SyconsciousAu
Getting comfortable
- Joined
- Sep 13, 2015
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Hello Everyone,
I'm in the market for a couple of new low light 2MP IR Domes to replace some Dahua 5MP box cameras (IPC-HF-3500) that have poor low light performance (0.08lux @ F1.2 in B&W). These are matched to some good (read expensive) fujinon lenses that will do F1.2 throughout the range.
I was doing up a spreadsheet to let me compare my options more easily when I realised that at first glance, the only difference that most people will see in these cameras is price, when in reality that is far from the case.
Now across the top of that table everything looks similar until you get to minimum illumination and even then, at first glance, the cheap $167 IPC-HDBW5221E-Z doesnt look like it gives up much in the way of low light performance to the $371 IPC-HDBW8281-Z which costs more than twice the price, and the $273 IPC-HDBW8231E-Z doesn't look like it gives up anything at all at all.
So it's a no brainer right. Get the cheap one because there isn't much difference between 0.005lux and 0.01 lux is there?
But what are those F numbers and what do they mean? F numbers, or F stop measures aperture, or the amount of light the lens is letting in. The Full F Stops go F1.0, F1.4, F2, F2.8, F4.0, F5.6, F8.0, F11.0, F16.0 and so on. For each full F Stop you go up you halve the amount of light getting in through your lens.
In my expensive Fujinon lenses and the even more expensive glass that sits on the front of my Digital SLR that F Stop stays constant throughout the range. In cheaper zoom lenses, such as the board lenses used in CCTV Dome cameras, the F-Stop increases as the lens is zoomed in. The F Stop figure you get is for the lens when it is zoomed out. Most manufacturers conveniently fail to mention that their lens gets slower (lets in less light) as you zoom in. I've done the calculations for these lenses above to make life easy but if you are interested in learning how to do it, here is a quick primer.
To compare apples with apples I've calculated the F numbers for each of the lenses at 4mm, 8mm, and 12mm for you, and what your approximate adjusted minimum illumination becomes (above in blue). As you can see the cheapest camera needs four times as much light as the most expensive camera despite only appearing to need twice as much. The other misleading thing I see in this area is they quote a minimum illumination for F1.2 but the lens on the camera is F2.0, so you need four times more light than that as a minimum.
Then you get to shutter speed and frame rate. Those light figures are usually based on the slowest shutter setting for the camera, 1/3 of a second, which gives you all sorts of motion blur and a maximum frame rate of 3 per second. Every time you halve the shutter speed you get half the light through to the sensor so you need to double the available light to the camera. For example to go from 1/3sec to 1/100 of a second you need 32 times more light. The less motion blur that is acceptable in your image, the higher the shutter speed you will need, and the more light you will need.
Unless stated otherwise, assume the gain is all the way up too for those minimum illumination figures. More gain gives more grain in the image. If you want cleaner images you need to reduce gain which means you need more light because more gain increases the sensitivity of the sensor, and less gain decreases the sensitivity of the sensor but gives a cleaner image, and means you need more light.
The other thing I will point out is the auto focus function on the IPC-HDBW8231E-Z and IPC-HDBW8281-Z vs "motorised focus", which sounds like auto focus but isn't. They sound very similar but one is manual but can be adjusted remotely, and the other is automatic. Your focus shifts between night and day having the camera auto adjust it's own focus when that happens is going to give you better night images.
You can also be sceptical of claims regarding IR illumination on the IPC-HDBW5221E-Z. It claims 50m but uses the same body and IR LEDs of the more expensive IPC-HDBW8231E-Z which needs half the light, and also claims 50m. Either they are lying about the low light performance of one, or the IR range of the other.
The point of all this is that you need to take the spec sheets with a grain of salt, work out how the camera will perform in your installation under the conditions that you intend to use it, and then decide if it is good value for money. Far too many people end up disappointed after buying a camera that looks good at first glace but doesn't do what they need. You get what you pay for. If it's cheap and the figures look really good, they are probably using rubbery figures.
I'm in the market for a couple of new low light 2MP IR Domes to replace some Dahua 5MP box cameras (IPC-HF-3500) that have poor low light performance (0.08lux @ F1.2 in B&W). These are matched to some good (read expensive) fujinon lenses that will do F1.2 throughout the range.
I was doing up a spreadsheet to let me compare my options more easily when I realised that at first glance, the only difference that most people will see in these cameras is price, when in reality that is far from the case.
| Specifications: | ||||
| Model | IPC-HDBW5221E-Z | IPC-HDBW8231E-Z | IPC-HDBW8281-Z | IPC-HDBW5421E-Z |
| Price - US$ | Camera = $167 | Camera = $273 | Camera = $371 | Camera = $195 |
| Image Sensor | 1/2.7” 2Megapixel progressive scan CMOS | 1/2.8” 2Megapixel Exmor R CMOS | 1/1.9” 2Megapixel progressive scan Exmor CMOS | 1/3” 4Megapixel progressive scan CMOS |
| Effective Pixels | 1920(H) x 1080(V) | 1920(H)x1080(V) | 1920(H)x1080(V) | 2688(H)x1520(V) |
| Scanning System | Progressive | Progressive | Progressive | Progressive |
| Electronic Shutter Speed | Auto/Manual, 1/3(4)~1/100000s | Auto/Manual, 1/3~1/100000s | Auto/Manual 1/3(4)~1/10000 | Auto/Manual, 1/3(4)~1/100000s |
| Min. Illumination | 0.01Lux/F1.4(Color); 0Lux/F1.4(IR on) | 0. 005Lux/F1.4( Color), 0Lux/F1.4(IR on) | 0.005Lux/F1.65 (Color), 0Lux/F1.65(IR on) | 0.01Lux/F1.4(Color); 0Lux/F1.4(IR on) |
| S/N Ratio | More than 50dB | More than 50dB | More than 50dB | More than 50dB |
| Video Output | 1 port | 1 port | 1 port | 1 port |
| Camera Features | ||||
| Max. IR LEDs Length | 50m | 50m | 30m | 50m |
| Day/Night | Auto(ICR) / Color / B/W | Auto(ICR)/Color/B/W | Auto(ICR)/Color/B/W | Auto(ICR) / Color / B/W |
| Backlight Compensation | BLC / HLC /WDR(120dB) | BLC / HLC / Ultra WDR(140dB) | BLC / HLC / WDR(120 dB) | BLC / HLC /WDR(120dB) |
| White Balance | Auto/Sunny/Night/Outdoor/Customized | Auto/Manual | Auto | Auto/Sunny/Night/Outdoor/Customized |
| Gain Control | Auto/Manual | Auto/Manual | Auto/Manual | Auto/Manual |
| Noise Reduction | 3D | 3D | 3D | 3D |
| Privacy Masking | Up to 4 areas | Up to 4 areas | Up to 4 areas | Up to 4 areas |
| Lens | ||||
| Focal Length | 2.7mm~12mm | 2.7 -12mm motorized | 4~8mm | 2.7mm~12mm |
| Max Aperture | F1.4 – F6.22 - Max Aperture – 2.921mm^2 | F1.4 – F6.22 - Max Aperture – 2.921mm^2 | F1.65 – F3.3 – Max Aperture – 4.616mm^2 | F1.4 – F6.22 - Max Aperture – 2.921mm^2 |
| F2.07 at 4mm 0.02 Lux (Approx) | F2.07 at 4mm 0.01 Lux (Approx) | F1.65 at 4mm = 0.005 Lux | F2.07 at 4mm 0.02 Lux (Approx) | |
| F4.14 at 8mm 0.08 Lux (Approx) | F4.14 at 8mm 0.04 Lux (Approx) | F3.3 at 8mm = 0.02 lux | F4.14 at 8mm 0.08 Lux (Approx) | |
| F6.22 at 12mm 0.22 Lux (Approx) | F6.22 at 12mm 0.1 Lux (Approx) | N/A but in theory F5 at 12mm = 0.05 Lux Approx | F6.22 at 12mm 0.22 Lux (Approx) | |
| Focus Control | Motorized | Auto | Auto | Motorized |
| Angle of View | H: 99°~34° | H: 99°(Wide)~36°(Tele) | H: 105°(Wide)~56°(Tele) | H: 100°~33° |
| Lens Type | Motorized/ Auto Iris(DC) | Motorized /Auto Iris(DC) | Motorized /Auto Iris(DC) | Motorized/ Auto Iris(DC) |
| Mount Type | Board-in Type | Board-in Type | Board-in Type | Board-in Type |
Now across the top of that table everything looks similar until you get to minimum illumination and even then, at first glance, the cheap $167 IPC-HDBW5221E-Z doesnt look like it gives up much in the way of low light performance to the $371 IPC-HDBW8281-Z which costs more than twice the price, and the $273 IPC-HDBW8231E-Z doesn't look like it gives up anything at all at all.
So it's a no brainer right. Get the cheap one because there isn't much difference between 0.005lux and 0.01 lux is there?
But what are those F numbers and what do they mean? F numbers, or F stop measures aperture, or the amount of light the lens is letting in. The Full F Stops go F1.0, F1.4, F2, F2.8, F4.0, F5.6, F8.0, F11.0, F16.0 and so on. For each full F Stop you go up you halve the amount of light getting in through your lens.
In my expensive Fujinon lenses and the even more expensive glass that sits on the front of my Digital SLR that F Stop stays constant throughout the range. In cheaper zoom lenses, such as the board lenses used in CCTV Dome cameras, the F-Stop increases as the lens is zoomed in. The F Stop figure you get is for the lens when it is zoomed out. Most manufacturers conveniently fail to mention that their lens gets slower (lets in less light) as you zoom in. I've done the calculations for these lenses above to make life easy but if you are interested in learning how to do it, here is a quick primer.
To compare apples with apples I've calculated the F numbers for each of the lenses at 4mm, 8mm, and 12mm for you, and what your approximate adjusted minimum illumination becomes (above in blue). As you can see the cheapest camera needs four times as much light as the most expensive camera despite only appearing to need twice as much. The other misleading thing I see in this area is they quote a minimum illumination for F1.2 but the lens on the camera is F2.0, so you need four times more light than that as a minimum.
Then you get to shutter speed and frame rate. Those light figures are usually based on the slowest shutter setting for the camera, 1/3 of a second, which gives you all sorts of motion blur and a maximum frame rate of 3 per second. Every time you halve the shutter speed you get half the light through to the sensor so you need to double the available light to the camera. For example to go from 1/3sec to 1/100 of a second you need 32 times more light. The less motion blur that is acceptable in your image, the higher the shutter speed you will need, and the more light you will need.
Unless stated otherwise, assume the gain is all the way up too for those minimum illumination figures. More gain gives more grain in the image. If you want cleaner images you need to reduce gain which means you need more light because more gain increases the sensitivity of the sensor, and less gain decreases the sensitivity of the sensor but gives a cleaner image, and means you need more light.
The other thing I will point out is the auto focus function on the IPC-HDBW8231E-Z and IPC-HDBW8281-Z vs "motorised focus", which sounds like auto focus but isn't. They sound very similar but one is manual but can be adjusted remotely, and the other is automatic. Your focus shifts between night and day having the camera auto adjust it's own focus when that happens is going to give you better night images.
You can also be sceptical of claims regarding IR illumination on the IPC-HDBW5221E-Z. It claims 50m but uses the same body and IR LEDs of the more expensive IPC-HDBW8231E-Z which needs half the light, and also claims 50m. Either they are lying about the low light performance of one, or the IR range of the other.
The point of all this is that you need to take the spec sheets with a grain of salt, work out how the camera will perform in your installation under the conditions that you intend to use it, and then decide if it is good value for money. Far too many people end up disappointed after buying a camera that looks good at first glace but doesn't do what they need. You get what you pay for. If it's cheap and the figures look really good, they are probably using rubbery figures.
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