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How the Alexa really works


Tom Yanowitz

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See Stuart, you talk about being calm under pressure and then you make comments like "That's when you get fired."

 

He's an inexperienced kid. Doesn't mean you need to flip out on him like a drill instructor. I don't have a lot of respect for that leadership "style" intimidation and beration. And you're not even paying the guy, yet.

No idea where you got the idea that Stuart meant to 'intimidate' Tom with this line. He's simply pointing out that making those kinds of comments at video village as a below the line technician can and most likely will get you fired. He then went out of his way to explain why. It's practical advice.

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I take it you subscribe to that style of "leadership" too Satsuki. Not surprised.



Yes it can, and no he is not working for either one of you.

I certainly would not tolerate anyone in my lighting or camera department being treated that way, and I have the lawsuits to prove it, not just words on the internet.

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See Stuart, you talk about being calm under pressure and then you make comments like "That's when you get fired."

 

 

 

He's an inexperienced kid. Doesn't mean you need to flip out on him like a drill instructor. I don't have a lot of respect for that leadership "style" intimidation and beration. And you're not even paying the guy, yet.

 

I'm not quite sure how I'm supposed to have intimidated him. I was remarking that as a DP, ignoring the opinions of the producers at the monitor is a good way to get yourself removed from a project. As I said, I've seen it happen.

 

I take it you subscribe to that style of "leadership" too Satsuki. Not surprised.

 

 

 

Yes it can, and no he is not working for either one of you.

 

I certainly would not tolerate anyone in my lighting or camera department being treated that way, and I have the lawsuits to prove it, not just words on the internet.

 

 

You have no idea how I run my camera and G&E departments. If I was into intimidation, and berating my crew, I doubt many of them would have stuck with me for the last five years.

 

As I've already said, there are many practical and political considerations when working on set, and DPs are not always able to work in a fashion that they consider ideal. Should you ever accidentally stumble onto a set, you might realize that.

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Tone begets tone... After four pages of Tom pushing an agenda which could get a beginning cinematographer in trouble because it does not take into account actual working practices, I think Stuart, Satsuki, and I are getting frustrated and the result is feeling the need to be more emphatic just because Tom doesn't seem to get the point and some impressionable student minds might actually start following his advice. As Stuart mentions, not every project has timed dailies on on-set timing to correct for this approach of exposing every set-up uniquely based on ETTR principles. Few directors either sitting next to the DP at the monitors would put up with exposures that are far off from the final look. If we are trying to avoid underexposure for what is intended as a dark moonlit scene, for example, we usually have to resort to tricks like darkening the monitor so that the director will stop saying that things look too bright. And certainly no one -- director, producer, editor, studio, etc. -- is going to put up with wild variations in exposure from shot to shot because ETTR is more important than consistency and continuity to the DP. And some shows just convert the recorded files and edit them, there are no timed dailies, and no DP wants everyone to see unmatched shots being looked at for months before the final color-correction.

 

And the political element cannot be ignored either, you can't tell a movie star that you'll fix how they look later in post even if that's true, they won't allow something live on the monitor or in dailies to go out if it is unflattering. So you have to do what you can in camera and on set to get closer to the final effect so you can then explain to the star and/or their support team that what little work left to do in post is minor.

 

Clearly after four pages, Tom is not easily intimidated.

 

Look, technically Tom has not said anything wrong but clearly there is a disconnect happening between theory and practice. Tom speaks like an engineer but that is only a small side of the art of cinematography. His advice is almost entirely fixated around two goals -- getting the lowest noise possible and giving post the most flexible file recording possible. These are useful principles to understand but these are not usually very high on the list of priorities for a cinematographer, we often value other things more highly.

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ETTR doesn't make sense for narrative cinematography where consistency of exposure within a sequence trumps exposure of individual shots. This isn't still photography. In a scene, noise levels and exposure values of edited shots have to be within a similar range, within reason.

 

Let's say you have a wide shot with a bright window on one side of the frame, a less bright lamp on the other side of the frame and an actor in the middle. Then in the medium shot the window is not in the frame but the actor and the lamp is. And in the close-up only the actor is in frame. If you apply the ETTR principle to this, the actor would be exposed differently in every set up and in trying to color correct him to a matching level in the edited footage, you'd basically have different amounts of noise on the actor.

 

ETTR only works as a vague principle -- i.e. avoid starving your sensor of light -- but it can't really be applied in practice for dramatic scenes. I mean to really apply it, every time an actor moved around a room in different light levels, you'd be riding the f-stop to keep him at the same exposure level, which makes no sense. If an actor is supposed to step out of the shadows, then he is going to be underexposed in the portion of the shot where he is in the the shadows.

 

Recommending using ISO 160 and ETTR practices might work if you are shooting visual effects plates but it has little to do with everyday working cinematography practices for dramatic fiction.

I haven't read this whole thread ... but, as usual, I would say to follow David Mullen's advice :)

 

As for ETTR, if you really want to, just lower the ISO on the camera and the video village will see an approximation of what you intended. My challenge is that I usually want to lower the ISO when shooting in bright daylight, but that's also where I would desire the most highlight range. Darned if you do and darned if you don't!

 

And in practice, the ability to shoot at low light levels is usually a much bigger advantage than a super clean file...

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I have not read the whole thread either, just most of the first couple pages.


But Stuart has shown similar hostility - and my criticism is directed solely at him - condescension to me, and that is the first thing I see trying to tune back in, which I reacted viscerally to. And he continues it with "Should you ever actually stumble onto a set, you might realize that."

Having worked on many sets with people who have absolute "scum of the Earth" attitudes, I tend to react negatively to people who perpetuate that sort of work environment. Whenever I am in a position of authority, I do my absolute best to protect those in my charge from that sort of absolutely shitty treatment.


Now that being said, I am not, in the least bit, defending Tom or his attitude.

And I respect the HELL out of your work, Mr. Mullen. Even if you WERE a tyrant, which I highly doubt from all the stuff of yours I've read, there are some people, a few a very few, who deserve it, and you'd fit that bill. You definitely know what you are talking about.


But this, unqualified, "I'm older than you, I have more credits than you, I've been doing this longer than you've been alive" thing is a classic logical fallacy better suited to political debates aimed at gaining the votes of the ignorant. Putting someone in their place I absolutely understand. But perpetuating what, frankly, should have died off in the McCarthy era, I find to be incredibly poor taste.

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Maybe everyone just needs to take a time out... I think what you are calling hostility is more frustration. Stuart is a nice guy, I've met him, and he's just trying to be helpful. It's hard to read tone and subtext on the internet so I would advise that we all take a step back and stop being so personal, just deal with the message and not the messenger, me included.

 

There are times when I've had to ignore certain posters for limited periods just because I find that they are punching all of my buttons. After awhile I find that I can engage them with more reserve than before.

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I have not read the whole thread either, just most of the first couple pages.

 

 

But Stuart has shown similar hostility - and my criticism is directed solely at him - condescension to me, and that is the first thing I see trying to tune back in, which I reacted viscerally to. And he continues it with "Should you ever actually stumble onto a set, you might realize that."

 

Having worked on many sets with people who have absolute "scum of the Earth" attitudes, I tend to react negatively to people who perpetuate that sort of work environment. Whenever I am in a position of authority, I do my absolute best to protect those in my charge from that sort of absolutely shitty treatment.

 

 

But this, unqualified, "I'm older than you, I have more credits than you, I've been doing this longer than you've been alive" thing is a classic logical fallacy better suited to political debates aimed at gaining the votes of the ignorant. Putting someone in their place I absolutely understand. But perpetuating what, frankly, should have died off in the McCarthy era, I find to be incredibly poor taste.

 

Here's the thing, Ari. you weren't even part of this conversation until you inserted yourself into it, apparently with the sole intent of criticizing both my temperament and my leadership style. As you were seemingly happy to make sweeping assertions about me, I'd thought I'd join in the fun, and make some about your lack of experience, something which is easy to do, given the complete lack of evidence to the contrary.

 

Seems to me that your involvement here has less to do with my comments to Tom, than it does with you being a little butt-hurt that I dared to question your attitude and language when describing the work of another DP, in another thread.

 

My experience and credits are a matter of public record. Anyone that cares enough can look at my work online and make up their own mind whether my opinion has any value. If only we could say the same for you.

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You're going to love this:



This forum requires a real name.

HOWEVER, the International Association of Theatrical and Stage Employes Local # 600, does not. You've made more than one assumption, then, I assume from Googling my name, Stuart, and finding nothing on my IMDB? I guess I know how pretty actresses feel with their more persistent male fans.

Why don't you call the Guild Office and double check on that, since you automatically defer to authority, place such an emphasis on "real sets," and have second guessed everything I have contributed in threads here you have read. I've worked on the same productions with Emmy and Oscar winners. So I know my way around a set, thank you very much.



David, you are right, and I am sorry for derailing this thread. But boy this guy reminds me of some of the real tyrants I have worked with, and have bitten my tongue so hard that it bleeds. They always manage to be so courteous and sound as if their parents taught them manners when they're on the phone, hiring you, too.

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You're going to love this:

 

 

 

This forum requires a real name.

 

HOWEVER, the International Association of Theatrical and Stage Employes Local # 600, does not. You've made more than one assumption, then, I assume from Googling my name, Stuart, and finding nothing on my IMDB? I guess I know how pretty actresses feel with their more persistent male fans.

 

Why don't you call the Guild Office and double check on that, since you automatically defer to authority, place such an emphasis on "real sets," and have second guessed everything I have contributed in threads here you have read. I've worked on the same productions with Emmy and Oscar winners. So I know my way around a set, thank you very much.

 

 

 

David, you are right, and I am sorry for derailing this thread. But boy this guy reminds me of some of the real tyrants I have worked with, and have bitten my tongue so hard that it bleeds. They always manage to be so courteous and sound as if their parents taught them manners when they're on the phone, hiring you, too.

 

So how about you quit avoiding the question and tell us what your 'Union' name is? Unless there's some reason why this should be a secret?

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But Ari.. there is something to be said for experience .. and that is usually by people older than you.. who have over time gained.. yes ..experience . And added to that neither you or Tom are actually DP,s.. you dont have the experience,and in Tom case,to know what he is talking about.. he has not shot a feature film,or light any big star,s, or dealt with their "people".. and he just wont except he's wrong.. and it frustrates people who are trying to advise a brick wall..

 

If I were a Cellist in a local amateur orchestra .. I would probably look a bit stupid if I met YoYo Ma and started to give him advise abut how he could play better.. but if I was a guy who worked at the factory .. that made the strings for Cello,s.. and I started advising YoYo Ma... I would be a total W**ker..

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So I mainly agree with David as usual, and need to clarify what I talk about and how I go about explaining myself on this particular topic, on this particular forum,

cause although it's day and night with my concerns and "attitude" in real life, you can't know that. (although I have to say you are quite quick about assuming that I'm the same in both settings)

 

Anyway, the creation of this topic and all the posts I made on it reflect how I want DPs and my self to learn :

-1/ understand the pure theory, the "perfect goal", what goes on in the camera and how to unlock its full potential etc.

So in our case, we're making the assumption that we have as much light as we want, that producers don't exist, that you can do whatever you want with your lighting, exposure...

 

- 2/ get to know and experience everything that goes on on a set that separates you from this perfection goal.

So as I said in the 1st page : not enough light, shoot without post production etc etc

 

- 3/ be able to make instant decisions on set that are the best compromise according to you between point 1 and point 2.

 

 

And this topic was solely dedicated to the 1st point.

I didn't want to start every single one of my posts by "in an ideal world", but maybe I should have.

 

So initially I was quite frustrated to get 80% of the replies dealing with how you can't actually shoot like this, and how I think like an engineer, and how I probably suck on the artistic side of cinematography etc..

 

But in the end all these arguments make for a better learning experience for anyone reading the topic, they get to have both sides of the coin (point 1/ and 2/) when I initially only intended to discuss point 1/.

 

 

Now how much you should know about the 1st point is open for debate, and sometimes yes it has more to do with pure curiosity and desire for technical mastery than "useful on-set" information.

I'm always in favor of learning 10 times more than just what's needed for the job, because I think it helps being more calm, confident, fast, and experimental once you're on the set.

 

Plus it prevents you from making little decisions that make no sense : like stacking NDs because you want to shoot a day ext. at 800, not because you want noise, but because you're afraid of shooting at anything else than 800 cause you heard this or that DP shoot at 800.

 

So I hope it clarifies the goal of the topic.

And I'm sure that, although few would admit it (and I never post on topics where I learn something either) that readers of this topic have a better understand on how the Alexa works (name of the topic, quiet different from "how to work with the alexa") than before.

 

PS : about how longer the color grading of an "ettr movie" (whatever that means) actually is compared to a film exposed classically. I'v tried both (and was the or with the colorist each time) and in my experience it's shorter with ETTR.

Because when you expose with ETTR : all the ratios/contrast are already set as you want them, it's just the global amount of light that has to be corrected. And dragging the "Offset" wheel to where you want your image takes 2 seconds.

So the overexposure lengthens the grading by 2 seconds per shot.

Where it gets shorter is that you don't encounter problems when you want to treat the shadows : no creations of unwanted artifacts, excess of noise, color banding etc. It's an issue colorists often spend quiet some time on : the dp made the shadows a bit too black, so he'll want to raise them a bit, but it starts to get messy and muddy because of a lack of info (cf. my post on the issue of how many values per stop the sensor records) etc etc. With ETTR that issue is virtually non existent.

(PSS: Yes, I know, you can also place your shadows exactly where you want in the first place)

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Thank you Tom for your thoughtful post. I agree that the theory and science behind something should be learned.

 

You bring up an important point, which is fixing things in post. There are two approaches -- one is to expose and light so conservatively as to provide maximum flexibility to make corrections in post, and the other is to learn to expose and light for the look you want so that any corrections in post are minimal (as for allowing other people to take over and make corrections without your involvement, that's a whole other issue.)

 

I've always advocated the second because the first approach never allows you to learn from your mistakes, you are always covered. And things can go aesthetically wrong in post sometimes if too much flexibility is allowed, there is something to be said with the look being clearly expressed in how the image was lit and exposed.

 

However, I am also a realist, I know that the number one thing that directors and producers like to do in post is make things a little lighter. So I expose with that in mind, I don't generally play too far in the underexposure range unless practical reasons give me no choice. With film, I usually rated 500 ASA film at 320 ASA, not just for the higher printer lights but because if I had to lift things by three or four points in post, I was still going to have a good print. Same thing for film going through a D.I. and the same thing for digital. But there's a big difference between shooting the Alexa at 500 ASA instead of 800 ASA (like I did on "90 Minutes in Heaven") or lighting a bit flatter and creating a LUT or LOOK for the camera to add contrast for the monitors and dailies so I naturally added a bit more fill to give myself more information in post... and using something like 160 ASA or using ETTR principles (which again would require timed dailies and living with a monitor image on set that was not exposed for the intended look, which is not going to happen on most shoots other than vfx units.)

 

So most cinematographers have learned through experience, some bad, to find a happy balance being shooting for the look they want and bringing something into post that is workable.

 

Now occasionally I do hear from colorists, just as I used to hear from print timers, about projects they were working on that were badly or inconsistently exposed while they were complimenting me for how close I was to the final correction in my original. Which always thought was me just doing my job. I think it was the discipline of shooting film for print, which did not have a lot of range for corrections in the shadows due to grain, that I carried over into digital. Basically it means expose consistently and correctly so that final color-corrections do not have to swing wildly in any directions, and have enough exposure so that noise does not kick in the moment you have to lift something.

 

But there are always the occasional mistakes (and one does not always shoot every shot that ends up in a movie) and there is the occasional scene shot under extremely low-levels of exposure. I once did some car stunt work at night on city streets in available light and was forced to rate the Alexa at 1600 ASA because the director wanted to use T/2.8 zooms for everything and the city had dim street lighting, but there was no way to light the streets for our shots (nor was it budgeted.) I knew that I was on the edge of having too much noise but since this was for HD broadcast, I had some flexibility to add noise reduction in post. But then when a stunt got misframed, the director asked me how much he could blow up the image for reframing in post, and I told him that the 1600 ASA was limiting his flexibility for enlargement -- the percentage of acceptable enlargement was smaller than normal. And then he asked if I could shoot with a 45 degree shutter angle, and again, I told him I couldn't give him another two stops of speed w/ lenses limited to T/2.8 (that would have required setting the Alexa to 6400 ASA). So you have to be flexible in how you approach things, but there are limits if you care about noise (in this case).

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I still think that ETTR has no practical application in cinematography other than a single shot sequence or shooting vfx plates. No one on a set watching monitors is going to accept every set-up in a scene being exposed differently with no connection to the preceding or following shot of the same actor in the same space, with the idea that it was all going to be matched later in post. I don't even think that is a good idea technically, it would be like in film mixing 50 ASA film and 500 ASA film in the same scene, just for the moments when you had enough exposure for the 50 ASA film.

 

And to follow ETTR to its limits, you'd have to give up on consistency in f-stop if the room had been lit to a base level -- let's say the master was lit to an f/4, but if a close-up didn't have a bright lamp or window in the shot, you'd have to open up to f/1.3 and if you panned into a bright window, you'd have to stop down to f/8, etc. Unless you lit everything to a high level and used ND filters to maintain the same f-stop as you used ETTR to expose each shot individually. And even that doesn't solve the problem of the monitor image being all over the map exposure-wise shot-to-shot unless you want live color-correction to happen on set.

 

Where ETTR is more practical is stuff like 2nd Unit work in exteriors, or montages -- for example, I did a montage of Jack Kerouac walking through some sunny woods for "Big Sur" and more or less watched the highlights to set the exposure on each set-up. But in this case, each shot was in a new location, it wasn't different sizes of the same set-up in the same light.

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Thanks for your posts David,

 

You bring up an important point, which is fixing things in post. There are two approaches -- one is to expose and light so conservatively as to provide maximum flexibility to make corrections in post, and the other is to learn to expose and light for the look you want so that any corrections in post are minimal (as for allowing other people to take over and make corrections without your involvement, that's a whole other issue.)

 

I've always advocated the second because the first approach never allows you to learn from your mistakes, you are always covered. And things can go aesthetically wrong in post sometimes if too much flexibility is allowed, there is something to be said with the look being clearly expressed in how the image was lit and exposed.

 

Actually before my school I would only be able to shoot on DSLRs etc that you can't really grade. So when I entered the school I was telling myself "finally I'm gonna be able to shoot raw etc"

But most of the students projects, even the ones with the Alexa, were recorded with the Rec709 LUT/space 'burned-in', so that we couldn't fix stuff in post, some projects wouldn't even have color grading.

So I guess it was partly because they want us do to most of the image on set.

 

Then grading is not just correction/ fixing mistakes of course and can be an extension of cinematography (like O'Brother).

 

 

I once did some car stunt work at night on city streets in available light and was forced to rate the Alexa at 1600 ASA because the director wanted to use T/2.8 zooms for everything and the city had dim street lighting, but there was no way to light the streets for our shots (nor was it budgeted.) I knew that I was on the edge of having too much noise but since this was for HD broadcast, I had some flexibility to add noise reduction in post. But then when a stunt got misframed, the director asked me how much he could blow up the image for reframing in post, and I told him that the 1600 ASA was limiting his flexibility for enlargement -- the percentage of acceptable enlargement was smaller than normal. And then he asked if I could shoot with a 45 degree shutter angle, and again, I told him I couldn't give him another two stops of speed w/ lenses limited to T/2.8 (that would have required setting the Alexa to 6400 ASA). So you have to be flexible in how you approach things, but there are limits if you care about noise (in this case).

 

Damn pretty tough situation.

What I hope we get in the future for digital cameras, is having B "specialty" low-light cameras, the same way we use specialty cameras for slow-motion, or "crash cams" etc nowadays

Maybe the Canon ME20F-SH.

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because they want us do to most of the image on set.

 

 

 

In my market, it's pretty much essential. I sometimes don't attend the color-timing for the movies I shoot, either because of other work, or occasionally just not being invited. In that situation, having my exposures and look already there in the image means that I'm much more likely to get what I want. If I am there, it means that the whole process is a little smoother, and there's less time wasted arriving at a desired look.

 

The other important reason for working this way is that my DIT has no time to make anything more than simple blanket corrections to dailies, so the look has to be there in camera, and the exposures have to be consistent. Sometimes buyers are shown the movie before it's color-timed, so it has to look as good as possible at all stages of post. Even if they don't show buyers, the producers like it to look visually coherent. They are not always the most imaginative of people, and trying to convince them that it will all look great in post can be a hard sell. They see mismatched color and exposure and it worries them, and they start to wonder how much it's going to cost to 'fix'.

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In my market, it's pretty much essential.

 

Especially in commercials where, after production wraps, I likely won't see anything until I see it on television.

 

"Ya know that window is pretty blown out."

"Yeah, I want it to be."

"But there's no information there."

"Good, that means they can't darken it in post."

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Especially in commercials where, after production wraps, I likely won't see anything until I see it on television.

 

"Ya know that window is pretty blown out."

"Yeah, I want it to be."

"But there's no information there."

"Good, that means they can't darken it in post."

:-D (That's the only thing I can add)

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And he said they took the Alexa over film cameras for The Revenant because they wanted the least possible noise.

Actually, they were going to shoot hybrid from day one. Alexa for the dark scenes and 65mm for everything else. They went testing and on the way back, their film got flashed by the airport. Evidently they lost something and it put a serious question into their heads. So they dumped the idea and went with the Alexa 65. What's frustrating is that there IS a bunch of 65mm film stuff that was fine and left on the cutting room floor.

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One more thing... Tom's ideas about imagers not having a native ISO can't be proven with science because as David and others pointed out, cinematographers are trying to get a certain look out of the imager. That look can't be quantified by science, just like film vs digital. People like the look of film, but science says it's substandard compared to similar resolution digital.

 

I have quite a bit of real-world experience with a variety of digital cinema cameras and this whole problem of native ISO being the best for protecting your highlights, has been accurate on every shoot, with every camera. I do work cameras at lower ISO's to help reduce noise because 800 on a lot of lower-end cameras, is noisy. Yet protecting highlights and getting a filmic image out of imagers which are being saturated with light more then their optimal level, can be challenging.

 

This just another result of how science and math have difficulty merging with art.

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Wow really ? 65 footage flashed at the airport damn...

Still I think that it could have looked great but given Iñárritu's new long and very complex shots style, 65 film would have been slightly too crazy no ?

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Ok but how do we define native ISO then ?

 

Some propositions :

- ISO at which the camera gives X stops of overexposure before clipping ?

- ISO at which the camera has the same number of stops of over and under exposure ?

This second points depends on what we include as dynamic range, which is, for the shadow end, pretty hard to do.

You have the choice to end the dynamic range in two ways: above a given SNR level (hard), or below a given number of values per stop (more straightforward).

 

Some examples with the Alexa :

- native ISO 1 = I want 7 stops of overexposure = 640/800

- native ISO 2 = I want 5 stops of overexposure = 160

- native ISO 3 = I want as much DR in the highlights and in the usable shadows.

3A : usable shadows stops = stops with 16 values or more. So DR = 12 and the native ISO 3a is 250/320 (+5.5/-5.5)

3B : usable shadows stops = stops with 64 values or more. So DR = 10 and the native ISO 3a is 160 (+5/-5)

 

The highlights stops each have about 500 values in arriraw.

Edited by Tom Yanowitz
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Well I bought one, & I am certainly not rich.

 

R,

Rich is a subjective term. To someone making $25,000 a year you might seem rich. A Dr. making $400,000 a year he would probably not.

Edited by Landon D. Parks
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Ok but how do we define native ISO then ?

 

Some propositions :

- ISO at which the camera gives X stops of overexposure before clipping ?

- ISO at which the camera has the same number of stops of over and under exposure ?

This second points depends on what we include as dynamic range, which is, for the shadow end, pretty hard to do.

You have the choice to end the dynamic range in two ways: above a given SNR level (hard), or below a given number of values per stop (more straightforward).

 

Some examples with the Alexa :

- native ISO 1 = I want 7 stops of overexposure = 640/800

- native ISO 2 = I want 5 stops of overexposure = 160

- native ISO 3 = I want as much DR in the highlights and in the usable shadows.

3A : usable shadows stops = stops with 16 values or more. So DR = 12 and the native ISO 3a is 250/320 (+5.5/-5.5)

3B : usable shadows stops = stops with 64 values or more. So DR = 10 and the native ISO 3a is 160 (+5/-5)

 

The highlights stops each have about 500 values in arriraw.

 

The problem with using such terms as SNR, or even 'Saturation', in areas where there is a predominance of Film film based photographers, is those are terms they are totally unfamiliar with.

 

Of course now, after digital cameras have become wide spread, some people may be more familiar. But even then, such terms not that well understood by many.

 

It doesn't help went the standards body sells the standard for a (in my opinion...) unreasonable price which limits general knowledge of such standards...

 

So, I've been tending to go for a process that doesn't use SNR or Saturation, but basically says where does 18% grey (disregarding whether it's 18% or the meter is calibrated to 18%...) fall in the resulting image in terms of the Waveform monitor in % IRE.

 

While that sort of display was predominantly used by analog and digital TV camera people, and not used much by 'photographers', it allows for an easy description of 'scene' brightness to 'recorded value'... and thence to 'displayed value'.

 

However, that's not the whole story, and that's where the 'dynamic range' comes in... another term not used by Film film photographers, but rather the term 'Latitude' was used in several different ways, but in general to indicate how much 'constrast' a scene code have, and still be recorded in some 'quality' way.

Edited by John E Clark
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The problem with using such terms as SNR, or even 'Saturation', in areas where there is a predominance of Film film based photographers, is those are terms they are totally unfamiliar with.

 

Of course now, after digital cameras have become wide spread, some people may be more familiar. But even then, such terms not that well understood by many.

 

 

The more we talk about these "new" notions, the faster they'll enter the realm of basic technical photo/cinematography knowledge I think.

 

 

So, I've been tending to go for a process that doesn't use SNR or Saturation, but basically says where does 18% grey (disregarding whether it's 18% or the meter is calibrated to 18%...) fall in the resulting image in terms of the Waveform monitor in % IRE.

 

That method would be ideal if manufacturers could allow us to display raw data on waveform monitors, but currently we only get access to a heavily modified (for display) data.

For example with the Alexa if you record in arriraw, what you see on scopes isn't arriraw but LogC.

So a middle gray exposed at ISO 800 with the camera on EI 800 will show up at 39% of the scope, but will be recorded at 15%.

So on set monitoring is a bit unreliable in that way.

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