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  • Hey all, just changed over the backend after 15 years I figured time to give it a bit of an update, its probably gonna be a bit weird for most of you and i am sure there is a few bugs to work out but it should kinda work the same as before... hopefully :)

Arri Alexa and Mysterium-X...

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Rodney and Alexa

He says Alexa takes 2 frames to combine them for HDR... thats cool. I wonder if the highlight frame has a faster shutter...

http://vimeo.com/10519628

Does he say Arri makes Optimo's?
 
jonnycom said:
Rodney and Alexa

He says Alexa takes 2 frames to combine them for HDR... thats cool. I wonder if the highlight frame has a faster shutter...

http://vimeo.com/10519628

Does he say Arri makes Optimo's?
Click to expand...

Not two frames but dual gain taps off the CMOS we call it Dual Gain Architecture-

The ALEV III sensor design provides 32 pairs of outputs. Each channel is divided into a high gain path (H) and a low gain path (L), resulting in 64 channels arriving at the 14 bit A/D converters. In the final images the lowlights are reconstructed from the high gain path and the highlights are reconstructed from the low gain path for an image containing meaningful information in all 16 bits.
 
Michael Bravin said:
Not two frames but dual gain taps off the CMOS we call it Dual Gain Architecture-

The ALEV III sensor design provides 32 pairs of outputs. Each channel is divided into a high gain path (H) and a low gain path (L), resulting in 64 channels arriving at the 14 bit A/D converters. In the final images the lowlights are reconstructed from the high gain path and the highlights are reconstructed from the low gain path for an image containing meaningful information in all 16 bits.
Click to expand...

Your statement leads me to believe that this dual gain tap is how the Alexa
derives it 13 stops of DR, and not how it achieves HDR. For me, 13 stops
of captured DR per frame is not HDR. So by this standard is there actually
going to be a HDR mode on the Alexa, as in 18 stops etc.?

Perhaps I have misunderstood you???
 
Martin Stevens said:
Your statement leads me to believe that this dual gain tap is how the Alexa
derives it 13 stops of DR, and not how it achieves HDR. For me, 13 stops
of captured DR per frame is not HDR. So by this standard is there actually
going to be a HDR mode on the Alexa, as in 18 stops etc.?

Perhaps I have misunderstood you???
Click to expand...

You would hope neither is true I would think.
 
Michael Bravin said:
Not two frames but dual gain taps off the CMOS we call it Dual Gain Architecture-

The ALEV III sensor design provides 32 pairs of outputs. Each channel is divided into a high gain path (H) and a low gain path (L), resulting in 64 channels arriving at the 14 bit A/D converters. In the final images the lowlights are reconstructed from the high gain path and the highlights are reconstructed from the low gain path for an image containing meaningful information in all 16 bits.
Click to expand...

This description of the latest sensor from Arri has been around for some time.

Is this what you was referred to as HDR on the Alexa? That phrase would seem to be new to the Alexa (and based on Rodney Charter's comment in a video?).

Is it the method used to arrive at the dynamic range the camera is currently touting (~13+ stops), or is it HDR in the accepted sense of generating images that have a greater range than what the camera can normally achieve in a single exposure?

-sc
 
David Mullen ASC said:
Where did Michael Bravin use the term "HDR" that he should now be accused of misusing it?
Click to expand...

David, I'm not sure Michael ever did. Rodney Charters described combining two frames, the second one "with highlights in mind", and outputing them. Here: http://reduser.net/forum/showthread.php?t=43257

He didn't use the term HDR, but some body in that thread did, and Michael hasn't corrected the notion.

I'm trying to figure out if Rodney was describing HDR (his phrasing implies some temporal difference between the frames), or if he was just attempting to describe what Michael has posted here (the dual gain channels), albeit not as accurately.

I tend to think it's the latter.

-sc
 
Yes, it would be nice if Michael Bravin could chime in here
and clarify the Alexa HDR issue.
 
Martin Stevens said:
Yes, it would be nice if Michael Bravin could chime in here
and clarify the Alexa HDR issue.
Click to expand...

He already has. He just gave you a very direct description of how the Alexa is maximizing its available dynamic range. I would suggest re-reading his last post, which is very clear, and not using someone else's slip of the tongue as some sort of accusation.
 
I have made no accusation. I was going by his direct response
to an HDR question from another post that he quoted. I was just
asking him to help me understand. There is no
subterfuge in my post.
 
I'm trying Jarred. :)
 
Rodney and Michael respond

Rodney and Michael respond

Rodney's here with Alexa and me and were sitting here reading this and laughing because we realize that a slight misunderstanding has blown up here. I posted the Dual Gain Architecure explanation. Rodney Twittered his understanding of how this worked. Now it should be pretty clear we achieve 13.5 stops of dynamic range using this technique. Arri never claimed HDR and Rodney was just explaning it as he understood it. Now it should be clear. Can we move on now? We need to get back to shooting with Alexa.
 
Michael Bravin said:
Rodney's here with Alexa and me and were sitting here reading this and laughing because we realize that a slight misunderstanding has blown up here. I posted the Dual Gain Architecure explanation. Rodney Twittered his understanding of how this worked. Now it should be pretty clear we achieve 13.5 stops of dynamic range using this technique. Arri never claimed HDR and Rodney was just explaning it as he understood it. Now it should be clear. Can we move on now? We need to get back to shooting with Alexa.
Click to expand...

You guys are going all out with the twitter/facebook presence and hyping up the Alexa outing. Interesting and good to see but it's starting to leave a bad taste in my mouth that's very un-Arri like. It's not the stately ARRI I've grown up to love and respect. Bill Benett's twitter page reads as if it's contrived. I'm not sure what to make of this. It is intentional? A response to Red?
 
Michael, now that you mentioned the way the dual channel system works (sorry if the name isn't correct), I don't understand one thing that I'd love to wrap my head around a bit more. It might not be super easy to break down for me, but I don't get the difference between gain and digital (i.e.:curves).

Is gain an analog version of adding an X number to each pixel? If so, don't both still originate from the same measurement? I mean, the measuring device is the only portion of a system that can have an impact on DR, as I understand it. All that matters is if you got a good measurement of it, or not, correct? If it wasn't too low to be drowned in noise, or too powerful to overload the photosite, correct?

If you would, how does increasing all values by a set measure, then merging both channels/frames help if you are already capturing RAW?
 
Michael Bravin said:
Rodney's here with Alexa and me and were sitting here reading this and laughing because we realize that a slight misunderstanding has blown up here. I posted the Dual Gain Architecure explanation. Rodney Twittered his understanding of how this worked. Now it should be pretty clear we achieve 13.5 stops of dynamic range using this technique. Arri never claimed HDR and Rodney was just explaning it as he understood it. Now it should be clear. Can we move on now? We need to get back to shooting with Alexa.
Click to expand...

Well, I'm glad you guys are gettinga kick out of it.

This corrects what Rodney said in the video, then, that Alexa does NOT have the capability of "taking a frame, then immediately taking another frame with highlights in mind, and combining the two..." (direct quote from his video http://vimeo.com/10519628), as he described?

If so, thanks for clearing up Rodney's misunderstanding.

-sc
 
Nothing Personal, Rodney Charters is Fantastic artist, but he is not very technical so I am not sure why Arri chose him for marketing as he has very little technical credibility which you can see now that he is spreading wrong info already and really does not understand the words he speaks. Again, nothing personal as Rodney is a great man, but I think Arri is doing more harm than good here.
 
Cüneyt Kaya said:
just to clarify, alexa has 13.5 stops with this technique, mx has 13.5 stops without, correct?
Click to expand...

Not to be overly whatever but I don't think technique is the best word; design might be better for what Arri have done.

I don't think this is some software trickery which could be added to a camera without it with a 'mere' firmware update, but a hardware choice based on the electrical architecture of the camera.

Then again, it is possible that something similar could be done in software; a high FPS design makes this much more attractive and less complex, one would imagine, to implement in software.
 
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