Optimize Shutter Speeds

JonSnow

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I was playing with the shutter speeds based on a few threads on this forum.

I've tested shutter priority and find that 1/30 to 1/120 have minimal difference in terms of cameras visibility, anything higher and it gets to dark. I then set the gain to 0-50 and that seems to be fine for now.

When i set the Exposure to Manual so i can set Shutter and Gain together, it's asking for a range in ms.

So how do i set a minimal shutter speed of say 1/120 in ms? What's the math to calculate it?

I've tried 0-8.3 ms and that's way to dark, i need to set it to about 0-70 ms to get a good image as the max value for my camera is 333.33 ms.
 

sebastiantombs

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To determine milliseconds just divide, as in 1 divided by 60 or 1 divided by 120.

8.3ms is the equivalent of 1/120 for example. Looking at the boxes for speed in the manual setting I set mine to 0.001 on the left and 16.66 (1/60) on the right for night profiles. That limits the slowest the shutter can go to 1/60, 16.66ms, to keep blur to a minimum. Your setting of 70ms is roughly 1/14 which will produce a lot of blur.

Also you need to be careful with exposure compensation and gain settings. Going too high with them will add noise and blur. The same is true of highlight compensation, backlight compensation and wide dynamic range (HLC, BLC and WDR).
 

Mike A.

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The math is there already... 1 divided by 120 = .00833. Move the decimal place to get to thousands = 8.3.

Yes, you'll see a big difference typically between Shutter Priority and Manual using the same shutter speed. The former is adjusting the gain (and other internal aspects apparently from my observation) as needed to make what it 'thinks' is an optimal image at that shutter speed. The latter doesn't.
 

wittaj

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The faster the shutter, the better the ability to freeze frame an image.

However, as you found out, the faster the shutter the darker the image at night.

It is a balance. You need to find the balance between shutter speed to eliminate blur, yet still produce a usable image.

But do not get carried away about a bright static image. You need to test it with motion at night and confirm that your settings result in clean captures of motion. Otherwise you can simply say what time something happened.

But 70ms you might as well leave on auto/default settings lol. The image will be nice and bright, but motion will be a complete blur.

Here is an example of a license plate. Shutter is 1/2,000, so the image is completely black except for a head/tailight and the plate. This would not be obtained with a 70ms shutter LOL.

1636999539514.png


You need to dial the camera in to your field of view.

In my opinion, shutter (exposure) and gain are the two most important and then base the others off of it. Shutter is more important than FPS. It is the shutter speed that prevents motion blur, not FPS. 15 FPS is more than enough for surveillance cameras as we are not producing Hollywood movies. Match iframes to FPS.

This is in general and your camera may not have all the same settings available to you, but will help you.

Many people do not realize there is manual shutter that lets you adjust shutter and gain and a shutter priority that only lets you adjust shutter speed but not gain. The higher the gain, the bigger the noise and see-through ghosting start to appear because the noise is amplified. Most people select shutter priority and run a faster shutter than they should because it is likely being done at 100 gain, so it is actually defeating their purpose of a faster shutter.

But first, run H264, smart codec off, CBR, and 8192 bitrate to start.

Go into shutter settings and change to manual shutter and start with custom shutter as ms and change to 0-8.3ms and gain 0-50 (night) and 0-30 (day)for starters. Auto could have a shutter speed of 100ms or more with a gain at 100 and shutter priority could result in gain up at 100 which will contribute to significant ghosting and that blinding white you will get from the infrared.

Now what you will notice immediately at night is that your image gets A LOT darker. That faster the shutter, the more light that is needed. But it is a balance. The nice bright night image results in Casper during motion LOL. What do we want, a nice static image or a clean image when there is motion introduced to the scene?

So if it is too dark, then start adding ms to the time. Go to 10ms, 12ms, etc. until you find what you feel is acceptable as an image. Then have someone walk around and see if you can get a clean shot. Try not to go above 16.67ms (but certainly not above 30ms) as that tends to be the point where blur starts to occur. Conversely, if it is still bright, then drop down in time to get a faster shutter.

You can also adjust brightness and contrast to improve the image.

You can also add some gain to brighten the image - but the higher the gain, the more ghosting you get. Some cameras can go to 70 or so before it is an issue and some can't go over 50.

But adjusting those two settings will have the biggest impact. The next one is noise reduction. Want to keep that as low as possible. Depending on the amount of light you have, you might be able to get down to 40 or so at night (again camera dependent) and 20-30 during the day, but take it as low as you can before it gets too noisy. Again this one is a balance as well. Too smooth and no noise can result in soft images and contribute to blur.

Do not use backlight features until you have exhausted every other parameter setting. And if you do have to use backlight, take it down as low as possible.

After every setting adjustment, have someone walk around outside and see if you can freeze-frame to get a clean image. If not, keep changing until you do. Clean motion pictures are what we are after, not a clean static image.
 

wittaj

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If you have enough light at night to run NR at 10, then you will get incredible results. Mine are a pixel mess at 10 except for the camera that is right at the door with a lot of light and not looking more than 10 feet out.

Just make sure your shutter settings are not auto and that you have the ability to adjust gain. I can run NR at 10 on auto, but then motion is a blur.
 

105437

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If you have enough light at night to run NR at 10, then you will get incredible results. Mine are a pixel mess at 10 except for the camera that is right at the door with a lot of light and not looking more than 10 feet out.

Just make sure your shutter settings are not auto and that you have the ability to adjust gain. I can run NR at 10 on auto, but then motion is a blur.
Yes, I have extra IR for this camera. The camera is a 5231, night motion is okay but not great... probably me expecting too much. Any thoughts on Auto Iris?
 

wittaj

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It sounds like you have enough IR that you could turn off the auto iris.

post a little video clip of your camera field of view with motion and let's see if we can help you dial it in.
 

105437

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It sounds like you have enough IR that you could turn off the auto iris.

post a little video clip of your camera field of view with motion and let's see if we can help you dial it in.
I appreciate that... I'm not able to tonight, but I'll try and come back to this. Thanks!
 

JonSnow

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I've got the shutter set to 0-16.6 and gain set to 0-70 for now, will test it for a few days, to see if it has better results than Auto.

At the moment i'm not using HLC, BLC and WDR, but should I? I suspect its best to keep it disabled if I want less motion blur.

Also to want to point out i'm using color night vision not B/W.
 

sebastiantombs

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Not bad on the coyote to my tired old eyes.

The thing about gain settings is that it seems specific to camera models. I have a few running quite high gain with no problem while others, if set that high, are a noisy, blurry, mess. It takes experimentation to find out what works for each camera. I normally don't use HLC, BLC or WDR. If I do use it I keep it as low as possible to avoid the noise and blur that it can introduce.
 

105437

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what are your settings on exposure comp and gamma ?
Here are my settings for exposure. A couple of weeks ago I did several tests at night with several different settings. This is what seemed to work best for my Dahua 5231.

Screen Shot 2021-11-16 at 11.52.08 AM.png
 

user8963

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you should use manual, mode and then custom !

thats why everything looks a bit awful (no sharpness, no contrast) .. your camera is using 100% gain
 
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user8963

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Thanks, suggestions on those settings and I'll test them tonight!
wittaj wrote it above.

seems that you are running an old firmware without exposure comp (i never understand what the camera change with this) ..

gamma is under picture tab
 

user8963

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hmm then maybe the 31er series doent have the feature.

to be fair it does not look that awful ;)

with your external pir you should have enough light to turn down gain (lower then the camera set it in auto mode).

some people like bright overall images , so its up to you how you set it
 
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