First low light/no light spotter

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phoenix
BRUCE ALMIGHTY
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Re: First low light/no light spotter

Post by phoenix » 22 Dec 2015, 16:36

FLD is short for "Fields"
In normal operation, the slowest shutter speed is 1/50 sec (1/60 for NTSC cameras), and that's the time for half the pixels in the sensor to be scanned.
A full field of sensor data takes 2 scans (this is called interlaced scanning with the first scan looking at the odd numbered rows of pixels and the second scan looking at the even numbered rows of pixels)
So, at 1/50 sec shutter speed the camera produces 25 frames per second which is fast enough to produce smooth video.
In slow shutter mode (or sense up or whatever other marketing name has been invented for the same thing) the number of frames per second is reduced to allow more time for signals produced by the incoming light to build up in each pixel.
For some reason, rather than simply show the actual shutter speed, camera manufacturers have decided to use the terms "field" to describe how often a the camera produces a complete image frame.
It's my understanding that 25 frames per second (PAL) is classed as 1 FLD (30fps for NTSC)
Therefore 2 FLD would be 12.5 frames per second
4 FLD would be 6.25 frames per second
As the FLD number in creases the time per frame increases and the number of frames per second decreases.
At 512 FLD the frames per second is 0.049 or, to put it the other way around it's 20.5 seconds per frame.
I think most cameras change the FLD value in powers of 2 so you can only have x2, x4, x8 ,x16, x32 ,x64, x128, x256 and x512
Hope that helps


Cheers

Bruce
LAND ROVER - THE WORLD'S WORST 4X4 BY FAR

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MrNewbie
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Re: First low light/no light spotter

Post by MrNewbie » 23 Dec 2015, 04:43

Now who in the world would know that?

Guess that's why he's called BRUCE ALMIGHTY !

thanks Bruce

4 is 6.2 fps
8 is 3.1 fps

128FLD from page 1 = .196fps lets call it .2, about 1 frame ever 5 seconds, not very darn good, not even useful as a spotter.
But it was interesting to see it.

lightmesser
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Re: First low light/no light spotter

Post by lightmesser » 23 Dec 2015, 20:20

phoenix wrote:FLD is short for "Fields"
In normal operation, the slowest shutter speed is 1/50 sec (1/60 for NTSC cameras), and that's the time for half the pixels in the sensor to be scanned.
A full field of sensor data takes 2 scans (this is called interlaced scanning with the first scan looking at the odd numbered rows of pixels and the second scan looking at the even numbered rows of pixels)
So, at 1/50 sec shutter speed the camera produces 25 frames per second which is fast enough to produce smooth video.
In slow shutter mode (or sense up or whatever other marketing name has been invented for the same thing) the number of frames per second is reduced to allow more time for signals produced by the incoming light to build up in each pixel.
For some reason, rather than simply show the actual shutter speed, camera manufacturers have decided to use the terms "field" to describe how often a the camera produces a complete image frame.
It's my understanding that 25 frames per second (PAL) is classed as 1 FLD (30fps for NTSC)
Therefore 2 FLD would be 12.5 frames per second
4 FLD would be 6.25 frames per second
As the FLD number in creases the time per frame increases and the number of frames per second decreases.
At 512 FLD the frames per second is 0.049 or, to put it the other way around it's 20.5 seconds per frame.
I think most cameras change the FLD value in powers of 2 so you can only have x2, x4, x8 ,x16, x32 ,x64, x128, x256 and x512
Hope that helps


Cheers

Bruce
Bruce did it again. Really impressive knowledge...
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MrNewbie
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Re: First low light/no light spotter

Post by MrNewbie » 24 Dec 2015, 02:40

The general idea was to test the Effio E vs the EJ230
It looks to be some sort of baseline test of some sort, it really should not apply here, remember Spotter VS scopeless.

I used the E bacause it already had a CS mount on it.
This is the exact setup used in this old video. Same parts, Unit slated for tear down.
viewtopic.php?f=29&t=10797

Took off the variable lens and put on a little 25mm lens.
The EJ is that cheap variable one that no one likes. This is what I call my T20 (non AS) on the EJ setup, pointed at tree, not ground..mistake.

There is a lot of static on this vid.. transmitter stuff for the most part.
To record from the left, Moved the little drv to the left, to record to the right, moved to the right.
After a while I figured 2 much RF cross talk. So I started turning the E off. Just about every time I forgot to hit the save changes.
You see me fooling around with the same buttons 10 times.

There is 10 minutes of fumbling and bumbling on this vid. There is a lot of pixelation on the vid, but it really did not look to bad on the screen.
It seemed to get better as I played around in the menus.

https://youtu.be/gcMUUyrC0YY

The EJ230 lost as far as I am concerned no need to watch the video unless you just wanna ck out the settings and watch me fumble

Pics at end of vid showing the parts used.
I'm trying to point to the EJ230's little red button, pic of the E's little 25mm lens (needed the little c-cs adapter spacer..found something,)
Duct tape to keep from moving focus on variable lens in the dark on the 230.

Yes, lots of ambient light tonight, but not as much as a clear night with stars or a moon in the sky.

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MrNewbie
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Re: First low light/no light spotter

Post by MrNewbie » 24 Dec 2015, 05:26

The Effio could see the light better for 3 compromises

Smaller wider angle lens lets in more light
Ezoom, the light has already been captured, can Ezoom with a bit of quality compromise to a reasonable degree.(fun to play with)
Slow shutter, a compromise just need to figure out how far to take it. (but you can control)

I'm kind of done with it, but it is going to need some IR light.
For my use as a spotter or in a stand, I'm going to point it down the way and watch my little screen with a beer in my hand.

I'd like to see someone make a low cost decent spotter


https://youtu.be/PRa2jekTXsQ

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MrNewbie
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Re: First low light/no light spotter

Post by MrNewbie » 30 Dec 2015, 04:45

This was a group project, perfect for low cost home use, the cameras were set to 8fld, and Bruce told us the frame rate above.

I think a few are missing the boat on this one. The whole premise is to utilize lower fps for more light.

2FLD sounds reasonable, 4FLD is pushing it. This means you need a camera with an osd..

Set the shutter control to manual (not auto) set it to 2 or 4fld. Now make your comparisons

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Re: First low light/no light spotter

Post by MrNewbie » 01 Jan 2016, 19:38

I do think I have a fun new years day present for all.

I think Bruce made a mistake, I never thought I would see the day.
Bruce may have? But I'm not sure...
From his post up above, we talk about fld in relationship to fps.

And states that 2FLD in relationship to 25fps=12.5fps..

So I guess a camera that normally sees at 50fps, can now see at 12.5fps at 2FLD.

What happened to everything between 50fps and 12.5fps..is it all gone?

I think its more like this.

2FLD=25fps
4FLD=12.5fps
8FLD=6.75fps
16FLD=3.4fps

ect...

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