auto iris vs. shutter speed question

[mike_va 0]

Does using an auto iris lens result in slow shutter speeds during the daytime?

 

I was just pondering this, thinking maybe it will attempt to reduce light to the default lowest speed e.g. 1/60s.

 

Whereas if an auto-iris lens was not used the camera would be forced to increase the shutter speed during the daytime.

 

Thanks for any help, have not found a good answer to this in my searches.

[Nimrod 0]

Auto iris refers to the CCD chip itself acting as a iris by electronically reducing its sensitivity and has nothing to do with the lens.

 

DC iris or “DC drive” is a mechanical iris in the lens that is controlled by a DC signal from the camera in proportion to the amount of light it is getting. This is the most used electro mechanical shutter type.

 

Video iris or “ video drive” is a mechanical iris in the lens that is controlled by feeding the video signal from the camera into the electronics in the lens were it processes the signal and controls the iris as in a DC drive. In a DC drive lens this processing electronics is inside the camera. Video drive type of electronic iris is old style and not used very much any more. Many box cameras still have a switch on them to select either “Video or “DC" drive.

 

EDIT: Some lenses have mechanical user settable irises that stay in a fixed position day and night.

[Soundy 1]

In my experience, "auto iris" and "DC iris" are almost always used to refer to the same thing; chip-controlled exposure is more commonly called "electronic iris". Many cameras differentiate by labeling the associated switch as "AI/EI", with a separate switch for "DC/video".

 

In any case, pretty sure the OP is talking about DC iris... and the answer is, "it depends". Most DC-iris cameras provide an adjustment for the user to set the drive level; if this is dialed down too much, the camera may compensate by lowering the shutter speed... depending on the camera's specific design, of course.

[mike_va 0]

In any case, pretty sure the OP is talking about DC iris... and the answer is, "it depends". Most DC-iris cameras provide an adjustment for the user to set the drive level; if this is dialed down too much, the camera may compensate by lowering the shutter speed... depending on the camera's specific design, of course.

 

Yep, I should have been more clear. I'm trying to get my head around why my axis 1344 are so much better capturing motion than my analog cameras (e.g. Bosch 0610) even in the daytime. Although I've got to admit I have not exhaustively played with the 0610's settings yet...

 

Another question I've had on my mind: does frame integration (sense up) still result in 30fps? This would be interesting, since you would still get 30 frames, with the possibility that one or two would be not blurry. Whereas with the 1344 for example at 1/6s you will only get 6fps max?

[Nimrod 0]

“In my experience, "auto iris" and "DC iris" are almost always used to refer to the same thing; chip-controlled exposure is more commonly called "electronic iris". Many cameras differentiate by labeling the associated switch as "AI/EI", with a separate switch for "DC/video".”

 

Yes, my mistake. My first definition should have said.

 

Electronic iris refers to the CCD chip itself acting as a iris by electronically reducing its sensitivity and has nothing to do with the lens.

 

Which leaves of course the original question of what is “auto iris”. Here are a few definitions from the web.

 

“A device for automatic exposure control in which a motor-driven diaphragm adjusts the aperture in response to a signal from a photocell detecting ambient light.”

 

“An Auto Iris Lens is a lens in which the aperture automatically opens or closes to maintain proper light levels on the security camera sensor. Works similar to the iris on the human eye to adjust for light. An auto iris lens is typically available in better security cameras.”

 

My take on this is that auto iris is a generic term for an electronically controlled iris. and it makes sence looking at the switches Soundy listed.

 

AI/EI - Auto iris or Electronic iris

DC/Video - DC iris or Video drive

 

If you use AI (Auto iris) then the DC/Video switch is enabled to control the iris in the lens.

[mike_va 0]

If you use AI (Auto iris) then the DC/Video switch is enabled to control the iris in the lens.

I get that part, but here's what I'm unknown on:

 

The camera has auto-iris will will reduce the amount of light, thus affecting the shutter speed (camera can also act to use the electronic shutter, and will slow it down as there is less light).

 

Which one wins? Does the auto-iris reduce light to the point where the shutter is set the slowest speed, which seems counter-productive to capturing moving objects?

 

Or is the camera smart enough to reduce it somewhat using the auto-iris, still allowing the shutter speed to remain high?

[rory 0]

If you use AI (Auto iris) then the DC/Video switch is enabled to control the iris in the lens.

I get that part, but here's what I'm unknown on:

 

The camera has auto-iris will will reduce the amount of light, thus affecting the shutter speed (camera can also act to use the electronic shutter, and will slow it down as there is less light).

 

Which one wins? Does the auto-iris reduce light to the point where the shutter is set the slowest speed, which seems counter-productive to capturing moving objects?

 

Or is the camera smart enough to reduce it somewhat using the auto-iris, still allowing the shutter speed to remain high?

 

What camera are you talking about? Movement is still fluid under low light unless you manually adjust the shutter or use DSS.

 

eg. Auto, real time video even in this low light

 

 

now adjustments to shutter manually: it gets slower and slower as it gets brighter:

 

 

 

[rory 0]

Yes, my mistake. My first definition should have said.

 

Electronic iris refers to the CCD chip itself acting as a iris by electronically reducing its sensitivity and has nothing to do with the lens.

 

Which leaves of course the original question of what is “auto iris”. Here are a few definitions from the web.

 

“A device for automatic exposure control in which a motor-driven diaphragm adjusts the aperture in response to a signal from a photocell detecting ambient light.”

 

“An Auto Iris Lens is a lens in which the aperture automatically opens or closes to maintain proper light levels on the security camera sensor. Works similar to the iris on the human eye to adjust for light. An auto iris lens is typically available in better security cameras.”

 

My take on this is that auto iris is a generic term for an electronically controlled iris. and it makes sence looking at the switches Soundy listed.

 

AI/EI - Auto iris or Electronic iris

DC/Video - DC iris or Video drive

 

If you use AI (Auto iris) then the DC/Video switch is enabled to control the iris in the lens.

 

yeah AFAIK basically the auto iris control in a camera uses a referenced level to mechanically move the Iris on the DC or Video lens back and forth as the light level changes. Electronic iris adjusts the level digitally only.

 

If you look at the AI on a Dome or Bullet TDN lens, it is actually built into the same mechanism as the IR cut filter, you can watch the iris open and close as you adjust the Iris level on the camera, or as the light level changes. I took the iris out one time to remove the IR Cut Filter .. that didnt go well .. the parts used are just little pieces of paper like material and the fragile thin metal holder bends easily .. camera still worked great at night but with the Iris sticking on that metal piece when it went to close for the day time, couldnt see anything but whiteout Manually releasing it only helped until it moved again the next day

[Soundy 1]

If you use AI (Auto iris) then the DC/Video switch is enabled to control the iris in the lens.

I get that part, but here's what I'm unknown on:

 

The camera has auto-iris will will reduce the amount of light, thus affecting the shutter speed (camera can also act to use the electronic shutter, and will slow it down as there is less light).

 

Which one wins? Does the auto-iris reduce light to the point where the shutter is set the slowest speed, which seems counter-productive to capturing moving objects?

 

Or is the camera smart enough to reduce it somewhat using the auto-iris, still allowing the shutter speed to remain high?

 

"Which one wins" would depend on the camera, its specific design, and its settings.

[rory 0]

Yep, I should have been more clear. I'm trying to get my head around why my axis 1344 are so much better capturing motion than my analog cameras (e.g. Bosch 0610) even in the daytime.

 

Are you testing this direct to a monitor or going through a DVR or IP encoder?

[mike_va 0]

Are you testing this direct to a monitor or going through a DVR or IP encoder?

In this case I've got the 0610 on an Axis 243 encoder.

[rory 0]

Are you testing this direct to a monitor or going through a DVR or IP encoder?

In this case I've got the 0610 on an Axis 243 encoder.

Maybe thats causing the problem?

If you test it direct into a monitor, without Sens up or DSS or anything like that, how is it? Have you also tested this with other cameras like the CNB?

[mike_va 0]

"Which one wins" would depend on the camera, its specific design, and its settings.

I can buy that. Just surprised not to see it mentioned more.

[mike_va 0]

What camera are you talking about? Movement is still fluid under low light unless you manually adjust the shutter or use DSS.

Bosch 0610 as an example. Let's say strongly backlit so the iris closes down. Does it close down enough to go the slowest shutter, or just enough to get to a moderate shutter speed?

 

Perhaps on the Bosch 0610 it is worked out, as there is a default shutter speed - it keeps it at least there until you run out of light. Simpler models like the 0355 do not have those options.

 

The other part was with frame integration, I wonder if that is a rolling average or accumulate and dump?

 

i.e. average sample 1-2-3-4-5-6 send average 2-3-4-5-6-7 send etc

 

or

 

average 1-2-3-4-5-6 send average 7-8-9-10-11-12 send

 

I tend to think of this in DSLR terms, where I know that 1/60 second is not fast enough to capture clearly something moving fast. E.g. if you looked at one frame of your DVR with an object moving quickly across. I've seen it on traffic cams, the picture that is posted when a car accident occurs and traffic is still going by. You can see the interlace, but there is also some motion blur.

 

I only see this on the P1344 at the lowest light with something moving pretty fast. I guess I'm just surprised that CCTV analog cameras are not more like DLSR's, where you have a choice in terms of priority. On the other hand, they are fine for someone standing in line at a bank.

[Soundy 1]

I guess I'm just surprised that CCTV analog cameras are not more like DLSR's, where you have a choice in terms of priority.

Better cameras will give you that control (to a degree)... but there's a wide range in CCTV cameras, just as there are in digital still cameras. A cheap P&S won't give you the same level of control as a 1Ds mk. III.

 

Keep in mind that your DSLR is also designed to be human-operated... most CCTV cameras won't even be accessible to change those settings regularly, so the extra expense of having extensive adjustments available would be lost outside the initial setup.

[mike_va 0]

If you test it direct into a monitor, without Sens up or DSS or anything like that, how is it? Have you also tested this with other cameras like the CNB?

I doubt it's the 243, since I have a CNB BBM24F on a 241S at the moment does the same thing with fast moving objects (squirrel jumping for example). Walking around type speed they are all fine. I'm not using DSS or Sens up normally.

[mike_va 0]

Better cameras will give you that control (to a degree)... but there's a wide range in CCTV cameras, just as there are in digital still cameras. A cheap P&S won't give you the same level of control as a 1Ds mk. III.

 

Keep in mind that your DSLR is also designed to be human-operated... most CCTV cameras won't even be accessible to change those settings regularly, so the extra expense of having extensive adjustments available would be lost outside the initial setup.

 

I appreciate everyone's patience explaining all this. I wonder if the Axis 1344 does so much better with fast motion being designed perhaps to be more like a digital camera.

 

I guess I see these at the point of being accessible to more people (kind of like other technology has developed e.g. camcorders), but the analog offerings seem to be lacking compared to the results I get with IP. At least with the stuff that's come out in the last few years. I have a 2120 that has poor low light and is still interlaced not progressive...

 

Especially when I think about the exposure metering and options that are built into DSLR's (some of it automatic) now it just amazes me that analog cameras seems to have kind of languished to a large extent.

 

It is interesting tonight I was reading about some minor vandalism that occurred in our neighborhood and just reading the responses in terms of cameras having become more acceptable, even google has a button for webcams on their maps now. I could theoretically add a coupla cameras to that for them...

[rory 0]

If you test it direct into a monitor, without Sens up or DSS or anything like that, how is it? Have you also tested this with other cameras like the CNB?

I doubt it's the 243, since I have a CNB BBM24F on a 241S at the moment does the same thing with fast moving objects (squirrel jumping for example). Walking around type speed they are all fine. I'm not using DSS or Sens up normally.

By the 241S you still mean an IP encoder?

If so then that is your issue, test it direct to a monitor.

Yes fast moving cars will be a little blur but you can adjust the shutter and the compensate the gamma etc for that application if needed.

[mike_va 0]

By the 241S you still mean an IP encoder?

If so then that is your issue, test it direct to a monitor.

Yes fast moving cars will be a little blur but you can adjust the shutter and the compensate the gamma etc for that application if needed.

Yep, an IP encoder.

 

I'll have to think about how to test with a monitor, I notice it on playback frame by frame. Watching the video for example it's not as noticeable as I think the brain kind of reconstructs what it wants to see. I think I understand the gamma idea, raise the shutter pic gets darker from fast shutter...I'll have to play with that I'm not even sure the old Bosch 0355 has shutter speed options.

 

Even with a fast moving car there is no adjustment required with the P1344.

 

Reading this website http://www.idealcctv.co.uk/cameraspecifications.html#Shutter

 

"Engineer Tip: Be sure to TURN OFF AES when an Auto Iris is being used"

 

There is not a rationale given, but it makes me wonder if it's relevant somehow.

[rory 0]

 

Reading this website http://www.idealcctv.co.uk/cameraspecifications.html#Shutter

 

"Engineer Tip: Be sure to TURN OFF AES when an Auto Iris is being used"

 

There is not a rationale given, but it makes me wonder if it's relevant somehow.

 

AES is EI.

we have the choice of only AI or EI in most cases.

[rory 0]

Yep, an IP encoder.

 

I'll have to think about how to test with a monitor, I notice it on playback frame by frame. Watching the video for example it's not as noticeable as I think the brain kind of reconstructs what it wants to see. I think I understand the gamma idea, raise the shutter pic gets darker from fast shutter...I'll have to play with that I'm not even sure the old Bosch 0355 has shutter speed options.

 

Even with a fast moving car there is no adjustment required with the P1344.

 

yes we have to adjust the shutter for faster movements ... but regular stuff should be fine.

Also price difference is huge between that P1344 and say a CNB

 

i havent had time to play with it as never had the need to catch traffic but installed a camera on the side of a building not too long ago which overlooks a road, the client is only recording the sidewalk though, not concerned about traffic which is masked out anyway so I didnt adjust anything for that, CNB VCM-24VF on Dahua DVR recording @ 7ps each. If anything the blur is really noticeable the closer the vehicle gets to the camera, cars further away seem to be okay in general. Converted to MP4 for youtube:

http://www.youtube.com/watch?v=3S-e12FmVAk

[mike_va 0]

we have the choice of only AI or EI in most cases.

Yep, I've learned something today.

 

Went downstairs and pulled the autoiris I've got on a LTC0355, then AES shows up in the menu. Otherwise says OFF or FL (flickerless) if autoiris lens present...

 

LTC0620 gives more flexibility, in that a default shutter can be used (until it runs out of light). May amuse myself over the next few days and tap into the autoiris drive just to see how much it is active at different default shutter speeds...

 

The other thing I may do is wire the iris to be open on some cameras, where they don't get a lot of light and see what happens. I have a lot of auto iris lenses, and not many of the standard type.

[Soundy 1]

As with still cameras, I think you'll find the level of control increases with the quality and cost of the camera.