Is This Diffraction ??
Apr 11, 2019 16:53:14 #
I took a series of shots at various F stops to see how well I did in cleaning my lens under normal shooting conditions, at least for me. My everyday lens is a Nikon 16-85 on a D7100 (used for this experiment). My normal f stop is F8, but will stop down to f11 in some instances and rarely f16 or above unless I am trying to capture the sun and create that star effect on the sun.
I have attached various shots of the same scene at different f stops. Once I hit f16 I noticed something in the upper left in the trees which I have circled the pic. Fstops below f8 did not show anything unusual so I have not posted them.
Is this diffraction or something else
Willie
I have attached various shots of the same scene at different f stops. Once I hit f16 I noticed something in the upper left in the trees which I have circled the pic. Fstops below f8 did not show anything unusual so I have not posted them.
Is this diffraction or something else
Willie
Apr 11, 2019 16:57:47 #
Apr 11, 2019 17:07:18 #
Diffraction causes blurring in the image. That looks like dust on the sensor, which will become more and more noticeable as the lens is stopped down further and further.
If you take a picture of a blank wall or sky, do you see a similar spot in the same part of the frame?
If you take a picture of a blank wall or sky, do you see a similar spot in the same part of the frame?
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Apr 11, 2019 17:12:05 #
Apr 11, 2019 17:12:28 #
I cropped out all but the circled section to see how the colors flowed. A bluish tinge on the northwest corner and a yellowish shade to the southeast corner. But no greenish or reddish. Diffraction of light separates all the colors so what is going on might not be diffraction alone.
Apr 11, 2019 17:12:57 #
I would try it again on a different scene.
It almost looks as if the sun came through a partial hole in the cloud cover and through the branches. Can't really tell what direction the sun would be.
Diffraction would show up as a general fuzziness, not a small blob.
The best way to see diffraction is with a point light source in the field of view.
It almost looks as if the sun came through a partial hole in the cloud cover and through the branches. Can't really tell what direction the sun would be.
Diffraction would show up as a general fuzziness, not a small blob.
The best way to see diffraction is with a point light source in the field of view.
Apr 11, 2019 17:23:52 #
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Apr 11, 2019 17:41:25 #
I think the red-circle spot is a light flare in the lens and / or filter, but the 'science' of this experiment is loose enough that it's hard to say what is occurring in the upper left corner.
What is a bit more obvious about f/22 is shown in this selective merge of the f/8 to f/22.
First, the sensor dust in the sky and upper right corner becomes more obvious, see yellow arrows / circle.
In the center of the frame, a loss of sharpness in the details of the reeds in the water would seem to indicate a lessen of the sharpness of the image due to diffraction. But, this is speculation as the location of the focus point(s) is unknown. And, the shutterspeed slowed where the softening could be simply movement of the reeds at 1/80 @ f/22 vs 1/200 @f/8.
Shooting indoors in better controlled conditions of a specific subject would be more likely to capture images to demonstrate the effect of diffraction.
What is a bit more obvious about f/22 is shown in this selective merge of the f/8 to f/22.
First, the sensor dust in the sky and upper right corner becomes more obvious, see yellow arrows / circle.
In the center of the frame, a loss of sharpness in the details of the reeds in the water would seem to indicate a lessen of the sharpness of the image due to diffraction. But, this is speculation as the location of the focus point(s) is unknown. And, the shutterspeed slowed where the softening could be simply movement of the reeds at 1/80 @ f/22 vs 1/200 @f/8.
Shooting indoors in better controlled conditions of a specific subject would be more likely to capture images to demonstrate the effect of diffraction.
Apr 11, 2019 21:30:10 #
brontodon wrote:
Diffraction causes blurring in the image. That looks like dust on the sensor, which will become more and more noticeable as the lens is stopped down further and further.
If you take a picture of a blank wall or sky, do you see a similar spot in the same part of the frame?
If you take a picture of a blank wall or sky, do you see a similar spot in the same part of the frame?
Dust on the sensor would appear as dark/black, not white.
Apr 11, 2019 22:06:31 #
Diffraction is separation of light into it's varying colors. There is even Something called a diffraction grating Which acts like a prism . In this image the diffraction is cause by direct sunlight and a fliter on the lens. Flare can show diffraction also
Apr 12, 2019 00:28:06 #
IDguy
Loc: Idaho
fjrwillie wrote:
I took a series of shots at various F stops to see... (show quote)
It is dust on your sensor. Shows up at higher f stops.
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Apr 12, 2019 05:15:38 #
wdross
Loc: Castle Rock, Colorado
fjrwillie wrote:
I took a series of shots at various F stops to see... (show quote)
Something else. Diffraction affects the whole image, not just a spot. It looks like a piece of debris being "kicked around" by the flapping of the mirror. It probably is on the end of the lense inside the body.
Apr 12, 2019 07:46:58 #
Everybody knows that diffraction or a general degradation of the image occurs with small apertures. I cannot see that with your f16 and f22 images.
Apr 12, 2019 07:49:10 #
Not diffraction. Not dust on the sensor (as has already been pointed out, that would appear black).
Seems to me to be something like a small water droplet on that corner of the lens that comes into focus at the smaller apertures because of the increased DOF. The image seems to have been shot at the wide angle end of the zoom lens, which of course means DOF is even "thicker" at small apertures.
Seems to me to be something like a small water droplet on that corner of the lens that comes into focus at the smaller apertures because of the increased DOF. The image seems to have been shot at the wide angle end of the zoom lens, which of course means DOF is even "thicker" at small apertures.
Apr 12, 2019 09:21:22 #
IDguy
Loc: Idaho
The assertion that dust spots are always black is nonsense.
But as you can see here this looks more like the examples with dust on the lens.
https://photographylife.com/how-to-spot-dust-on-your-dslr-sensor
But as you can see here this looks more like the examples with dust on the lens.
https://photographylife.com/how-to-spot-dust-on-your-dslr-sensor
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