AF with adapted lenses.
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Ray

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Re: Sony Kicks Butt
« Reply #43 on: June 13, 2015, 07:30:08 PM »

These are almost surely mechanical/electronic issues with the lenses and/or adaptor. Best taken up with Metabones IMO.

-Dave-

Indeed! There are many comments on internet forums by people who have returned their adapters to Metabones and/or who have expressed puzzlement why some of their Canon lenses work reasonably well,  but other lenses don't. There seems to be a lot of 'hit and miss' issues.

Some folks have even found it necessary to use an allen key to unscrew the mounting plate and fiddle with the springs because their adapter has too tight a fit to the camera body. I just don't want to unwittingly get involved in such problems.
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Ray

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Re: Sony Kicks Butt
« Reply #44 on: June 13, 2015, 07:38:52 PM »

So what you're concerned about is basic function of AF with adapted lenses.

Not quite. I want to know whether I can expect full functionality, when using Canon lenses. There are so many caveats on the Metabones website.

For example, I might be initially excited about the 4k video capability of the A7R2, then become disappointed if my Canon lenses, or certain Canon lenses, do not allow use of all the video features that the A7R2 boasts.
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Ray

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Re: Sony Kicks Butt
« Reply #45 on: June 13, 2015, 07:41:29 PM »

The RAWs aren't 11 bits. Dynamic range in the deep shadows is not affected.

That's good to know. I don't own any Sony cameras so I'm not familiar with many details. I got the 11 bit RAW concept from comments on Dpreview.
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Ray

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Re: Sony Kicks Butt
« Reply #46 on: June 13, 2015, 07:44:33 PM »

That's for previous Sony bodies.

Apparently things are very different with the A7R2.

Let's hope so. However Metabones own website doesn't make any such claims. I've seen one anecdotal comment at Dpreview of an example of a Canon lens used with the A7R2, which seemed to have an AF performance as good as the same lens used on a Canon body. But one can't draw conclusions from such isolated, non-scientific examples.

As I've mentioned, there seems to be a lot of 'hit and miss' issues when using an adapter. The Metabones website lists some the issues to be aware of. In particular, Canon lenses that predate 2006 might not work as expected. (My Canon 100-400 was bought in 2003).
Lenses that have some slight technical malfunction, perhaps due to a knock, which is not serious enough to noticeably affect performance on a Canon body, might  noticeably affect performance when attached to a Metabones adapter, and so on.
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dreed

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Re: Sony Kicks Butt
« Reply #47 on: June 14, 2015, 12:22:23 AM »

That's for previous Sony bodies.

Apparently things are very different with the A7R2.

Yes, the way I read it is that Sony have designed the A7R2 autofocus in a way that it works well with metabones adapting to Canon lenses. Maybe that is taking it a bit too far but if it knocks down the price barrier to entry for your brand .... It would make a lot of commercial sense for Sony to have improved AF performance with metabones because it instantly expands their target market for the camera body.

If the A7R2 AF works at least as well as the 5D2 AF then I can easily see those that have not upgraded their 5D2 saying "Yes, finally I have a camera that I want to upgrade to!"
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LKaven

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Re: Sony Kicks Butt
« Reply #48 on: June 14, 2015, 03:04:44 AM »

The A7rII has "399 focal plane phase detection AF points" (cf, Sony Press Release).  I don't know why they don't say that it has "on sensor" PDAF, but I presume this is what they mean.

AreBee

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Re: Sony Kicks Butt
« Reply #49 on: June 14, 2015, 04:10:21 AM »

Luke,

Quote
The A7rII has "399 focal plane phase detection AF points" (cf, Sony Press Release).  I don't know why they don't say that it has "on sensor" PDAF...

Marketing.
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BartvanderWolf

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Re: Sony Kicks Butt
« Reply #50 on: June 14, 2015, 08:30:02 AM »

Marketing.

Hi Rob,

It's probably similar to what several other manufacturers use, but with maybe more of them. Maybe they use a different system?
Are you suggesting that they aren't Phase detect sensors?  Any evidence for that?

Cheers,
Bart
« Last Edit: June 14, 2015, 08:47:05 AM by BartvanderWolf »
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== If you do what you did, you'll get what you got. ==

Bernard ODonovan

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Re: Sony Kicks Butt
« Reply #51 on: June 14, 2015, 11:30:37 AM »

That's good to know. I don't own any Sony cameras so I'm not familiar with many details. I got the 11 bit RAW concept from comments on Dpreview.

Ray this may interest you:


"Lucy Stooles reply to Dave Etchells • 4 days ago

The ARW 2.3 format lossily encodes an 11-bit subset of a 14-bit range of ADU values, at best. This is further reduced in some shooting modes, including bracketing. Does the A7rII use the same lousy "raw" format as the previous A7 bodies? *That* is the question whose answer distinguishes an expensive consumer product from a tool for real critical work.


   
    Dave Etchells reply to Mod Lucy Stooles • 3 days ago

    Same lossy compression scheme, but see notes elsewhere here. I underscored the seriousness of the issue with Sony, and they clearly understand the magnitude of the issue. They didn't promise any ETA, but I do think we'll see firmware updates at some point that will address this.

    The person I was talking with was Mr. Kimio Maki, the gentleman who's led Sony's entire mirrorless development strategy, since the original NEX-5. I think he's gotten the message, and is in a position to do something about it :-)"

   

From here:

http://www.imaging-resource.com/news/2015/06/10/sony-rx10-ii-rx100-iv-and-a7r-ii-announced-were-blogging-live-from-the-pres

You will also find a petition here with 1,447 supporters to date:

https://www.change.org/p/kazuo-hirai-enable-uncompressed-or-lossless-compression-raw-files-on-the-a7-cameras-and-future-f-e-mount-cameras

 ;)
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AreBee

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Re: Sony Kicks Butt
« Reply #52 on: June 14, 2015, 12:56:50 PM »

Hey Bart,

Quote
Are you suggesting that they aren't Phase detect sensors?

Not at all. Sorry for the confusion.

I cynically assumed that a marketing person at Sony figured that "399..." would sound more impressive to potential buyers than suitable alternative descriptions, such as Luke's.
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Telecaster

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Re: Sony Kicks Butt
« Reply #53 on: June 14, 2015, 05:09:04 PM »

Apparently things are very different with the A7R2.

I'd recommend a wait & see approach concerning the A7r2's AF performance with adapted SLR lenses. When the Oly E-M1 was announced, with on-sensor PD-AF for better compatibility with Oly's 4/3 SLR lenses, there were many early enthusiastic reports regarding AF performance with these lenses. In reality the PD-AF, while greatly improved over that of CD-AF only Oly m43 cameras, is neither as fast nor as accurate as the camera's CD-AF with native m43 lenses. The lenses themselves are the bottleneck. With the A7r2 the scenario is made even more complex via a required 3rd party adaptor that needs to "speak" both FE and EF.

-Dave-
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LKaven

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Re: Sony Kicks Butt
« Reply #54 on: June 14, 2015, 05:49:41 PM »

The RAWs aren't 11 bits. Dynamic range in the deep shadows is not affected.

I'm thinking this needs more clarification.  I'd love it if someone has a technical reference to how these raw values are derived.  It seems to me at least at first that the demands of fast readout, both in terms of pixel clock speed and overall communications bandwidth, could compromise dynamic range on both ends.

Ray

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Re: Sony Kicks Butt
« Reply #55 on: June 15, 2015, 05:24:07 AM »

Ray this may interest you:


"Lucy Stooles reply to Dave Etchells • 4 days ago

The ARW 2.3 format lossily encodes an 11-bit subset of a 14-bit range of ADU values, at best. This is further reduced in some shooting modes, including bracketing. Does the A7rII use the same lousy "raw" format as the previous A7 bodies? *That* is the question whose answer distinguishes an expensive consumer product from a tool for real critical work.


   
    Dave Etchells reply to Mod Lucy Stooles • 3 days ago

    Same lossy compression scheme, but see notes elsewhere here. I underscored the seriousness of the issue with Sony, and they clearly understand the magnitude of the issue. They didn't promise any ETA, but I do think we'll see firmware updates at some point that will address this.

    The person I was talking with was Mr. Kimio Maki, the gentleman who's led Sony's entire mirrorless development strategy, since the original NEX-5. I think he's gotten the message, and is in a position to do something about it :-)"

   

From here:

http://www.imaging-resource.com/news/2015/06/10/sony-rx10-ii-rx100-iv-and-a7r-ii-announced-were-blogging-live-from-the-pres

You will also find a petition here with 1,447 supporters to date:

https://www.change.org/p/kazuo-hirai-enable-uncompressed-or-lossless-compression-raw-files-on-the-a7-cameras-and-future-f-e-mount-cameras

 ;)

Thanks for helping to clarify that issue, Bernard. It seems that the RAW files are in fact 14 bit, but the in-camera processing pipeline uses a lossy 11 bit encoding algorithm.

The following blog from Diglloyd provides some details and examples of artefacts.
http://diglloyd.com/blog/2014/20140212_2-SonyA7-RawDigger-posterization.html

Considering that the main advantages of a BSI sensor are its greater light-gathering capacity resulting in greater dynamic range, as well as less interference and crosstalk from light bouncing around the electronics and wiring which are normally in front of the photodiodes, it seems very odd that Sony would not offer at least an option for an uncompressed 14 bit output to maximise the potential benefits of the BSI sensor, even though choosing such an option would no doubt slow down frame rates and result in larger files.

I can only presume that Sony's marketing department have advised that 90% of their customers wouldn't notice any improvement using uncompressed or lossless 14 bit RAW files. Also, I get the impression that most people using cameras with RAW capability don't even shoot in RAW mode in any case.

Perhaps of more concern is the possibility that the BSI sensor has its own technical disadvantages which are more significant than the disadvantages of 11 bit in-camera processing, and that an uncompressed 14 bit option would tend to reveal such flaws in the new technology. Just speculating here.  ;)
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hjulenissen

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Re: Sony Kicks Butt
« Reply #56 on: June 15, 2015, 07:00:19 AM »

"...the disadvantages of 11 bit in-camera processing..."
I suggest that calling this 11-bit in-camera processing is as misleading as calling my inkjet printer 1-bit.

While it may have some correctness to it, it only serves to confuse the reader.

I think that "lossy 14-bit raw" is a better term. It seems to be a format that (at best) have the precision of 14 bits raw, at worst, something worse than 14 bits raw.

-h
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LKaven

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Re: Sony Kicks Butt
« Reply #57 on: June 15, 2015, 09:34:07 AM »

I suggest that calling this 11-bit in-camera processing is as misleading as calling my inkjet printer 1-bit.

While it may have some correctness to it, it only serves to confuse the reader.

I think that "lossy 14-bit raw" is a better term. It seems to be a format that (at best) have the precision of 14 bits raw, at worst, something worse than 14 bits raw.

In another sense, both are wrong.  The truth seems to lie somewhere in between the two, in a more complicated story.  There is a critical dependency on the local distribution of values.

Quote
This from Alex Tutabalin, via Lloyd Chambers:

1) In each 32 pixel block we have 16 pixels of single color.

2) For the 16 pixels of each color:
- two 11-bit values ('base pixels') are stored exactly. The minimum and maximum values in block
- two 4-bit coordinates of min/max pixels in block are stored too.
- and 14 7-bit deltas for remaining 14 pixels.

= 11 + 4 + 11 + 4 + 14 * 7 = 128 bits for 16 pixels = 8 bits per byte

3) 'delta' pixel value is calculated from delta, minimum and maximum:

step = (maximum - minimum)_rounded_to_the_nearest_largest_power_of_two / 128. This 'step' is the same for all 'delta' pixels in block
(smallest integer power of two (1,2,4....) such that step*128 > max-min)

pixel value = minimum + delta_recorded_for_this_pixel * step.

So, if data range within 16 pixels is too wide, then “step size” of each transition increases, so posterization occurs.

Ray

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Re: Sony Kicks Butt
« Reply #58 on: June 15, 2015, 09:35:30 AM »

I suggest that calling this 11-bit in-camera processing is as misleading as calling my inkjet printer 1-bit.

While it may have some correctness to it, it only serves to confuse the reader.

I think that "lossy 14-bit raw" is a better term. It seems to be a format that (at best) have the precision of 14 bits raw, at worst, something worse than 14 bits raw.

-h

Doing a bit more research on the subject, I came across the following explanation by someone with the name of Akuba on the Fredmiranda site at  http://www.fredmiranda.com/forum/topic/1247655/147

Hope it's okay to reproduce his comment here.

"There is nothing unclear about the bit depth of the Sony RAWs. The encoding algorithm used for the Sony a7/a7R RAWs takes the original 14 bit values and maps them to 11 bit space (a bit more on this below) and then the 11 bit values are further compressed into 8 bits per pixel by delta-encoding them in fixed-length 16 pixel blocks as follows: 11-bit minimum value for the block, 11-bit maximum value for the block, 4-bit index of the minimum value in the block, 4-bit index of the maximum value, 14 7-bit deltas from the minimum value for the other 14 pixels. This uses 11+11+4+4+(14x7) = 128 bits per 16 pixels or 8 bits per pixel.

This encoding algorithm is why the a7R always produces files that are just over 36 million bytes (7360 x 4912 single color pixels multiplied by 8 bits per pixel divided by 8 bits per byte plus a small variable overhead for metadata). A good aspect of this algorithm is that it is computationally cheap as it does not need to do any data analysis and simply encodes with one pass over the data. A bad aspect is that it is not adaptive and as a result uses a fixed amount of storage which wastes space for images that don't need it and doesn't give additional space to files that would benefit from it.

Note that this encoding is doubly lossy: There is guaranteed data loss on the first step (the mapping from 14 bits to 11) and potential data loss on the second step (the delta-encoding in 16 bit blocks). The reason the second step may not lose data is that if the difference between min and max is less than 128 (the maximum value that can be expressed in 7 bits) then this step ends up being lossless. Since smooth gradients are most likely to have small deltas in values and since one is most likely to notice dataloss in smooth gradients, the second step is statistically more likely to be lossless when it counts most. It is this delta-encoding step that almost certainly explains the artifacts that some people have noticed on high-contrast transitions but these seem to me to be negligible in the grand scheme of things. The first step is for me much more concerning as it is lossy with regard to the total tonal range expressible in the RAW. Without new firmware, the a7/a7R will not produce a RAW file with more than 2048 values per channel.

Circling back to the "doing justice" comment, the 14 to 11 bit mapping is not quite as bad as it sounds as it is not a simple bit shift. A 3 bit shift would have the effect of binning every set of 8 consecutive 14-bit values into the same single value in 11-bit space. The Sony RAWs are instead mapped on a curve and devote more of the 11 bit space to the portions of the exposure range that should benefit from more tonality. I believe this is why Sony considers it "visually lossless". This mapping approach means that for example the mid tones might consider every set of 2 consecutive values the same instead of every 8. However since there are still only 2048 possible values the piper then gets paid in the shadows where 16 values might get lumped together in the down conversion. At the end of the day no matter how well they slice the 11 bits it still does limit the total tonality of the image and it means the files can't take as much processing as losslessly stored 14 bit files from the same sensor could."
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LKaven

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Re: Sony Kicks Butt
« Reply #59 on: June 15, 2015, 09:59:40 AM »

So, I'm reading this to say that the application of the inverse tone curve during raw generation pushes 14 bit sensor values down to 11 bit stored raw values, which are then inflated back to 14 bit values during capture by applying the tone curve.

It looks like the tone curve is not a continuous function, but a set of discrete multipliers.  It favors highlight compression.

I'm wondering, could this be done on the sensor?  It would certainly make moving frames off the sensor faster, and it can be done in a single pass on the fly.  That would certainly make it harder to change.

[Sometimes I think Sony loves compression.  Remember the minidisc?  They must have a compression laboratory.]

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