Author Topic: Minimum Shutter Speed at Varying Frame Rates & Motion Blur  (Read 647 times)

lcombs

  • Newbie
  • *
  • Posts: 20
    • View Profile
Hi,
I am working with a 2.1 and am having some issues with motion blur.

I am not lacking in light so the exposure is as low as possible as for obtaining the sharpest images...

I can only get images without blur at frame rates above 10k fps.

But with the same set 1.0us exposure, the images I get out of anything lower than 10k fps have definite motion blur. 

If the shutter speed is the same, why am I having blur? What part of this am I missing?

I would love to have a lower fps & higher res but there's no point if there's blur...

Thank you in advance!
Laura

Nikon1

  • Sr. Member
  • ****
  • Posts: 352
    • View Profile
Re: Minimum Shutter Speed at Varying Frame Rates & Motion Blur
« Reply #1 on: May 04, 2020, 10:31:55 AM »
Hi, is the Actuall Shutter Speed exactly the Same in both Cases, or is it just the Same Shutter angle?
 For Identical Shutter angles, this would make Sense, since Exposure changes with framerate (BTW. Does Image Brightness change at lower FPS Settings, when leaving all other Settings and Lens Settings / Light the Same?), if the Shutter Speed is displayed the Same for both cases, and one has motion blur, the other not, this would really be Strange...?

lcombs

  • Newbie
  • *
  • Posts: 20
    • View Profile
Re: Minimum Shutter Speed at Varying Frame Rates & Motion Blur
« Reply #2 on: May 04, 2020, 11:00:30 AM »
Hi, is the Actuall Shutter Speed exactly the Same in both Cases, or is it just the Same Shutter angle?
 For Identical Shutter angles, this would make Sense, since Exposure changes with framerate (BTW. Does Image Brightness change at lower FPS Settings, when leaving all other Settings and Lens Settings / Light the Same?), if the Shutter Speed is displayed the Same for both cases, and one has motion blur, the other not, this would really be Strange...?

Thank you for your response... I've attached some images of what i'm seeing...the sharper image is from a 19k fps, 640x120 (1.00us and 7 degree shutter) and the one with motion blur is with the 5k fps, 800x480 (1.00us 1degree shutter)...

Nikon1

  • Sr. Member
  • ****
  • Posts: 352
    • View Profile
Re: Minimum Shutter Speed at Varying Frame Rates & Motion Blur
« Reply #3 on: May 04, 2020, 11:06:35 AM »
Well, that really seems wrong...
 Is this reproduceable, since the Unsharp drop could also have been moving just much faster or something like this.If it is like this all the Time, then there is something strange going on.

lcombs

  • Newbie
  • *
  • Posts: 20
    • View Profile
Re: Minimum Shutter Speed at Varying Frame Rates & Motion Blur
« Reply #4 on: May 04, 2020, 11:09:42 AM »
Drop speed is the same...and results are consistent. I'm about to go take a 1.4 and see if it does the same.

Nikon1

  • Sr. Member
  • ****
  • Posts: 352
    • View Profile
Re: Minimum Shutter Speed at Varying Frame Rates & Motion Blur
« Reply #5 on: May 04, 2020, 11:15:35 AM »
But brightness stays the Same between both shots with different Framerates?
 Because if it is the Same, Exposure time should be identical....?
 Could you export a Frame with The Motion blur and upload that here?
 Maybe its some kind of ghosting or some other weird sensor or processing/ Software Artifact?

lcombs

  • Newbie
  • *
  • Posts: 20
    • View Profile
Re: Minimum Shutter Speed at Varying Frame Rates & Motion Blur
« Reply #6 on: May 04, 2020, 11:25:29 AM »
The 1.4's don't have this issue. But I will go grab a couple of raws...

skronstein

  • Krontech
  • Full Member
  • *****
  • Posts: 114
    • View Profile
Re: Minimum Shutter Speed at Varying Frame Rates & Motion Blur
« Reply #7 on: May 04, 2020, 09:17:54 PM »
When the camera's shutter is "closed" it ignores most, but not all, light. This is due to something called parasitic sensetivity, which is how sensetive the sensor is while it is "closed." The image sensor in the 2.1 is affected by this much more than the one in the 1.4; its parasitic sensetivity is 10-20 times higher than on the 1.4.
The 2.1 was really intended to be used with longer shutter times, as in filmmaking. When very short shutter times are used, the light from parasitic sensetivity can actually become visible, as in your 640x120 picture. That is what causes the blur.

lcombs

  • Newbie
  • *
  • Posts: 20
    • View Profile
Re: Minimum Shutter Speed at Varying Frame Rates & Motion Blur
« Reply #8 on: May 05, 2020, 05:56:16 AM »
When the camera's shutter is "closed" it ignores most, but not all, light. This is due to something called parasitic sensetivity, which is how sensetive the sensor is while it is "closed." The image sensor in the 2.1 is affected by this much more than the one in the 1.4; its parasitic sensetivity is 10-20 times higher than on the 1.4.
The 2.1 was really intended to be used with longer shutter times, as in filmmaking. When very short shutter times are used, the light from parasitic sensetivity can actually become visible, as in your 640x120 picture. That is what causes the blur.
Thank you. I'm glad to know it isn't something I was doing. But is this something that can be helped by changing the software? I'd imagine not since the culprit is the sensor. But we didn't purchase the 2.1 for "filmmaking." It seems i've run into issue after issue with the 2.1. It is a great "filmmaking" camera. But hardly comparable (for us anyway) to the 1.4. The slightly larger sensor size does not make it worth having when given all these other issues we've had with it.

Nikon1

  • Sr. Member
  • ****
  • Posts: 352
    • View Profile
Re: Minimum Shutter Speed at Varying Frame Rates & Motion Blur
« Reply #9 on: May 05, 2020, 06:02:42 AM »
Well, i dont know how long the Parasitic Sensitivity lasts (is it for the whole Rest of the time untill the Next Frame gets captured? or just a part of that time?). But i think, a mechanical shutter would eliminate this problem, but at 1Ás pretty tricky to build, because its really crazy short... 
 An other option would be to Strobe your lights in Sync with your exposure, because if there is no light coming in on the Sensor (or at least a lot less) the Parasitic Sensitivity would matter much less, and would possible not be even visible.

lcombs

  • Newbie
  • *
  • Posts: 20
    • View Profile
Re: Minimum Shutter Speed at Varying Frame Rates & Motion Blur
« Reply #10 on: May 05, 2020, 12:45:17 PM »
The 1.4's don't have this issue. But I will go grab a couple of raws...
Could you elaborate on why this happens? I'm having a difficult time finding anything online about it.

Nikon1

  • Sr. Member
  • ****
  • Posts: 352
    • View Profile
Re: Minimum Shutter Speed at Varying Frame Rates & Motion Blur
« Reply #11 on: May 05, 2020, 08:01:16 PM »
The 1.4's don't have this issue. But I will go grab a couple of raws...
Could you elaborate on why this happens? I'm having a difficult time finding anything online about it.
I dont quite understand the Question?
 Its quite common apparently, that Camera Sensors will be affected by Light coming in, even when they should not be . Always asked myself, why Digital Cameras use Mechanical Shutters up to this day, because i find the Concept very obsolete. Moving parts = Failiure Points...  However, i think now i understand. Most of those Sensors in DSLRs or DSLMs propably share the same problem of parasitic sensitivity and try to solve it by using a Mechanical Shutter additionaly.
 as skronstein Said, this Camera is targeted a lot more towards filmaking, and i as a Filmmaker love it this way. I am a bit with you, the bigger sensor is somewhat of a downside for me (since i allready got tons of expensive lenses for the smaller 1.4 Sensor, hoping a higher Resolution version coming out...), but it gives better sensitivity less noise, more Shallow depth of field and allows for a lot of other great lenses. If i want to use 1" Field of View, i can still go back to 1280x720, which gives better framerate and is still very useable, since its an Standard resolution and 16:9 aspect ratio.
 So i guess, i cant really complain too much about the bigger sensor, i think most other people in Filmmaking than me would maybe even argue that the Sensor is still too small now...
 Also, the 2.1 Colors are just that much better for me.
 I dont know the Details, but i think this could be an differnt Type of sensor or something. Different Types of sensors do different thing, this one does a lot of things better, but has more Ghosting apparently...

skronstein

  • Krontech
  • Full Member
  • *****
  • Posts: 114
    • View Profile
Re: Minimum Shutter Speed at Varying Frame Rates & Motion Blur
« Reply #12 on: May 06, 2020, 11:42:41 AM »
Here are the options I know of to help combat parasitic sensitivity:

- increase the shutter angle to help overcome the light from parasitic sensitivity. You can do this by using a higher framerate with the same shutter time. A longer shutter time with the same framerate would also help against parasitic sensitivity, but you need the shutter time to be as short as possible to prevent motion blur, so that won't help here.

- use a strobed light so that the camera only receives light while the shutter is open. Under IO Settings, you can find the Frame Sync Output options, which output 5v over the BNC connector or IO 2 when the shutter is open. This can be used to synchronize lights to the camera's shutter. Since this setup allows the lights to be off while the shutter is closed, the effect of parasitic sensitivity would be greatly reduced.

- use the 1.4 instead. The 1.4 uses the LUX1310 image sensor instead of the LUX2100 image sensor. There is something about the way the LUX1310 is designed that makes the parasitic sensitivity much lower.