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03-23-2016, 09:08 PM   #1
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DA15 gremlin dust . . .

Hello Pentaxians, I have a question regarding my beloved DA15. I bought it second hand and have owned it for over 2 years now, taking care of it as best I can. Indeed, it has served me very well, but lately I have been noticing an issue with extreme flare in some pictures with high contrast. The first was over a year ago taking city shots at night, and I noticed when working on them in Lightroom that a couple of shots had pretty extreme "flaring" of some sort, even though the rest of my pictures exhibited nothing similar to this phenomenon and appeared fine. This resurfaced late last year at a sunrise shoot ( again, only a few photos exhibited this flaring ) and last week highlighted the worst case yet while chasing some lightning. It was bad enough that I could see it straight away on the camera preview and had to put the lens back in the bag! I can't really see much of a pattern here, but I assume that a strong point of light taking a certain path through the lens is causing this.

What do you think it might be? Dust in the lens? I keep the lens front and rear elements as clean as I can; however if I look through the rear element of the lens toward a light source I can see some dust, but nothing that looks too major. Looking through the lens from the front element shows up what looks like a bunch of small "pin prick" looking spots that appear to be scattered in/behind/on the front element. Alas, perhaps it's suffering from gremlin dust rather than pixie dust. I'm open to also consider the sensor to be the issue, but none of my other lenses seem to do this.

One last consideration is that I've always found my copy to be reasonably sharp, but it seems that recently the border sharpness has dropped off quite dramatically, so I might have to get the lens looked at anyway.

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03-23-2016, 09:32 PM   #2
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Ugh....
03-23-2016, 09:36 PM - 1 Like   #3
dms
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Likely fungus growing--would explain reduced resolution and increased flare, and you see it from what you say.
03-23-2016, 10:42 PM   #4
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Could also be decentering.

03-24-2016, 03:32 AM   #5
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QuoteOriginally posted by Focusrite Quote
Hello Pentaxians, I have a question regarding my beloved DA15. I bought it second hand and have owned it for over 2 years now, taking care of it as best I can. Indeed, it has served me very well, but lately I have been noticing an issue with extreme flare in some pictures with high contrast. The first was over a year ago taking city shots at night, and I noticed when working on them in Lightroom that a couple of shots had pretty extreme "flaring" of some sort, even though the rest of my pictures exhibited nothing similar to this phenomenon and appeared fine. This resurfaced late last year at a sunrise shoot ( again, only a few photos exhibited this flaring ) and last week highlighted the worst case yet while chasing some lightning. It was bad enough that I could see it straight away on the camera preview and had to put the lens back in the bag! I can't really see much of a pattern here, but I assume that a strong point of light taking a certain path through the lens is causing this.

What do you think it might be? Dust in the lens? I keep the lens front and rear elements as clean as I can; however if I look through the rear element of the lens toward a light source I can see some dust, but nothing that looks too major. Looking through the lens from the front element shows up what looks like a bunch of small "pin prick" looking spots that appear to be scattered in/behind/on the front element. Alas, perhaps it's suffering from gremlin dust rather than pixie dust. I'm open to also consider the sensor to be the issue, but none of my other lenses seem to do this.

One last consideration is that I've always found my copy to be reasonably sharp, but it seems that recently the border sharpness has dropped off quite dramatically, so I might have to get the lens looked at anyway.
From what I can see the spots are all seven sided which coincides with the number of aperture blades.

Have you tried the same shot as you have shown but running through the full set of apertures from f4 to f22?

Also, do you have a filter mounted on the lens?

There is the possibility that you are seeing reflections off the surface of the sensor reflected back from a glass interface in the lens or from the rear surface of any attached filter.

Regards

Chris
03-24-2016, 05:37 AM   #6
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I Second the question about a lens filter. Normally, dust gives you decreased resolution, but doesn't make the patterns you see in these photos, UNLESS the dust is grabbing / deflecting light.

IF you don't have a filter and can't see any foreign objects in the lens, then I would think your lens needs repair. There is likely an element out of alignment that is grabbing light and allowing it to bounce around in the lens = Decreased sharpness / artifact.


Summary: If not a lens filter, probably a broken lens
03-24-2016, 06:17 AM   #7
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Thanks for the replies everyone!

I usually don't use filters except for the occasional ND or CPL, and such is the case with all the photos shown; no filter was on the lens at the time. Neither did I have the forethought of testing the lens at different apertures; the last shot was the only time so far that I've noticed the effect whilst out in the field, and I was more concerned with getting some lightning photos while the storm lasted! ( I posted one in the Photo Critique forum if anyone's interested . . . After discussing my lens issues you can give me pointers on my photography as well Just a little self advertisement )

I just about had kittens at the suggestion of fungus ( I've already isolated the lens from all my others! ), but perhaps I didn't describe the internal spots and their scattering well enough. Nonetheless, I'm taking it seriously and I think I'll visit a lens repairer tomorrow and get it checked out anyway. A decentred lens makes sense for something that is coming and going, and I want my DA15 back in top form!
03-24-2016, 06:53 AM - 2 Likes   #8
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Those pin picks are probably actually micro droplets of redeposited lubricants which are acting like tiny lenses when light passes through them. It's a similar phenomenon to when you get raindrops on the front of your lens. Decentering would cause edge softness and significant chroma effects around the edges.

03-24-2016, 07:14 AM   #9
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QuoteOriginally posted by dcshooter Quote
Those pin picks are probably actually micro droplets of redeposited lubricants which are acting like tiny lenses when light passes through them. It's a similar phenomenon to when you get raindrops on the front of your lens. Decentering would cause edge softness and significant chroma effects around the edges.

Sounds right to me
04-08-2016, 01:37 AM   #10
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Just a little update for those who are interested, and unfortunately it's not good news. The repairer had a look at the lens and noticed that it did have what appeared to be small particles of sand, but aside from that he didn't notice any lubricant droplets or anything much else of interest. Upon testing it, he agreed that the borders are extremely soft, so he disassembled the lens to have a look and clean out any foreign particles that he found.

What he found was that there are a couple of lens elements in the rear element group that are supposed to be cemented together, but have come loose ( quoting from memory ). He also discovered that there is significant wear in the focusing system that allows the barrel to wobble quite severely ( didn't even notice until he showed me! ) and would likely affect the image quality, albeit marginally. The wear is most likely from foreign particles getting into the lens, and I do recall accidentally introducing the lens to the beach a little while back thanks to an unattended camera/tripod and high winds; so it's occurrences like that which would precipitate this kind of thing happening.

He got some quotes for parts to complete a full repair, and he estimated that it would probably cost me about as much to buy another second-hand DA15! It's still usable as it is, but the borders are terrible at anything below f11. So, not the best of news, and now I have to decide whether I want to shell out for another one or not. At least the repairer didn't charge me anything for his time thus far; he said he doesn't like to kick a bloke when he's down!

So the exact reason for the odd flaring is still unknown ( I didn't even think to ask when I picked the lens up ), but thanks everyone for chipping in with your 2 cents anyway!
04-08-2016, 01:48 AM - 1 Like   #11
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Sorry to hear that, but thanks for reporting back.
04-09-2016, 10:11 AM   #12
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QuoteOriginally posted by Focusrite Quote
Just a little update for those who are interested, and unfortunately it's not good news. The repairer had a look at the lens and noticed that it did have what appeared to be small particles of sand, but aside from that he didn't notice any lubricant droplets or anything much else of interest. Upon testing it, he agreed that the borders are extremely soft, so he disassembled the lens to have a look and clean out any foreign particles that he found.

What he found was that there are a couple of lens elements in the rear element group that are supposed to be cemented together, but have come loose ( quoting from memory ). He also discovered that there is significant wear in the focusing system that allows the barrel to wobble quite severely ( didn't even notice until he showed me! ) and would likely affect the image quality, albeit marginally. The wear is most likely from foreign particles getting into the lens, and I do recall accidentally introducing the lens to the beach a little while back thanks to an unattended camera/tripod and high winds; so it's occurrences like that which would precipitate this kind of thing happening.

He got some quotes for parts to complete a full repair, and he estimated that it would probably cost me about as much to buy another second-hand DA15! It's still usable as it is, but the borders are terrible at anything below f11. So, not the best of news, and now I have to decide whether I want to shell out for another one or not. At least the repairer didn't charge me anything for his time thus far; he said he doesn't like to kick a bloke when he's down!

So the exact reason for the odd flaring is still unknown ( I didn't even think to ask when I picked the lens up ), but thanks everyone for chipping in with your 2 cents anyway!
QuoteOriginally posted by Focusrite Quote
reed that the bor
QuoteOriginally posted by Focusrite Quote
rticles getting into the lens
Well im sure someone would buy it for like 200 or so.... and then get yourself and top shape one :P
04-10-2016, 11:47 AM   #13
osv
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the blue trailing orbs coming off of bright light look like sensor flare, see a7 examples here: https://www.pentaxforums.com/forums/76-non-pentax-cameras-canon-nikon-etc/241...-so-far-7.html
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