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05-15-2016, 12:30 PM   #1
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Possible fogging issue with FA20

The story here is that I recently acquired the FA20, partly in preparation for the K-1 and partly to try an ultra wide lens. After receiving it, I noticed some internal fogging on the back of the rear element. (See the first picture below.) It is not very noticeable at first and just looking through the lens with a flashlight, it doesn't seem to have any affect. I had it inspected by a local camera repairman and he seemed to think it was OK, so I opted to keep it. I had not yet taken many pictures with it, but so far it seemed OK to me as well.

Fast-forward to about a week ago when I was doing some test shooting with the K-1 and the FA20. I took the picture below and a few other similar ones and immediately noticed that the flaring on the brightest streetlight seems exaggerated and "dirty" to me. Right around the streetlight, it looks like there is fog in the air, but I double checked at the time and there was no noticeable fog in the air. Further, a few other shots taken with the K35/2 didn't show similar "dirty" flaring.

So my questions are:
1. Could this flaring be exaggerated by the fogging in the lens or is this normal flaring for this lens?
2. If this is caused by the lens fogging, would people recommend trying to have it cleaned?
3. Besides Eric Hendrickson, are there others who do lens CLAs?

Pentax K-1 + FA20, f5.6, handheld 1/3s, ISO 800:

100% crop:

05-15-2016, 12:55 PM   #2
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It looks like haze or dirt to me.
05-15-2016, 03:08 PM   #3
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It looks like fungus to me. That's not a cheap lens, get it cleaned before it etches the glass.
05-15-2016, 03:58 PM   #4
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Inspect the lens carefully. Shine a flashlight in there. Check the back element, look at the insides, look at the aperture blades from both sides (are they oily, shiny, dirty?). It could be fungus or hazing.. if you send it to a repair store soon enough, it can still (hopefully) get fixed.

Also, did you use some kind of lens hood? Filter? This might affect results and cause odd reflections, flares

05-15-2016, 04:18 PM   #5
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PM DCShooter...... see if he can help
05-15-2016, 04:19 PM   #6
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It's not fungus. Fungus looks totally different, more like filaments.

This is quite a common problem with this lens (and the A version as well which shares the same optical design) and it's lens separation of 7th and 8th element (7th group from the front). The aging adhesive becomes opaque, causing the cloudiness (probably caused by oxidation as air gets in between the elements).

You need to have the cemented pair separated, cleaned and re-bonded, but not many repairer offer this service. Also, it can't always be cleaned 100% and you may still notice a very slight cloudiness, though it shouldn't be enough to affect your photos.
05-16-2016, 03:34 PM   #7
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Thank you all for your replies!

I have examined the lens a number of times and have not seen anything out of the ordinary besides the affected element that I have shown here. The aperture blades look clean to me. There are some minor scratches on the front element, but I don't think they are likely to be causing any problems in the images. In these test shots I had a brand-new and clean UV filter on the lens (mainly for the physical protection), which I doubt was involved in the flaring.

I would still be interested to know if anyone has insight into whether the hazy/dirty flaring could be or is likely caused by the lens fog/haze/etc. This is a question I would like to answer because I would not necessarily go through with a cleaning if the fog/haze/etc. had no impact on the images (and if it was not going to get worse, like fungus). Personally, I think the flaring in this case is likely made worse by the lens fog/haze/etc., but I would like to get more opinions on it.

In the meantime, I will PM dcshooter and see if he has any input to give on this issue.
05-16-2016, 03:57 PM   #8

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you won't know for sure if it's cleanable or not until it gets torn down... if it's between cemented elements like tom says you got a problem.

a lot of legacy lenses will have haze/fog on the first element surface facing each side of the aperture blades, because that's what's exposed to contamination, it can usually be cleaned up pretty easily.

that pic looks like it was shot in heavy mist, you can quantify it by taking the same shot with a different lens, see how the shots compare in the flare area around the street light.

05-17-2016, 07:27 PM   #9
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QuoteOriginally posted by osv Quote
that pic looks like it was shot in heavy mist, you can quantify it by taking the same shot with a different lens, see how the shots compare in the flare area around the street light.
I have not done rigorous testing, but I did make note that there was no visible fog or mist in the air when I took the picture. I also took some similar shots with the K35/2 at the same time that do not show such extensive flaring. There was some flair from streetlights, but much more controlled and cleaner looking with that lens.

I have been talking with dcshooter a little, and it seems likely I will be sending it to him for a CLA.

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