Epic HDR

[Emmanuel Decarpentrie]

 

Your explanation is flat-out impossible.

 

 

My post was directed to Georg, as you should have known by reading it, but do you even bother to read my words? I'll pass the ad hominem arguments you seem to be fond of: they are totally irrelevant.

 

What exactly makes my explanation "impossible", according to you? Do you have any argument other than your trivial "you're just plain wrong, no matter what you say". Perhaps you should read "what I'm saying" a little more carefully, although it certainly isn't written as gracefully as your own prose (I'm not a native english speaker)?

 

I agree that, in the "analog film world", it would have been impossible to make two samplings of the same exposure: the shutter must close between two consecutive "readings" (sort of speaking). But in the digital world (with CMOS technology), why would that be impossible? Unlike CCD sensors, a CMOS sensor allows us to "read" each pixel individually.

 

Let's assume we want to make 2 readings of a standard exposure (1/48th of a second). We want the first sampling (reading) to take place early so as to capture 8 times (3 stops) less charges than what is accumulated during the entire cycle.

 

What, according to you, is impossible in the following sequence:

 

1) RESET of a pixel at T0. Start accumulating charges.

2) First reading of this very same pixel at T1=1/(48*8)=1/384th of a second after T0.

3) Second reading of the pixel at T2=1/48th of a second after T0.

4) "Stop accumulating charges" by... a RESET.

5) Start cycle all over again (after the required time, depending on shutter "angle").

 

BTW, an "exposure", by definition, takes place between two consecutive resets.

 

 

Where it does matter is in the engineering. It's clearly easier to start an exposure and take two readings than to start, read, clear, start, wait the longer time, and read again.

 

You got it perfectly right indeed ;) This is rather comforting...

 

But I don't think that "to make two consecutive exposures" would make such a big difference in engineering complexity. It's only an extra "reset" signal to generate. No big deal. The real difference between the "two consecutive exposures" approach and Red's own HDR would be visible on fast moving objects, where you would get a trailing ghost image of the moving object. Even if it's just 1/8th of the exposure time, it is still enough to be quite visible on fast moving objects. That's all the difference an extra "reset" makes ;) So why would you even bother to make two consecutive exposures if it would only give inferior results?

[Keith Walters]

What, according to you, is impossible in the following sequence:

 

1) RESET of a pixel at T0. Start accumulating charges.

2) First reading of this very same pixel at T1=1/(48*8)=1/384th of a second after T0.

3) Second reading of the pixel at T2=1/48th of a second after T0.

4) "Stop accumulating charges" by... a RESET.

5) Start cycle all over again (after the required time, depending on shutter "angle").

 

What is impossible is defining the above as:

 

"they sample (read) the same exposure twice" (your words).

There is nothing wrong with your English, I just don't buy your explanation.

[John Sprung]

So why would you even bother to make two consecutive exposures if it would only give inferior results?

 

The one reason to use two exposures is Adam Wilt's idea: To do the long first, then the short, so as to have trailing rather than leading streaks on bright objects.

 

 

 

-- J.S.

[Tom Lowe]

Oh no. I might have known. Bloody "Film maker's gang" is back to his old tricks again.

There goes the neighbourhood.... :lol:

 

:lol: Is this what you've sunk to, Keith? Grammar policing? :P

 

I hate this system here at c.com where you have like 3 minutes to make corrections, or it gets locked! I'm much too sloppy of a writer.

[Adrian Sierkowski]

Become a Sustaining member ;) we can edit things for longer.

[Emmanuel Decarpentrie]

The one reason to use two exposures is Adam Wilt's idea: To do the long first, then the short, so as to have trailing rather than leading streaks on bright objects.

 

 

That is correct! However, I am convinced that moving objects would be separated by a "gap" (I can't find a better word to explain it) if one decided to use this "two consecutive exposures" approach. And to fill that "gap" would be very tricky, to say the least. Results would be inferior, I have no doubt about that.

 

I just don't buy your explanation.

 

Well, that is your right. I can't find a better explanation tough. Marketing considerations aside, we must differentiate RED's method to achieve HDR (which is quite unique in this industry) from regular exposure bracketing (i.e. multiple consecutive exposures) which would be very tricky to use on moving objects. The difference might be trivial to you (I agree: it's just a missing "RESET" signal), but it is far from insignificant in reality.

 

I just made this picture to simulate the "motion" difference between classic exposure bracketing (aka. "multiple exposures") and Red's "Magic Motion" as well as The Foundry's "MNMB" (More Normal Motion Blur).

 

You may claim there is absolutely no difference between those 3 methods, that it's all marketing bull****, but I beg to differ. To me, the differences are obvious.

Edited October 19, 2010 by Emmanuel Decarpentrie

[Emanuel A Guedes]

Oh no. I might have known. Bloody "Film maker's gang" is back to his old tricks again.

There goes the neighbourhood.... :lol:

 

His?! Keith, there's something wrong with your grammar again. ;)

[Keith Walters]

You may claim there is absolutely no difference between those 3 methods, that it's all marketing bull****, but I beg to differ. To me, the differences are obvious.

To you, they might be.

 

Not sure what your simulations are supposed to prove.

You could also "Simulate" HDR much more convincingly by shooting on film!

You're also completely missing the point.

I'm not interested in simulations, or hearing people's explanations of how they think things might work that they haven't actually seen yet.

I also don't want to see heavily staged "set pieces" where we have no idea of what the eactual lighting conditions were.

[Keith Walters]

His?! Keith, there's something wrong with your grammar again. ;)

There you go again, lapsing into plain English when you get excited :rolleyes:

[John Sprung]

However, I am convinced that moving objects would be separated by a "gap" (I can't find a better word to explain it) if one decided to use this "two consecutive exposures" approach. And to fill that "gap" would be very tricky, to say the least.

 

Here's where we need to find out a number. How long does it take to read and clear the chip? If our two exposures are, as before, 20 milliseconds and 2.5 milliseconds, and the gap is perhaps in the dozens of microseconds, it might not look bad at all. It could be too small to resolve in most cases. Even if it's in the low hundreds of microseconds, it might be worth a try.

 

 

 

 

-- J.S.

[Keith Walters]

:lol: Is this what you've sunk to, Keith? Grammar policing? :P

 

I hate this system here at c.com where you have like 3 minutes to make corrections, or it gets locked! I'm much too sloppy of a writer.

Well, how about you brown-bag it at work for a week, or pass on one weekly fix of Terrence Malick DVDs, (whoever he is) and buy yourself a lifetime membership. Even Jim Jannard doesn't have one of those :P

[Emanuel A Guedes]

There you go again, lapsing into plain English when you get excited :rolleyes:

 

C'mon Keith, I would never excite myself with a beard. For your information, once my best second half and I, we both share different native languages (I don't speak her native one, she does not speak mine), we give some use experience of deploying a common tongue instead, most international english. No trouble with the grammar we use. ;)

[Keith Walters]

C'mon Keith, I would never excite myself with a beard. For your information, once my best second half and I, we both share different native languages (I don't speak her native one, she does not speak mine), we give some use experience of deploying a common tongue instead, most international english. No trouble with the grammar we use. ;)

That's MUCH better.

[Tom Lowe]

Well, how about you brown-bag it at work for a week, or pass on one weekly fix of Terrence Malick DVDs, (whoever he is) and buy yourself a lifetime membership. Even Jim Jannard doesn't have one of those :P

 

Well I was trying to save my money to cover all my bets with you jokers. :lol:

[Keith Walters]

Well I was trying to save my money to cover all my bets with you jokers. :lol:

Entirely understandable :P

[Emmanuel Decarpentrie]

Here's where we need to find out a number. How long does it take to read and clear the chip? If our two exposures are, as before, 20 milliseconds and 2.5 milliseconds, and the gap is perhaps in the dozens of microseconds, it might not look bad at all. It could be too small to resolve in most cases. Even if it's in the low hundreds of microseconds, it might be worth a try.

 

We don't need to wait for the whole chip to be read or reset: due to the rolling shutter, all that matters is a single pixel (or, more precisely, a line of pixels). In theory, the "reset" of a pixel could take place right after it has been "read", which would indeed put the whole "gap" in the "dozens of microseconds", perhaps even less (I don't have the exact number). However, I still have the intuition that it would be a mistake to try to combine two pictures whose exposure didn't start at the very same time. I could be wrong though. It's definitely worth a try. I hope someone from Red or Arri will test this, at least to try to obtain an effect similar to a "second curtain flash" instead of the "first curtain flash" Magic Motion's effect.

Edited October 22, 2010 by Emmanuel Decarpentrie

[Emmanuel Decarpentrie]

(I don't have the exact number)

 

BTW, this number is pretty easy to evaluate, if we have the total time it takes for a sensor to "read-reset" itself. We just have to divide the full "Read-Reset" cycle time by the number of lines. Am I wrong?

 

Since Jim said the "Read-Reset"'s cycle time of EPIC's MX is around 5ms and it's number of lines is 2560 (in 2:1 mode), that would put the number we are looking for to a 2 micro-seconds figure! Still enough to get a little gap on moving objects, but would that gap ever be noticed or hard to fill? It's hard to say...

[Adrian Sierkowski]

That's if they're reading 1x line at a time, what if it's binned in 3 lines @ a time, or 4 lines @ a time etc . Just knowing it takes 5ms to read/reset the sensor doesn't help out unless we know it's read 1 line at a time, instead of multiple lines (which would be plenty possible and may be how they got the read/reset of the whole sensor down.)

[Stephen Williams]

Well I was trying to save my money to cover all my bets with you jokers. :lol:

 

Max & I our looking forward to receiving our payout.

[Emmanuel Decarpentrie]

That's if they're reading 1x line at a time, what if it's binned in 3 lines @ a time, or 4 lines @ a time etc . Just knowing it takes 5ms to read/reset the sensor doesn't help out unless we know it's read 1 line at a time, instead of multiple lines (which would be plenty possible and may be how they got the read/reset of the whole sensor down.)

 

Very good point indeed! I took a single line because, as far as I'm aware of, that's what (most) rolling shutter are working with. But it could very well be 4 or even 5 lines, although I have some doubts. It would be very easy to verify: a simple whip pan would give us enough deformation to check if we have some sort of "staircase" effect on the verticals. If so, we just have to count how many pixels per stair, and that's it. It would even be easier if we decreased the motion blur by increasing the shutter "speed".

 

The reason I doubt this is what they are doing to reduce the Read-Reset is that I guess I would have noticed this staircase effect: I'm very fond of whip pan effects, and I've shot more than 100 hours of footage (including many RS tests) on the Red-One ;)

[Tom Lowe]

Max & I our looking forward to receiving our payout.

 

Stephen, do you have the link handy for the bet? Are you sure you might not lose?

[Keith Walters]

Stephen, do you have the link handy for the bet? Are you sure you might not lose?

"Are you sure ... you might not lose?"

What the hell does that mean? :blink:

Why do I get the feeling extracting the winning bet from you is not going to be easy :rolleyes:

[Adrian Sierkowski]

True True Emmanuel; now all we need out is the epic ;)

[Tom Lowe]

"Are you sure ... you might not lose?"

What the hell does that mean? :blink:

Why do I get the feeling extracting the winning bet from you is not going to be easy :rolleyes:

 

Lol. I wonder if we measure which films in LA are shooting chemical film right now vs Red, Alexa, Genesis, etc, what the percentage would be? What about NYC?

 

I'll try to dig that thread up. I'll probably lose, but I'd like to take a crack at investigating what the numbers are. ;)