What is the resolution of your DSLR? The DSLR that I have with only 8 megapixels, is a Canon 20D. This was a "breakthrough" in technology when it was introduced. It has an APS-C sized sensor, and pretty good low light performance. It basically opened up the DSLR field when it was introduced.
But things have moved ahead considerably since that time. Especially low light performance and pixel density.
I'll bet your DSLR has much higher resolution than 8 megapixels. It probably also has a fairly large sensor. APSC or larger.
Also, you almost certainly have a larger, higher quality lens than that of the security camera. If an 8 megapixel security camera that sells for $200 could do what your DSLR can do, your DSLR would also sell for around $200.
I'll bet that your DSLR and lens cost a bit more than that.
Also, remember that you're shooting video with the security camera, and that video is being compressed with a form of lossy compression. Your DSLR is shooting a still image, and can shoot in RAW most likely, or, if shooting a JPG, is set up to use much less "vigorous" compression.
The security camera likely has:
lower actual "megapixels" than your DSLR
a tiny, and lower quality lens system
a much smaller sensor
far greater image compression
You are expecting too much from the video camera. And this is in good light. At night, things will be even more disappointing. What you see on shows like CSI, etc., where they magically "enhance" crappy surveillance video is pure fantasy. Even with very sophisticated software, you are limited by the quality of the original image capture and the compression that has been used on that image.
Like everyone is saying:
For good license plate reading, you need a choke point or choke points that restrict the position and angle of the cars so that a camera can be set up to view the license plates from a more or less perpendicular angle, and with enough "zoom" to get a lot of pixels on the plate.
You also will need illumination such that you can always be shooting at a high shutter speed to eliminate motion blur, and ideally use a reasonable aperture to get good depth of field and sharpness.
But remember that, just as with your DSLR, if you use too small of an aperture, your images will then suffer from the blurring effects of diffraction. The smaller the sensor, the more pronounced the diffraction will be.
For an 8 megapixel APS-C sized sensor, you don't want to go smaller than f/11 or so or you begin to lose sharpness. For the tiny sensors in these security cameras, you need to stay even wider open. But helping you out is the fact that a smaller sensor gives inherently deeper DOF for any given aperture.
The old masters in the "f/64 club" were shooting with view cameras, often onto glass plates measuring 8" x 10". Now that's a big sensor!
We can't get away with that using 35mm film, or our smallish digital sensors. If you look at resolution graphs for various lenses, you'll often see that the sweet spot for sharpness is a few stops closed from wide open. f/5.6, for example, is often the area where a DSLR's lens may produce its sharpest images.
Anyhow, there's a lot to this. And a real lot to performing license plate reading. Don't believe what you see on CSI.
I have a program called Topaz AI Sharpen, that uses AI to "fill in the blanks" so to speak, so you can upsample digital images for making huge prints. It uses analysis of millions of images to "learn" what will look good to the human eye as it upsamples.
It's fantastic for this purpose.
But I've played with it to pull more detail from security camera frames, and while it can really help, it cannot magically "enhance" the way the fake stuff on CSI does. It makes mistakes that, while they make an image look good to the eye from an aesthetic point of view, they actually can reduce the ability to read text. To be fair, that's not what the program is designed to do.
Anyhow:
Good angle toward the license plate.
Good illumination
Close enough zoom to get enough pixels on the plate
Fast shutter speed
Properly selected aperture
That's what you need.
This is just like shooting with a DSLR. But you have to work with the real characteristics of the security camera.
