2mp versus 4mp with 1.8 sensors for LPR

[Billyjack5]

Saw that the ITC237-PW6M-IRLZF1050-B is now being offered in a 4mp version. Both have 1.8 sensors and from unrelated threads the suggestion would be that the 2mp would be better in low light conditions. Since the AI on this camera is dependent on clarity of plate reads, any sense of whether it's worth upgrading to the 4mp version? I have the 237 and have generally been happy with it, but I'm always chasing clearer plate reads.

 

[biggen]

A 2MP sensor at 1/1.8 will have better light collecting ability than a 4MP sensor at 1/1.8. My belief is that 4MP+ isn't ever needed for LPR duty.

Are you missing plates now? What is your distance to target?

 

[Billyjack5]

A 2MP sensor at 1/1.8 will have better light collecting ability than a 4MP sensor at 1/1.8. My belief is that 4MP+ isn't ever needed for LPR duty.

Are you missing plates now? What is your distance to target?

Distance to target is 87" with a 35 degree angle.
The 237 firmware wants plate pixels to be at least 140. Mine caps are usually less but the AI still works. I'm not missing many captures but am wondering if the 4mp version might help flesh out clarity of the plate images. The 237 firmware, as Wildcat_1 noted in his review, has more limited settings than standard Dahua firmware.

 

[genelit]

Do you use the ANPR features built in the ITC237?

As an alternative I would recommend the 7442H-Z4, it is really a nice piece of kit but with some more zoom (at least from the top of my head). It doesn't have all the ANPR-processing that ITC237 has, but depending on your needs this could be used.

I have both cameras and I think they both perform really really good.

Here are 2 pictures from about 40m / 120ft with the 7442H-Z4 fully zoomed in.
Running the Video Metadata or ANPR Smart Plan it collects plates.

 

[Billyjack5]

Do you use the ANPR features built in the ITC237?

As an alternative I would recommend the 7442H-Z4, it is really a nice piece of kit but with some more zoom (at least from the top of my head). It doesn't have all the ANPR-processing that ITC237 has, but depending on your needs this could be used.

I have both cameras and I think they both perform really really good.

Here are 2 pictures from about 40m / 120ft with the 7442H-Z4 fully zoomed in.
Running the Video Metadata or ANPR Smart Plan it collects plates.

View attachment 110211

View attachment 110212

I bought the 237 for the ANPR features and it works well. I'm stretching its 50mm zoom with my 87" capture distance and angle, though, and am wondering if it makes sense to upgrade.

 

[genelit]

Ok! No, it doesn't make sense to upgrade.
I agree with @biggen and for LPR you don't need the extra mp.

 

[Billyjack5]

Good to know. Appreciate the responses. Genelit, if you've used the 237 for a while, I may drop you a line about some of the settings.

 

[genelit]

Sure, do so.
But even better if you put it here for future reference for others, if that's OK with you.

 

[foxden]

In Russia we have such a saying "Shilo for Soap" which means (meaningless or short-sighted exchange, leading in the long run to the preservation of the existing situation or to its deterioration.) You have the same situation. I use several ITC237s in different places, and even at the maximum distance declared by the manufacturer, everything works well.
Here's an example: Camera 30 meters (98.4252ft) away from where license plates were detected.

 

[Billyjack5]

Appreciate the responses. One thing I've noticed with the 237 that there seems to be a capture area within which the AI works and outside of which it doesn't work, at least as well. When I view my 237 on Blue Iris, especially at dusk, the textures in the upper and lower quarter of the field of view is slightly blurred, like a letterbox effect. Anyone else notice this or have any thoughts?

 

[wittaj]

I do not have that camera, but run a Z12E as an LPR, and we notice similar stuff at dawn and dusk hours - that is just a difficult time period for the camera zoomed in so much. As long as the plates are read, that is all I care about!

 

[foxden]

Appreciate the responses. One thing I've noticed with the 237 that there seems to be a capture area within which the AI works and outside of which it doesn't work, at least as well. When I view my 237 on Blue Iris, especially at dusk, the textures in the upper and lower quarter of the field of view is slightly blurred, like a letterbox effect. Anyone else notice this or have any thoughts?

no. I have a clear picture on all cameras.

 

[Billyjack5]

I do not have that camera, but run a Z12E as an LPR, and we notice similar stuff at dawn and dusk hours - that is just a difficult time period for the camera zoomed in so much. As long as the plates are read, that is all I care about!

Dahua's documentation for the 237 ANPR camera is actually pretty good and while it suggests the middle of the FOV is the best capture area, it doesn't outright say it. But given this letterbox-like effect, I'm thinking I need to adjust mine up slightly, which is easier said than done. The 237 uses a teeth like up and down adjustment, which is far less exact than the set screw. It's a real pain when trying to make these small adjustments because you end up having to adjust the entire mount.

 

[Billyjack5]

I

no. I have a clear picture on all cameras.

I only see it at dusk. During the day and night the picture is clear. It's weird.