What are these spots!?

mporter012 · Dec 10, 2018

I bought a Nikon 24mm 1.8G lens recently off eBay and I'm just getting around to editing and noticing these spots. Are these just from dust on the outside of lens? I'm usually pretty good about keeping the lenses clean.

Luckless · Dec 10, 2018

Could be that your sensor is getting has picked up a few bits of dust or gunk.

Since it is a digital rig, it may be worth doing a white wall test with a few lenses -
Photograph an evenly lit wall with a few different settings, with a reasonable exposure. Wide open and stopped way down, and then with a few different lenses if you have them. If the spots are showing up in the same spots across different lenses, then you know you should be looking to your sensor. If they show up only with one lens, then you know that is your problem.

But another good point to look at: Double check you're not applying some weird pre-set to the images on import. Traced a friend's problem back to them accidentally applying some manual spotting work from one photo to all of their photos. Needless to say an overlay of spotting for a specific photo probably isn't all that helpful in the vast majority of other photos.

jim10219 · Dec 10, 2018

I would check the sensor first. That's mostly likely the cause of the spots. Dust and dirt on the lens won't show up as spots on the image. They cause other problems like flare, lack of clarity/contrast, a lack of sharpness, etc.

Luckless · Dec 10, 2018

jim10219 said:
I would check the sensor first. That's mostly likely the cause of the spots. Dust and dirt on the lens won't show up as spots on the image. They cause other problems like flare, lack of clarity/contrast, a lack of sharpness, etc.

I may be lacking coffee today. (In fact, I know I'm lacking coffee, but the forgetfulness might not be related.) But can't lens dust begin showing up as visible shadows as you get toward the wider end of lenses? I'm completely drawing a blank as to what focal length, apertures, and focal distances you need before that becomes an issue, which is part of why I didn't want to rule out the lens entirely as an issue.

MattKing · Dec 10, 2018

Luckless said:
I may be lacking coffee today. (In fact, I know I'm lacking coffee, but the forgetfulness might not be related.) But can't lens dust begin showing up as visible shadows as you get toward the wider end of lenses? I'm completely drawing a blank as to what focal length, apertures, and focal distances you need before that becomes an issue, which is part of why I didn't want to rule out the lens entirely as an issue.

Nope, lenses aren't generally capable of imaging things on their surface. They all start focusing at least a small distance away from that surface.

shutterfinger · Dec 10, 2018

Are the spots on all images? In the sample image they could be b1rds.

Run the sensor cleaning built into your camera then do a white wall test with the 24mm. If the spots are there in the same place try a different lens.
Dust/scratches on the rear of a lens show up in an image but I don't think they will be sharp.

wiltw · Dec 10, 2018

MattKing said:
Nope, lenses aren't generally capable of imaging things on their surface. They all start focusing at least a small distance away from that surface.

Some time ago I did a little test...deliberately put a large object on the surface of a lens to see the impact on image quality.

The shot wide open (f/2.8)

Then at f/16

The OP photo shows sensor dust, well defined and especially noticed at small f/stops

Theo Sulphate · Dec 10, 2018

Those spots remind me of the notorious oil spots on the Nikon D600 sensor - a camera-body operational problem that was fixed in the D610.

I'd bet there's something on the sensor - try another lens and see if the problem remains or disappears - that will be your clue.

ced · Dec 11, 2018

Well I too agree that the spots are gunk on sensor related.

mporter012 · Dec 11, 2018

Luckless said:
Could be that your sensor is getting has picked up a few bits of dust or gunk.

Since it is a digital rig, it may be worth doing a white wall test with a few lenses -
Photograph an evenly lit wall with a few different settings, with a reasonable exposure. Wide open and stopped way down, and then with a few different lenses if you have them. If the spots are showing up in the same spots across different lenses, then you know you should be looking to your sensor. If they show up only with one lens, then you know that is your problem.

But another good point to look at: Double check you're not applying some weird pre-set to the images on import. Traced a friend's problem back to them accidentally applying some manual spotting work from one photo to all of their photos. Needless to say an overlay of spotting for a specific photo probably isn't all that helpful in the vast majority of other photos.

Will start here tomorrow, and see what I find. Thanks for pitching in! I'll post sample photos and see what we come up with.

What are these spots!?

mporter012

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What are these spots!?

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