Epic HDR

[Tom Lowe]

Saul, I hope you are not arguing or speculating that perhaps good cameras should be kept out of the hands of people without a lot of money? It seems like maybe you are implying that if everyone has a nice camera, somehow this will lead to an overall negative impact on movies at the cinema?? I would argue quite the opposite. When I go to the cinema, I am appalled by what I see. I would say that over 90% of movies in cineplexes are total garbage.

 

Do you think the quality of novel writing went down when everyone could afford an ink pen and sheets of paper? Hardly.

Edited October 16, 2010 by Tom Lowe

[Tom Lowe]

Nothing wrong with democratizing the art and the experience of cinema, of course. But at what expense? Now almost everyone seems to be making an HDSLR or RED feature film, whether they are feature worthy or not. By most statistics, attendance to movie theaters is significantly down from 30 years ago, HDTV, BlueRay, home theaters and a million movie releases competing for fewer and fewer viewers are slowly choking it.

 

I would suggest that the horrendous piece of crap movies being cranked out with massive budgets by major studios and shot almost entirely on film up until this point are what is truly hurting the movie industry. I don't think you can blame this on Red cameras or Canon 5D2s!

[Saul Rodgar]

Your claim that going to the movies these days is a dreadful scenario points at the fact that because there are so many more movies being released these days -all competing for a smaller pool of viewers and therefore appealing to the lowest common denominator in order to do well at the box office- they are not as good as they used to be. In a way, there was a democratization of the multi-million budget movies, so to speak. Which by your implicit admission is not necessarily a good thing.

 

More movies= higher number of crappy movies.

 

And the pen and ink analogy is not so valid because film making is always been a group effort, while writing is generally done by a single person. If a novel were comprised by a chapter written by a separate person, I think there would be far fewer books of note out there.

 

More later, running late for a shoot.

[Tom Lowe]

Your claim that going to the movies these days is a dreadful scenario points at the fact that because there are so many more movies being released these days -all competing for a smaller pool of viewers and therefore appealing to the lowest common denominator in order to do well at the box office- they are not as good as they used to be. In a way, there was a democratization of the multi-million budget movies, so to speak. Which by your implicit admission is not necessarily a good thing.

 

More movies= higher number of crappy movies.

 

The actual number of films released DROPPED significantly in 2009 and 2010 (http://www.mpaa.org/Resources/091af5d6-faf7-4f58-9a8e-405466c1c5e5.pdf).

 

Saul, it doesn't matter if 500 movies a year get made, or 250,000 movies a year get made. It doesn't matter if 20 million films get made every year. Only a couple hundred films get distributed in cineplexes each year. There are roughly 100,000 novels written every year, but only about 250 novels are printed by the major publishing houses every year. It doesn't matter if 300 novels are written every year, or 300 million novels... still, only 250 a year will be published by the majors.

 

So you cannot blame indie filmmakers for the absolute garbage films Hollywood has been spitting out. Those are 50 million + films, with A-list actors, unlimited film and gear, etc. It's their own fault that their movies suck. Some kid with a Canon 7D is not causing Hollywood to put out crappy major films.

 

How exactly was there a "democratization of the multi-million budget movies"?? You still need tens of millions of dollars to make them. How is that democratic???? Can the average person pick up an ARRI 435 and go shoot a 5 million-dollar film?

[David Mullen ASC]

I don't think it matters much one way or the other; the indie film scene was just as vibrant and active when digital tools were poor and film was dominant -- I shot some cheap 35mm and 16mm features myself back in the 90's. What you see now is the emergence of micro-budget cinema made even cheaper than ever, and looking better than was possible before. I don't see that as a bad thing, but it's not a huge leap over what these young people did before with Hi-8 and Super-8 and whatnot, it just looks better. It's not better-written or better-acted, the ideas aren't better, it just looks better, and for that, maybe it's taken a bit more seriously. On the other hand, if everything gets lifted up together in terms of picture quality, then you don't particularly stand out any more than you did before.

 

But I can't see it as a bad thing, the access to better imagemaking tools. Certainly when I was a teenager, a DSLR shooting HD would have been a lot of fun.

 

More movies just means more movies -- more crappy ones but probably more good ones too. The only downside is really the volume problem, with ad budgets low and the market more scattered, it's harder to get seen by large audiences. The appeal of filmmaking has generally been a bit different for many people than the appeal of creating modern painting or other fine arts; there was the potential of reaching large numbers of people because it was a popular art and it was entertainment, and it was consumed by groups rather than individuals. That's very appealing, the idea of an audience sitting down to watch your movie, captive for two hours in the dark, a communal experience. Now it's this different experience of people sending each other links to short works on the internet -- a situation that favors the shortest pieces possible, easily downloaded and consumed.

 

But I digress, my main point is that people take the technology far too seriously, on both sides of the debate. It's dangerous to live or die by the sword of a particular piece of technology; you have to be working on a higher plane than that.

 

But as artists of course we get passionate about our tools, but we have to see that some of that is emotional, only part of that is practical. But I can respect great artists that talk lovingly about a particular tool, they've earned it, it's just harder to take other people, bystanders, who talk about which image technology is good or bad but aren't producing anything of interest either way!

[Tom Lowe]

More movies just means more movies -- more crappy ones but probably more good ones too.

 

Exactly.

 

Part of the "democracy" perhaps of Red cameras, for example, is an ability to make a $200,000 movie and then have it look good. 200K is a lot of money, but it's not like trying to raise 5 million. It's actually doable for most Americans with motivation and some talent and a couple years to beg their relatives.

 

In a $150K budget, for example, film cameras, film stock, and film processing and editing could actually chew up a large amount of that budget rather quickly. But who really wants to be spend years of their life rounding up $150K, and then have to make the movie on a sub-standard HVX200 720p camera that is not up to cinema/film standards? That is where Red comes in and democratizes the image quality.

 

In fact, I could make a strong argument that digital cameras actually exceed chemical film now in some areas.

Edited October 16, 2010 by Tom Lowe

[K Borowski]

They used to shoot major historical events with 35mm Mitchells (albeit B&W, when amateurs had color 8mm).

 

Then, with the arrival of television, 16mm became the norm. Color reversal was arguably a big improvement over B&W neg., but now major historical events are often shot on cameraphones. Tiananmen Square was, I believe, captured on either VHS or 8mm analog videotape and physically smuggled out. The famous "photo" of the man standing in front of the tank was an enlargement from a field of that tape.

 

 

It's absolutely better to have a major event captured on a cell phone, or VHS, than nothing at all, but with the "democratization" as Tom calls it of the film/video industry, this merely seems to have the effect of diluting the budgets for real PROFESSIONALS who will lug 60 lbs. of gear around, if need be, to get the shot. I do not think an "industry" composed almost entirely of underpaid individuals, working another 9-5 can do the same job as dedicated pros, eeking out a living, but being able to pay the bills without a waiter job to boot.

 

 

Look at the events in the newsprint industry. Laugh all you want at the printed page, but those papers, for 50c a day, are what FUNDS a lot of the AP/Getty guys and the big city papers that are then linked to Google for everyone to read for free.

 

Have any of you started to notice the huge drop in writing quality that we're seeing hitting news sites? I was shocked to see a blog entry listed with a major headline on Yahoo News, my goto source for casual reading.

 

 

I think the same phenomenon is eventually going to hit broadcast TV next and even Hollywood entertainment. There's only so much water and the pool, and I'm afraid that it's going to get to the point where there are a bunch of guys splashing their feet in puddles.

[Dom Jaeger]

Aside from a devaluation of the term 'cinematographer' (which any halfwit with a DSLR now wants to call themselves) of course democratisation of film tools is a good thing. Personally I think it happened years ago with the advent of cheap 8mm consumer cameras. Many great filmmakers started there and learned the basics of movie making. But now it seems people want to jump to cinema quality before they know the difference between a t stop and an f stop.

 

I think a lot of people have bought the idea (vigorously marketed to them) that access to an affordable camera with 35mm film quality will somehow solve all their problems. For documentary work or the like it's no doubt a boon, but for features the camera is only one factor. You still need a significant budget for script development, lenses, lighting, art production, post work, decent actors and crew. Without any of these your film will still most likely look rubbish no matter how good the camera is. In fact a super sharp, wide latitude camera sensor will just highlight the deficiencies in production value. Low budget indy films have been around forever but it's never the image quality that makes them a hit.

 

You might be forgiven for thinking that the advent of cheap, high quality cameras would have freed up film budgets to spend more on scripts, art direction and paying for good crews, but it seems the opposite has happened. Because the camera package costs nothing producers now feel that the crew should come cheap too. (I know that's a broad generalisation, please correct me if I'm wrong.)

 

Another thing that gets overlooked is that unless you're looking for theatrical release 35mm film quality is kind of unnecessary - the high end digital cameras already available (or S16) are perfectly adequate for most projects. And theatrical distribution will remain as hard to crack as ever. Investing in the latest RED camera in the belief it will be somehow revolutionary and cheering on the death of film won't change that one iota.

[Tom Lowe]

Aside from a devaluation of the term 'cinematographer' (which any halfwit with a DSLR now wants to call themselves)

 

How is this any different from people calling themselves "photographers"? Millions do.

 

I think a lot of people have bought the idea (vigorously marketed to them) that access to an affordable camera with 35mm film quality will somehow solve all their problems.....You still need a significant budget for script development, lenses, lighting, art production, post work, decent actors and crew. Without any of these your film will still most likely look rubbish no matter how good the camera is.

 

Who exactly believes this? I have seen this strawman assertion hundreds of times, but I have never seen anyone post anything here -- or on any other film-related forum -- stating that a new camera was going to make their actors or script or blocking or location or rehearsal or soundtrack or dialog better. Can you point us to one single post on cinematography.com or any other forum on the entire internet where even one human bring actually believes this?

 

Another thing that gets overlooked is that unless you're looking for theatrical release 35mm film quality is kind of unnecessary - the high end digital cameras already available (or S16) are perfectly adequate for most projects. And theatrical distribution will remain as hard to crack as ever. Investing in the latest RED camera in the belief it will be somehow revolutionary and cheering on the death of film won't change that one iota.

 

Actually, the resolution of Bluray exceeds the standard resolution of typical cineplex projection (somewhere between 700 and 1000 horizontal lines), so you could argue that a Bluray-bound project actually requires better image quality than a multiplex chemical print. A Sony EX1 might be "perfectly adequate" for you, but maybe not good enough for others. I would not shoot on one, because the quality simply is not there to make a cinematic project, beginning with the lack of dynamic range and recording quality.

Edited October 17, 2010 by Tom Lowe

[Saul Rodgar]

They used to shoot major historical events with 35mm Mitchells (albeit B&W, when amateurs had color 8mm).

 

Then, with the arrival of television, 16mm became the norm. Color reversal was arguably a big improvement over B&W neg., but now major historical events are often shot on cameraphones. Tiananmen Square was, I believe, captured on either VHS or 8mm analog videotape and physically smuggled out. The famous "photo" of the man standing in front of the tank was an enlargement from a field of that tape.

 

 

It's absolutely better to have a major event captured on a cell phone, or VHS, than nothing at all, but with the "democratization" as Tom calls it of the film/video industry, this merely seems to have the effect of diluting the budgets for real PROFESSIONALS who will lug 60 lbs. of gear around, if need be, to get the shot. I do not think an "industry" composed almost entirely of underpaid individuals, working another 9-5 can do the same job as dedicated pros, eeking out a living, but being able to pay the bills without a waiter job to boot.

 

 

Look at the events in the newsprint industry. Laugh all you want at the printed page, but those papers, for 50c a day, are what FUNDS a lot of the AP/Getty guys and the big city papers that are then linked to Google for everyone to read for free.

 

Have any of you started to notice the huge drop in writing quality that we're seeing hitting news sites? I was shocked to see a blog entry listed with a major headline on Yahoo News, my goto source for casual reading.

 

 

I think the same phenomenon is eventually going to hit broadcast TV next and even Hollywood entertainment. There's only so much water and the pool, and I'm afraid that it's going to get to the point where there are a bunch of guys splashing their feet in puddles.

 

Well said. Thank you.

[Saul Rodgar]

 

 

So you cannot blame indie filmmakers for the absolute garbage films Hollywood has been spitting out. Those are 50 million + films, with A-list actors, unlimited film and gear, etc. It's their own fault that their movies suck. Some kid with a Canon 7D is not causing Hollywood to put out crappy major films.

 

How exactly was there a "democratization of the multi-million budget movies"?? You still need tens of millions of dollars to make them. How is that democratic???? Can the average person pick up an ARRI 435 and go shoot a 5 million-dollar film?

 

I am not blaming anyone, I am saying all those people are crowding the field.

 

And what I meant about the "democratization of the multi-million budget movies"is that there were a lot many more multi-million dollar features being produced before 2007 than ever before. Sure, not everyone got to shoot one, but more people did than ever before. And a lot of viewers stayed home in spite of that.

[Saul Rodgar]

 

 

More movies just means more movies -- more crappy ones but probably more good ones too.

 

 

I disagree on a purely empirical basis. Obviously I can't see every movie shot on HD out there, but of what I have seen, 99.9% is garbage. Obviously that is also subjective. Anyone else that saw those same movies could say they were awesome.

 

There is a Ravi Shankar documentary movie shot in the late 60s, when there was a huge explosion of Indian music and culture in the west. In it he talks about all these people who went to his California school to study classical Indian music. Trouble was, he said, almost everyone expected to be able to master a raga, in all its complex, nuanced and difficult nature in just a couple of sessions. My take on the HD / RED / HDSLR is that a lot of people (spurred by companies ads) come to filmmaking the same way.

 

I get it all the time. Someone hires me wanting to spend a couple of thousand dollars, say, but expecting results that compare with movies that cost millions. "Why not?" they say. "We have a RED," or what have you.

 

A race to the bottom, that is what it is.

Edited October 17, 2010 by Saul Rodgar

[Tom Lowe]

I disagree on a purely empirical basis. Obviously I can't see every movie shot on HD out there, but of what I have seen, 99.9% is garbage.

 

Hahaha. So basically, it's about the same percentage as Hollywood films....

[K Borowski]

Actually, the resolution of Bluray exceeds the standard resolution of typical cineplex projection (somewhere between 700 and 1000 horizontal lines), so you could argue that a Bluray-bound project actually requires better image quality than a multiplex chemical print.

 

Tom is right here. Of course, it's thanks to 2K mastering that this is the case. With the exception of S35 blowups (16mm is also marginally better, I'd say, than the blowup days), film prints look worse, some having lost half the resolution of a decade ago.

 

If someone would have put money into low-cost high-speed 4K filmouts straight to print stock, you could have 100% change in resolution of film prints in the other direction.

 

I don't know how Blurays are compressed, either. 2K digital projectors run movies that are usually around 250GB after compression. I haven't figured out GB per minute, but I assume Blurays are compressed four or five times as much. And blurays aren't viewed on cinema sized screens, so the requirements for focus are still higher for a big screen than a 60" screen.

 

 

Tom, I've heard a lot of photographers, cinematographers talk about how their new camera was going to help them take better pictures, shoot better movies. I was in that boat myself at one time. It's even true to the extent that there's a certain level of professional goodies that a SKILLED shooter can take advantage of.

 

Many many people don't get past the stage of F/stops and lighting though. For them, even VHS-C is all they need. Some of them are walking around shooting with RED, some of them even walk around shooting 16- or 35mm. So it's not something solely reserved for digital. There's a lot of hyping people do about new film stocks on here too.

 

 

If you can't see it, I'm sorry, you're going to have to take my word for it. I'd stake that there's five hundred examples on here from the past year alone you could dig up.

 

 

 

As for Cinematography, I disagree that the camera you own makes you a cinematographer. I'd say it's more the lights you have access to and your skill at using them.

 

There are plenty of photographers, like Ansel Adams, who needed no knowledge of lighting for literally any of their professional work. Cinematography takes understanding of lighting, exposure, filtration, and focus to a whole new level beyond that.

 

 

There was an ad for the Canon EOS 5D last night entitled the art of cinematography or some such line, and they had I think a fictional director talking about how the camera was so easy to rig (said dramatization under it). So Canon didn't even bother to bring a real DOP in to pitch their product; they dragged the word cinematography through the mud there. Like it takes a light-weight camera to do a dolly shot off the edge of a bridge :rolleyes:

Edited October 17, 2010 by Karl Borowski

[David Mullen ASC]

There are all kinds of cinematography, some of which use natural light only... but to become a professional Cinematographer with a capital "C", obviously you have to know lighting, it's a major part of one's career and time, and probably one of the major reasons you get hired, your skill at doing it.

 

But in the overall scheme of things, half a cinematographer's job is knowing what NOT to light and knowing when to use natural light, and knowing how to take advantage of it, capture it, and manipulate it (which may or may not take some lighting of course.)

[Hal Smith]

I'm going to put it on a file hosting site when I've checked it with enough versions of Windows. One of the problems at the moment is that it's almost impossible to send an executable file as an email attachment these days no matter how you try to disguise it. The email servers assume its a virus and it simply never arrives at the other end, as I only recently discovered!

 

And simply changing the extension to .dat doesn't work because?

 

Are you using something like gmail or aol where since it's free you have to take what you get? I use a commercial ISP that runs all my mail through Postini first which catches viruses without restricting access. In exchange for my money they also cache one year's worth of email.

 

On the general "quality" subject: The early release trailers for "Dan in Real Life" were apparently not mass produced. I was stunned when one came on at an AMC I frequent. Photo-optically printed and apparently not high speed duplicated it looked like it had been hand etched on a 60' screen. All the discussion about acquistion systems is rather moot when 99% of what you see at the multiplex has gone through a process that strips every last bit of quality off in the pursuit of cheap...cheap...cheap...distribution costs.

[Emmanuel Decarpentrie]

So it is regular HDR - two SEPERATE exposures, one normal and one for highlight recovery. Great, they have trouble with motion rendering already (like all shutter-less cameras) and now they put two exposures taken at different times over each other just to claim superior DR?

 

Again: this is NOT what they are doing! Re-read what I've said before or what the paper on Provideocoalition is clearly explaining. Allow me to repeat for the fourth time: they don't "take two exposures at different times", they sample (read) the same exposure twice. Combining those two samples is pretty straightforward, because they both come from the very same exposure! In other words, the shutter didn't (close) reset itself between those two samplings. And that is a very clever (simple) way to achieve an actual increase in DR! I'm wondering why no one did it before them...

 

The only problem might have come from the combined motion blur, but I have to admit the naturally combined motion blur actually gives excellent results. Hence the name "Magic Motion" I guess. The "Magic Motion" truly makes it like it was shot with a mechanical shutter, like the D20-D21. Why? I have no clue...

 

But should you dislike this "Magic Motion" thing, you still have the Foundry's solution, which I'm pretty sure will give outstanding results (I use the Foundry's products on a regular basis).

[Keith Walters]

Would you guys mind terribly taking your endlessly tedious tumescent fantasies of cinematic relevance somewhere else?

 

The main thrust of this thread is that Red are once again making extraordinary claims, not backed up by any extraordinary evidence. We've heard all that "film is dead" shɨt far, FAR too many times before. Even if and when it does die, I doubt too many of you are in line for a share of the estate.... :rolleyes:

 

I'll reserve judgement until I've see some real-world footage in a real-world situation, but at the most it sounds like Epic might actually be the camera that the Red One was hyped to be, except nowhere near as cheap as it was hyped to be.

 

It also still smells rather strongly to me that the Epic HDR function is heavily dependent on "Special Sauce" algorithms that are still "in development". If a key product specification stands or falls on the availability of software that has yet to be fully developed, that is the classic defintition of "Vaporware". Doesn't mean the software never will be developed, only that you have no way of knowing when that will happen, and whether the final product will live up to the original hype.

 

The other concern is that even it the HDR function may actually be seen to work in "stunt exposure" situations, this does not necessarily mean it will emulate the much desired **overall** logarithmic response of film emulsion. So you might well be able to pull off lamp filaments and shadows in the same frame; doesn't mean everything else in the scene is going to to get the same level of "USSR Model farm" care.

[Keith Walters]

Again: this is NOT what they are doing! Re-read what I've said before or what the paper on Provideocoalition is clearly explaining. Allow me to repeat for the fourth time: they don't "take two exposures at different times", they sample (read) the same exposure twice. Combining those two samples is pretty straightforward, because they both come from the very same exposure! In other words, the shutter didn't (close) reset itself between those two samplings. And that is a very clever (simple) way to achieve an actual increase in DR! I'm wondering why no one did it before them...

 

I've re-read it.

 

A. They don't appear to be saying what you think they're saying and

B. Your explanation is flat-out impossible. No amount of exclamation marks, underling, capital letters or bullying manner is going to make you right.

 

Why can't you all be more like Jim Jannard or Graeme Nattress? They rarely tell us anything useful either, but at least they're polite about it :D

[Keith Walters]

And simply changing the extension to .dat doesn't work because?

How should I know? I presume the mail filter looks inside the file for signs of executable code and rejects anything that could even remotely turn out to contain a virus.

 

 

Are you using something like gmail or aol where since it's free you have to take what you get?

 

GMAIL sends them off just fine as it happens. And it receives them OK as well. It does take its time in accepting them sometimes, but they get there eventually.

 

Unfortunately I have no control over what happens once they leave the GMAIL universe. In a lot of cases, they simply never arrive. There is no notification on either end that they haven't been accepted, they just evaporate.

 

 

I use a commercial ISP that runs all my mail through Postini first which catches viruses without restricting access. In exchange for my money they also cache one year's worth of email.

Yeah, well GMAIL gives me about 7GB of storage and (currently at least) there is no storage time limit. They use start-of-the-art virus and Spam filtering; their spam hit rate is about 99% accurate.

I also have a Yahoo mail account that I started in 1998, and I apart from stuff I deliberately delete, everything I've ever sent or received is still in there.

[Keith Walters]

I would suggest that the horrendous piece of crap movies being cranked out with massive budgets by major studios and shot almost entirely on film up until this point are what is truly hurting the movie industry. I don't think you can blame this on Red cameras or Canon 5D2s!

Aw, Jeez. You broke the needle on my Dumb-O-meter again, Tom. I'll have to compose this response blind.

 

You can't blame the RED cameras for the fact the people are still shooting on film?! :blink:

Well ye-e-a-h .... I think you can pretty much blame modern video cameras (not just the RED though) for the fact that people do still shoot on film. And last time I looked, some pretty humungous-budget features have been shot on video.

 

As a general rule of artistic endeavour "horrendous piece of crap" generally tends to translate to "something the likes of me (ie not myself, yourself)could never in a million years hope to even come vaguely close to emulating".

 

That sad fact is, the average Fanboy/Wannabe would have trouble putting together a coherent cornflakes commercial, much less something people would actually pay to watch.

 

An impossible project is a handy substitute for a life, it's true :P

 

By the way Tom, how is your bet coming?

[Tom Lowe]

Keith, you might have missed my point. I was saying that you cannot blame a bunch of kids running around with Canon 7D cameras for the bullshit movies Hollywood continues to put out.

 

And, yeah, the bet seems to be coming along rather nicely, despite the year+ long delay in Epic. My friends in LA tell me Reds, Alexa and other digital cameras have taken over entire the town. Especially Reds. ;)

[Keith Walters]

My friends in LA tell me Reds, Alexa and other digital cameras have taken over entire the town. Especially Reds. ;)

Hang on there.

You'll have to forgive my ignorance; I do live on the other side of the world.

 

The only movie making centre I both know about and know people there, and has the initials "LA", is Los Angeles, on the Pacific side of the US if I remember correctly.

 

But from what you said, there must be another centre of cinematic excellence somewhere which also has the initials "LA" with quite different standards of what constitutes "excellence".

Damn that's confusing.

 

So what's this other "LA" you're talking about? Or do you mean Latin America? (And how come nobody there speaks Latin?)

 

Waidaminnit!

"have taken over entire the town"?!!

 

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

There goes the neighbourhood.... :lol:

[John Sprung]

There are plenty of photographers, like Ansel Adams, who needed no knowledge of lighting for literally any of their professional work.

 

I don't think it's accurate to say that Adams was ignorant of lighting, or that he chose to ignore it. Instead, the scale of his subjects was such that he really had no choice but to wait for natural light to do what he wanted. No doubt he knew from experience the path of the sun, and took his chances on overcast and clouds, waiting, waiting, and only shooting what met his standards.

 

That being said, of course, you're right that he wouldn't have known how to tell a grip to set a net.

 

 

 

 

-- J.S.

[John Sprung]

Allow me to repeat for the fourth time: they don't "take two exposures at different times", they sample (read) the same exposure twice. Combining those two samples is pretty straightforward, because they both come from the very same exposure!

 

Let's look at this using some numbers which may clarify why it doesn't make much difference. Suppose we start with 25 fps (easier to work with than 24), and a 180 degree shutter for the long or full exposure. This gives us an exposure of 1/50 second, or in an easier form, 20 milli-seconds. Suppose we want a three stop difference between the long and short readings. Three stops is a factor of 8, so the short reading/exposure/whatever would be (20/8) msec = 2.5 msec.

 

According to the given explanation, the short thingy overlaps the first 2.5 msec of the long thingy, which then continues for another 17.5 msec.

 

If, instead, the two were done consecutively, with little or no gap between them, you'd have a highlight thingy of 2.5 msec immediately followed by the shadow detail thingy of 20 msec, for a total of 22.5 msec, instead of 20 msec.

 

If you looked very carefully at the image of a uniformly and rapidly moving point source, you might be able to detect the difference between overlapped and consecutive thingies. Other than that, visually, the difference doesn't much matter.

 

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.

 

 

 

 

-- J.S.