Help tweaking 4K-T

biggen

biggen

Known around here
May 6, 2018
2,797
3,208
Trying to dial in my 4K-T 3.6mm covering a lighted sidewalk in front of my home. Street lamp is approx 40' from the camera. What I'm finding is that people's faces seem to be "blown out" when walking directly under the light. Here is a video of a runner last night going under the light:

Dropbox

www.dropbox.com www.dropbox.com

Here is a 200% magnification of him running under the light with his face washed out:

Untitled.png

Here are a few frames past the light and we can start to see detail in his face:

Untitled2.png

Night Settings:

Untitled3.png
Untitled4.png



The street lamp is one of those older high pressure sodium bulbs that casts a horrible yellow hue on everything. I've also found that I can't run my shutter slower that 1/120 have to run my shutter at speeds of factors of 120 or I will get horizontal rolling banding due to flicker/shutter speed problems. I really need more focal length as I'm just slightly past the edge of the Identify in the D.O.R.I. table. I may try tonight playing with manual backlight correction to see if I can dim the area under the light some which should bring detail back to the face at the expenses of dimming the surround area though.

Any thoughts or suggestions to not have a blown out face for people under the lamp?
 
Last edited:
I think in your situation you have to force a shutter at a constant shutter and not a range. When you give it a range, it will move towards the slower shutter. Try only 1/120 and other faster variants and see if that helps.

What are your other settings for brightness, contrast, gamma, etc. as they come into play as much as shutter speed. Given that light, you may need to have brightness below 50 along with gamma below 50.

Using backlight at night may improve the static image, but at night it tends to make motion a lot worse. Work on the settings first.

The DORI numbers are estimates provided by the manufacturer and are subject to interpretation and probably developed under ideal best case scenarios. You may get closer than most at night given your light, but a complete stranger will still be tough.

Our long time resident camera expert Wildcat ran the Dahua 4K/X 8MP 1/1.2" sensor thru the paces. Keep in mind this 4K/X camera is incredible. It claims a DORI slightly better than the 4K/T, but the analogy is the same.

He had the 3.6mm version and here is the screenshot from 40 feet in the ideal daylight, which based on DORI numbers is the supposed IDENTIFY distance for this camera with the 3.6mm lens and I think most of would agree that this is not IDENTIFY quality, even if digitally zoomed in (thus showing similar to LUX numbers that DORI numbers are estimates and a manufacturer can make it whatever they want and personally I found they need to be cut in half or more during the daytime and even more for nighttime):


1663106750107.png




I have the 4K/X and 4K/T and they are incredible cameras, but I wouldn't use it for IDENTIFY past 15-20 feet, or half of what the DORI number is.
 
  • Like
Reactions: JDreaming, CanCuba, Parley and 2 others
wittaj said:
I think in your situation you have to force a shutter at a constant shutter and not a range. When you give it a range, it will move towards the slower shutter. Try only 1/120 and other faster variants and see if that helps.

What are your other settings for brightness, contrast, gamma, etc. as they come into play as much as shutter speed. Given that light, you may need to have brightness below 50 along with gamma below 50.

Using backlight at night may improve the static image, but at night it tends to make motion a lot worse. Work on the settings first.

The DORI numbers are estimates provided by the manufacturer and are subject to interpretation and probably developed under ideal best case scenarios. You may get closer than most at night given your light, but a complete stranger will still be tough.

Our long time resident camera expert Wildcat ran the Dahua 4K/X 8MP 1/1.2" sensor thru the paces. Keep in mind this 4K/X camera is incredible. It claims a DORI slightly better than the 4K/T, but the analogy is the same.

He had the 3.6mm version and here is the screenshot from 40 feet in the ideal daylight, which based on DORI numbers is the supposed IDENTIFY distance for this camera with the 3.6mm lens and I think most of would agree that this is not IDENTIFY quality, even if digitally zoomed in (thus showing similar to LUX numbers that DORI numbers are estimates and a manufacturer can make it whatever they want and personally I found they need to be cut in half or more during the daytime and even more for nighttime):


1663106750107.png




I have the 4K/X and 4K/T and they are incredible cameras, but I wouldn't use it for IDENTIFY past 15-20 feet, or half of what the DORI number is.
Click to expand...

Thanks! I added the image adjustments to the main post. The only thing I have done in that menu was pull gamma down as I read from @Wildcat_1 that can help reduce the AGC noise that is introduced. I put I'll try shutter priority with a fixed 1/120 shutter tonight and see what that looks like.

Yeah, I do think I'm probably about 15' past what I would consider the Identify mark for this camera. Really need about double the focal length.
 
  • Like
Reactions: JDreaming and Parley
Yeah try dropping brightness to 35 and then work up from there. And have contrast be 8 points or so higher than brightness.

I think those two changes, coupled with a fixed shutter speed will get you a lot closer.

I have had to run fixed shutters on a few cams as well. Unfortunately it means a small period of time of washout at sunrise, but the night performance improved tremendously with the fixed shutter over a range.
 
  • Like
Reactions: JDreaming, Parley, tmxv4128 and 1 other person
Excellent. I may delay this camera to switchover to night profile 10 or so minutes after sunset to prevent washout with that fixed shutter speed.

I'll give it a try tonight and report back. Thanks!

@wittaj Would you recommend fixed at Shutter Priority or fixed at Manual?
 
Last edited:
bigredfish said:
Agreed on manual 1/120 exposure or faster. Shutter priority never gives me good results at night.

Also agree the true ID range for the 3.6 is closer to 20-25ft. I have both the bullet and turret
Click to expand...
Alright I’ll make sure it’s in manual. I’d consider moving to the bullet 4K-X in 6mm but I’m concerned it’s close focus distance at 42’ is basically where the street light is.

I guess there must be a physical lens limitation somewhere causing the close focus distance to be so far away.The problem is the close focus distance seems to be damn near the limit of the truthful ID range.
 
Well a heater which is not what I bought it for ;) and better min illumination /Fstop.
IR at night seems better than my standard 5442’s and the IR LEDs are different, all along the bottom. Two far two near. It’s also supposed to have EPTZ but I haven’t figured out how to access it yet … in another week or so I’ll be able to compare them at the same location
 
  • Like
Reactions: samplenhold, JDreaming, biggen and 1 other person
You must log in or register to reply here.
Top Bottom