Vari-focal vs fixed-lens?

[ipmania]

I a hobbyist in photography and in the camera world, zoom lenses (which I am thinking equate to "vari-focal" lenses) generally have a smaller aperture than prime lenses ("fixed-lens" lenses).

Thus prime lenses capture more light and are better in low light. Often prime lenses are cheaper too because they don't have a complicated zoom mechanism. As an example, the common 50mm f/1.8 lens often quite cheap. And compared to the MUCH more expensive 24-70 f/2.8 zoom lens, the cheap and cheerful 50mm f/1.8 captures more than twice the amount of light (f/1.8 is more than 1"stop" of light "faster" than f/2.8; 1 stop of light being twice as much light)

Is this the same in the security camera world?

For example, a camera that is well thought of around here is the vari-focal:

EmpireTech 4MP 2.7mm-12mm Lens Turret Camera IPC-T5442T-ZE White, currently $189 USD.

But there is a similar fixed lens camera:

Loryta 4MP Turret AI IP Camera Fixed Lens IPC-T5442TM-AS 2.8mm, currently $159 USD. This one being the 2.8mm "fixed lens" model, there are others also available in 3.6 and 6mm.

As expected the fixed lens Loryta is cheaper than the vari-focal Empiretech.

However, there isn't a mention of the aperture (the f/1.8, f/2.8 etc. that I talked about earlier when it comes to camera lenses).

What is the aperture of a fixed-lens camera like the Loryta? And if it is significantly larger, will cameras like the Loryta be better in low light?

 

[wittaj]

Yes and no relating these types of cameras to hobby or professional photography cameras.

Loryta and Empiretech are the same, they are both international Dahua OEM cameras sold by @EMPIRETECANDY. It is better to refer to them as 5442 for the fixed lens and 5442-ZE or 5442-Z4E for the two varifocal options.

Yes the apertures are discussed in the tech specs. The fixed lens 5442 has a better aperture - f/1.6 for the fixed lens compared to up to f/1.8 for the varifocal at min zoom. I think it goes to like f/2.0 at max zoom.

And yes the fixed lens is cheaper than the varifocal for as you called the additional moving parts.

The key is to get the correct camera for the intended purpose.

A 2.8mm fixed lens is great for an overview or IDENTIFY within 12-15 feet. You get the varifocal if you need to IDENTIFY at 35ish feet.

If you know you need a fixed lens optical length, then yes the fixed lens version will provide slightly better image due to the better f-stop. But to most we don't notice it and opt for the varifocal due to being able to be used in more locations, and most of us end up wishing we had more optical zoom, so with a fixed lens, you are stuck.


Now in terms of their performance compared to a "real" camera, you might have to forget what you know about DSLR and high end photography cameras LOL as you play with these. Almost everyone that has come here with experience in DSLR cameras struggle with these cameras. Every one of these cameras have more processing of the images than a DSLR camera. Some are worse than others. Then there is the compression of the video, etc. Turn off NR on one of these cameras and you will see how much processing is used.

You will find a BIG difference between photography equipment and these cameras. Things like trying to match focal lengths are tough because it may be crystal clear on high end DSLR and not be clear with these types of cameras. Digital zoom works better on DSLR cameras than these. The sensors and optics just are not at the same level. These cameras are designed for 24/7 use with abuse from the elements. DSLR cameras are designed for a different working environment and purpose. Hang a DSLR camera outside and see how long it lasts LOL! But the quality would be better for the time it was working (but also a lot more storage needed too).

Remember these are surveillance cameras, not DSLR cameras, so you have to check your expectations. For example, you can see individual hairs and skin pores with DSLR photography equipment and you won't with these kinds of cameras. These are for a different use and different expectations.

• Sensor Size - a full frame DSLR sensor size is 864mm^2; whereas a 1/2.8" sensor popular on many cameras would be 20mm^2, so the "real" camera can collect over 40 times more light than a surveillance camera. And this doesn't even account for less light available for an 8MP versus 2MP for the same size sensor.
• Shutter Speed (Exposure) - Taking a picture with a "real" camera, you can slow the shutter down to 1/2s or longer for a nice clean picture of a person not moving. Perps rarely stand still and we need a shutter of at least 1/60s to minimize the blur.
• Aperture - With a "real" camera you focus on a specific part of the field of view, while a surveillance needs to focus on things in the foreground and background, which means the aperture is smaller, further compounding the light issue.
• Compression - A single 8MP image from a "real" camera could be upwards of 5MB of storage. In surveillance cameras, if you record at 15FPS, every second of video could be 75MB or more, which could equate to 6.5TB per day per camera. Obviously most are not going to have that kind of storage, so lossy compression algorithms are used to reduce storage and network bandwidth requirement, and that can add noise.
• Environment - a "real" camera is used mainly under ideal conditions, whereas a surveillance camera is going 24/7 in every type of element, so the design and size impacts its capabilities.

What most of us have found is that for surveillance cameras, you need to get the optical length for the distance you want to IDENTIFY. That is more important than MP or focal length. Digital zoom doesn't work well with these cameras, it needs to be optical zoom.

The Importance of Focal Length over MP in camera selection

At the urging of several folks here, I created a thread to show the importance of focal length and how focal length can be more important than megapixels (MP). I mentioned some of this in the post regarding The Hookup’s latest video demonstrating different cameras, including one sold from a...

ipcamtalk.com

 

[bigredfish]

Yes same theory

Here's the detailed specs from Dahua's site

Varifocal

https://www.dahuasecurity.com/products/All-Products/Network-Cameras/WizMind-S-Series/4MP/IPC-HFW5442E-ZE=S3

Fixed

IPC-HFW5442T-ASE - Dahua International

IPC-HFW5442T-ASE

www.dahuasecurity.com

What Im not certain of is whether the described "Max Aperture" is at it smallest zoom of 2.8mm or its largest at 12mm? It cant apply to both and I think it refers to the fully un-zoomed 2.8mm focus..

Notice on PTZs they commonly call out the Max Aperture range-

https://www.dahuasecurity.com/products/All-Products/PTZ-Cameras/WizSense-Series/SD4/4MP/SD49425GB-HNR

Max. Aperture - F1.6–F3.6

 

[Mike A.]

The fixed is marginally better but these are relatively low-quality lenses/sensors and the image quality isn't at that same level. i.e., They're both kinda crappy compared to photography lenses go. So as long as the added cost doesn't hurt, you might as well go with the "zoom" vs "prime" since it's more flexible as far as application and you get basically the same out of it. If you have a particular use where you know the fixed works you can save a little money and get slightly better results. But it's not like you're going to see some big benefit in terms of image quality/low-light capability.

 

[samplenhold]

I have four 5442 cams. Two are fixed focal lengths of 2.8mm and 6mm turrets. A third cam is the varifocal turret 2.7-12mm and the fourth one is the bullet Z4E varifocal 8-32mm.

As far as the three turret cams, I really can't see the difference. Yes the two fixed lens cams look better on paper than the varifocal, but I see no real difference in real life.

The two fixed turrets were chosen for their specific FOV. The varifocal turret was needed since I needed more zoom than 6mm for its particular purpose.

The bullet Z4E was chosen for even more zoom that was needed for that deployment.

I should also point out that these varifocal cams are not really like a zoom DSLR in that the lens is really not designed to be zoomed in and out a lot. They are really designed to be set at one FOV and kept there.

 

[ipmania]

Thanks, everyone, for the answers and advice. Based on that, I'll go with a single varifocal 5442 turret camera and move it around the house using a bucket-and-2x4 test rig and test for the "best" focal length.

If a location has a "best" focal length that is very close to one of 2.8, 3.6, or 6mm, I'd then get a fixed-lens 5442 with the appropriate lens and thus benefit from the slightly better light capture and sharper(?) image that a fixed-lens can provide (plus the small cost savings).

Thanks again for the fast and detailed answers!

 

[Mike A.]

Also along this same line to consider going into this is that these things tend to multiply, new/better cams come out, and where/what you thought you wanted to do with a cam initially can change quite a bit once you have things up and running and live and learn for a while. Very few of my cams are the same cams in the same location with the same view as when I first put something up. Having vari-focal ability makes them more useful however/wherever they may end up.

Another aspect related to photography that you might appreciate re vari-focals is the ability to best frame the shot for what you're trying to accomplish. You can't do the equivalent of moving your feet as easily to do so with these cams and post-processing doesn't work in the same way in most cases to help you much. Sometimes things are kind of in between, or you'll want to get something out of the view, and as above if you need more focal length there aren't many fixed length cams above 6mm as you might have with longer prime lenses. You can in some cases swap lenses but not as easily as with a camera.

Long way of saying that generally I think that the vari-focals are worth the relatively small incremental cost/performance difference. If I could have bought my better fixed cams like the 4K-X with variable focus I would have even it if cost a little more and I lost a little in performance. Surveillance cams have much more practical aspects as far as their use vs being more about absolute image quality in the case of photography.

 

[ipmania]

Also along this same line to consider going into this is that these things tend to multiply, new/better cams come out, and where/what you thought you wanted to do with a cam initially can change quite a bit once you have things up and running and live and learn for a while. Very few of my cams are the same cams in the same location with the same view as when I first put something up. Having vari-focal ability makes them more useful however/wherever they may end up.

Another aspect related to photography that you might appreciate re vari-focals is the ability to best frame the shot for what you're trying to accomplish. You can't do the equivalent of moving your feet as easily to do so with these cams and post-processing doesn't work in the same way in most cases to help you much. Sometimes things are kind of in between, or you'll want to get something out of the view, and as above if you need more focal length there aren't many fixed length cams above 6mm as you might have with longer prime lenses. You can in some cases swap lenses but not as easily as with a camera.

Long way of saying that generally I think that the vari-focals are worth the relatively small incremental cost/performance difference. If I could have bought my better fixed cams like the 4K-X with variable focus I would have even it if cost a little more and I lost a little in performance. Surveillance cams have much more practical aspects as far as their use vs being more about absolute image quality in the case of photography.

Very true. I guess I am getting caught up in my photography equipment geekiness and am chasing that 1/2 stop of extra light... I do that for my (photo) camera gear (and thus have too large a collection of lenses...) but I take your point that security cameras can be redeployed and my mind could change regarding field of view.

So with your advice, I think I will change my choice of security camera to varifocal 5442 turret cameras. Thank you again.

 

[Sammyf]

Thanks, everyone, for the answers and advice. Based on that, I'll go with a single varifocal 5442 turret camera and move it around the house using a bucket-and-2x4 test rig and test for the "best" focal length.

If a location has a "best" focal length that is very close to one of 2.8, 3.6, or 6mm, I'd then get a fixed-lens 5442 with the appropriate lens and thus benefit from the slightly better light capture and sharper(?) image that a fixed-lens can provide (plus the small cost savings).

Thanks again for the fast and detailed answers!

Remember to test the locations both night and day time. If you plan to use the AI of the cameras for human or vehicle detection (IVS), I would also test how those work in each location that otherwise seem good. Some fields of view are hard for the AI to work reliably, so you might want to e.g. place an overview camera to trigger the cameras placed for capturing the face for the identifying shot.

 

[Mike A.]

That's a better way to go starting out at least. You've already avoided the typical approach of buying a big box set of 2.8mm cams to put everywhere, so you're headed in the right direction and avoided wasting some money from the start. ; )

Once you have some up you'll better understand what you really need/want. Nothing wrong with fixed cams if they do what you want to do. You may find that in some cases that's a perfectly fine way to go. But wait until you know that's the case before going out and buying a bunch of them. Also sometimes things are good enough. If you find a deal on a fixed cam that you wouldn't have otherwise and you want it, no reason to avoid it. In addition to my good cams I also have some crappy little Wyze cams scattered around that I picked up cheap. They suck in many ways but as a fill-in cam to watch the inside of my shed or the cat door, etc., it's $15 spent and ehhh... good enough, done.

 

[Virga]

Recently I got advice similar to, "Remember to test the locations both night and day time." from another forum member, and it is right on.
Being in a dark area, over the next couple of weeks, I additionally discovered that the amount of moonlight materially impacted what the camera could see at night.
I'd guess half a stop or so, though that is totally a guess to make a point and I could be way-off.

 

[wittaj]

Like I said you have to forget what you know about real photography cameras lol.

For most of us we don't see a difference between the fixed and varifocal image.

Keep in mind these are not infinity focus cameras and some have very defined distances for focus and depending on your field of view you may have an out of focus image unless you take the camera apart and focus it to your field of view.

The varifocal has better focus since you can change it from the computer, plus it adds audio that can come in handy.

 

[samplenhold]

No need to decide on all of the cams at once. Get that varifocal and try it out in different places, day and night. Walk it and view the video. Get your expertise up to the point that you can make good predictions of what cam is best for each deployment.

 

[Virga]

We all have a common interest in light since we are making images/video and are deploying cameras for that purpose.
I have a growing interest in night images because of my site conditions, and because it has been pointed out in threads here that daytime images are easy, test for night images.
Yesterday I noticed a new phenomenon, which is not to say that it may not have happened before, just that it hit my radar.
I have two cameras on test rigs at 90 degrees toward the same general area.
The night image was noticeably better lit than other nights, more so than a brighter phase of the moon.
It was raining/drizzling, but the image area was better illuminated than it usually is.
I thought nice, now how do I do that all the time.
Then I realized this had to do with the fact that the foreground of the image area is a light/white-ish concrete, the coating of water on the concrete was creating a mirror effect, the IR illumination was likely reflecting off the wet concrete and lighting up the image better than probably LED lights would.
Of course, we can't hope for bright moonlight and/or drizzle on reflective surfaces all the time, but just to note how much difference conditions other than the hardware can make on images.

 

[wittaj]

We all have a common interest in light since we are making images/video and are deploying cameras for that purpose.
I have a growing interest in night images because of my site conditions, and because it has been pointed out in threads here that daytime images are easy, test for night images.
Yesterday I noticed a new phenomenon, which is not to say that it may not have happened before, just that it hit my radar.
I have two cameras on test rigs at 90 degrees toward the same general area.
The night image was noticeably better lit than other nights, more so than a brighter phase of the moon.
It was raining/drizzling, but the image area was better illuminated than it usually is.
I thought nice, now how do I do that all the time.
Then I realized this had to do with the fact that the foreground of the image area is a light/white-ish concrete, the coating of water on the concrete was creating a mirror effect, the IR illumination was likely reflecting off the wet concrete and lighting up the image better than probably LED lights would.
Of course, we can't hope for bright moonlight and/or drizzle on reflective surfaces all the time, but just to note how much difference conditions other than the hardware can make on images.

Yep, rain, moon, snow, seasonal changes, etc. all affect night-time performance.

That is why it takes some time to dial these things in. Typically if you dial them in for worse case (least amount of light), then they will perform better with moonlight or snow cover or wet pavements.

 

[Virga]

On a regular basis I am reminded that most optional things worth doing are not easy, simple, or for the faint of heart.