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Old January 3rd, 2008, 12:12 AM   #1
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Shutter speeds in 25p mode

unlike every other camera I have ever used when in 25p mode (not 30p) my shutter is 1/33 at it's normal slowest setting not 1/25. Why is this?
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Old January 3rd, 2008, 01:32 AM   #2
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I noticed something similar in the "NTSC Area."

My guess is that Sony figured 1/25 is the same as "shutter off" and so did not bother to include the menu item.

Of course, for the classic 180 film look, 1/50 would be the shutter of choice, though I have long favored the 360 shutter (shutter off) that these progressive cameras offer as an improvement over the longstanding limitations of film.
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Old January 3rd, 2008, 04:45 AM   #3
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I've been experimenting with the shutter recently too and noticed he same thing Phil. Turning the shutter off definitely does the trick though.

I'm not sure if it's just something I'm doing wrong but I'm finding that I have to play with the shutter speed a lot just to get rid off frequency induced rolling effects when shooting near any kind of electric light with this camera. Maybe this is only common in CMOS cameras as I've never noticed it before with the XH-A1.

Shooting indoors with an NTSC setting is for me impossible, I have to select a PAL frequency in order to have any chance of canceling out the effect.
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Last edited by Paul Joy; January 3rd, 2008 at 07:39 AM.
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Old January 3rd, 2008, 06:06 AM   #4
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Quote:
Originally Posted by Paul Joy View Post
Shooting indoors with an NTSC setting is for me impossible, I have to select a PAL frequency in order to have any chance of canceling out the effect.
I've noticed the same problem shooting 24p with the SI-2K. Iron ballasted fluro lights causes rolling bands. HF ballasted fluros and HMIs are fine. Shooting 25p is a perfectly valid solution. Depending on your NLE it can be pretty simple to slow 25p down to 24p losslessly when you strike lighting that you have no control over.
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Old January 3rd, 2008, 07:16 AM   #5
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I am a little confused:
Is it now possible to switch to 1/50 shutter speed when shooting 25p or is it not? (Not having 1/50 for 25p would be a real drawback!)
Thanks for feedback in advance.
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Old January 3rd, 2008, 07:45 AM   #6
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Originally Posted by Michael Mann View Post
I am a little confused:
Is it now possible to switch to 1/50 shutter speed when shooting 25p or is it not?
Yes you can select 'Speed' mode and choose 50. I prefer to use the 'Angle' mode and dial in 180 degrees, which does the same thing but also changes with framerate, so if you overcrank or change framerate the shutter speed (exposure time) changes relatively.

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Old January 3rd, 2008, 07:55 AM   #7
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Thanks, Paul, good to hear that!
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Old January 3rd, 2008, 12:53 PM   #8
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Thanks for the thread.

Paul, as I've never used "Angle" wouldja mind elaborating on "I prefer to use the 'Angle' mode and dial in 180 degrees, which does the same thing but also changes with framerate". Would really appreciate it.

Somewhere along the line I picked up that 1/48 was about the optimum and while it can't always be there and there are no absolutes, thats usually been my target.

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Old January 3rd, 2008, 02:02 PM   #9
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Hi Ray.

I don't think there are any hard and fast rules, but using a shutter speed twice that of the recording frame rate is a popular setting for trying to achieve film like footage. So using a shutter speed of 48 for 24p shooting means that your exposing each frame for half of it's available exposure period.

If however you increased your frame rate to 48p then to keep the shutter per frame at the same relationship you would also need to increase shutter to 96.

Using angle is something that has been passed down from film cameras where a rotating disk passes over each frame of the film. The 'angle' of the cutout area of the disk changes the amount of exposure each frame gets.

Obviously with an electronic shutter this isn't happening physically, but it allows you to apply a setting that will remain constant no matter how you vary the frame rate.

This is a good illustration of how shutter angles work in film cameras...

http://en.wikipedia.org/wiki/Shutter_angle

regards

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Old January 4th, 2008, 02:39 AM   #10
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Paul,

Look at my short, "My Autumn's Done come", the first few shots suffer from the rolling band problem due to light frequency problems. I didn't really notice it until the edit which was annoying!
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Old January 4th, 2008, 04:40 AM   #11
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What about the special feature to "remove" this kind of blink problem in lights ?
You can select the frequency of the blink, and it adds a kind of filter for that frequency... I don't remember the name of this option.
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Old January 4th, 2008, 05:11 AM   #12
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Originally Posted by Phil Bloom View Post
Look at my short, "My Autumn's Done come", the first few shots suffer from the rolling band problem due to light frequency problems. I didn't really notice it until the edit which was annoying!
I did notice that Phil, it's a real shame that it's made it to your edit which is otherwise so nice. I've started reviewing all indoor footage now after the first take. I can just about see the effect in the LCD with the info turned off but so far the problem is not appearing with the shutter matching the frequency of the light so from now on I'm just going to use 50 when shooting with lights.

Do you know what settings you used for those shots?

One other thing I've noticed is that sometimes the rolling bars will appear in the LCD to begin with but then after some camera movement (at least that's how it feels) it will fade. I'm not really sure what could be causing that but it's certainly one of the things to be careful of when shooting under electric light.

Sebastien, the feature is called 'flicker reduction' and I didn't find it to be very effective, at least when trying to use 720/60 under lighting.
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Old January 4th, 2008, 10:14 AM   #13
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Were they fluorescent lights?
It's probably due to older low-frequency-ballast fixtures. Newer fixtures have a faster response time.
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Old January 4th, 2008, 10:26 AM   #14
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I see the effect with regular (non fluorescent) bulbs too. I think it's to do with the frequency of the power supply.
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Old January 4th, 2008, 10:49 AM   #15
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IMHO I don't find the rolling bands in the opening of Phil's DoneCome MASTERPIECE at all distracting (I barely noticed the effect in the first few viewings).

Simply put, 60Hz into 50Hz don't go (or vice-versa) hence the 'beat' effect.
This is a common problem to workaround with CCD cameras as well, just manifests as a slightly different effect (rolling bands i.s.o. pulsing)

This brings me to thinking about how well the EX1 could shoot a CRT screen (remember them?), providing the shutter matches the refresh is there any rolling (or other) artefact present that one would not expect from a CCD?
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