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Old Feb 7, 2012, 2:32 PM   #1
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Default Stakeout of Car license plate at night without flash?

Stakeout of Car license plate at night without flash?
(Moderator, if this belongs in a better place, please put it there)

OK, I took on a job last week that I didn't think would be that hard.

It's this sign placing company, (places home-builders signs along the roadway directing to home-builders new homes) They do about 75 home complexes in the area.
Competing sign-placers or homeowners taking them down because they don't like them, are stealing signs. It is legal to place these signs if you register with the city.
You place them between sidewalk and street. It is illegal to take them down if your not the owner. Placed only on the weekend.

They pay me $20 an hour on stakeout and $200 if I get the license place of thieves. Then they take them to court.

I got very lucky and the company that hired me was very happy and want me to do more. However, my problem is Because of headlight glare, it is difficult to take pictures of license plates at night. I found most of mine washed out... see some pics below. I managed to get one only because I was able to manipulate it in Photoshop. This week, I'm going to experiment on my own car at night under same circumstance, between 5-6am, total darkness except for the cars headlights/taillights and "some" streetlights. I tried doing it from a stakeout, but couldn't get a clear shot of plates, so I got behind them and took the pics as I drove by, hence the headlight glare, washing out the plates.

What settings should I use for this? I have a Nikon D5100 using a 18-70mm lens. Here are the pics I took below.
Flash is NOT an option as the company don't want the thieves to know as they've been known to come after the ones taking the pictures.

In this picture, the plate was "barely" visible. PhotoShop brought it out as you see below.


Here you can see the plate is washed out, like my other 10 I took. At least I got the guy in it.


Here I tried to get the pickup with the driver putting the sign in truck with virtually no light... not very good.
Getting the plate number is the most important, but if I can get the actual act and the person, (ie can't say someone else used his truck)




Any help is appreciated.
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Old Feb 7, 2012, 2:43 PM   #2
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I would be going manual exposure rather than the prog mode that you are using. The problem is that the camera tries to get a good approximation for exposure from the entire scene, however, as the background is very dark it tries to lighten everything up, this is exactly what you don't want on the reflective number plate.

Work out what a good exposure is (approx) by doing your own testing and then punch that into the camera. If you are a little out that is fine, PP will bring it back, but if you keep doing it the way you have then as you say the results are just blown out plates. Also, you will have a faster shutter speed when you get the exposure so then you will have less blur.
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Old Feb 7, 2012, 3:32 PM   #3
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Quote:
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I would be going manual exposure rather than the prog mode that you are using. The problem is that the camera tries to get a good approximation for exposure from the entire scene, however, as the background is very dark it tries to lighten everything up, this is exactly what you don't want on the reflective number plate.

Work out what a good exposure is (approx) by doing your own testing and then punch that into the camera. If you are a little out that is fine, PP will bring it back, but if you keep doing it the way you have then as you say the results are just blown out plates. Also, you will have a faster shutter speed when you get the exposure so then you will have less blur.
Maybe "if I have enough time" do the preset manual focus on the plate, then after a few quick shots, flip it to P and try to get the person and car more clear? If the plate comes out, everything else will be dark. But, plates are the most important.

Thanks Mark! I almost places this post in the general, but did the other automobile area.
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Old Feb 7, 2012, 4:01 PM   #4
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I didn't pay too much attention to this when it was first discussed, but if I recall correctly, the D5100 has linear gain. If you expose at ISO 100 (if memory serves), you have all the exposure you're going to get and 14 bits of data in your raw file. If you have good PP software, you can adjust the EV to shift the exposure to the same value you would have gotten at ISO 1600, so you can set the gain after the fact and optimize for either the license plate or the person in the photo. I have not tried any of this -- only read about the reality of the gain being linear on your particular camera and how it can be used. If memory serves (and it seldom does...), the assertion was that camera actually always operates at the same bias internally and just shifts the data in software to make the desired gain anyway. FWIW
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Old Feb 7, 2012, 4:17 PM   #5
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Quote:
Originally Posted by jack55 View Post
Maybe "if I have enough time" do the preset manual focus on the plate, then after a few quick shots, flip it to P and try to get the person and car more clear? If the plate comes out, everything else will be dark. But, plates are the most important.
Mark is talking about Manual Exposure, not Manual Focus. Use Autofocus to get the focus right, but use manual exposure to get the license plate properly exposed.

You might also try Spot Metering, which uses the current focus point to set the exposure. (See page 68 of the D5100 Reference Manual.) Place the spot over the license place, take the shot, and you should have a properly exposed photo of it.
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Old Feb 7, 2012, 4:20 PM   #6
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Personally, I would hesitate to do any postprocessing on any photo that was to be used as evidence in the prosecution of a crime, however minor. I would do whatever I could to get the shot I wanted straight out of the camera.
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Old Feb 7, 2012, 8:47 PM   #7
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Quote:
Originally Posted by tclune View Post
I didn't pay too much attention to this when it was first discussed, but if I recall correctly, the D5100 has linear gain. If you expose at ISO 100 (if memory serves), you have all the exposure you're going to get and 14 bits of data in your raw file. If you have good PP software, you can adjust the EV to shift the exposure to the same value you would have gotten at ISO 1600, so you can set the gain after the fact and optimize for either the license plate or the person in the photo. I have not tried any of this -- only read about the reality of the gain being linear on your particular camera and how it can be used. If memory serves (and it seldom does...), the assertion was that camera actually always operates at the same bias internally and just shifts the data in software to make the desired gain anyway. FWIW
That went over my head... could you explain better in a dummy version?
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Old Feb 7, 2012, 8:56 PM   #8
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Quote:
Originally Posted by TCav View Post
Mark is talking about Manual Exposure, not Manual Focus. Use Autofocus to get the focus right, but use manual exposure to get the license plate properly exposed.

You might also try Spot Metering, which uses the current focus point to set the exposure. (See page 68 of the D5100 Reference Manual.) Place the spot over the license place, take the shot, and you should have a properly exposed photo of it.

Personally, I would hesitate to do any postprocessing on any photo that was to be used as evidence in the prosecution of a crime, however minor. I would do whatever I could to get the shot I wanted straight out of the camera.
Thanks for the tips and correction...

Ahhh... that is what I meant, manual exposure, not focus. My mistake.
I was going to use spot. Gonna try it on my car tonight.
Also, they had been winning in court without pictures, just the verbal license plate number saying what they saw. Some got off by saying someone else used the car with said license number (like they do with the traffic camera lights). So I'm the first to use a camera to show both the person, car & plates. On what you said about post PP, I'll have three pics, one with one camera preset on the license plate, then grab my other camera set for the car and person. That should eliminate the need for PP...
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Nikkor 18-140mm f/3.5-4.5D ED VR
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Old Feb 7, 2012, 9:09 PM   #9
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Last question! What max ISO should I use before it's too grainy?
I know it has the same sensor as the D7000, so it should be pretty good in low light, right?
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Old Feb 8, 2012, 1:24 AM   #10
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I can understand someone being upset enough about a sign in front of their house, but someone driving about to pull them up? In full size pickups with the price of gas?

Is someone paying them to do that?

Quote:
Placed only on the weekend.
If it was in my front yard, and I knew about the restrictions, and if it was still there at 12:00:01 Monday, it would find its way to the trash.

Not just that someone did it - when they did it.
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