No 1/25 shutter speed, why? at DVinfo.net

Jon Shohet · November 11th, 2010, 02:07 AM

Yes yes, I know, If you don't follow the 180 degree shutter rule then you are an amateur ;)
But in all honesty, I use 1/25 speed frequently on my Sony V1 in progressive scan mode, it really helps in low light situations and I'm fine with the results.
If there is a 1/30 setting on the EOS video mode, why not 1/25 for us PAL shooters?
Do you find any issues shooting 1/30 in 1080p25?

Thanks,
Jon

Bruce Foreman · November 11th, 2010, 12:38 PM

Jon, you said:

"Yes yes, I know, If you don't follow the 180 degree shutter rule then you are an amateur ;)"

That's a bunch of BS. The 180 degree shutter "rule" came about because film cameras running at 24 fps had a rotating disk shutter with half of it (180 out of 360 degrees) "cut out". Purely a mechanical thing.

In our cameras today we have a sensor being scanned and the only reason to "emulate" the 180 degree mechanical shutter is to try to preserve the same amount of "motion blur" those mechanical shutters used to get. You don't even have to get 1/48th of a second shutter speed to get close. 1/50th or 1/60th gets close enough in many cases.

And your second question:

"If there is a 1/30 setting on the EOS video mode, why not 1/25 for us PAL shooters?
Do you find any issues shooting 1/30 in 1080p25?"

I just checked my 550D and I can't go lower in shutter speed than 1/30 in either NTSC or PAL mode. There may be a configuration item buried in one of the menus that would change that but I have a Veterans Day ceremony to get to and can't "dig" into it. (I never even broke the wrap on the manual but will look at the online manual to see if I can find something.

As far as issues shooting 1/30 in 1080p25 you may only encounter one. Shooting around flourescents (including the CFLs that are replacing lightbulbs) and incandescent lighting where you may get intereference banding from the 50Hz line frequency. So under those circumstances you should likely use 1/50th shutter speed.

Jon Shohet · November 11th, 2010, 04:14 PM

I was being cynical of course. Bruce, some people would condemn you for speaking such heresy ;)

180 Degree Shutter – Learn It, Live It, Love It

In any case, I mentioned the 180 degree shutter rule because it perhaps would explain why Canon didn't bother to include 1/25 shutter speed on a 25p video capable camera. dunno.

Yes, I did run into problems - shot with the 60D for the very first time a few days ago. I had to shoot some video projection and got a lot of flickering with 1/50 in 1080p. I wanted to try different shutter speeds and was surprised to discover the camera only goes down to 1/30 even in PAL mode...

Bruce Foreman · November 11th, 2010, 09:39 PM

Try 1/60th.

What is the line frequency there? 50Hz or 60Hz.

Jon Shohet · November 12th, 2010, 01:07 AM

Israel is a 50Hz country. But there was a lot of flickering in 1/50.
As this was a payed gig and it was my first time shooting video on a DSLR, I got the job completely done first with the V1, then took some shots with the 60D as a "bonus".
I did not have time to experiment too much, but at the same distance to the video projection, the V1 at 1/25 exhibited no flickering while the 60D at 1/50 did. I did not try 1/30.

Jon Shohet · November 13th, 2010, 01:13 AM

Playing around some more with the camera, I now find that in 720p50, lowest shutter speed is 60?!?
Am I missing something here? I think my body was packaged for the US market. Could it be that only bodies for PAL countries have 1/25 1/50 options?

Jon Shohet · November 15th, 2010, 12:51 AM

Looking at user manuals, it seems all EOS video DSLRs have this limitation - 1/30 in 1080p and 1/60 in 720p.
This is regardless of frame rate, so I guess there's a different reason for this limitation.

Anyone knows why this is?

And, I still would love to hear from PAL shooters if you have any reservations about shooting 1/30 in 1080p or 1/60 in 720p and why...

Many thanks,
Jon.

Jon Shohet · November 18th, 2010, 07:00 AM

Sorry I keep bumping this up despite the lack of interest ;)

I'm finding it impossible to shoot LCD screens with the 60D, regardless of shutter speed settings. I'm really frustrated at the exclusion of slower shutter speeds in video mode.

Has anyone else found it problematic to shoot screens/projections with out scan line flickering?
Any solutions?

Chris Medico · November 18th, 2010, 08:01 AM

There is no simple solution to the problem with that camera. You are actually seeing the rolling shutter effect which is "beating" against the refresh rate of the displays. Since the imager is read in strips the flickering looks like a roll up the screen.

You can try different refresh rates on the display and hopefully find a combination that minimizes the effect. If not you will need to use a different camera.

Chris Hurd · November 18th, 2010, 08:06 AM

Quote:

Originally Posted by Jon Shohet

I think my body was packaged for the US market. Could it be that only bodies for PAL countries have 1/25 1/50 options?

Within the Canon EOS line of Digital SLR cameras, there is no distinction between PAL or NTSC -- there are no separate models for each market. There is only one model, sold worldwide. Hope this helps,

Lee Ying · November 18th, 2010, 08:15 AM

Quote:

Originally Posted by Jon Shohet

I'm finding it impossible to shoot LCD screens with the 60D, regardless of shutter speed settings. I'm really frustrated at the exclusion of slower shutter speeds in video mode.

Has anyone else found it problematic to shoot screens/projections with out scan line flickering? Any solutions?

The problem is not shutter speed, it is the frame rate with which you are shooting. Your frame rate has to match that of the original content.
Most highend LCD and projectors can detect the content frame rate, and display it accordingly. My guess is that the content was 24p and you are filming it at 25p, thus the flicker.
Fortunately, Canon T2i has all four frame rates commonly used in video. Just go thru each of them, 24p, 25p, 30p and 60p and leave the shutter speed at 1/30. Chances are you will find one that eliminates the flicker. Let us know if the problem goes away.

Jon Shohet · November 19th, 2010, 12:17 PM

Thanks for the responses guys,
The video projection I shot was PAL footage using a PAL projector, so I'm not sure original footage's frame rate was the issue.

I tried shooting my PC monitor. It's refresh rate is fixed at 60hz, and indeed shooting at 60p did produce the least line flickering, but it wasn't gone altogether.
Without doubt, the faster the shutter speed, the worst the flickering gets, regardless of chosen frame rate, so I do think slower shutter speeds would have helped, but I could be wrong of course.

I think Chris M is probably on the right track, and this is more of a sensor issue than a frame rate issue. As I said, my Sony V1 - which is also a cmos rolling shutter - captured the video projection without issue at 1/25 in 25p. But perhaps the canon's larger sensor + line skipping makes it incapable of avoiding this problem.

Anyway, I'm only making guesses here...
The bottom line is I could not get a clean shot of my PC monitor at any setting with the 60D.
if anyone has any more useful insight I'd be glad to hear
many thanks,
Jon

Matt Davis · November 21st, 2010, 02:53 PM

The awful truth here is that you're bumping into the limitations of the design.

If you're out there shooting video where LCD monitors, LCD lighting, Fluorescent lighting and data monitors all need to be shot with stable images, you're not going to get that out of a DSLR, and you're not going to get that out of a lot of 'prosumer' camcorders (like the JVC HM100) either.

Cameras like the EX1 have an 'Electronic Shutter Control' where you can, to a hundreth of the shutter speed, dictate the exact requirement. In PAL land, I've filmed a European car with LED running lights, and they pulsed at 50th and flickered at 60th. We needed something silly like 50.17th.

Don't get me started on the nightmare of filming things lit by domestic or industrial LED lamps - not video lamps, but 'mood lighting' and such. Strobing, flickering, humming, and this gives the EX1 a severe workout. My 550D just has to sit there and take it.

If you really really need to control flicker, and want the whole DoF thing, you need to think about migrating to something like an AF100, F3 or some other proper full-on pro camera.

Jon Shohet · November 22nd, 2010, 04:09 AM

Thanks, Matt.
Disappointing, but I am more and more inclined to accept this indeed a limitation of the camera and not user error, so at least I know in advance how to approach the situation.
Shame, because I do face shooting video projections quite often, exactly in the type of shoots I was hoping to utilize the 60D for.

With the moire and aliasing issues, people suggest using blurring filters and reducing sharpness in-camera.
Are there any "tricks" to at least mitigate the effects of LED/LCD flicker/pulse with the EOS cameras?

November 11th, 2010, 02:07 AM	#1
Jon Shohet Major Player Join Date: Dec 2007 Location: London, UK Posts: 277	No 1/25 shutter speed, why? Yes yes, I know, If you don't follow the 180 degree shutter rule then you are an amateur ;) But in all honesty, I use 1/25 speed frequently on my Sony V1 in progressive scan mode, it really helps in low light situations and I'm fine with the results. If there is a 1/30 setting on the EOS video mode, why not 1/25 for us PAL shooters? Do you find any issues shooting 1/30 in 1080p25? Thanks, Jon

November 18th, 2010, 08:01 AM	#9
Chris Medico Inner Circle Join Date: Aug 2006 Location: Efland NC, USA Posts: 2,322	There is no simple solution to the problem with that camera. You are actually seeing the rolling shutter effect which is "beating" against the refresh rate of the displays. Since the imager is read in strips the flickering looks like a roll up the screen. You can try different refresh rates on the display and hopefully find a combination that minimizes the effect. If not you will need to use a different camera. __________________ http://www.LandYachtMedia.com

November 21st, 2010, 02:53 PM	#13
Matt Davis Trustee Join Date: Aug 2005 Location: Berkshire, UK Posts: 1,562	The awful truth here is that you're bumping into the limitations of the design. If you're out there shooting video where LCD monitors, LCD lighting, Fluorescent lighting and data monitors all need to be shot with stable images, you're not going to get that out of a DSLR, and you're not going to get that out of a lot of 'prosumer' camcorders (like the JVC HM100) either. Cameras like the EX1 have an 'Electronic Shutter Control' where you can, to a hundreth of the shutter speed, dictate the exact requirement. In PAL land, I've filmed a European car with LED running lights, and they pulsed at 50th and flickered at 60th. We needed something silly like 50.17th. Don't get me started on the nightmare of filming things lit by domestic or industrial LED lamps - not video lamps, but 'mood lighting' and such. Strobing, flickering, humming, and this gives the EX1 a severe workout. My 550D just has to sit there and take it. If you really really need to control flicker, and want the whole DoF thing, you need to think about migrating to something like an AF100, F3 or some other proper full-on pro camera. __________________ Director/Editor - MDMA Ltd: Write, Shoot, Edit, Publish - mattdavis.pro EX1 x2, C100 --> FCPX & PPro6

November 11th, 2010, 12:38 PM	#2
Bruce Foreman Trustee Join Date: Nov 2006 Location: San Angelo Texas Posts: 1,518	Jon, you said: "Yes yes, I know, If you don't follow the 180 degree shutter rule then you are an amateur ;)" That's a bunch of BS. The 180 degree shutter "rule" came about because film cameras running at 24 fps had a rotating disk shutter with half of it (180 out of 360 degrees) "cut out". Purely a mechanical thing. In our cameras today we have a sensor being scanned and the only reason to "emulate" the 180 degree mechanical shutter is to try to preserve the same amount of "motion blur" those mechanical shutters used to get. You don't even have to get 1/48th of a second shutter speed to get close. 1/50th or 1/60th gets close enough in many cases. And your second question: "If there is a 1/30 setting on the EOS video mode, why not 1/25 for us PAL shooters? Do you find any issues shooting 1/30 in 1080p25?" I just checked my 550D and I can't go lower in shutter speed than 1/30 in either NTSC or PAL mode. There may be a configuration item buried in one of the menus that would change that but I have a Veterans Day ceremony to get to and can't "dig" into it. (I never even broke the wrap on the manual but will look at the online manual to see if I can find something. As far as issues shooting 1/30 in 1080p25 you may only encounter one. Shooting around flourescents (including the CFLs that are replacing lightbulbs) and incandescent lighting where you may get intereference banding from the 50Hz line frequency. So under those circumstances you should likely use 1/50th shutter speed.

November 11th, 2010, 04:14 PM	#3
Jon Shohet Major Player Join Date: Dec 2007 Location: London, UK Posts: 277	I was being cynical of course. Bruce, some people would condemn you for speaking such heresy ;) 180 Degree Shutter – Learn It, Live It, Love It In any case, I mentioned the 180 degree shutter rule because it perhaps would explain why Canon didn't bother to include 1/25 shutter speed on a 25p video capable camera. dunno. Yes, I did run into problems - shot with the 60D for the very first time a few days ago. I had to shoot some video projection and got a lot of flickering with 1/50 in 1080p. I wanted to try different shutter speeds and was surprised to discover the camera only goes down to 1/30 even in PAL mode...

November 11th, 2010, 09:39 PM	#4
Bruce Foreman Trustee Join Date: Nov 2006 Location: San Angelo Texas Posts: 1,518	Try 1/60th. What is the line frequency there? 50Hz or 60Hz.

November 12th, 2010, 01:07 AM	#5
Jon Shohet Major Player Join Date: Dec 2007 Location: London, UK Posts: 277	Israel is a 50Hz country. But there was a lot of flickering in 1/50. As this was a payed gig and it was my first time shooting video on a DSLR, I got the job completely done first with the V1, then took some shots with the 60D as a "bonus". I did not have time to experiment too much, but at the same distance to the video projection, the V1 at 1/25 exhibited no flickering while the 60D at 1/50 did. I did not try 1/30.

November 13th, 2010, 01:13 AM	#6
Jon Shohet Major Player Join Date: Dec 2007 Location: London, UK Posts: 277	Playing around some more with the camera, I now find that in 720p50, lowest shutter speed is 60?!? Am I missing something here? I think my body was packaged for the US market. Could it be that only bodies for PAL countries have 1/25 1/50 options?

November 15th, 2010, 12:51 AM	#7
Jon Shohet Major Player Join Date: Dec 2007 Location: London, UK Posts: 277	Looking at user manuals, it seems all EOS video DSLRs have this limitation - 1/30 in 1080p and 1/60 in 720p. This is regardless of frame rate, so I guess there's a different reason for this limitation. Anyone knows why this is? And, I still would love to hear from PAL shooters if you have any reservations about shooting 1/30 in 1080p or 1/60 in 720p and why... Many thanks, Jon.

November 18th, 2010, 07:00 AM	#8
Jon Shohet Major Player Join Date: Dec 2007 Location: London, UK Posts: 277	Sorry I keep bumping this up despite the lack of interest ;) I'm finding it impossible to shoot LCD screens with the 60D, regardless of shutter speed settings. I'm really frustrated at the exclusion of slower shutter speeds in video mode. Has anyone else found it problematic to shoot screens/projections with out scan line flickering? Any solutions?

November 19th, 2010, 12:17 PM	#12
Jon Shohet Major Player Join Date: Dec 2007 Location: London, UK Posts: 277	Thanks for the responses guys, The video projection I shot was PAL footage using a PAL projector, so I'm not sure original footage's frame rate was the issue. I tried shooting my PC monitor. It's refresh rate is fixed at 60hz, and indeed shooting at 60p did produce the least line flickering, but it wasn't gone altogether. Without doubt, the faster the shutter speed, the worst the flickering gets, regardless of chosen frame rate, so I do think slower shutter speeds would have helped, but I could be wrong of course. I think Chris M is probably on the right track, and this is more of a sensor issue than a frame rate issue. As I said, my Sony V1 - which is also a cmos rolling shutter - captured the video projection without issue at 1/25 in 25p. But perhaps the canon's larger sensor + line skipping makes it incapable of avoiding this problem. Anyway, I'm only making guesses here... The bottom line is I could not get a clean shot of my PC monitor at any setting with the 60D. if anyone has any more useful insight I'd be glad to hear many thanks, Jon

November 22nd, 2010, 04:09 AM	#14
Jon Shohet Major Player Join Date: Dec 2007 Location: London, UK Posts: 277	Thanks, Matt. Disappointing, but I am more and more inclined to accept this indeed a limitation of the camera and not user error, so at least I know in advance how to approach the situation. Shame, because I do face shooting video projections quite often, exactly in the type of shoots I was hoping to utilize the 60D for. With the moire and aliasing issues, people suggest using blurring filters and reducing sharpness in-camera. Are there any "tricks" to at least mitigate the effects of LED/LCD flicker/pulse with the EOS cameras?