[donpjt]

Hi All,

Last week I posted a thread on my 50mm D-FA Macro lens having probable fungus and I asked for help and many of you generously replied. So I got the lens exchanged from KEH and I received the replacement lens today. But this one also seems to have a problem. There seems to be internal streaking and marks on the rear internal element. It is noticeable only if you shine a Flashlight through the lens, by just peeking through the lens, its not noticeable at all.. None of the other elements have it. Wondering if I should return this one as well

Before that can anyone take a closer look and advise whether it will affect the image quality or whether I should keep it.....

Thanks again.

Here is a link to my last post

https://www.pentaxforums.com/forums/58-troubleshooting-beginner-help/278895-m...s-problem.html

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Last edited by donpjt; 11-20-2014 at 06:13 PM. Reason: added more details

[luftfluss]

Oil?

[sergysergy]

It looks like cleaning marks (and a little bit like planet Earth)?

[waterfall]

Maybe streaks from a sloppy CLA job? If it is oil, shining a tight flashlight beam at an angle will produce diffraction, showing as a rainbow of color bands within the streaks.

[dms]

If it was BGN or better I would return it and ask for (and never was a problem for me) them to pay return postage (they will have you print a prepaid label) and ask for another copy.

[donpjt]

If it was BGN or better I would return it and ask for (and never was a problem for me) them to pay return postage (they will have you print a prepaid label) and ask for another copy.

This is the second copy I got after returning the first one. They were supposed to be in EX condition, both of them and the first one had fungus.. Overall this one looks better and newer, but unfortunately it came with this problem. If I return it this time I will just get a refund instead of an exchange, i don't want to take the risk to getting another faulty one!

Too bad I really liked this lens, I will have to wait or buy from b&h or adorama...

---------- Post added 11-20-14 at 09:02 PM ----------

It looks like cleaning marks (and a little bit like planet Earth)?

lol.. Planet Earth.. thats right, I never thought of that

[stevebrot]

It looks like cleaning marks (and a little bit like planet Earth)?

Maybe streaks from a sloppy CLA job? If it is oil, shining a tight flashlight beam at an angle will produce diffraction, showing as a rainbow of color bands within the streaks.

Looks like the results of a cleaning attempt.

Taking a flashlight to the lens as you have done is entirely appropriate and the best way to scan for internal fungus hazing and such. Time to talk to KEH again, I fear. They should have caught this.


Steve

[dms]

I am not thrilled w/ KEH's new site, but I think two not as advertised lenses is unfortunate but not that uncommon. As long as they are willing to work w/ you, warranty the stuff for 6 months, and refund totally the shipping I still think (based on my experience--anyway up to about 6 months ago) they are about as risk free as you can get on used equipment.

I would say roughly 1 out of 4 purchases I got from KEH were not as advertised/not acceptable--and in each case they refunded all expenses (both ways). I did not keep careful records but over the past several years I likely purchased about 12-15 (mostly) lenses and cameras (mostly BGN) and believe I sent back 4 of them. I remember as follows: a takumar lens was mechanically defective, a mechanical part was missing on an Adaptall-2 lens, and in another case the lens was decentered, and also an auto extension set was not auto [in that case they mailed me back a second set--which also was not auto].

Although the following application of the above statistics are very crude/of low confidence level, but given the application--so what. My experience means (very roughly) 1 out of 16 purchases will be not as advertised followed by a second not as advertised. Of course you would hope they made some extra effort w/ the mailing of the second lens--but maybe not.

[stevebrot]

My experience means (very roughly) 1 out of 16 purchases will be not as advertised followed by a second not as advertised.

My experience has been one item out of everything (20+) that I have ordered from KEH in the last 6 years has been defective or other than advertised. I believe this compares well to my purchases from Adorama during the same period where I also had to send one item back as unacceptable. Compare both to eBay and the PF marketplace* where my send back or price-negotiate rate is close to 30% and KEH looks pretty good.


Steve

* One marketplace purchase involving a camera and three lenses resulted in the camera and two of the lenses being "negotiated" as being not as described. Not good.

[Wild Mark]

Certainly looks like cleaning marks. That will cause some loss of contrast and being macro that is not desirable as it will affect perceived sharpness.

If you got it for a really good price then maybe send it to Eric for a clean. He will sort it out - that way you will have a top notch lens with no further worries.

I hope it is not the same lens with a bodgy clean job?

[donpjt]

Certainly looks like cleaning marks. That will cause some loss of contrast and being macro that is not desirable as it will affect perceived sharpness.

If you got it for a really good price then maybe send it to Eric for a clean. He will sort it out - that way you will have a top notch lens with no further worries.

I hope it is not the same lens with a bodgy clean job?

Thanks for the tip. It was not at a bargain price and so this time probably I'll send it back and get my money back instead of getting another one. I'll try for EX+ or LN the next time instead of EX for more expensive items the next time.

I did a lens IQ test and the lens IQ was the same for the last one and this one as well, so Its sad that I have to send it back, since the IQ is pretty good. see the result in my next post

[donpjt]

Gotta disagree with Mark here. Not worth a return in my opinion.

If you can only see it when shining a strong flashlight through it and not when holding it up to the light, then it is honestly not an issue, since it's not going to affect sharpness or contrast to any perceptible degree. It takes a lot more than you would think for that to happen, and certainly not something as minor as this. The flashlight test will tell you a lot of truths about the condition a lens is, but it will tell you a lot of lies about how serious any problem you see is, too. Just look at all that dust (actually not a bad level at all).

Probably dried cleaning fluid, as some others have said. If it were dried oil or plasticizers, you would see a perceptible haziness to the lens when holding it up in front of a window, etc. Even brand new lenses will have internal cleaning fluid marks if you look closely enough. Dust too. All of your other lenses probably already have as bad or worse on their front and back surfaces while you are shooting with them, even after giving them a microfiber wipe or a hit with a lens pen, which both will leave similar residue. And you'll see the same if you look hard enough even on a brand new return from a CLA.

I'm not sure this one has actually been opened, since I don't see any obvious marks on the rear mount screws, and most DA lenses have to have at least part of the rear mount removed in order to remove the rear group for cleaning. Of course, I might be missing something, as the photos are rather low res.

Looking at the pics you linked to form the firs tlens you sent, I'm not sure that's fungus, either, although it's hard to tell with the angle. If the mark was on the actual size of the lens, rather than the front or back surface, it looks like it's just that some of the blacking on the ground glass side of the lens group had chipped off. Probably wouldn't have affected anything. If it was on a "surface" of the lens, then it looks more like cement separationthan fungus. Now that would have been a problem. Spilled milk at this point, I guess.

Thanks for the advice. Well, I did check all my other lens, from the very old ones to the new ones, none of them have any remains of any cleaning inside. This is the only one that has this much remnant inside. I'm not sure if its supposed to have as much marks inside and I'm not sure if it will impact picture quality.. probably not now, but any kind of dried remnant can act as a magnet for other dirt and over time, it could become more clogged though it might not be a problem right now. hmm. Either way I did a sharpness test for the lens, and I'm posting the results, if anyone's interested enough to see and comment

Link to lens test from f2.8 to f 16 when it loses sharpness

DFA 50 mm test - Imgur

[stevebrot]

Gotta disagree with Mark here. Not worth a return in my opinion.

If you can only see it when shining a strong flashlight through it and not when holding it up to the light

Lens was EX. Internal marks should not be present.


Steve

[donpjt]

Called the guy at KEH, He didn't seem to happy about the exchange as he asked whether the marks affect image quality, and it is too early for me to say whether it will because I have hardly used it.. So I just told him that its not something I have on any other lens. I also added that the marks were more in accordance to a BGN or UG Lens and not an EX one. Either way I emailed him a picture of the mark, but there was not much response..

Isn't there something about KEH return policy that sometimes you might have trouble returning if you have a bad return history or something like that..

[Wild Mark]

Gotta disagree with Mark here. Not worth a return in my opinion.

If you can only see it when shining a strong flashlight through it and not when holding it up to the light, then it is honestly not an issue, since it's not going to affect sharpness or contrast to any perceptible degree. It takes a lot more than you would think for that to happen, and certainly not something as minor as this. The flashlight test will tell you a lot of truths about the condition a lens is, but it will tell you a lot of lies about how serious any problem you see is, too. Just look at all that dust (actually not a bad level at all).

Probably dried cleaning fluid, as some others have said. If it were dried oil or plasticizers, you would see a perceptible haziness to the lens when holding it up in front of a window, etc. Even brand new lenses will have internal cleaning fluid marks if you look closely enough. Dust too. All of your other lenses probably already have as bad or worse on their front and back surfaces while you are shooting with them, even after giving them a microfiber wipe or a hit with a lens pen, which both will leave similar residue. And you'll see the same if you look hard enough even on a brand new return from a CLA.

I'm not sure this one has actually been opened, since I don't see any obvious marks on the rear mount screws, and most DA lenses have to have at least part of the rear mount removed in order to remove the rear group for cleaning. Of course, I might be missing something, as the photos are rather low res.

Looking at the pics you linked to form the firs tlens you sent, I'm not sure that's fungus, either, although it's hard to tell with the angle. If the mark was on the actual size of the lens, rather than the front or back surface, it looks like it's just that some of the blacking on the ground glass side of the lens group had chipped off. Probably wouldn't have affected anything. If it was on a "surface" of the lens, then it looks more like cement separationthan fungus. Now that would have been a problem. Spilled milk at this point, I guess.

Excellent point dcshooter. I guess I was engaging my OCD mindset I don't like seeing any marks and as such the psychology for me is a lens with marks means it is not any good. Perhaps I am a little to sensitive to grime

It always comes down to sharpness. I looked at the tests and it does seem like the lens is a little soft at f16 and f22 (a macro lens of this type should have almost no diffraction IQ loss). But to be true I can't be sure if the softness is expected or not.