5D Mark II Shutter Exposed! (Part II)

[Mark Hahn]

Originally Posted by Jon Fairhurst

The longest possible shutter would be 1/30 minus the read-reset time, which your test shows to be 23us (1/43410 seconds.) The result? 1/30.02. The question is, what did they implement?

Regarding faster shutter times, they are useful for special effects. The Normandy scene in Saving Private Ryan is one of the more famous examples.

In fact, we just used a fast shutter the other day when I was cutting steel with a ceramic saw blade. Sparks were flying all over the place! With a fast shutter, the sparks have enough of a tail to show motion, but they come and go in a random way. A long shutter would give long tails and a different, smoother feel. Personally, I liked the fast shutter. It's more brutal. ;)

I don't think you need to test them though. My test shows that we get fast shutter speeds that line up fairly well with what the camera shows. I don't really care about an accurate number. Just dial it up to get the specific look you want for the specific situation. In general, we can only crank it as fast as the light allows anyway.

I don't really need to test anything but this damn thing has gotten me obsessed.

By coincidence with your comment about it being able to go all the way to 1/30, I just measured a real 1/30 exposure time (to within my accuracy). I don't know if my previous 1/33 was a bad measurement or if there is variance. I think I forgot this time to lock the exposure so I'm redoing it. It was a dark background and if I forgot to lock the exposure that may have something with going all the way to 1/30.

By the way, it is really easy to tell when you get the full 1/30. The place where the band starts on the first frame is where it ends on the second. That means there is exposure happening even when the reset/read lines are off the screen (of course). Data would then be pouring out 75% of the time (when the read lines are on-screen).

P.S. I put this in the other thread by accident at first. I want to keep that thread short and just post final results there. Maybe it was stupid to start that thread. Especially if those results turn out to be wrong.

[Jon Fairhurst]

Originally Posted by Mark Hahn

This time I was holding the flash next to the mic and I saw no difference between sound and frames.

Thanks for confirming it.

We bash Canon for the strange frame rate and no manual control, but in all fairness, they got a lot of stuff right with this camera.

[Jon Fairhurst]

Originally Posted by Mark Hahn

1309 lines would be an exposure rate of 1/33. This makes quite a bit of sense if you think they designed it to get as close to 1/30 as they possibly could. They only missed by 10%.

This agrees with my gut feel. When recording stuff in really dark conditions, the camera immediately goes to 1/30 @ 3200 ISO. And it looks much more smeared than normal video from the camera.

There was a guy here who complained that his night video looked horrible. He pointed out the noise, but it was probably the frame rate that was the most irritating, assuming there was motion or that the camera was handheld.

The moral of the story is to get the fastest lenses you can for night shooting and find just enough light to get 1/40 (displayed.) If forced to run 1/30, put the camera on a tripod immediately!

If it can do 1/33, why did it do 1/50 when the read-out was 1/40. Weird.

I'm thinking that the engineers were shot and the product shipped. This seems like a classic "ran out of time" compromise. It's also possible that they ran out of firmware storage space.

I'm going to redo 1/30, 1/40, and 1/50 in multiple recordings to see if I can get them to vary.

One variation to consider is Highlight Tone Priority. That setting changes the base ISO from 100 to 200. It's possible that it messes with the shutter as well.

[Jay Bloomfield]

@Mark,

Thanks for working so hard on this issue. I said that when the 5D2 came out, that: a) it probably would try to shoot at 1/60, if it could and b) it probably could shoot at 1/30 in low light conditions. Given the 30fps frame rate (and assuming the engineers weren't all shot too soon), that's how it would be designed. The only thing it can't do is to emulate shutter speeds below 1/30. Most camcorders do this by frame accumulation. But given the incredible low light performance, frame accumulation would just be a nice special effect, just like the Pvt. Ryan high shutter speed stuff would be. Basically, for video, you're mostly in the 1/30 to 1/125 range anyway, so the 5D2, even without manual control, does a pretty good job.

[Jon Fairhurst]

Originally Posted by Jay Bloomfield

...The only thing it can't do is to emulate shutter speeds below 1/30. Most camcorders do this by frame accumulation...

Of course, we can accumulate frames in post just as well as it could be done in the camera, so it's a feature that we don't really need.

Manual control and 24/25p on the other hand...

[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?

It might be nice.

[Chris Barcellos]

So this makes me wonder how close are other camera rigs to their stated settings. For instance, when my Sony FX1 is set a 1/60th and aperature 5.6, am I really getting exactly that, or is Sony ballparking it too ?

And even in a film camera , aren't there variances from camera to camera, to some degree, depending on physical state of camera,

[Bill Binder]

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?

Nope, no one has thought of or actually asked Canon to do anything like that. Brilliant idea!

[Bill Binder]

.................

[Greg Joyce]

Originally Posted by Bill Binder

Nope, no one has thought of or actually asked Canon to do anything like that. Brilliant idea!

Bill and Jay,

I thought that was a great idea -- and it seems do-able via firmware without eating into Canon's camcorder business -- so I forwarded it to Canon support telling them so. I've already got my Nikon manual primes so this would be a nice improvement to the workflow.

And, like I said, pretty do-able, right? I mean it seems like an eminently reasonable request.

[Jay Bloomfield]

Originally Posted by Chris Barcellos

So this makes me wonder how close are other camera rigs to their stated settings. For instance, when my Sony FX1 is set a 1/60th and aperature 5.6, am I really getting exactly that, or is Sony ballparking it too ?

And even in a film camera , aren't there variances from camera to camera, to some degree, depending on physical state of camera,

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.

[Greg Joyce]

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?

Originally Posted by Greg Joyce

Bill and Jay,

I thought that was a great idea -- and it seems do-able via firmware without eating into Canon's camcorder business -- so I forwarded it to Canon support telling them so. I've already got my Nikon manual primes so this would be a nice improvement to the workflow.

And, like I said, pretty do-able, right? I mean it seems like an eminently reasonable request.

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...

[Mark Hahn]

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.

[Jon Fairhurst]

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!

[Mark Hahn]

Originally Posted by Jon Fairhurst

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.