I suppose there is really no way of knowing for sure. However, with HDV camcorders, the aperture, shutter and gain are stored with the frame-specific metadata and there is software that will display the information as the video is played. There is a lot of free stuff, but the one payware program that does a nice job with HDV files is:

DVMP Pro 3 - view and edit date/time stamp, datacode/datecode, timecode, and camera exposure details in HDV and DV AVI files

But all we can say for sure, is that what is displayed in RT on the HDV camcorder's LCD matches up against what is stored in the file. I do know that for a variety of consumer and prosumer HDV camcorders, people have made careful studies of how each mode (including "locking the exposure" tweaks) work. When I mean "mode", I mean things like "Auto", "Tv", "Av", "Fireworks", "Spotlight", "Sunset", "Cinema", etc. People have figured out the algorithms that the camcorder uses to vary gain, shutter, aperture and internal variable ND filters.

Maybe someone with a Mac knows of a software package that can display the frame-specific metadata for QT MOV files, but I've never seen one. All I've seen are metadata editors that display and alter the header metadata.

response from Canon
 

Originally Posted by Jay Bloomfield:

In all the clamoring for manual control and 24/25p, has anyone suggested that maybe Canon should modify the firmware so that: a) the correct shutter, aperture and ISO are displayed in the video mode and b) that this same information is preserved in the MOV file in the frame-specific metadata?

Well it seemed like a reasonable request to me.

From Canon:

Thank you for contacting Canon product support. We value you as a Canon
customer and appreciate the opportunity to assist you with your EOS 5D
Mark II.

There are currently no plans to add additional video support to the 5D
Mark II, however, future cameras may offer more features.

We have forwarded your suggestion through our Customer Feedback process...

bad news
 

Getting back to the original topic, I've got some really bad news. I had hoped that the actual speed used was at least a fixed function of the locked readout. That is far from the truth.

I tried another series of videos comparing the locked readout values to my values measured with the strobe flash and here are the results. Note that they were shot in this order, exposure was always locked, light was varied often after the lock. I spoke the locked readings at the beginning of each video so I am confident the results are accurate.

For some reason during this run the slowest speed was 1/33 instead of 1/30. I've seen this before.

ISO speed measured

1431 200 40 33.33
1435 100 40 50.05
1435-2 100 40 50.05
1436-1 100 50 100.21
1436-2 100 50 99.98
1437 100 60 99.75
1438-1 100 80 99.98
1438-2 100 80 100.21
1439 100 100 107.96
1440 100 125 140.10
1441 100 160 166.50
1442 100 200 197.67
1443 100 250 215.37
1444 3200 25 33.27
1445 3200 30 33.27
1446 3200 40 33.20
1447 2500 50 33.10
1448 1600 150 33.17
1449 800 150 33.17
1450 800 40 33.17
1451 100 40 49.82
1452 125 40 33.??
1453 400 50 33.??
1454 100 320 300.63
1455 125 40 33.??
1456 100 40 49.76
1457 100 50 98.16

Note that things are somewhat predictable at ISO 100 and when I varied it by starting at 100. When I started at 3200 and 1/25, the speed seemed to get "stuck" at 33, which is worst-case blur.

When using impossible readouts like 1/25 I showed in another thread that it varies the ISO without telling you. So I suspect that when it was stuck at 33 it was actually varying the ISO for each reading. I wish I could accurately measure ISO like I do the speed.

The worst news is that you can't trust any particular speed reading to give you a reasonable speed. 30, 40, & 50 can give you 33 which is horrible. 50 can give you anything from 33 to 100, which is also horrible.

The only thing totally predictable is that 25 and 30 will give you 33, which makes sense. Starting at 100 may be predictable. That would mean that the flashlight trick would work, but holding your hands over the lens wouldn't.

If I had an infinite time to spend on this, I'd try a series of runs where I start at 100, 200, 400, etc. and then for each ISO I'd go from 1/30 on up. In other words I would be looking to see what ranges of ISO give predictable results.

Great work, Mark! (And, as you wrote, "bad news.")

One surprise is that 1/50 (displayed) is yielding 1/100. That's different than earlier tests that showed 1/40 and 1/50 to have the same result of 1/50 (or with my tests, ~1/45). Any ideas why this might have changed?

From what I see, the worst news is that when the ISO increases above 100, the shutter speed displayed is irrelevant. It's always a mushy 1/33. The only solution is to throw enough light at the subject to get 100 ISO and 1/40 displayed. That gives an actual 1/50, which is as close as we can get to a film look shutter.

I assume that you had Highlight Tone Priority turned off. If you don't mind one additional test, you might check 1/40 and 200 ISO with HTP turned on. From what I understand, HTP moves the base ISO from 100 to 200 in movie mode.

The bottom line is that we'd want to shoot outdoors with HTP off and enough ND filters to hit 1/40. When we go indoors, we'd want to turn HTP on, take the ND filters off and throw enough lights at the subject to get 1/40 and 200 ISO - assuming that we get the desired results from further testing.

Again, thanks for your efforts!

I think one reason my results varied so much is that after locking exposure I would often change the lighting. I think this may have kicked in the "hidden ISO" changing, although if exposure was locked I have no idea why anything should change.

I use C3 for all video shooting so I no I have no weird settings like HTP. I see no reason to complicate things until I get something repeatable and understandable.

In any case, the 1/50 result in your recent test is at odds with the previous tests - by 2:1. I can't quite get my head around that one.

Understood. Get a good foundation and then add no more than one variable at a time.

Still, HTP seems like it might be a helpful tool.

Also helpful is knowing what settings don't matter. For instance, knowing that anything over 100 ISO displayed is actually 1/33 means we don't have to sweat getting the light just right so we get 1/50. That can save a lot of time on the set. Just dial the ISO above 100 and shoot.

Holy Cow, I didn't notice that everything above ISO 100 was 1/33. That is really extreme. I went to my earlier data and noticed I had shot everything at 100. I guess they are trying to keep the ISO at a minimum. So they use whatever ISO they have to for correct exposure at 1/33.

I wonder how bad 1/33 looks? It certainly isn't anything we had wished for.

Almost everything that you've seen from the 5D MkII that's not outdoors during daylight has apparently been shot at 1/33.

No wonder people have been complaining about a non-film, soap opera look. It's not just 30p; it's a ~325 degree shutter!!!

Not only do we need fast lenses, we need lights! (or sunshine.)

Or a 360 degree shutter. The test before this last one was giving me a full 1/30 speed. I could hold my finger on the lcd where the band started, advance one frame, and see the band end at exactly the same place. This time there was the small (10%) difference in position when I held my finger there.

That would mean LaForet's video was all 360 shutter. I'm going to go back and look at his blur.

I wonder if the difference between 1/30 and 1/33 was some kind of compression time problem. This last test was of a blanket with a fuzzy pattern and the 1/30 result test was a blank wall.

Once again I am totally confused.

I looked at the Laforet first scene where the guy crosses the screen to kiss the girl. It was a dark scene and no lens could have allowed enough light to get to ISO 100.

If the exposure was 1/30, then I should have seen blur as wide as the distance he moves each frame, right? The blur was much smaller than that, maybe one fourth (90 degrees?). His hand moved 22 pixels and the blur on his sleeve looked like about 6 pixels.

P.S. I don't see how it could make any difference but this latest test was locked at f1.4 and the previous was locked at f5.6. Could the algorithm behave differently when we lock (electronically isolate) the lens?

P.S.S. Looking at the numbers closer (I used excel this time), I found that the strobe lasted about four lines. The smallest number of lines in a fast band was around 300 so that source of error was small.

P.S.S. Could my test be flawed? When a fast strobe can fill the entire screen with light, which happens often, that means it exposes for a long time, close to the 1/30, right? How can this thinking be wrong?

I have an idea. I'll do my flash test and then in the same scene wave my hand in front of the lens or get some other kind of motion in. Then I can compare the blur to the speed.

Mark:

Very interesting data coming out of your experiments. Now, you're probably going to hate me for this, but I assume your tests have been performed with Nikon lenses to take focal length out of the equation. Maybe you should try again with canon lenses and different focal lengths and that might throw very different data your way at iso speeds higher than 100. If that works out to be correct, canon effectively worked out a system to really prevent us users from ever hoping to have any sort of manual control. If you use nikons to control aperture, shutter speed effectively goes out the window at iso's higher than 100. Use canons and shutter becomes predictable but only as a function of focal length and aperture is fixed at certain positions.

The only way we could ever hope to effectively control shutter speed would have to be by tricking the camera into thinking the lens was always fixed at the focal length that gives us the shutter speed we expect. Maybe a custom nikon mount that somehow faked canon lens info into the camera? :)

P.S. Laforet shot usng canon glass.

I have used a Canon 35mm 1.4 for all tests. On the next-to-last test I had it locked by rotation to 5.6. On this latest test it was locked at 1.4.

Are you saying that maybe my results are the way they are because it doesn't know the focal length? I will try a quick run without locking/rotating the lens. If it changes my focal length it won't really matter for the purpose of this test.

No, what I'm saying is that the camera might be trying to adhere to the 1/focal length rule to set your shutter speed. Since your lens is a 35mm lens, the camera might be trying to stick to 1/35 which sounds plausible, given your 1/33 results. The same battery of tests might yield diffrent results with:

a)Unlocked lens
b)Longer focal lengths, like a 50mm, 85mm or a 135mm

Mark employed the lens twist method (as I understand it) so the camera was unaware of what lens he used. As such, the 1/focal length rule should not be a factor.

Mark, I just want to say thanks for doing this work (and Jon before you)... Like many others, I'm following this with great interest. Very very useful!

If you don't untwist, the camera will use 1/focal length for video recording. I rarely shoot less than 50mm, so everything's fine even in low light.

Isn't it true though that sometimes the camera will switch f-stop while shooting if the lens is not locked (rotated)?

P.S. As I said before, all my tests before now had the lens locked (rotated).

This means giving up aperture control, and allowing the camera to dictate shutter - not fine for me at least. Shooting at say 135mm is a joke under these conditions.

After three months switching between EF and Nikkor lenses on the 5D, I find Nikkors are the only way to go for the control I need. I find the numbers posted in this thread invaluable.

It's tricky to get the f-stop where you want it, but once there you can lock it (for one take! then go through the process again). However, the shutter will vary with focal length. I think your work is all about gaining control of the camera through better understanding the shutter (and readouts). I think the way you've gone about it (rotated) is correct. This is the only means (along with using Nikkors) that we can do serious work with the camera. Perhaps the one exception to this rule is when shooting with EF lenses in the 50mm range, where they will shoot 1/50th.

I haven't been able to test this because I'm still waiting for my 100-400 to arrive, but IIRC the camera doesn't go faster than 1/125s at any focal length, which would be a 90° shutter angle. I can live with that. Dodging the 360° shutter is my main interest.

It is a false rumor started by Canon in their manual.

I showed on page 3 of this thread it going to 1/300 and others have shown even higher. Think about it, if can only go down to ISO 100, what can it do if you put more light in? It has to go to a faster speed. It has no choice.

More bad news ...
 

I did a really quick run with just one setting. I put on my 24-105 lens and set it to c3 (my standard video setup). I noted that as I changed the focal length the speed reading would change to match, verifying what people have said.

I then set the lens to 105mm and locked the exposure. My readings were locked at 1/125 second, f4, ISO 1600.

Then I started the video. It ran for about 20 secs and then got darker by at least one stop. I don't know what changed. My setup didn't appear to change.

The 1/125 speed setting was ignored. It used 1/33 second constantly before and after the brightness change. So the readings are pretty much ignored even after locking them.

I would need to do more tests but I suspect the discovery that it always uses the slowest shutter when over ISO 100 is true even when the lens is not locked and the focal length is long.

And you can forget about the 1/focal length rule. It is definitely ignored after the video starts.

Nice work Mark. Once your findings are definitive you'll need to do a "5D Mark II Shutter Exposed! (Part III)' thread and get Chris to lock it down as a sticky.

This knowledge is essential!

Good news!
 

I made some similar tests to Mark's, and the results basically agree. Unfortunately, my flash is slow (it turns on within a line or so, but fades slowly at the end.) Because of this, I just did rough line counts, eying the point at which the light started to fade. Sure enough, 1/40 displayed yielded 1/49. 1/50 and 1/60 yielded 1/93. I'll defer to Mark's numbers, as his flash is crisper.

The really good news is that my tests were done with HTC (Highlight Tone Priority) enabled. That limits the ISO to no lower than 200. I also captured two videos - one with HTC on and another with it off. Sure enough, the gain is roughly twice as high with HTC enabled.

So, what does all this mean (assuming Nikon or untwisted/mylar lenses)?

1) When shooting in low light, just dial the ISO to whatever you need. (by low light, I mean above 100 ISO normal or above 200 ISO with HTP enabled.) This will give you a consistent 1/33 (or so) shutter. Yeah, it's mushy, but you'll have no problem editing your stuff together.

2) When you want something closer to a film shutter outdoors or with lots of power, adjust for 1/40 and 100 ISO. Add ND filters as needed. It's not 180 degrees, but it's close (216 degrees.)

3) When you are shooting indoors, you can get an extra stop or so and maintain the 1/50 shutter by enabling HTP. Set to 1/40 and 200 ISO.

4) The camera supports faster shutter speeds starting at 1/100 with 1/50 displayed. Frankly, there's some conflicting data at 1/50, I'd adjust to 1/60 to be safe. At faster speeds, you can simply dial for exposure, or do tests to see if you are getting the result that you want. I'd lean toward practice, rather than numbers and theory.

BTW, to achieve HTP, go into the menu and select the custom functions (the Camera icon), use the wheel to select the 2nd submenu (Image), and use the wheel again to select the third variable (HTP). Hit the select button to enable/disable it.

So, filmmakers. Start buying lights or shoot outdoors, if you want a film-like shutter speed.

I'm happy to see I wasn't crazy. I am still pi**ed off that we are stuck with 1/33 at night.

But how did Laforet get low blur at night? I still want to do the combined strobe flash with moving object (blur) test. I can do the flash and then move something, like waving my hand.

I'm wondering the same thing. I'm also wondering why the flash test shows 1/50 grouped with 1/60 (displayed), yet my turntable test and your fan test grouped 1/50 with 1/40.

We've got some more digging to do...

I apologize but the whole Laforet blur problem was nonsense. I calculated it wrong before.

It takes him 2 seconds to walk half the width of the screen. That is 16 (960/60) pixels per frame. His blur was close to that amount.

So we have pretty much done everything we can to understand the behavior of the camera with the f-stop locked. I'm sure it wouldn't be much harder to understand how the unlocked f-stop behaves also but I don't really care.

It behaves two ways depending on whether the ISO reads at 100 (200 with htp) or not. At ISO 100 the speed takes on a finite number of values depending on the speed reading which we can show in a table. Above ISO 100 the speed is always 1/33 (or 1/30).

I would like to point out that it misbehaves at times. I usually see 1/33 as the slowest speed, but I definitely saw a full 1/30 for at least one scene. Entries in the speed table for ISO 100 will vary. The reading 1/50 has shown both 1/50 and 1/100.

I suspect the variance it that even with the exposure locked, the camera feels free to change readings when the video starts. So if a reading is borderline, it can change when you start rolling. Locking the exposure works but that is all. It doesn't lock anything that makes up the exposure. We will just have to live with that.

Now that I am done studying this all I can say in summary is that the control of the video sucks more than I expected. I guess I will be shooting with a locked aperture using Mylar and with a constant speed of 1/33.

The only silver lining in this cloud is that we know 1/33 looks good in the video we've seen everywhere. Maybe that is part of the "lushness" we see in the video. I guess the zealots that want the "film-look" are just screwed. There is no way that I can see how you could reliably get the same 1/50 or even 1/60 in every scene.

Jon, you are a good writer, do you want to write the "Ultimate guide to 5D2 exposure behavior" and put it on your blog? We could all double check it and then post links to it. I don't have a blog and I think the info should be posted somewhere permanently.

I think the manual describes when the f-stop is changed so that could be thrown in also, even though the manual lies here and there.

one more optimistic thought
 

Maybe having all night/dark shots at 1/33 and all day/bright shots at 1/50 would not be such a bad thing. Cutting between two such scenes is going to look different no matter what. Dark scenes could be lush and bright scenes could be sharp, timing-wise. It may look quite good actually.

Is really the 1/focal length rule true? I mean as in, the shutter speed will be 1/50 when using a 50mm lens? Why is that? It doesn't make any sense?

Any way. If it actually is true why not just attach an af confirm chip to the adapter(nikon, m42 or what ever) which is programmed to tell the camera a 50mm lens is attched?

EDIT:
Ok... to hasty there. Will read this thread through properly now. :)

If you look back a few posts in this thread (I know it is hard to read) you will see that the 1/focal length is applied to the reading reported at the bottom of the screen, but that reading is totally ignored once shooting has started. So the whole rule is a non-issue.

So I was trying to come up with some simple rules based on what you guys have come up with. I think I would like a bit more clarity in the findings you've developed, and I am wondering if this fits:


When shooting video with Nikon lenses or any lens where you are setting aperature manually:

Rule 1. Camera shoots at 1/33 of a second, any time the ISO is above 100, or above 200 with HTP mode adapted. There is no way around this no matter what shutter speed reads out on the LCD.

2. At ISO 100, or 200 with HTP set, you can adjust shutter speeds higher.

a. 1/40th gets you close to a 180 degree shutter effect.

b. 1/50th and up can get you anywhere from 1/50 to 1/100

Is this where we are at, in simple terms ?

You nailed it.

The actual table for speeds with ISO 100 is ...

Reading, actual

25, 33 ?
30, 33 ?
40, 50
50, 50 or 100
60, 100
80, 100
100 100
125 125
160 160
200 200

60 was measured a total of one time so it may vary like 50. 40 and 50 were measured a lot of times. 80 was measured only twice but it is believable since 60 and 100 agreed.

It would be pretty easy to guarantee 100. It is a shame it is so fast. I don't think it would look good.

It appears that it runs at 50 or 100 at low readings and then runs at the indicated speed above 100. The point where it switches between 50 and 100 can vary.

ReWrite:


When shooting video with Nikon lenses or any lens where you are setting aperature manually:

Rule 1. Camera shoots at 1/33 of a second, any time the ISO is above 100, or above 200 with HTP mode adapted. There is no way around this no matter what shutter speed reads out on the LCD.

Rule 2. At ISO 100, or 200 with HTP set, you can adjust shutter speeds higher.

a. 1/40th gets you close to a 180 degree shutter effect.

b. Actual shutter speed you will get are as follows:

25 -> 33 ?
30-> 33 ?
40 -> 50
50 -> 50 or 100
60 -> 100
80 -> 100
100 -> 100
125 -> 125
160 -> 160
200 -> 200

Is this regardless of AF confirm chip on a nikon lens?

It looks good except for some small things.

2.a isn't quite true and I don't think it really belongs in this kind of reference information.

aperature is misspelled.

Feel free to post this on any forum. Just give Jon and me some credit. Also link to this thread.

Chris, most of what you wrote is true, except this:
It looks like 1/50 displayed yields 1/100, but there is some conflicting evidence here. I'd go with 1/60 or 1/80 displayed for a 1/100 shutter.

And I'd add...

c. Higher displayed shutter speeds (1/125 and up) deliver ever higher speeds, well beyond the 1/125 limit stated in the manual.

Wild guess: If the camera doesn't know the real aperture, and it reports 00, then these results hold true.

I think 1/50 needs to say "50 or 100". I've seen each multiple times, as you have also.

Yes, the table stopped at 200 only because the error in my readings started getting really bad. If you go back to my long table you can see the actual measurements for 250 and 300.

It reports 2.0 with the chip

How's this for a further rewrite

ReWrite Draft 2:


When shooting video with Nikon lenses or any lens where you are setting aperture manually:

Rule 1. Camera shoots at 1/33 of a second, any time the ISO is above 100, or above 200 with HTP mode adapted. There is no way around this no matter what shutter speed reads out on the LCD.

Rule 2. At ISO 100, or 200 with HTP set, you can adjust shutter speeds.

1/25 -> 1/33 ?
1/30-> 1/33 ?
1/40 -> 1/50
1/50 -> 1/50 or 1/100
1/60 -> 1/100
1/80 -> 1/100
1/100 -> 1/100
1/125 -> 1/125
1/160 -> 1/160
1/200 -> 1/200

Rule 3. With a non-aperture control lenses, higher shutter speeds will also be attained, despite Canon indications of limited speed of video at 1/125 for video shooting.

Looks good again.

I'd pull the 1/25 and 1/33. I don't know why I added them. You can't get them at ISO 100. You have to go up to ISO 3200 to get speeds below 40.

Rule 3 has some grammar issues (you don't want grammar Nazi attacks). If you forgive me here is a rewrite ...

Rule 3. With a non-aperture control lens, even higher shutter speeds than the 200 shown can be attained, despite Canon's indication of the limited speed of 1/125.