M video "ripples"

[gpwhite]

Advertisement (gone after registration)

I wonder if any M videographers out there might have experienced a problem I just encountered and could offer advice...

 

Yes, I am a bit embarrassed to be asking about *video* with an M. But I shot one little project for a colleague, and the daylight results were pretty good... so I purchased the 98% mark-up Leica microphone and plan to shoot a couple of videos over the holidays (so people can speak with their images) rather than stills. So, I will finally learn about the true focus Leica had in mind for the M !

 

I tried two indoor test runs with the Noct, wide open, where my Luna Pro found EV 10 to EV 11. I set ISO 800 and WB worked well on video when you manually set it to the scene. But I found a rippling effect in the video images during playback on a computer. The horizontal disturbance looked like capturing the rolling refresh rate of a television picture in a still photograph (sorry, I do not know the proper name for this phenomenon). Guessing that the Leica video capture might not be up to the contrast of f/0.95, I tried the 50 APO, wide open. The rippling was less pronounced, but still apparent. Back to the Noct @ f/4 (what a waste!), and the video came out quite well.

 

Can anyone shed light, , on this ripple effect and suggest how I might be able to shoot at f/0.95 or f/2? My fantasy of becoming an f/0.95 videographer seem to have been dashed.

 

Peter

[Rick]

I wonder if any M videographers out there might have experienced a problem I just encountered and could offer advice...

 

Yes, I am a bit embarrassed to be asking about *video* with an M. But I shot one little project for a colleague, and the daylight results were pretty good... so I purchased the 98% mark-up Leica microphone and plan to shoot a couple of videos over the holidays (so people can speak with their images) rather than stills. So, I will finally learn about the true focus Leica had in mind for the M !

 

I tried two indoor test runs with the Noct, wide open, where my Luna Pro found EV 10 to EV 11. I set ISO 800 and WB worked well on video when you manually set it to the scene. But I found a rippling effect in the video images during playback on a computer. The horizontal disturbance looked like capturing the rolling refresh rate of a television picture in a still photograph (sorry, I do not know the proper name for this phenomenon). Guessing that the Leica video capture might not be up to the contrast of f/0.95, I tried the 50 APO, wide open. The rippling was less pronounced, but still apparent. Back to the Noct @ f/4 (what a waste!), and the video came out quite well.

 

Can anyone shed light, , on this ripple effect and suggest how I might be able to shoot at f/0.95 or f/2? My fantasy of becoming an f/0.95 videographer seem to have been dashed.

 

Peter

 

Was your light source LED or fluorescent tubes?

[adan]

Try shooting at a lower ISO when using f/0.95.

 

What RickLeica alludes to with his question (ironic that his signature reads "flickr" ) is that some light sources actually do flicker, LED and fluorescent among them. At about 50-60 hertz (times per second).

 

Since the M shoots 25 frames per second, light flickering at 50-60 times per second will go light-to-dark-to-light-to-dark during each frame.

 

And IF your video shutter speed (which is not the same as the frame rate) is fast enough, it will record the flickering, just as in your analogy to shooting stills of TV, as bands across the frame.

 

Reduce your ISO, (or, as in your previous attempts, the aperture) and the shutter speed will reduce to something closer to 1/25 second, wherein all the pixels will capture both the "light" and "dark" moments of each flicker - as constant, even illumination.

[Rick]

Adan is correct and beat me to the punch. I assumed you would respond that your lighting was one of the choices.

 

These light sources are are off and on 60 times per second. The M can record video at 24-25 times per second. During this frame rate (when the sensor is recording a frame) the M shutter can be open for 1/24 - 1/4000 sec during each frame.

 

You would want to keep the shutter speed at 1/24 sec to maximally reduce the effect Adan describes under these lighting conditions. This may be difficult at f.95 as you will obviously overexpose. So, you will need ND filters to shoot at .95. Such is the life of the videographer.

 

By the way, the variation between your Noctilux and the 50/14 is due to shutter speed differences.

[gpwhite]

Adan is correct and beat me to the punch. I assumed you would respond that your lighting was one of the choices.

 

These light sources are are off and on 60 times per second. The M can record video at 24-25 times per second. During this frame rate (when the sensor is recording a frame) the M shutter can be open for 1/24 - 1/4000 sec during each frame.

 

You would want to keep the shutter speed at 1/24 sec to maximally reduce the effect Adan describes under these lighting conditions. This may be difficult at f.95 as you will obviously overexpose. So, you will need ND filters to shoot at .95. Such is the life of the videographer.

 

By the way, the variation between your Noctilux and the 50/14 is due to shutter speed differences.

 

Many thanks to you and Adan! The light sources in both test runs were incandescent halogen bulbs over some blend of daylight. But, as you both explain clearly, the phenomenon can be addressed by decreasing exposure. I am happy to try ISO 200 or ISO 400 and look forward to those results.

 

I had a hunch that I was doing something in the wrong direction, so thanks for the explanation.

 

Peter