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Issue with black bars appearing on my photos

lena -  
jeannets Posted messages 28449 Registration date   Status Contributor Last intervention   -

Hello, 

After taking photos of the fireworks during the evening of December 31st, I noticed bands

present on my photos. I cleaned my lenses and my sensor, I took another photo but the bands are still present. 

Here is a photo of a white wall with the black bands attached. 

At the same time, what is paradoxical is: when I film, the black bands are more present in the video.

Has anyone identified the problem? And if yes, would anyone have a solution?

Thanks in advance. 

3 answers

  1.
    jeannets Posted messages 28449 Registration date   Status Contributor Last intervention   Ambassador 6 616
     

    In my opinion, the videos are recorded at a much lower definition, like 720x500 or something in that range... While your photos should be taken at much higher definitions (as with many) and the electronics don’t keep up in that context...

    I suppose you confuse a camera with a "Smartphone"... You don’t provide the exposure values either... Such as ISO sensitivity, aperture and shutter speed... while you take shots in the dark surrounding your scene... which requires good photography technique and equipment, it isn’t something you do like a portrait or a daytime landscape...

    I suppose the shot is slow (like 10 seconds) you press the button then move your device right away... and that gives the trails you have... At a minimum the device should be mounted on a sturdy tripod, itself well placed on the ground and the photo triggered by a remote... that’s the minimum

    That’s briefly my point of view...

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  2. Anonymous user
     
    Hello,

    Was the photo taken next to artificial lighting (bulb, decorative lights, etc.)?

    If so, this is likely a flicker (banding) problem.

    In France, mains electricity is at 50 Hz. Put simply, that means the power "flickers" 50 times per second. That is too fast for the human eye, but the camera can see it.

    To avoid the problem, set the shutter speed to a similar frequency or a multiple (1/50, 1/100…).

    For the technical explanation: the photo is recorded progressively, from top to bottom. If the shutter operates at a different speed than the mains, the camera will record these small variations while it is "drawing" the photo.

    If you’re using a smartphone, it may be set to 60 Hz, the frequency of mains in America. Check the photo app settings, or use manual mode to force a shutter speed suited to the situation.

    Finally, be careful, because some luminaires operate a bit strangely and will flicker at a slightly shifted frequency. This is notably the case with my Xiaomi bulbs; I have to set my camera to values different from the mains.

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  3. jeannets Posted messages 28449 Registration date   Status Contributor Last intervention   Ambassador 6 616
     

    Hello... Yes, it’s full of subtleties, which make it very hard to guess, especially by luck;

    Currently, there is a lot of LED lighting and in public places, their power is not negligible and the currents of these circuits are also proportional to the magnetic field, the stronger it is...

    In these installations, there is little 50Hz, it is often the unknown...(Sorry Gadjow)

    indeed, to reduce the size and weight, it is the technique of switched-mode power supplies; the 220 is rectified and then chopped into square signals at a much higher frequency, to induce a high-frequency transformer and reproduce a voltage compatible with the LEDs, under a high current... that’s the principle and this frequency can be around 30,000 Hz... It is regulated... smartphones and other audio systems or walkie-talkies are also suspected ...

    Anyway, a photo like that is taken around 1/30 of a second, or less, on a stable tripod, an aperture set to maximum for that and a trigger... the black bands should be absorbed by the targeted image.

    There you go, happy continuing.

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