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by natureshooter606 on Sat Oct 10, 2020 1:33 pm
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Image


Hi All,

I have a question for you. How much of a concern do you think that this little yellow piece of debris is underneath the front element of this lens? Will it impact image quality at all? So far I haven't been able to detect an issue on images but I also haven't done extensive testing yet. Curious what you all think.

It's frustrating because it's smack dab in the center.... but I also at the same time don't know if it will actually make a difference .
 

by SantaFeJoe on Sat Oct 10, 2020 1:45 pm
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It seldom affects image quality to any noticeable extent. Maybe on a macro lens that focuses really close up.

https://photographylife.com/what-to-do-with-dust-inside-lens

Joe
Learn the rules like a pro, so you can break them like an artist.  -Pablo Picasso
 

by DChan on Sat Oct 10, 2020 6:21 pm
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Agreed with Joe.

If it's your lens, just shoot a whole bunch of pictures with it and see if you notice any difference in image quality. If you don't, everything else is just psychological.
 

by aolander on Sat Oct 10, 2020 7:17 pm
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Don't worry about it.

https://www.lensrentals.com/blog/2011/08/the-apocalypse-of-lens-dust/

https://www.lensrentals.com/blog/2008/10/front-element-scratches/
Alan Olander
Minnesota
 

by natureshooter606 on Sat Oct 10, 2020 7:31 pm
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Thanks guys... I needed to be talked down and you have helped. It's hard to get over the psychological aspect of the dust on a brand new lens (well it's not new, it's used.. i bought it from someone... so it's new to me I guess) but I'll get over it. I just did some tests and I really can't see it... I did find a few dust spots on my brand new R5 sensor though..... argh. I shouldn't have looked :-).

But I digress. Thanks again for the help.
 

by E.J. Peiker on Sat Oct 10, 2020 10:54 pm
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Probably never see it in a picture except when you are shooting directly into the sun where it will cause flare.
 

by natureshooter606 on Sun Oct 11, 2020 11:44 am
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E.J. Peiker wrote:
Probably never see it in a picture except when you are shooting directly into the sun where it will cause flare.



Thanks, E.J. Your suggestion here prompted me to do some very quick (and admittedly very unscientific) testing this morning. Here's an image out of the 24-105 pointed directly into the sun. Obviously there's a fair bit of flare... a bright prism-like spectrum spot and a darker purple circle a bit lower.

Image




I then dialed down exposure compensation and took another. Again, a bright prism-like spectrum spot and then the darker purple circle.


Image




This got me a bit concerned as I'd be unhappy if the debris were causing this... I don't make it a habit to shoot directly into the sun, but for sunsets or other images it certainly happens from time to time and the impact in this image is very noticeable.

But then I started thinking... well how would a different lens perform? So I put my 17-40mm EF on the camera and tried to take some very similar images at a similar focal length with similar settings.  Interestingly, we see a very similar flare pattern, although the 17-40mm clearly has less flare than the 24-105mm. In the first photo below, the spectrum and purple spots are overlapping, and in the second photo they are separate by some distance. They are obviously much weaker than in the 24-105, but they are there and have similar characteristics.

Image


Image





So I guess the question is...   do we think that the debris in the 24-105 has anything to do with the flare shown in the images, or do both of these lenses just produce flare regardless of debris (albeit in varying degrees of severity)?

And separately... this is my first mirrorless camera. Is there anything I should be aware of with shooting the sun? On rare occasions I'd pop a super tele on my 7d or 1dm2n and take some sunset photos low to the horizon for a big fireball (obviously being very careful never to actually look through the lens). I'm a bit worried this might melt the mirrorless sensor. Anyone have any thoughts on that?

But not trying to hijack my own thread too much... for the most part, curious about everyone's thoughts on the flare :-)
 

by DChan on Sun Oct 11, 2020 12:47 pm
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If I shoot directly into the sun, I expect flare. I'd suggest keep experimenting with other lenses of yours. There's theory, and then there's reality.
 

by E.J. Peiker on Sun Oct 11, 2020 2:07 pm
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It's possible that it is due to that spot but without seeing exactly how the dust lines up with the frame, I can't say.  If it is in the same spot from center but upside down then that's likely the cause.  For example, lets say the dust is just above the centerline of the lens when the lens is mounted and the spot shows up in the photo just below the center of the photo then that is likely the cause.
 

by SantaFeJoe on Sun Oct 11, 2020 3:25 pm
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If both lenses are producing similar flare, it is highly unlikely and nearly impossible that the debris is causing the flare. You don’t mention whether you see any debris in the 17-40 lens, but I am assuming not.  I have a 500 f4 that has a lot of dust in streaks under the front protective element(?) and never have seen any flare from it, even when shooting towards the sun. I have gotten that purple flare even when shooting film. It is not unusual at all. I believe that it comes from the lens coatings. 

This is my lens. The four cone shaped dust streaks are visible around the edges, along with much more dust on the inner surface of the front glass.
Image




Joe
Learn the rules like a pro, so you can break them like an artist.  -Pablo Picasso
 

by Jeff Colburn on Tue Oct 13, 2020 12:37 pm
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Hi,

Both of my Canon L lenses came from the factory with lots of dust inside. And I swear more has accumulated over the years. But the dust isn't causing any problems with picture quality.

Have Fun,
Jeff
Fine Art Prints and Stock Photography of Arizona www.JeffColburn.com See my ebooks in the NatureScapes Store 25 Places To Sell Your Photographs And Photography Skills and The Vanishing Old West - Jerome
 

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