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This is another case of having to figure out what they're doing in the firmware, which isn't easy, and doesn't always make sense. You have to test it to know for sure. Typically, they use the entire image to calculate exposure, and when you include more pixels in an increased FOV, those pixels are now used as well. If it's sampled, the groups of pixels have different averages than the individual pixels, which can also change the exposure setting. In my Dahua image, the exposure is darker at 3MP because it includes more of the sky, which is brighter, and I have auto-exposure enabled. Is your Dahua image fixed exposure on both? It appears so, because they match quite closely. No telling why Dahua chose to directly sample some and scale others - this makes no sense, and causes customer confusion and unhappiness. Most sensors/processors have sampling commands built in to generate full FOV images of lower resolutions, so they didn't even have to do any special work to implement it. At least now you know what's happening!

For IP cams, the recorded file size is determined by the bit rate settings. FPS and resolution don't affect it unless you use variable bit rate, and then it depends on the scene complexity, movement, and noise. If you use constant bit rate, here's how to figure it out, using 4096 kb/s as an example. It's important to note the difference between kb/s (bits) and kB/s (bytes): 4096 kbitps / 8 = 512 kBytes per second 412 kBps * 60 = 31 MB/minute 31 MB/minute * 60 = 1.8 GB/hour So, 4096 kb/s bit rate recording full time uses 1.8GB per hour. 2048 kb/s cuts that in half, and so on. Variable bit rate may be somewhat lower, but it depends on the image.

The cams may be failing, the POE ports may be dropping out, or the cabling may have problems. When they drop out, can you ping them or view the image from a browser? You may need to match network settings, since the NVR tends to use a different subnet than your home network. I'd switch the ports for the two dropping out cams with two good ones at the NVR first, because it's easy. If the problem continues, try running a separate cable to one or both of the problem cams. Still dropping out? Swap the problem cams with good cams. If the NVR POE board is failing, it may be too loaded with 10 cams. Try disconnecting a couple of good ones to see if the problem cams stay online. At some point, the cause of the problem should become clear.

Reducing sharpening can also help, but this is a typical Hik 2CD2xxx low light image. They all show the horizontal line noise until you add extra illumination. You can also increase the maximum exposure time, but anything longer than 1/30 second will cause image blur for moving objects. You might want to set up day and night profiles, as the high noise reduction will make for a softer image in the daytime, and WDR works well in the daytime to get details in the shadows, but increases noise at night.

If the field of view is the same for both 1080p and 3MP, they're using compression on the 3MP image, though sampled images can still have different FOVs. If the FOV is smaller for 1080p than for 3MP, they may not be sampling. One way to tell for sure is to open both images in a paint program, copy the 2MP image, and paste it over the 3MP image. If it lines up exactly once you get it centered, it's reading pixels directly. If one part lines up and the rest is off center, they're sampled. Here are some examples. Dahua HFW3300C with 2MP overlaid on 3MP - everything lines up because both are directly sampled (note the exposures are different due to the different FOV): Hik 2032 (Swann version) with 2MP and 3MP overlaid transparently - scaled images only line up in the center, then get out of alignment:

A bit off topic, but here are my thoughts. I haven't compared the 4300S images much recently, and have been running it in 3MP mode with a 25mm lens for a while, so not a typical install with the target well outside the IR range. The Dahua directly samples sensor elements for both images, so that shouldn't make a difference. I'd expect the 2MP image to be very slightly better, since it's more from the center of the lens, which is general brighter and sharper than the edges, but the real area difference is pretty small. It's also getting more of the image from the brighter area of the IR spotlight, which should help as well, but can change the exposure. My best guess is that it's changing exposure times going from 3MP to 2MP, but you'd have to test it to know for sure. The Dahua will let you set a fixed exposure time, so that's what I'd do for testing - set it for 1/30 or 1/25 sec fixed (or whatever) and compare the images to see if the noise is still different. If you still see an obvious difference, post images in a new thread. I don't think there's a way to read the actual exposure settings from the camera when it's set for variable exposures, but I could be wrong.

When I did the testing, iPads were still pretty expensive, my budget was smaller, and my wife uses hers a lot so it wasn't a good option to take it over for a few days! I'm starting to increase my price range, and now that she has a Surface Pro 3, I may test out the iPad for a few days. I was using IP Cam Viewer Pro on the iPhone, and it worked great. Kept the phone's display on all the time, stayed connected, and never crashed. I'm still liking the idea of an inexpensive Windows tablet, but I've got a growing collection of marginal solutions already, so the iPad's probably the next bet.

The majority of decent IP cams today have 1/3", while the cheapest ones have 1/4" sensors. 1/2" is becoming less common, though is still readily available if you don't mind paying more. 1" sensors are awesome and will definitely solve your low light problems, but at a very high cost, both for the camera and the lens. I don't know who makes them these days, as it's a very specialized market, but I'm sure someone does. I doubt you'd get by for less than $5k for a camera/lens combo, but I could be wrong. As for bad pixels, I've never seen one on a new IP camera (admittedly small sample for me, only a dozen or so), but have seen a good number of them on used cameras that have been in service a while. It takes a lot of bad pixels to cause image problems; a few bad pixels won't affect anything on a MP camera.

Most cameras work this way: 2MP - 1920 x 1080 pixels (1080p is a standard, but there are 2MP cams that aren't 1080p) 3MP - 2048 x 1536 pixels (or whatever; 3MP isn't a standard, and actual resolution may vary; this is typical Dahua resolution) 3MP will show the exact same pixels as 2MP, plus additional pixels all around. For the Dahua 3MP resolution listed above, you'd get 128 more pixels horizontally, giving 64 more pixels per side, and 456 more pixels vertically, for 228 more pixels each top and bottom. You don't get any better resolution in terms of pixels per foot (or whatever), just more field of view for more coverage. This would give a slightly wider and definitely taller 4:3 image compared to the wide-screen 16:9 1080p image. Some cams handle this differently, like Hik's 2CD2xxx series, which have a smaller HFOV at 3MP than at 2MP, but this isn't typical. Likewise, the Axis specs listed above show that you get less FOV horizontally, and you'd have to look at the images to see if it's the same pixels as 2MP but fewer horizontally, or if it's sampled. How each cam handles this depends on how the firmware is written, and you can't be completely sure until you see the actual images at each resolution. Likewise, how your NVR handles this will depend on the software. It may refuse to record 3MP, it may compress it down to 2MP, distorting the image, or it may trim it to 2MP.

I had good luck with Yawcam when I tried a few years ago: http://www.yawcam.com/

I've been experimenting with compact alway-on solutions to run 8-10 hours a day, and the Android solutions I've tried have not been reliable over that time frame. I've tried a Galaxy Tab 2 10.1 tablet, a big Acer Android all-in-one, an iPhone, and an ancient laptop, and only the iPhone would work reliably all day, but the display was too small. The others would drop wireless and disconnect (despite being 5' away from a Ubiquiti access point), or the app would shut down randomly and need to be restarted. This was using both IP Cam Viewer Pro and the Blue Iris app. The laptop ran XP and used the client view for Blue Iris, but was quite old, and would crash randomly. I believe a newer model would hold up better, but haven't tried one. At this point, I'm thinking about about an inexpensive Windows tablet. If you need a big display, something like what BW suggests is more likely to be stable than the Android devices I've tried, since it's a generic Windows PC. The monitor will probably draw more power than a Celeron NUC. This has the option of letting you run a variety of software, as well as being able to change monitors easily.

If you don't care for the input from people who do this kind of work all the time, you do have a few other options: - Buy some different cameras and test them to see the differences for yourself. - Take the salesman's/marketeer's/website's word on which will fill your needs. - Put yourself in the hands of a professional and let them take care of it. The first way is the best way, but takes time, work, and money up front. On the upside, you learn quite a lot about cameras doing this, and don't have to rely on other people's advice. This is how most of the users here have learned about cameras, what works, and what doesn't. The second way is something many people do the first time, then never again. The third way is good if you choose your professional well, but you're paying extra for the years of experience they've gathered following the first path. If you choose poorly, you're back on the second path.

Here it is for $88 with free shipping to the US (don't know about your location): http://www.aliexpress.com/item/Dahua-3mp-ip-camera-IPC-HDW4300S-3MP-Small-IP-IR-Dome-Camera-ONVIF-Profile-S-H264/1397329554.html All AE warnings and precautions apply, as usual. I bought mine from a US vendor for a good bit more, because I wanted better support, having had previous experience with Dahua factory non-support. My 4300S is only slightly better than my Hik 2032s, and the dynamic range and WDR both are not much better than my 3300C. The Vivotek and Sony from korgoth's posts are far better than any inexpensive camera I've tested. There's a reason the Vivotek 1.3MP costs $600. Look at his tests, set up your 4300S in a similar test, and see how it looks. That's the best comparison.

Always hard to say exactly what the marketing means in real world terms without testing. The camera world is full of great sounding specs that are not very good in real life. This IPC-HFW8301E you linked, for instance, is called "Ultra-Smart". What the heck does that mean? It's just a marketing term, though it's presumably anchored in real-life improvements like better software and a faster CPU. My guess is that it uses a faster CPU to provide more image processing. Whether it's as good as the cams that cost twice or 4 times as much would require testing. Not everybody specs WDR in dB, but more are starting to do that, which is good. If you look at the specs for this IPC-HFW8301E, it says WDR 120dB, so that tells me it's for the WDR processing. Looks like it's $390 shipped from China, while the 4300S is $86 shipped, so I'd hope it would perform better than the 4300S at 4x the cost. We already know the 4300S WDR is not very good compared to the Sony and Vivotek.

I seem to remember a thread where it doesn't like a "." in the email name. joe.blow@gmail.com wouldn't work, but joeblow@gmail.com would. Apparently, gmail in particular doesn't care if you have the period in there or not. I may be mis-remembering this, but it's worth a try.

Inexpensive cams use simple software WDR, which generally applies different levels of processing to the extreme ends of the histogram. Better WDR can come from a variety of techniques, like logarithmic sensors (not so common), image processing hardware, or multi-exposure image processing. The Vivotek listed above uses multi-exposure processing, which works fine in bright light, but becomes harder to use at long exposures for low light because there's not enough time to get multiple exposures of the same image: http://www.vivotek.com/wdr/ http://en.wikipedia.org/wiki/High_dynamic_range_imaging It's definitely possible to have a poor dynamic range image from a sensor with good dynamic range, but generally, these inexpensive sensors don't have great dynamic ranges. Better sensors cost more, and you need more powerful CPUs and more memory to process multiple images into one in realtime, all of which adds to the cost. You have to figure a complete camera that costs $85 from China doesn't have a high priced sensor or lens. It's quite amazing that they work as well as they do.

It's a combination of sensor and software, I believe, but I don't know much about the low-level implementation of WDR beyond the theory. Generally, inexpensive cams have mediocre WDR. I don't care much for Dahua's WDR on either my HFW3300c or HFW4300s; it tends to make the image washed out before it improves things much. I may not have the latest firmware, though. Typically, to get better WDR performance, you have to pay more money. Korgoth does some nice WDR comparisons in this thread: viewtopic.php?f=19&t=35128&start=30 The cheapest cam he shows with great WDR is the Vivotek IP8355H, which is a $700, 1.3MP cam. Next comes the Sony EB632R, which is 1080p and runs $1300.

Note that you can't get support directly from Dahua, and will need to get support from whoever sells you the camera for firmware updates and such. Ebay vendors often don't offer this, so be sure to check with whoever you choose.

To avoid motion blur, you need to set the maximum exposure at 1/30 sec, or 33 ms, depending on how your cam sets it. This will be good for people walking or slow cars, but for running people or faster motion, you need 1/60 sec (17 ms). If you're on PAL, that may be 1/50 sec. The low motion blur setting probably uses 1/30 or 1/25 sec, but I like to set it manually to be sure. The problem is that this limits the light it captures, and the image gets noisy unless you have good lighting or a large sensor with a fast lens, as the posters above mentioned.

There's a thread here on a Dahua reboot problem. Might want to go straight to page 4. viewtopic.php?f=19&t=39039 This also happens sometimes when one's bad out of the box. Cables get loose in shipping, for instance, and it's a pain to open them up and check everything. If you have a DC supply, try that and see if it still reboots.

Most IP cams will let you view them from their IP addresses. Best bet is to try it on a PC first. You'll need to connect to it anyway to set it up. Whether you can view it on the phone will depend on if there's an app for that. If AvertX has an app, that should do it. If not, check to see if IP Cam Viewer by Robert Chou supports that brand. There's a free and paid version for iOS and Android, and it's one of the better IP cam apps.

Even if your time and frustration are worth nothing, the payback of going with inexpensive no-name cams often isn't worth it. All it takes is one glitch that you have to spend hours dealing with to make you wish you had gone for Hik or Dahua. At least their problems are well documented by the community.

That cam has motorized zoom? That can cause differences in the FOV, of course. Does it remember different zoom levels for different resolution settings? I'd assume they keep the same setting for each resolution change, but assumptions can be wrong. It's always hard to say what Dahua's thinking when they implement their firmware. Assuming no zoom changes, it looks like they mix direct sampling and scaling. I'd call it lazy or uninformed programming, because it's easy enough to scale the images - the sensor typically has scaling modes built in for all the common resolutions. I don't know why anyone would do that on purpose, as it creates customer confusion and unhappiness. I haven't compared the 4300S to my HFW3300C, but the image on the 4300S is definitely less saturated, as BW says. It's also a little less noisy with better detail at night compared to the Hik 2032, which it was mounted next to for a while. Not a huge difference, but noticeable. 5MP only gives you 1.4x the linear resolution of 1080p. I'd select 2 or 3 1080p cams over one 5MP, since you can get much better coverage of key areas with 3 cams than with one.

When I said most use the same FOVs for similar aspect ratios, I meant within one camera model/lens/sensor combo, not across models. Different models with different sensors and different lenses are going to have different FOVs, even if the resolution and focal length specs are the same. Sounds like the Dahua 5MP does a mix of direct sampling and pixel scaling for their different resolutions, which doesn't make any sense to me, but I quit buying Dahua after my last 4300S 3MP. Here are the FOVs I measured on the 4300S. You can see that the 16:9 resolutions all have the same FOV, as do the 4:3 resolutions. The measured resolution is also slightly different from what they spec. At the time, their spec was only for 3MP/4:3; they didn't include a spec for the 16:9 settings. That may have changed. Dahua HFW4300S Resolutions: 3MP = 2048 x 1536 1080P = 1920 x 1080 SXGA = 1280 x 1024 1.3MP = 1280 x 960 720P = 1280 x 720 D1 = 704 x 480 OEM 3.6mm lens - Dahua's original lens 3MP, 1.3MP, D1 = 70 degrees H, 51 degrees V 1080P, 720P = 65 degrees H, 36 degrees V SXGA = 65 degrees H, 51 degrees V One option is to change the lens for a wider view, but that's also unpredictable, due to the issues we've been talking about.

The other thing you won't know about until you have the camera is how well the firmware works and how adjustable it is. This is another tricky area on little-known cams, or even older name-brand cams. As for WDR, my experience is that it's valuable in the daytime, but increases noise too much at night. Many modern sensors and firmware go for high contrast images to make them pop, but you lose details in the shadows. Inexpensive WDR can help bring the details out of the shadows and keep the too-bright areas from washing out, but it depends a lot on how it's implemented. Best bet is to have day/night profiles where you can optimize the settings for each set of conditions, and this gets back to having flexible firmware. I don't buy cams without WDR and profiles any more.