Dumb questions of the day: if 4mp cam needs more light than a 2mp cam with the same size sensor....

[Sybertiger]

....is there a way to set the 4mp into 2mp pix mode so that the 4mp cam only needs the same amount of light?

In other words, if you purchase said 4mp cam thinking it will do just fine in low light but it turns out you overestimated the amount of light available at night is there a way to configure a 4mp Dahua cam to function as a 2mp Dahua cam (assuming the cams are using the same size sensor). I would assume NOT since the only option is to set up the 4mp cam to stream out video as a 2mp cam and that's really a post-capture processing function....therefore the 4mp cam will never be able to operate as well in as low light as the 2mp cam.

 

[redpoint5]

That's not a dumb question at all. It should technically be possible to trade pixels for light sensitivity. I doubt there's any way to do it with current firmware though.

 

[bigredfish]

Others will likely have a better technical explanation but, No.
The 4MP sensor still has approx 2x more pixels and they are roughly 1/2 as big thus allowing less light in per pixel.

 

[Mike A.]

As security cams do it generally no. The sensor remains the same and the camera just presents a lower apparent resolution.

Some phone and other camera sensors can do what's called "pixel binning" at the level of the sensor to combine multiple smaller pixels into a larger pixel to increase sensitivity/reduce noise. Search for that term and you'll find explanation and examples. So possible but no security cams are doing that as far as I know.

 

[wittaj]

Downrezing a camera does not work - It is still using the 4 million pixels - the camera doesn't change the "pixel resolution screen" on the camera when you go from 4MP to 2MP. The sensor still needs 2 times the light going from 4MP to 2MP, so the native 2MP camera will result in a better image at night. The firmware will make some algorithm attempt at downrezing it, but it could be a complete crap image or a somewhat usable image, but if there is a concern that the 4MP isn't performing or wouldn't perform well at night, then it is better to go with the 2MP.

I have a 4MP and 2MP on the same 1/2.8" sensor and the picture quality is quite different between the two and the 2MP kicks it's butt at night.

In most instances, you want to get a camera that will perform at your location for the worse situation, which for most of us is at night when it is dark and there is little to no light. If a camera performs at night, it is easier to tweak settings to make it work during the day than it is the other way around.

My 2MP cameras outperform my neighbors 4K (8MP) cameras....why....because they are both on the same size sensor.

When we had a thief come thru here and get into a lot of cars, the police couldn't use one video or photo from anyone's system but mine. Not even my other neighbors $1,300 8MP system provided useful info - the cams just didn't cut it at night.

My neighbor tried the "I will just downrez the 8MP to 2MP" and the image was a soft dark mess.

His system wasn't even a year old and after that event has started replacing with cameras purchased from @EMPIRETECANDY here based on my recommendation and seeing my results. He is still shocked a 2MP camera performs better than his 4k cameras and he cannot figure out why downrezing from 8MP to 2MP doesn't work properly... It is all about the amount of light needed and getting the right camera for the right location and downrezing doesn't change the physics of the camera.

 

[wittaj]

An analogy to try to understand why cameras need so much more light - let's look at a 4MP camera and this 4MP needs at least two times the amount of light as a 2MP for the same size sensor. The sensor size is the same in each camera, but when you spread the "pixel resolution screen" of 4MP worth of pixel holes across the same size sensor, it now has double the holes, but also double the "screen material" than the 2MP.

Kind of hard to explain, but lets try to use a window screen as an analogy - take a window where the opening is fixed - that is the sensor - you add a screen to it (that represents 2MP) and looking out through the screen is a little darker outside because of the screen material. Now replace that screen with one that has two times the amount of holes (now it represents 4MP) and it will be darker looking through it because (while the resolution would be better) there is a lot more screen material and the window opening is the same size.

So if your house is like most where the top pane is glass with no screen and the bottom half is window with the screen and you see something outside during the daytime - do you sit down to look out through the screen or do you stand up to look a the object through the window with no screen?

And that is accentuated even more at night time. Look out your window with and without the screen and it will be darker looking through the screen than without it. If you are looking out your window to see the stars or the moon, do you look out the part of the window with the screen, or the upper portion without the screen material?

Now obviously as it relates to a camera, you need to balance the amount of pixel holes with the screen material - too few holes (and thus less screen material) and the resolution suffers, and too many holes (and thus more screen material) and the more light that is needed.

 

[Sybertiger]

I was thinking that maybe in the firmware there may be a way to combine two adjacent pixels into one so that you effectively would have more info/light or something like that.

 

[Sybertiger]

How well would you expect an IR floodlight to overcome the deficiency of a 4mp cam such that it works as well or better than a 2mp cam at night (same size sensors)?

I'm asking these question regarding a system I will set up for my parents who are 500 miles away. I don't have easy access to their environment to gauge night-to-night lighting conditions so I have to guess and wing-it to a certain extent. No cams purchased yet.

 

[wittaj]

Yeah, the firmware isn't that smart. Once you start doing that, then the image becomes way too processed and you end up with crap link Reolink does where if the object isn't moving it looks ok, but add movement and blur city.

Certainly with enough light (white or IR) you can mitigate the differences between the two.

 

[bigredfish]

More light (IR or white light) is always better!
Sure, adding light will help mitigate but it depends on what you’re trying to capture.

The good news is you can add IR and get some distance and a great image. The less good news is the external IR won’t adjust to close objects like smart IR is intended to. So you’ll have to play with exposure and gain and reach that happy medium of far vs close objects.

 

[johnfitz]

I had the same dumb question of the day 4/3/2022!

do not buy a 4MP camera that is anything smaller than a 1/1.8" sensor | IP Cam Talk