Iris confusion

M

makeall6

Member
Here is what I don't get. I just returned from a shoot and had the camera in auto iris. I was shooting someone at a podium and it looked dark but the iris was not all the way open. That isn't right. So I threw it in manual, opened it all the way up and it still looked dark. Then I went full auto and all looked great. Back at it studio the footage looked OK but with a bit of noise since full auto must have upped the gain. Coming from a traditional broadcast camera I am a tad confused with iris protocols on the 200. Also, I was shooting an interview yesterday, had two lights on the subject, auto iris, it was NOT open all the way but could not get a 70% zebra anywhere on the subject's face. I just don't get it. Any help will be greatly appreciated. Shooting 1080p 59.94 shutter at 60fps. ( that shutter concept still bothers me. On my old camera I just turned the shutter off. But this camera it always seems on at 60fps. But Barry says that is normal and fine.)

Best.
Tom
 
Here is some info from an article I read awhile back that explains how the iris changes as you zoom in or out. It will not stay at a fixed value when you zoom:

Fixed lens cameras are a balance between focal range, convenience and optical quality. The LEICA DICOMAR lens on this camera is definitely a compromise between the three. The lens has a variable aperture of F2.8 to F4.5, depending on the focal length. Unfortunately the lens only stays at F2.8 at the very wide end of the focal range. As you zoom in the lens aperture ramps almost instantly, and it isn’t until you go beyond 84.6mm (185mm in full frame 35mm film equivalent) that it remains constant at a rather slow F4.5. Below is a list of focal ranges where the aperture value changes on the lens:
 
makeall6 said:
Here is what I don't get. I just returned from a shoot and had the camera in auto iris. I was shooting someone at a podium and it looked dark but the iris was not all the way open. That isn't right. So I threw it in manual, opened it all the way up and it still looked dark. Then I went full auto and all looked great. Back at it studio the footage looked OK but with a bit of noise since full auto must have upped the gain. Coming from a traditional broadcast camera I am a tad confused with iris protocols on the 200. Also, I was shooting an interview yesterday, had two lights on the subject, auto iris, it was NOT open all the way but could not get a 70% zebra anywhere on the subject's face. I just don't get it. Any help will be greatly appreciated. Shooting 1080p 59.94 shutter at 60fps. ( that shutter concept still bothers me. On my old camera I just turned the shutter off. But this camera it always seems on at 60fps. But Barry says that is normal and fine.)

Best.
Tom
Click to expand...

Hey Tom,

If you're going to take the time to light your subject, you're probably going to want to turn off the auto iris and manually expose to get the look you want.

Can you explain what you mean by turning the shutter off and that it always seems to be at 60 fps? Did you mean turning the auto shutter off? and 1/60?
 
Also remember the Target Brightness that we talked about a few weeks ago that's built into every scene file. Take a look at that and see what it's set for in the scene that you were using. Maybe it's set low on the scene that you were using.
 
Thanks Brad. What I mean by shutter is on all my previous cameras ( last one was a JVC 700U with Fuji glass ) you could turn the shutter completely off. The 200 you cannot. So Barry Green stated that with the 200 the shutter is never really off but as long as you keep it at 60fps if you are shooting 59.94p then the shutter is basically off anyway. He explained it well but I guess I still don't fully understand. So, the bottom line is that when I shoot indoors with lights, the image just seems dark. Waveform at about 60 IRE.

Thanks.
Tom
 
The shutter is a way to artificially limit how much light gets into the camera. When the shutter is set to "off", there is no artificial limit and the maximum amount of light flows (as in, the maximum that's possible at the given frame rate).

For any given frame rate, there is a maximum amount of time that light can flow in. When shooting at 30 fps, the maximum time is 1/30 of a second. When shooting at 60 fps, the maximum is 1/60. That's just the laws of physics. The shutter cannot be open longer than the frame rate of any given frame. So if you shoot 60p at 1/60 shutter, that is identical to having the shutter off. The shutter is not shutting, it's not limiting the light flow. When shooting 24p, the maximum amount of time the shutter can be open is 1/24 of a second.

You can set the shutter to a shorter duration (i.e., 60 fps at 1/250) and that's fine. The shutter will prematurely cut off the flow of light, making the image darker and giving less time for motion blur to accumulate.

If you turn the shutter "off", you disable that limiting capability, and the maximum amount of light will flow, and the maximum amount of motion blur will accumulate. But, again, the maximum amount of time is the reciprocal of the frame rate, so at 48 fps the maximum longest shutter speed possible is 1/48; at 120 fps it's 1/120, etc.

Therefore, if you're shooting 60p and you manually set the shutter to 1/60, you will be accomplishing the exact same thing as turning the shutter off.

Now, you can also select a special "slow shutter speed" mode, where (for example) you have footage at 60 fps and a shutter speed of 1/30. Physically that's not possible, so the camera "cheats" - you don't actually get 60 discrete frames per second in that case. The camera will hold the frame for the full duration of the shutter speed, and then will write out as many frames as it can, but it cannot and will not produce 60 distinct frames in that case. Instead, you'd get 30 distinct frames, each one duplicated in the video stream.

For maximum light flow into the camera you want to set the iris to maximum open, and turn the ND filter switch to OFF, and establish as slow a shutter speed as is appropriate for the type of video you're shooting. If shooting UHD/60p or 1080/60p, set your shutter speed on 1/60th.

For the most-open iris possible, set the camera on as wide a zoom setting as you can get. The iris will be f/2.8 at full wide angle, but if you zoom in to 90mm, the iris will be a maximum of f/4.5, so setting the lens wider can get you up to 1.333 stops brighter exposure.

If you need the images brighter than what these settings produce, you have four more options:

1) turn up the gain or ISO to achieve sufficient brightness. More gain will result in more grain in the image though.
2) use the HIGH SENS mode. This will double the brightness while keeping the noise in check.
3) use a slower frame rate, which will let you open up the shutter more. 30p allows a 1/30 shutter, which is twice as bright as 60p's 1/60th. 24p allows a shutter as low as 1/24, which is 2.5x as bright as 60p's 1/60th.
4) use the slow shutter speeds. Slow shutter speeds will cut your effective frame rate and will make your motion blurrier, but they will let more light in. You can take the shutter as low as 1/2 second, but when you do so you get an effective frame rate of just 2 fps, so everything will be super smeary and super blurry. But man, will it be bright!
 
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Why is it then that so many people say that you should set your shutter to twice the speed of your frame rate? Seems like I have been doing the wrong thing for years:) I have never tried this, but instead blindly followed that rule...is there any visual difference besides a loss of light ?
 
Because the shutter speed effects not just your exposure, but your motion blur. The 180 degree rule, or "doubling your frame rate" produces the most natural looking movements.
 
I took Barry's advice from an earlier thread and he also mentions this in one of the tutorial videos. The dvx200 has the option to display either shutter speed or angle, so if you set the angle 180 degrees, it eliminates the need for resetting your shutter speed if you're changing frame rates.
 
SO, If you set the DVX200 to angle, then you should double the shutter speed of the frame rate? When using angle and you want to blur water falls, or fast moving action, lower the shutter speed, like if your shooting at 24FPS, then set your shutter speed to 1/40th instead of 1/50th, right?
I'm so use to the 180 rule, what is the benefit of shooting the other way?
 
Thanks Barry. That is a great and very informative explanation. Thanks again. You need to travel the country for Panasonic and offer seminars.
 
So Barry, I apologize if I sound like a broken record but just so I am clear on this shutter issue. On the 200 there is no way to actually turn "off" the shutter with a switch or menu item, correct? I now do understand that having the shutter speed at 60 when shooting 60p is the same as having the shutter off. I was just so used to just "turning" the shutter "off" with my previous cameras. Thanks to you and everyone on this forum.
 
Brad Forman said:
Because the shutter speed effects not just your exposure, but your motion blur. The 180 degree rule, or "doubling your frame rate" produces the most natural looking movements.
Click to expand...
If shooting film-like footage, yes. If shooting video-looking footage, then no, this advice is absolutely wrong and should not be followed.
 
greytail said:
Why is it then that so many people say that you should set your shutter to twice the speed of your frame rate? Seems like I have been doing the wrong thing for years:) I have never tried this, but instead blindly followed that rule...is there any visual difference besides a loss of light ?
Click to expand...
Because lots of people confuse two different things and don't know what they're talking about, generally. Hate to be harsh, but that's the way it is -- people pick up something and then just repeat it without understanding the root reasons why.

If you're shooting FILM-style footage, then yes, doubling the frame rate with your shutter results in the most film-like motion. Film cameras have (generally) 180-degree shutters, which means the frame is exposed for half of its duration. 24 fps footage is exposed at 1/48, 30fps footage is exposed at 1/60, etc. That is fine and appropriate if you are shooting film-looking footage.

But video is not that way and hasn't been. The look of "video" - the "live" or "reality" look of news, sports, events, etc, has always been 60 fps at 1/60th. If you double the shutter speed to 1/120, you are unnecessarily throwing away half your light and getting unnecessarily stacatto movement.
 
Brad Forman said:
I took Barry's advice from an earlier thread and he also mentions this in one of the tutorial videos. The dvx200 has the option to display either shutter speed or angle, so if you set the angle 180 degrees, it eliminates the need for resetting your shutter speed if you're changing frame rates.
Click to expand...
Yes, that's entirely appropriate for shooting slow-mo, as the shutter speed ramps with the frame rate.
 
7DDude said:
SO, If you set the DVX200 to angle, then you should double the shutter speed of the frame rate?
Click to expand...
If shooting film-style footage, yes. If shooting video-style live footage, this would be a poor decision and would unnecessarily cause losing 1/2 of your light.

When using angle and you want to blur water falls, or fast moving action, lower the shutter speed, like if your shooting at 24FPS, then set your shutter speed to 1/40th instead of 1/50th, right?
Click to expand...
Yes, although "lower" could be confusing, so I'd rather use "lengthen". The longer the exposure time, the blurrier the footage will be.

I'm so use to the 180 rule, what is the benefit of shooting the other way?
Click to expand...
The benefit is that when shooting video footage, you'll get twice the light and proper (familiar) motion rendition.
 
makeall6 said:
On the 200 there is no way to actually turn "off" the shutter with a switch or menu item, correct?
Click to expand...
That is correct. The only way to disable the effect of the electronic shutter is to set it to the reciprocal of the frame rate (i.e., 1/60 for 60 fps, 1/24 for 24 fps). There is no separate "shutter off" button or switch or function.
 
Barry, so you are loosing light when shooting in the Angle Mode & Doubling your shutter speed? How do both of these modes affect V-Log? I understand what V-Log is and basically how and why. So could you benefit shooting in shutter mode for more light and being set to V-Log to allow you to grade and make adjustments in post? Would you still get a film look or would the shutter mode defeat that purpose being a video looking mode?
 
The shutter doesn't determine whether something is "film-look" or "video-look"; that is done primarily through the frame rate. And the look that we have known over the last century as the "film look" is 24 fps, with a shutter somewhere between 150 to 220 degrees, generally settled on 180 degrees.

On the other hand, the look we all recognize as the "video look" is due to 60fps (either fields or frames) video shot at generally a 1/60th shutter. That's the "live" look, the "looking through a window" look.

Neither has anything to do with V-Log. V-Log is neither "film" or "video", it is just a different way of working, in which you delay all grading, color, and contrast decisions to post-production. V-Log is generally used more for those wanting a film look, yes, but it is more likely due to the anticipated post-production workflow than any other factor; "live" footage doesn't generally undergo a lot of post production; sports and news and events are usually delivered as they were shot, whereas film-style footage is generally anticipated to undergo more post-production, and since V-Log requires substantial post-production to make it viewable and attractive, it is naturally therefore more associated with "film"-style footage. But there is no requirement. You could shoot UHD 60p in V-Log if you wanted to, there's nothing stopping that.
 
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