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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 :)

rodney charters mx and alexa

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This is all a tremendous tempest in a teapot. Who cares about this test? Who among us who actually has an MX Red, is going to run out and buy an Alexa? With this cost difference, even if the worst perception of this test were accurate (and it's clearly not) who is going change brands? Who cares? The current Red-MX set-up is so astonishingly good, compared to all the professional alternatives a very short time ago, that there is just no point in talking about it. If people want to shoot with the Alexa for whatever reason, God bless them. If clients want you to use an Alexa and they want to pay for it, God bless them too. Meanwhile, look what we have and we know we have it. This is all very tiresome.
 
HD-SDI output

HD-SDI output

Looks like at least 3 stops to me... ? :)
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Again an interesting comment.

As the LOOK AROUND is a 50% opacity black overlay, it suggests we are seeing about a 2:1 reduction in output video level in that area.

If the camera were sending a linear light output to the HD-SDI display, that would in turn suggest a 1 Stop difference in sensor output level.

... but as the camera output is Gamma coded (i.e. it is REDcolor) the implication is that it represents a larger number of Stops than that.

I think I'd be adjusting the camera's CURVE data ...
 
I certainly didn't know this, but Rodney states in another video that Alexa actually records in a semi-HDR mode by taking two frames for every single frame of recorded media. One reflects the settings you chose in the system, then one that automatically adjusts and captures into the highlights, then combining them before the final image is recorded- hence the added DR he is saying the Alexa has.

http://vimeo.com/10519628
 
Michael Totten said:
Pawel are you sure about this?

My technical knowledge doesn't go so deep as sensor design... but I'm pretty sure I have always read that there is a direct correlation between the size of the pixel/photosite, the amount of light the sensor is able to 'see' and then process cleanly (which relates back to dynamic range as well).

I guess the less noisy the shadows the more acceptable that particular part of the range / image; hence = more DR ?

Am I wrong in thinking this? If so, someone set me straight.
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There is nothing techincal about my remark. I pointed out a common misconception.

The light gathering capacity must be calculated by using amount of light per area, and not per pixel. Comparing a single small pixel to a large one is simply a logic problem because both sensors have the same (or similar) size.

Therefore their light gathering capcity is about the same, all other things being equal. In other words, there is absolutely no relationship between pixel size and DR of the entire sensor.

Another problem is with the caveat: not all pixels are equal, but that's a different story, not related to the size.
 
Pawel Achtel said:
There is nothing techincal about my remark. I pointed out a common misconception.

The light gathering capacity must be calculated by using amount of light per area, and not per pixel. Comparing a single small pixel to a large one is simply a logic problem because both sensors have the same (or similar) size.

Therefore their light gathering capcity is about the same, all other things being equal. In other words, there is absolutely no relationship between pixel size and DR of the entire sensor.

Another problem is with the caveat: not all pixels are equal, but that's a different story, not related to the size.
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Not quite:
Given the same sensor design the amount of noise per pixel would be the same regardless of the pixel size since the noise is generated by heat and other factors related to the circuitry on the sensor. Now since the bigger pixels gather more light(ie. signal) the s/n ratio is higher for larger (pixel).
Read "cleaner image"
The key here is "all things being equal" which is absolutely NOT the case here:
the sensors are different, the dsp is different, the firmware is different.
Simplifying the comparison to pixel size is being very naive to say the least...
 
PaulClements said:
But something really bugged me about the video when I watched it. Then I realised that it seems that every time the Red monitor path is shown the camera recording the monitor is tilted towards the light altering its auto exposure or the auto exposure is being adjusted...

Paul

EDIT: Perhaps it's not the angle of the phone camera, but it's exposure certainly seems to alter. The last two images might be slightly misleading perhaps because there does appear to be a fairly decent exposure just after. Though I can't be 100%.
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If what you are saying is that it is utterly ridiculous to draw conclusions based upon a net compressed video of an image that has passed through no less than three different imaging systems separate from the one actually being tested, then I agree 100%. I will give most people the benefit of the doubt and suggest that what folks are really responding to are Mr. Charters' opinions. That is where the weight is. The image is of no real value at all.

This evaluation should really only have value to Mr. Charters though, if it is truly a representation of how he and his crew will be working with the gear, how it will fulfill their particular needs, and just what he can expect to get from it, given their own methodology. The rest of us will need to gather our own data and get our own hands on in order to reach meaningful conclusions for ourselves. I believe that is what Mr. Mullen has expressed, and I certainly won't argue with that.
 
What's going on with RED's HDR? Any news about that?

We have to beat Alexa in DR tests !
 
clarification

clarification

Pawel Achtel said:
But, that's what I said...:biggrin5:
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to be perfectly clear:
For the same component design(DSP, S/W, sensor design)
Bigger pixel(sensor) WILL deliver cleaner picture because of natively higher signal to noise ratio. three smaller pixels will have three times as much noise (as one pixel three times the size)so the signal to noise ratio will be lower for smaller pixel.
I hope this should be clear now.
What should also be clear is that this rule does not apply here as we are dealing with two completely different sets of components.
apples and oranges:wink5:
 
Chris Parker said:
wow. lots of people willing to discredit lots of other people's opinions very quickly and skip straight to mud slinging and wild accusations. seems odd. but i guess that's life.
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It depends on whether you see this forum as a way to keep up with the tech at RED and how to apply that knowledge to making great images,
OR,
more like the digital age equivalent of hanging out at the pub with a bunch of camera geeks?

I see value in both aspects, but the way they mix in here can cause many a reasonable cameraman to bemoan the signal to noise ratio. Just sayin'

Cheers - #19
 
Scott: Charters is not saying "this is our methodology" he is saying that (compared to RED) "Alexa has "three stops more Dynamic range" it is worth the "extra 25K price" and in "the real world Alexa is King" and "People will be lining up to get Alexa" and so on and so forth. This does not sound like something Charters expects any of us to disagree with, no matter what our shooting method. This is no time to be coy. If the Alexa is in some way superior, it will have to be shown with a better testing method than Charters'.
 
I just hope that when Rodney Charter realizes he has made some gross errors in his test
that he..... 1) Post an error free test, and 2) apologizes here on RedUser.

His test is so off it's disturbing.
 
Blair S. Paulsen said:
It depends on whether you see this forum as a way to keep up with the tech at RED and how to apply that knowledge to making great images,
OR,
more like the digital age equivalent of hanging out at the pub with a bunch of camera geeks?

I see value in both aspects, but the way they mix in here can cause many a reasonable cameraman to bemoan the signal to noise ratio. Just sayin'

Cheers - #19
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Again. Blair brings in the sage wisdom.

David
 
If a DP or AC decides to whack a couple of RAW cameras on tripods, point them at one of the rental team and compare them back-to-back on a monitor, then that's their problem and, so long as they're happy with the results of such poorly thought out tests, then good luck to them. Everyone has an opinion. Everyone has a preference. We all, from time to time, make hurried, flawed evaluations of various products and if a professional DP is relying on an onset monitor to evaluate his pictures well then...

But when they post the 'results' of such a poorly considered, unscientific, from-the-hip test online, then that, IMHO, opens them up to all the criticism that comes their way. Don't want public criticism? Keep your views between you and your crew. Wanna publish your results? Do it properly.
 
Bill Anderson said:
Scott: Charters is not saying "this is our methodology" he is saying that (compared to RED) "Alexa has "three stops more Dynamic range" it is worth the "extra 25K price" and in "the real world Alexa is King" and "People will be lining up to get Alexa" and so on and so forth. This does not sound like something Charters expects any of us to disagree with, no matter what our shooting method. This is no time to be coy. If the Alexa is in some way superior, it will have to be shown with a better testing method than Charters'.
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You misunderstand me.

He isn't suggesting that we should take his methodology into account, I am. We need to consider the differences in the way we work. For example, he seems to suggest that he is making exposure descisions based upon what he sees in the monitor... Me not so much. I employ other tools. I need to take this into account.

Also, there seems to be a question as to whether or not his crew set up the monitor correctly. If that were the case, then perhaps his team is ill-equipped to get good results from the Red. Your crew may be more Red proficient than his and you must take that into account.

I'm not suggesting that his methods are poor, or that his crew is inept, so please don't jump to those conclusions. What I am saying is, that ultimately it is about what you and your team are comfortable shooting, and able to get the most from. Rodney Charters can't tell you that, and this little video doesn't begin to address your particular issues, or mine for that matter.

Edit: If I am being coy with regard to Mr. Charters it is out of respect for what he has been able to accomplish. I hold him in some regard, so my eyes will be open to this issue. (But then they already were.) I'm not a member of The Red Army, so I can afford to be coy.
 
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