Light spot in center of sensor

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Bman70 Junior Member • Posts: 43
Light spot in center of sensor

Well I was shooting at the sky to check for dust, and it seems the center of the exposure is just a shade lighter than the rest. It's hardly noticeable until I crank up the contrast like I do when checking for dust particles. I haven't seen this before, but I don't do this test very often, and I think this is the first time with this lens (100-400GM).
Offhand, I'm wondering if the metering setting could do this? I have it set for Multi mode though, not Center. Is it just the telephoto superpower trying to zoom in on space?

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Chris R-UK Forum Pro • Posts: 20,718
Re: Light spot in center of sensor

Strange.

I can’t imagine that it is anything to do with the metering system or the lens.  It might be some kind of post processing being done by the camera and it gets fooled by the more or less blank screen.  Could it be the moon peeping through clouds - that was my first thought when I enlarged the image?

You could try repeating the shot and see if it recurs.  You could also try shooting raw instead of JPEG.

If it doesn’t go away, try posting on the Sony forum.

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Chris R

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Doug Haag Senior Member • Posts: 2,210
Re: Light spot in center of sensor
1

Bman70 wrote:

Well I was shooting at the sky to check for dust, and it seems the center of the exposure is just a shade lighter than the rest. It's hardly noticeable until I crank up the contrast like I do when checking for dust particles. I haven't seen this before, but I don't do this test very often, and I think this is the first time with this lens (100-400GM).
Offhand, I'm wondering if the metering setting could do this? I have it set for Multi mode though, not Center. Is it just the telephoto superpower trying to zoom in on space?

Perhaps instead of worrying about it, you can think of it as a "feature".  As in: "Sony cameras are clearly better than others because none of the others can claim a light spot."

It appears they also feature a "dark spot" at about 4 O'clock,

sybersitizen Forum Pro • Posts: 17,512
Re: Light spot in center of sensor

Bman70 wrote:

I haven't seen this before, but I don't do this test very often, and I think this is the first time with this lens (100-400GM).

Try other focal lengths and other lenses and see if it changes.

Offhand, I'm wondering if the metering setting could do this?

No. The metering mode is irrelevant.

OP Bman70 Junior Member • Posts: 43
Re: Light spot in center of sensor

Doug Haag wrote:

Bman70 wrote:

Well I was shooting at the sky to check for dust, and it seems the center of the exposure is just a shade lighter than the rest. It's hardly noticeable until I crank up the contrast like I do when checking for dust particles. I haven't seen this before, but I don't do this test very often, and I think this is the first time with this lens (100-400GM).
Offhand, I'm wondering if the metering setting could do this? I have it set for Multi mode though, not Center. Is it just the telephoto superpower trying to zoom in on space?

Perhaps instead of worrying about it, you can think of it as a "feature". As in: "Sony cameras are clearly better than others because none of the others can claim a light spot."

It appears they also feature a "dark spot" at about 4 O'clock,

Haha well Sony is usually ahead of the competition. Yes the 4 o'clock is a dust ball on the sensor, there are also a bunch of smaller particles. Time to get out the rocket blower.

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OP Bman70 Junior Member • Posts: 43
Re: Light spot in center of sensor

Chris R-UK wrote:

Strange.

I can’t imagine that it is anything to do with the metering system or the lens. It might be some kind of post processing being done by the camera and it gets fooled by the more or less blank screen. Could it be the moon peeping through clouds - that was my first thought when I enlarged the image?

It was a pure blue sky, I just put it in grayscale in Photoshop because it's easier to see any sensor dust. I did have the 1.4x teleconverter on, I wonder if that has anything to do with it. It was a RAW shot, converted to DNG with Adobe DNG Converter.. now there's another link in the chain to check.

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Chris R-UK Forum Pro • Posts: 20,718
Re: Light spot in center of sensor

Bman70 wrote:

Chris R-UK wrote:

Strange.

I can’t imagine that it is anything to do with the metering system or the lens. It might be some kind of post processing being done by the camera and it gets fooled by the more or less blank screen. Could it be the moon peeping through clouds - that was my first thought when I enlarged the image?

It was a pure blue sky, I just put it in grayscale in Photoshop because it's easier to see any sensor dust. I did have the 1.4x teleconverter on, I wonder if that has anything to do with it. It was a RAW shot, converted to DNG with Adobe DNG Converter.. now there's another link in the chain to check.

Definitely try it without the teleconverter.  If you had a filter on the lens, try taking that off as well.

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Chris R

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Mark Scott Abeln
Mark Scott Abeln Forum Pro • Posts: 15,573
Infrared?

I’ve seen spots like that with some lenses when shooting infrared. This is a known problem, solved by using lenses that don’t have that property.

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OpticsEngineer Veteran Member • Posts: 6,784
Re: Light spot in center of sensor
1

My canon sx40 at full zoom has that light spot in center if there is even a tiny bit of a fingerprint on the front lens. I mean so minor that you can’t even see it is on the lens with pretty good flashlight shining in it. Cleaning my sx40 front lens with a micro fiber cloth fixed it. I would try that if I saw that in another lens.

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