What Is A Normal Shutter Speed For Identification At An Entrance

Hi.

I have an entrance that have some low light concerns. We are not talking dark, just challenging enough to make shutter speed an issue. People are generally passing inn trough the entrance at walking pace, trough a depth of field at about 6 meters from the camera, and often passing underneath the camera. Because of the lighting situation the iris is practically always fully open, and consequently the depth of field is pretty short. The entrance opens into a large room, so the depth of field needs to stay where it is. I have been nagging the higher powers for some more light, but get a pretty harsh no, for customer comfort reasons.

I have been setting the shutter speed at 1/100s-1/125s because of what I perceive as motion blur. If people are moving at at a "determined" pace, and with the head swinging, I get blurry faces at 1/30s and 1/50s. I have set gain and iris to suit the light coming from the faces, not the area behind the faces. What happens in overexposed or underexposed areas is of no interest, as the camera is dedicated for the task of capturing identifiable faces. I have turned off wdr because it just made the overexposed areas outside visible. I imagine this would leave less “greytones” for the face. I also noticed image distortions that I have decided must be the result of dual exposures. I have turned blc on and off without seeing any significant improvement. And when it got dark outside, blc apparently confused the automatic gain control. So I turned it off.

The problem I get, with these settings, is that I get very little contrast in the faces. Even with ppm at 250+, eyes become dark pits, blonde eyebrows disappear, and the faces get so smoothed out that it is difficult to determine the shape of the nose and chin. I have set bitrate to max, quality to max, and even reduced frame rate to get more bits/image. The camera uses h264 for compression. Sometimes I get maybe one or two usable images, but often I get none.

I have intentionally left out make and model of the camera, because I have tried different cameras, and because I hope for more general answers to the following questions.

I was wondering what other people use for shutter speeds in these situations? Am I too mental about the shutter speed? And have I made any obvious errors in my setup?


Good description.

First question - do you require color? If not, have you used IR?

Secondly, how good in low light are the cameras you have tried?

There are a number of ways to improve low light performance - as you mention iris and shutter speed. The other 'big' one is the low light sensitivity of the camera, some cameras are just a lot better than other ones (e.g., Ranking IP Camera Low Light Performance). To that end, any 'general' answer needs to directly address the low light performance of varying models.

Third, can you share an example face shot? For example, you mention "very little contrast in the faces" but I am not sure how much / bad that is, as people's judgment on this can vary. This (and the models) would help us get a better sense of what optimizations are available.

I require color.

The camera is supposed to deal fairly well with low light, as I am told by the data sheet and the supplier. I have another camera, that is performing better, in mind, but I have to justify the extra cost. And that is sort of why I am asking a general question about the shutter speed. I am pretty sure what is wrong in the scene, and how to fix it. It is whether or not it is normal to set maximum shutter speed to be 100+ to capture faces, which is my question.

I can't send any images because of boring legal reasons.

By "very little contrast" I mean that there is not enough difference in color between the pixels in the face, for the h264 encoder to understand that there is detail there. Other features, like writing on clothing, is sharp and clear on the person.

But I don't want to focus on the optimizing stuff. I really just want to know if it is normal with short shutter speeds, because I suspect this is one of the questions that will pop up in the discussion about the cameras. Questions like "Do you really ned the short shutter speed? We usually use 1/30 in other places, and have gotten only positive reports about how pretty the pictures are." If 1/30 is really the standard for identification purposes, then what I perceive as motion blur may have some other cause, or may simply be a figment of my imagination.

"I really just want to know if it is normal with short shutter speeds, because I suspect this is one of the questions that will pop up in the discussion about the cameras."

It depends how fast someone is moving / walking. 1/30s is a 'standard' because that is associated with the most common max frame rate (30fps). However, if a person is moving sufficiently fast, you might very well need 1/60s or higher.

But there is no shutter speed that is "the standard for identification purposes." It's purely a factor of how fast the object is moving, keeping in mind that the shorter the shutter speed, the less light passes through and the higher the gain has to kick in, causing more noise, etc.

Can you share the models you have tried? This would help us give you more concrete feedback.

It is the Avigilon H3 series 1 and 2mp fixed dome cameras, and the 3mp wdr fixed dome camera.

I'll just make a photo montage with images at different shutter speeds. That should demonstrate the issues to the boss.

The reason why I was wondering about a typical shutter speed, is because i have several entrances with motion blur on bobbing heads, until I set it to below 1/100s. It seems to me that 1/100s is the pain threshold for heads swinging and people walking. I was wondering if other people had the same experience.

I suspect those are the non 'LightCatcher' Avigilon models. Please confirm.

Avigilon, like most manufacturers today, offer 'super' low light camera models that make a significant different in dark conditions.

Non Lightcatcher / non IR Avigilon cameras are not particularly strong in low light. You can see our 2013 Avigilon H3 test report. Since then, there's been a lot of newer much better low light cameras, surely including Avigilon's own LightCatcher but also new models from Bosch, Panasonic, Samsung, Sony, etc.

Couple questions:

If the shutter speed is set to 1/50 and someone is walking slowly without bobbing and weaving, does the head shot contain what you would consider adequate amount of detail/contrast, without blurring?

If it doesn't, what ss is necessary (assuming a slow moving image)?

As John says it matters how fast the subject is moving to determine blurring. In the end though, what matters is how fast the subject is moving thru the frame/FOV.

A level, straight-on shot at a subject moving directly toward the camera is going to have less blur than one where the subject is moving at an angle toward the camera.

Is the distance to target always the same (approx.)?

Are people coming at different angles thru the pinch point?

Can you reduce the angle of the shot by moving the camera back and using a longer focal length?

Wow, it's like I could have written this myself!

One of our customers is a higher-end restaurant chain, who also like to keep the lighting dim at night. Since every site has its own design "oddities", the lighting for the ID shot at some is also particularly tricky, between backlighting, small overhead pin lights, etc.

In the past we've generally used Panasonic SuperDynamic cameras for this purpose (CW or CP484 with SDIII, later CW504 with SD5), but there are instances where even these couldn't really get a good image... and as in your case, management is adamant that the lighting will not be changed to improve facial shots.

Their current spec is Axis P3384 cameras for all public areas, as the Lightfinder feature works very well with the overall dim lighting. There are a couple of instances where we use the WDR function instead, but for the most part the better exposure is more important than "pretty" balanced images.*

For ID shots, I find what usually works better than WDR, is to set them to Lightfinder, enable BLC, then create custom exposure zones using mid-grey-level objects that are under approximately the same lighting as faces will be once inside - door mullions work surprising well for this, or sometimes a bench or planter just inside the door.

I'd have to check, but I'm pretty sure I'm using a 1/60 minimum shutter speed on these - still get a little blur if someone is walking briskly, but since people usually come in the door and stop to look around and/or wait for a hostess, that's not a major problem most of the time. Most sites have a hostess stand right there, and we'll try to aim cameras so it's in or near the edge of the frame, so we get faces as people are talking to the hostess.

*What would really be ideal in this situation is if the camera could automatically switch between LF and WDR modes based on lighting level, while not changing day/night (or IR Cut) mode as we too want them to always be in color... but currently the only way to do this is to have it switch WDR modes based on using the day/night mode switch as a trigger. The problem I found with that is, when it switches to night mode (ICR out), then toggles LF on... the exposure suddenly increases enough that the camera soon goes back to day (ICR in), which triggers a toggle to WDR... which makes the image dark enough to trigger ICR out... and these cameras also have no adjustment for that trigger level (or didn't at the time), so the only way to counter the hysteresis was to fiddle endlessly with exposure settings. So I just set them all to LF and left it at that.

If someone stops or slows down I get a clear picture at longer shutter speeds. And if they walk towards the camera, and the face somehow stay pretty still in the camera, I get a clear image. So I am pretty sure it is motion blur.

How do I "set the p3354 to lightfinder"? I have two, and can't find any setting for it. All I do is set the exposure zones and fiddle with the gain. I have tried the p3354 in the positions of the Avigilon cameras, and fell I get better images. So I guess that is where I'll end up.

I feel i have gotten a fair bit of answers to my question. Thanks all for playing:)

If someone stops or slows down I get a clear picture at longer shutter speeds. And if they walk towards the camera, and the face somehow stay pretty still in the camera, I get a clear image. So I am pretty sure it is motion blur.

If the problem is there at 1/30 and not at 1/125, then yeah, it's probably motion blur. Part of the trick is to make sure they slow down, either by having a host/hostess right there to greet them, or an obstacle like a host stand podium, or something else to capture their attention momentarily.

How do I "set the p3354 to lightfinder"?

In the P3384 it's under Setup -> Video & Audio -> Camera Settings:

You can also use the buttons in the top menu bar (if the P3354 is the same as the P3384):

Actually, I think those two buttons to toggle WDR and LF are reversed (clicking "Lightfinder mode" turns on WDR)... but you can experiment with that. Going through the Setup page is the sure way to do it.

The P3354 spec sheet doesn't list WDR so it may be a little different, but either way, I'd expect the option to be under Camera Settings.

On my p3354 I have a checkbox for turning wdr(wide dynamic contrast) on or off. When I turn it off, I get a new slider under exposure, called "exposure value", that does not seem to do very much. And I don't have any extra lightfinder buttons on the live feed page. Just scale and stream choice.

The p3354 has firmware 5.60.1.1, which I believe is the latest. I guess "wdr off" means "lightfinder on" then. Thank you for the help:)