The 180 Degree Shutter

tuco · 09-22-2010, 11:27 AM - **1 Like**

Originally posted by TheoSixx

...
35mm lens adapters going on the front of a prosumer video camera have a spinning disc between what it produces in light and what the camera's mounted lens 'captures'.
While they do a fair job of enhancing DOF issues, they also rob light and the shooter has to be 'wide open' all the time--- -which, when you think about it, is what shallow Depth Of Field is all about- right?
SO- does it make any sense to pay a couple three grand for a whiz bang adapter like that, when a ND (or two) and opening the iris up all the way can do the same?

Do a fair job at DOF? My experience from using one is they do an excellent job at shallow DOF. They are FF. Yes, it makes sense if you want selective DOF. I've found you will not even come close with prosumer video cameras with ND filters and opening the iris up compared to a 35mm adapter (not counting DSLRs). I have one if you follow the link below.

Not all 35mm adapters are spinning discs. Some vibrate. Some adapters are better than others at the light loss. The one on my vidoe camera loses about a stop. Which is not too big a problem since I shoot with f1.4 and f1.2 lenses on it.

Here is a sample 720p/24 video shot with an 35mm adapter if interested.

Last edited by tuco; 09-22-2010 at 05:06 PM.

excanonfd · 09-22-2010, 10:33 PM

That's a great looking video. The sound effects might have been a bit over the top in the beginning but really good production. Automatic film agitator; could accommodate any roll film sizes and even cut films, looked like a developing tank for 4x5 cut film towards the end of the video. Pretty impressive invention!

Thanks,

tuco · 09-22-2010, 10:50 PM

Originally posted by excanonfd

That's a great looking video. The sound effects might have been a bit over the top in the beginning but really good production. Automatic film agitator; could accommodate any roll film sizes and even cut films, looked like a developing tank for 4x5 cut film towards the end of the video. Pretty impressive invention!

Thanks,

Thanks. Yeah, I intentionally made the sounds over the top

I'm a little disappointed with Vimeo's quality. After about a week they convert it to MP4 and really compressed the heck out of it to the point things are blurry. The original upload was about 480MB and they showed that for a while. Now its compressed down to 176MB. I guess that's what you get with a free account so buck up.

Yes, it does 135, 120 and 4x5 sheet film.

tuco · 09-24-2010, 09:36 AM

Originally posted by TheoSixx

what is is about Vimeo? they must not use real video servers.
you have to hit play, then pause, then wait for the entire segment to load- even then, when you hit play again, it still stutters along.

WOW- what a lot of work went into designing the thing, making the thing, then making the video depicting it all! Nice job.
...

Why thanks. I think it's your flash player on your web browser. I click play and it starts right away.

The machine has times and agitation profiles programmed in to aid developing BW film. I don't have to stand in front of a clock and watch it for say 18 minutes agitating every 15 seconds which can be the case for one of my developers when I'm expanding the dynamic range on the negative, for example. I still shoot film when I want BW because I prefer the look of real BW over imitation, color converted gray scale from my digital camera. Plus mechanical medium format cameras are just plain fun to shoot.

deltoidjohn · 09-24-2010, 10:46 AM

Originally posted by TheoSixx

DSLR's have always been video cameras. The sensors are derived from video cameras. The analog signal traveling from the sensor to the on-board processor is video.

Um, how so? It is one single exposure, so it hardly qualifies as video in any way, shape or form. There is a physical shutter/mirrow block which opens for the duration of one exposure. There is no sequence of images (except in burst mode, but they are processed individually and not as video) and they do not replicate constant motion. Except in the case of live-view, of course.

deltoidjohn · 09-24-2010, 10:59 AM

Originally posted by future_retro

Can someone please elaborate on this? I just got a handycam and it [shockingly, for sony] has shutter priority mode

I'm a total video beginner and while I didn't plan on extensively learning the in's and out's like I did with dslr's, this concept really intrigues me, even though I'm not very concerned with the "film look" for my quick-and-dirty snowboard videos

Sorry I just saw this today, i'll try and expand on this a little for you.

Standard video (PAL or NTSC) is usually 60i or 50i. This means the screen is refreshed 50/60 times every second. With film, and with most DSLR's, the frame rate is 24p so there is less than half as many sampled moments of time per second. When there are more sampled moments, there is less gaps in between movements, so you don't need to blur your images to fill those gaps in the movement.

Here's a very basic visual representation. The dots/dashes below represent how a moving object (eg a tennis ball) would appear as it travels across the screen in different frame rates:

60i (fast shutter) .......................................
24p (slow shutter) ---------------------------
24p (fast shutter) . . . . . . . . . . . . .

With a fast shutter and slower refresh rate, you can see that the object would appear to jump across the screen.

Slowing the shutter down introduces blur, so the object (eg the tennis ball) no longer appears sharp in still images (it should be a circle but now it's a line!) But it gives a much more accurate portayal of where and how that ball is travelling.

With the 60i, even though it is using the same fast shutter speed as the 'jumpy' 24p, it still accurately tracks the motion of the ball because it samples more data.

tuco · 09-24-2010, 08:21 PM

A rule of thumb is the shutter speed should be 2X your frame rate. So for 24fps a 1/48 shutter works out nice, for example. Interlaced video scans twice (odd and even lines) to make one frame.

mwilloam · 11-26-2010, 11:57 PM

Originally posted by tuco

A rule of thumb is the shutter speed should be 2X your frame rate. So for 24fps a 1/48 shutter works out nice, for example. Interlaced video scans twice (odd and even lines) to make one frame.

This "rule of thumb" seems to be misinterpreted as a blanket practice. It is true that most often films shoot with a 1/48 shutter while exposing 24fps but this has to do more with the motion blur alone. a 1/48 shutter is just "a look" as is a shutter of 1/2000. But, for instance, if you're shooting a high speed to slow-mo recording at 1,000,000fps there is no need to have a "180 degree shutter" as 1/,000,000/sec shutter will be enough to capture an image without any blur.

All I'm saying is that the 180 degree "rule" is just based on a common practice in film and broadcast because a shutter of ~ 1/48 -> 1/60 gives the most realistic representation of motion blur and that anything higher starts looking choppier, which can be ok, if used for an effect ie .. "Gladiator" "Private Ryan".

I often use a 360 degree shutter (1/24, 1/30) for low-light/low-movement scenes such as interviews to capture more light with less gain and it looks fine.

09-22-2010, 11:27 AM - 1 Like	#16
tuco Pentaxian Join Date: Jul 2009 Location: Pugetopolis Posts: 11,026	Originally posted by TheoSixx ... 35mm lens adapters going on the front of a prosumer video camera have a spinning disc between what it produces in light and what the camera's mounted lens 'captures'. While they do a fair job of enhancing DOF issues, they also rob light and the shooter has to be 'wide open' all the time--- -which, when you think about it, is what shallow Depth Of Field is all about- right? SO- does it make any sense to pay a couple three grand for a whiz bang adapter like that, when a ND (or two) and opening the iris up all the way can do the same? Do a fair job at DOF? My experience from using one is they do an excellent job at shallow DOF. They are FF. Yes, it makes sense if you want selective DOF. I've found you will not even come close with prosumer video cameras with ND filters and opening the iris up compared to a 35mm adapter (not counting DSLRs). I have one if you follow the link below. Not all 35mm adapters are spinning discs. Some vibrate. Some adapters are better than others at the light loss. The one on my vidoe camera loses about a stop. Which is not too big a problem since I shoot with f1.4 and f1.2 lenses on it. Here is a sample 720p/24 video shot with an 35mm adapter if interested. Vimeo Last edited by tuco; 09-22-2010 at 05:06 PM.

09-24-2010, 10:59 AM	#21
deltoidjohn Forum Member Join Date: May 2010 Location: Gold Coast, QLD Posts: 88	Originally posted by future_retro Can someone please elaborate on this? I just got a handycam and it [shockingly, for sony] has shutter priority mode I'm a total video beginner and while I didn't plan on extensively learning the in's and out's like I did with dslr's, this concept really intrigues me, even though I'm not very concerned with the "film look" for my quick-and-dirty snowboard videos Sorry I just saw this today, i'll try and expand on this a little for you. Standard video (PAL or NTSC) is usually 60i or 50i. This means the screen is refreshed 50/60 times every second. With film, and with most DSLR's, the frame rate is 24p so there is less than half as many sampled moments of time per second. When there are more sampled moments, there is less gaps in between movements, so you don't need to blur your images to fill those gaps in the movement. Here's a very basic visual representation. The dots/dashes below represent how a moving object (eg a tennis ball) would appear as it travels across the screen in different frame rates: 60i (fast shutter) ....................................... 24p (slow shutter) --------------------------- 24p (fast shutter) . . . . . . . . . . . . . With a fast shutter and slower refresh rate, you can see that the object would appear to jump across the screen. Slowing the shutter down introduces blur, so the object (eg the tennis ball) no longer appears sharp in still images (it should be a circle but now it's a line!) But it gives a much more accurate portayal of where and how that ball is travelling. With the 60i, even though it is using the same fast shutter speed as the 'jumpy' 24p, it still accurately tracks the motion of the ball because it samples more data. Last edited by deltoidjohn; 09-25-2010 at 12:45 AM.

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09-22-2010, 10:33 PM	#17
excanonfd Veteran Member Join Date: Jan 2010 Location: Vancouver, BC Posts: 1,421	That's a great looking video. The sound effects might have been a bit over the top in the beginning but really good production. Automatic film agitator; could accommodate any roll film sizes and even cut films, looked like a developing tank for 4x5 cut film towards the end of the video. Pretty impressive invention! Thanks,

09-22-2010, 10:50 PM	#18
tuco Pentaxian Join Date: Jul 2009 Location: Pugetopolis Posts: 11,026	Originally posted by excanonfd That's a great looking video. The sound effects might have been a bit over the top in the beginning but really good production. Automatic film agitator; could accommodate any roll film sizes and even cut films, looked like a developing tank for 4x5 cut film towards the end of the video. Pretty impressive invention! Thanks, Thanks. Yeah, I intentionally made the sounds over the top I'm a little disappointed with Vimeo's quality. After about a week they convert it to MP4 and really compressed the heck out of it to the point things are blurry. The original upload was about 480MB and they showed that for a while. Now its compressed down to 176MB. I guess that's what you get with a free account so buck up. Yes, it does 135, 120 and 4x5 sheet film.

09-24-2010, 09:36 AM	#19
tuco Pentaxian Join Date: Jul 2009 Location: Pugetopolis Posts: 11,026	Originally posted by TheoSixx what is is about Vimeo? they must not use real video servers. you have to hit play, then pause, then wait for the entire segment to load- even then, when you hit play again, it still stutters along. WOW- what a lot of work went into designing the thing, making the thing, then making the video depicting it all! Nice job. ... Why thanks. I think it's your flash player on your web browser. I click play and it starts right away. The machine has times and agitation profiles programmed in to aid developing BW film. I don't have to stand in front of a clock and watch it for say 18 minutes agitating every 15 seconds which can be the case for one of my developers when I'm expanding the dynamic range on the negative, for example. I still shoot film when I want BW because I prefer the look of real BW over imitation, color converted gray scale from my digital camera. Plus mechanical medium format cameras are just plain fun to shoot.

09-24-2010, 10:46 AM	#20
deltoidjohn Forum Member Join Date: May 2010 Location: Gold Coast, QLD Posts: 88	Originally posted by TheoSixx DSLR's have always been video cameras. The sensors are derived from video cameras. The analog signal traveling from the sensor to the on-board processor is video. Um, how so? It is one single exposure, so it hardly qualifies as video in any way, shape or form. There is a physical shutter/mirrow block which opens for the duration of one exposure. There is no sequence of images (except in burst mode, but they are processed individually and not as video) and they do not replicate constant motion. Except in the case of live-view, of course.

09-24-2010, 08:21 PM	#22
tuco Pentaxian Join Date: Jul 2009 Location: Pugetopolis Posts: 11,026	A rule of thumb is the shutter speed should be 2X your frame rate. So for 24fps a 1/48 shutter works out nice, for example. Interlaced video scans twice (odd and even lines) to make one frame.

11-26-2010, 11:57 PM	#23
mwilloam New Member Join Date: Oct 2010 Location: United States Posts: 14	Originally posted by tuco A rule of thumb is the shutter speed should be 2X your frame rate. So for 24fps a 1/48 shutter works out nice, for example. Interlaced video scans twice (odd and even lines) to make one frame. This "rule of thumb" seems to be misinterpreted as a blanket practice. It is true that most often films shoot with a 1/48 shutter while exposing 24fps but this has to do more with the motion blur alone. a 1/48 shutter is just "a look" as is a shutter of 1/2000. But, for instance, if you're shooting a high speed to slow-mo recording at 1,000,000fps there is no need to have a "180 degree shutter" as 1/,000,000/sec shutter will be enough to capture an image without any blur. All I'm saying is that the 180 degree "rule" is just based on a common practice in film and broadcast because a shutter of ~ 1/48 -> 1/60 gives the most realistic representation of motion blur and that anything higher starts looking choppier, which can be ok, if used for an effect ie .. "Gladiator" "Private Ryan". I often use a 360 degree shutter (1/24, 1/30) for low-light/low-movement scenes such as interviews to capture more light with less gain and it looks fine.