Black patch in the photo when using check for dust

[Tang Ziheng]

I encounter a problem-when I take the photos of an aeroplane flying in the sky,a black patch will appear in the sky in the photo if I use "check for dust",and each time this patch will appear in different areas,I was wondering whether there is someone who can help me solve this problem.

[MarkLawrence]

Providing examples of what you are seeing will allow for better assistance to the problem.

[Tang Ziheng]

Just like this.

[MarkLawrence]

That looks like vignetting on the corner of the image. You can Google search for the causes of vignetting because there are several potential causes.

[JamesDC152]

IMO if that was vignetting it would be black in the top left and right corners as well, which it isn't. therefore I don't think it is, it's just the heathaze/atmosphere closer to the earth than the sky, which sometimes happens

[mahagonny]

You can see clearly that it is a vignetting.

[JamesDC152]

You can see clearly that it is a vignetting.

Vignetting is a reduction of an image's brightness or saturation toward the periphery compared to the image center. From what I see, this is only from the bottom of the image frame, not the top.

[MarkLawrence]

Unless that is an edited image and the top has already been cropped - regardless, there are issues.

[MarkosVicioso]

Just like this.

I don't think that's vignetting, Looks like it's a light dimming due the conditions of the moment illumination. Should be ok in my opinion.

[Tang Ziheng]

And I have an original image which wasn't edited.I also think that is not vignetting.Because the black patch only appear at the bottom of the left corner.But in different image it shows in different area,like right corner at the bottom.So what's the problem?

[seahawk]

The Equalize filter redistributes the brightness values of the pixels in an image so that they more evenly represent the entire range of brightness levels. When you apply this command, Photoshop Elements finds the brightest and darkest values in the composite image.

So there is something dark there - maybe a dark cloud?

[zomeu]

More precisely, the equalizing (and the "check for dust" function in JP is an equalizer just less progressive (different curve) than in PS or PSE) considers the darkest pixel of the image as black (RGB 0,0,0) and the brightest as white (RGB 255,255,255). The color for intermediates is function of the highest value of the pixel between R, G and B (a kind of "dark grey" like R70, G80, B70 will be green).
Equalizing filter tries to make the distribution of luminances as flat as possible.
If the original distribution in the picture is near of the total dynamic range, the corrections will be weak and the equalized image will be near the original. A strong equalization shows an unbalanced distribution of tones and à lower contrast (black is not black and white is not white).
The black patches in your photo show that these pixels are among the darkest (lowest luminance levels) in the image, that's all...