White spots in (some) photos: Nikon 600mm f4 G VR. Lens dust?

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Luskentyre

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Hello, whilst I have been following these forums for some time, it's the first time I'm posting within these forums (hoping someone will be able to help shed some light). I have recently purchased a used 600mm f4 G lens from MPB & have noticed some white spots appearing in a couple of photos (in fact, I have taken hundreds of photos & they do not appear in the vast majority of them). Not sure if it's a coincidence, but they appear in strong sunlight & out of focus backgrounds- but not all the time. I have uploaded some photos within the below link to illustrate the issue (not the best photos- apologies). The spots appear on the both the one with the horse & the bird, but not within one with the blue sky or the deer.

https://share.icloud.com/photos/0baA3ys6ZRN2gIZMRHNWzgpIA

I guess my question is whether it's caused by dust within the lens elements? I purchased it in "excellent" condition from MPB, and they are fine to take it back, but I'm happy with it in every other way & therefore am reluctant to return it unless it's internal lens dust (I did give it the rocket blower treatment, and I couldn't observe the issue again, but then again we've not had sunny weather here recently, so I haven't been able to rest it properly!). I can certainly see some dust within the lens when shining a flashlight, but that's to be expected when it comes to a used lens? Any ideas/thoughts? Many thanks in advance for the help!
 
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Luskentyre said:
Hello, whilst I have been following these forums for some time, it's the first time I'm posting within these forums (hoping someone will be able to help shed some light). I have recently purchased a used 600mm f4 G lens from MPB & have noticed some white spots appearing in a couple of photos (in fact, I have taken hundreds of photos & they do not appear in the vast majority of them). Not sure if it's a coincidence, but they appear in strong sunlight & out of focus backgrounds- but not all the time. I have uploaded some photos within the below link to illustrate the issue (not the best photos- apologies). The spots appear on the both the one with the horse & the bird, but not within one with the blue sky or the deer.

https://share.icloud.com/photos/0baA3ys6ZRN2gIZMRHNWzgpIA

I guess my question is whether it's caused by dust within the lens elements? I purchased it in "excellent" condition from MPB, and they are fine to take it back, but I'm happy with it in every other way & therefore am reluctant to return it unless it's internal lens dust (I did give it the rocket blower treatment, and I couldn't observe the issue again, but then again we've not had sunny weather here recently, so I haven't been able to rest it properly!). I can certainly see some dust within the lens when shining a flashlight, but that's to be expected when it comes to a used lens? Any ideas/thoughts? Many thanks in advance for the help!
Click to expand...
They look like insects. That would explain why the pattern where the spots show up isn't consistent. Little bugs will show with the longer lenses. Just a guess.
 
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Many thanks for the response @Shaggstone & @MrFotoFool. I did suspect it was atmospheric dust, but had some lingering doubts as the bird photo was on a different day/in a different location to the pony one. It was also strange to see white dots as I’ve only seen dark dots before (e.g.when I had sensor dust on my D800). I will do some more testing today (the weather is looking a bit better here today) & hopefully I can keep this lens! Thanks again for your support/comments.
 
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Thank you @dabhand16. That’s a fair point, although what’s strange is that I’ve had my 200-500 for over a year & never had this issue with that lens. Furthermore, the spots were only appearing within the out of focus areas, and that was what made me think it was lens dust.
 
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Luskentyre said:
Thank you @dabhand16. That’s a fair point, although what’s strange is that I’ve had my 200-500 for over a year & never had this issue with that lens. Furthermore, the spots were only appearing within the out of focus areas, and that was what made me think it was lens dust.
Click to expand...

You could try to replicate the issue under controlled conditions to see if the 'pattern' of spots is constant.
 
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Thanks again @dabhand16 (& everyone else who has chipped in, of course!). Luckily, it turned out to be a sunny day today here - I managed to do quite a bit of testing under various conditions & I could not replicate the issue again, which leads me to conclude that it was caused by atmospheric issues (insects/dust etc) as a number of you have pointed out above. I'm glad I can keep the lens, for I was very happy with it in every other way- once again, thanks for all the support! Best Regards, J!
 
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Luskentyre said:
Thank you @dabhand16. That’s a fair point, although what’s strange is that I’ve had my 200-500 for over a year & never had this issue with that lens. Furthermore, the spots were only appearing within the out of focus areas, and that was what made me think it was lens dust.
Click to expand...
That may be saying something about the optical quality of the 200-500. Then again, it may be saying something about the optical quality of your 600mm!
 
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