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Cops are now blinding the camera when you record them. Is there any way to prevent the camera from getting blinded? I've read about astronomers that block/filter out the sun light of stars to find planets. Can it be applied to flashlights too somehow? I have a vague memory of a special lenses that are used for welding, can it be used for flashlights?

The simplest way would be to have two cameras one meter apart on a mount but that's expensive and will not work if two cops decide to act corrupt and blind both cameras.

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    \$\begingroup\$ Back in the day in saucy magazines there were ads for a device that was essentially a lens hood with a 45° mirror and a side opening in it, so that you could shoot girls on the beach while seemingly aiming the camera at the sea. These things need to be revived. \$\endgroup\$
    – xenoid
    Aug 21, 2021 at 17:28
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    \$\begingroup\$ What kind of a camera are we talking about here? A DSLR with a telephoto lens or a cellphone? \$\endgroup\$ Aug 21, 2021 at 19:51
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    \$\begingroup\$ @IlmariKaronen Currently only a phone camera. I was hoping there was an advanced DSLR camera that could handle this issue. \$\endgroup\$
    – Dari_we
    Aug 21, 2021 at 22:01
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    \$\begingroup\$ @Rafael Legislation against police shining a flashlight at someone? \$\endgroup\$ Aug 21, 2021 at 23:27
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    \$\begingroup\$ here's a silly suggestion: bring more cameras than they have flashlights. \$\endgroup\$
    – user253751
    Aug 23, 2021 at 8:49

8 Answers 8

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There's not much you can do to prevent a bright light pointed at your camera from causing lens flare that obscures the scene. But there are some things that can sometimes help.

The main thing to do is simply try to prevent the light from getting into the camera in the first place:

  • If you're shooting with a long lens, make sure to use a good lens hood. It won't stop bright lights in the scene you're shooting from blinding your camera, but it can prevent someone outside the scene from interfering with your photography. And in some cases you may be able to turn your camera away from the bright light and still at least capture what's happening nearby.

  • If you don't have a lens hood (e.g. you're shooting with a cell phone), just putting your hand (or a piece of paper, or whatever) between the light and the camera to shade it can help a lot.

  • Even if the light source is inside the scene you're shooting (and you can't or don't want to turn the camera away from it), just blocking it e.g. with your fingertip can eliminate or at least dramatically reduce the flaring. This is one of the rare cases where you may want your finger in the picture!

  • Of course, if there happens to be a convenient signpost or other obstacle that you can maneuver to be between the light and your camera, that can work even better than your finger. I've used this technique myself e.g. to shoot halos and other atmospheric phenomena near the sun, as in this example image from an earlier answer where I used a pedestrian crossing sign to block the sun:

    Example image with pedestrian crossing sign blocking the sun

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    \$\begingroup\$ That's exactly what humans (and statues) do to protect their vision from veiling glare \$\endgroup\$
    – Ruslan
    Aug 23, 2021 at 20:38
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Yes there is.

The way is to use manual exposure adjusted for the shooting conditions. You can determine the exposure parameters for example by selecting a certain aperture and exposure time in manual mode with auto-ISO, aim at some direction where there is no bright light source, then half-press the shutter button, then see if the selected ISO is acceptable. If the ISO is acceptable, select it manually. If the ISO is not acceptable, then you need to either adjust the aperture and/or exposure time and retry.

Of course the bright light source causes flaring at the lens but at least it doesn't blind the entire camera.

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  • \$\begingroup\$ An effective suggestion. I don't know why you were marked down. +1 \$\endgroup\$ Aug 21, 2021 at 17:53
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    \$\begingroup\$ I don't get the logic behind this. Set ISO for the dark & the flashlight will flare it out completely. Set it for the light & the rest is going to be just black. There's got to be 10 stops or more between the two. \$\endgroup\$
    – Tetsujin
    Aug 21, 2021 at 18:05
  • \$\begingroup\$ Well, it may depend on the brightness of the scene and the power of the flashlight. My understanding is that most bright light sources even at night cause only flaring instead of blinding the entire camera. However, I have no experience with police flashlights so I don't know how bright a police flashlight is. Usually flashlights are designed to make the area where you point them acceptably bright, perhaps a bit brighter than streetlights make it. A streetlight doesn't blind the camera but causes flaring. Of course if the flashlight is very near the camera, then it may be too bright. \$\endgroup\$
    – juhist
    Aug 21, 2021 at 19:02
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    \$\begingroup\$ I just tested this with a cellphone camera (Samsung S8+), a dimly lit room and a bike headlamp. Doesn't work. Most (basically all) of the interference comes from flaring, not from the exposure metering getting confused. (In fact, the automatic exposure seemed pretty spot on in all tests, or at least as good as it could possibly be under the circumstances.) I guess an older camera with poorer exposure metering might benefit from this. \$\endgroup\$ Aug 21, 2021 at 20:02
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    \$\begingroup\$ @PeterCordes: I mean that I could never get a significantly better shot using manual exposure in "pro" mode (and/or exposure adjustment in normal photo mode) than by just shooting normally with auto exposure and ±0 adjustment. If the light was off to the side, the automatic metering seemed to mostly ignore it; if it was right in the middle and pointed straight at the camera, there was so much flaring that no amount of exposure adjustment could produce a useful image anyway. In any case, adjusting exposure up also brightened the flare, often making the image worse, not better. \$\endgroup\$ Aug 22, 2021 at 9:38
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Depending on the flashlight, an infrared camera tuned for near infrared frequencies is likely to work.

There are many vendors of infrared conversion services, some infrared converted cameras in the used market, and YouTube videos for do it yourself conversion of various camera models.

Flashlights are typically optimized for visible frequencies.

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  • \$\begingroup\$ This is a great point! Most sensors now have IR blocking filters, so it's a bit of a challenge to implement. Maybe a Raspberry Pi with the Pi NoIR camera? \$\endgroup\$
    – uhoh
    Aug 22, 2021 at 1:48
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    \$\begingroup\$ @uhoh There are numerous companies offering conversions and many YouTube videos with do it yourself instructions for removing the hot mirror. \$\endgroup\$ Aug 22, 2021 at 1:56
  • \$\begingroup\$ Oh that's great; perhaps add that back into your answer? Just fyi the OP recently mentioned they are currently using a cell phone. I added an answer just now and linked to your answer. \$\endgroup\$
    – uhoh
    Aug 22, 2021 at 2:09
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To minimize flare:

  • Keep the front of your lens clean at all times, no pocket dust or finger prints. Keep a lens-cleaning supplies (at least a lens cloth) handy and use it regularly.
  • In a pinch or emergency, wipe the lens with the cleanest bit of clothing you can come up with, like a shirt tail.

Possibility of a filter?

Many flashlights are now white light LEDs, which have a peculiar spectrum due to the way they the light is produced; a blue LED and a yellow semi-transparent phosphor. The spectrum drops at extreme blue and red, but so does the sensitivity of the color filters on the camera's sensor.

@BobMacaroniMcStevens's answer mentions near IR which is a great idea of you can find the right sensor that doesn't have a NIR blocking filter built in. That would not be any help for a tungsten-halogen light which would be extremely bright in NIR, but it would probably work well to block LED light.

The problem though is that there won't be any other NIR light to illuminate the scene unless you are lucky, and flashes on camera phones are also white light LEDs so will be of no help. Same problem for LED street lights.

Perhaps the minimum around 500 nm is a third place for a filter, but again if white light LEDs are what's illuminating the scene, it provides no benefit.

Keep your cell phone lens very clean is your best bet, it can make a huge difference.


white LED spectrum

Source

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    \$\begingroup\$ So, carry a big incandescent flashlight yourself, to illuminate the scene in IR? Preferably one that doesn't look like it could double as a truncheon (especially a long black C or D-cell Maglite); you don't want to look "armed" if the police are already harassing you while you try to record. \$\endgroup\$ Aug 22, 2021 at 2:18
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    \$\begingroup\$ @PeterCordes Good idea! One could modify it with a filter to minimize visible light as well, so it would not present a challenge to anybody else's vision or photography. It would probably be somewhat reddish, but could be completely dark if one was using pure NIR sensitivity. \$\endgroup\$
    – uhoh
    Aug 22, 2021 at 2:24
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    \$\begingroup\$ @PeterCordes just use IR LEDs like the ones used in NightShot-capable cameras. \$\endgroup\$
    – Ruslan
    Aug 23, 2021 at 11:37
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Short answer is no, not really. Any filter that blocks the stronger (near) full spectrum of the flashlight will also block the weaker light of the scene/background.

Astro filters are typically color filters only affecting small portions of visible light.

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Double down. Use your own high-intensity lighting to flood the scene with light.

A flashlight is bright at night, but shining a flashlight into the camera in full daylight sun, for example, won't really do much at all because the camera is exposing for the enormous abundance of light in the scene and the relative contribution from the flashlight is correspondingly diminished. This is increasing the signal (scene) to noise (flashlight) ratio by boosting the amount of usable illumination in the scene.

A couple of aftermarket automotive LED HID headlights with a 12V battery pack would work. Of course, now you're engaging in a flashlight arms race with the police, so...

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  • \$\begingroup\$ Why not use a camera flash instead of LED headlights? \$\endgroup\$
    – bdsl
    Aug 22, 2021 at 21:18
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    \$\begingroup\$ @bdsl Because OP is recording video. \$\endgroup\$
    – J...
    Aug 22, 2021 at 22:05
  • \$\begingroup\$ Thanks, I missed that detail. \$\endgroup\$
    – bdsl
    Aug 22, 2021 at 22:09
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Depending on how the flashlight is held, a half ND filter might improve the situation.

Something like this:

HalfND

Half ND Filter

Covering the lower half of the shot with the ND part, might allow you to get the face/upper body of the cop, in case they are holding the flashlight at waist height. (pretty situational, though)

(I would also recommend a lens hood anyway)

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If a flashlight is aimed directly at your camera at night, this will create high contrast in the scene between the flashlight and its flare, and the subject which is in the dark.

You can fix that by reducing the intensity of the light, but you can also fix it from the other end, by increasing the amount of light on the subject. During the day, this is usually done with fill-in flash or reflectors.

Therefore, a practical solution is to wear a white t-shirt, which will reflect the light from the flashlight towards the subject of the picture. This will not fix the lens flare, but it will light the subject better, and it is plausibly deniable and inconspicuous.

However that requires you to be perhaps closer than you would like.

The other solution is to have friends, which means having more cameras (and witnesses) than there are flashlights.

You could also play with the camera settings to decrease contrast, to make sure dark areas are not pure black but still contain usable detail that can be recovered via post processing. Perhaps use night mode, or manual mode. Using the highest quality setting and lowest compression will help.

Another thing you could do is simply hide the phone.

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