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01-01-2010, 03:53 PM   #1
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My DA 16-45mm a lemon?

Happy New Year! I hope you all have a prosperous new year to start off the new decade.
I took a few images with my DA 16-45 last night to see what I'd get. They're not really long exposures since there was a full moon out that limited the exposure times to a few minutes at the most. What surprised me was that there is a red circular ghost showing up in the images. At 16mm it's at the center, while at 45mm it's off to the right of center.

This first image was taken at ISO 200, 21mm, f 16 and 123.0 seconds.



This second was taken at ISO 400, 45mm, f 16 and 72 seconds. I used my K100DS for these shots.



No ghosts show up in the images taken during the day. The lens does have some back focussing though.
Any thoughts on what is causing the ghosting? The front element had a little bit of dust on it and the rear element looked normal as far as I can tell, no dust, scratches, smears etc., when I inspected the lens this morning.
Does Pentax honor the one year warranty when a lens is bought from an ebay dealer? It was listed as a new lens.

01-01-2010, 03:57 PM   #2
axl
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Any filters on the lens?
01-01-2010, 04:08 PM   #3
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You have a bit of flare. It isn't unusual in this type of picture, especially with a zoom lens.
Your equipment is fine.
01-01-2010, 05:09 PM   #4
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QuoteOriginally posted by axl Quote
Any filters on the lens?
yeah take the filter off for these sort of shots.

01-01-2010, 05:12 PM   #5
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QuoteOriginally posted by tux Quote
yeah take the filter off for these sort of shots.
exactly what I thought but wasn't sure if there was any filter in the first place. But looking at the shots, that was my first impression.

BR
Peter
01-01-2010, 06:10 PM   #6
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I forgot to add that I didn't use a filter with these shots. Is the DA 16-45 prone to flares?
I tried my Tamron 28-75 lens not too long after these and the shot came out fine.
01-01-2010, 07:50 PM   #7
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QuoteOriginally posted by RollsUp Quote
What surprised me was that there is a red circular ghost showing up in the images. At 16mm it's at the center, while at 45mm it's off to the right of center.... No ghosts show up in the images taken during the day.
Any thoughts on what is causing the ghosting? The front element had a little bit of dust on it and the rear element looked normal as far as I can tell, no dust, scratches, smears etc., when I inspected the lens this morning.
Just a guess here, but that looks like snow on the ground, and you're in Alaska -- maybe the "ghosting" is really just very light condensation on the front element of the lens, due to temperature change? The halos around the fireworks look like there's some mist or light snow in the air, and a healthy cross-wind, so the condensation might have moved off-center between the two shots. And any condensation surely would have evaporated indoors overnight.

(I'd call this the "snow drift" hypothesis. )
01-01-2010, 08:10 PM   #8
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Looking at that second shot, it's very clear that the lens had moisture on the front element. Look at the bright street light on the left. All the green flaring off the light is a sign the lens was fogged/frozen up and it caused all sorts of issues. Taking a lens out of a warm building and out into the cold can easily do this.

Your lens is fine, it was just the conditions.

01-01-2010, 08:58 PM   #9
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Other than the back focus the lens has I am glad it's fine. And yes I am in Alaska and that is snow on the ground.

I was wondering how the second image got those effects. A few ATVs came up to the hill I was on and passed by upwind from me so probably the snow that they kicked up got on the lens.

How long should a lens acclimate before taking it out of a bag and start taking photos? I estimate the body and lens were in the bag roughly tens minutes from the time I took it out of the house (70* -72* F) to the time I took it out of the bag to set it up on the tripod at about 0* F with the wind chill down to about -20* F. I then waited another ten minutes more for the fireworks to start before taking any photos.

Also, I'm curious as to why the photo I took with the tammy right after I got home doesn't show any fogging on the image. I just took it out of the house, replaced the 16-45 with it and set it up on the tripod to take a test shot at ISO 200, 28mm, f16 and 164 secs.

01-02-2010, 09:58 AM   #10
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I had a similar situation occur when I was shipboard off of Hawaii. I came out on to the weather deck and started taking some pictures of flight operations. Looked down to check the images and they were - well very out of focus. Later when I uploaded the images to a laptop I was able to see that they were "fogged". It all cleared up with in a few minutes. So its the extreme change in the operating environment. How long? A few minutes - exactly, I do not remember.

As to why it did not happen to your Tamrom - different construction, I would venture to say. That does not imply that the Tamron is any better or worse, just different.
01-03-2010, 02:13 AM   #11
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Thanks, interested_observer. I guess I just have to watch for fogging when I use this lens in cold temps. But I think the ghosting in the above images are flare as Wheatfield said earlier. I used the same combo earlier today in 10 deg temperatures excluding windchill. I didn't keep it in the bag very long from the time I took it out of the house to taking my first photo and I didn't see any fogging in any of my images.
01-04-2010, 11:59 PM   #12
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The back focus you mentioned.

Do you use a K-10D? My 16-45 also provides back focus, as do all the other lenses I use. I don't think the lens is the culprit- it's the positioning of the chip!

To fix this in the K-10D you need to load the v 1.1 firmware and execute a particular series of button presses on startup. This will get you to the debug menu, and by navigation you get to the focus correction bar.- focuses in nanometres. If you have backfocus, move the slider right, and vice versa. then exit, and test, doing careful focus checks at moderate apertures, different zoom lengths etc.

I've found now, that the focus is accurate, red target can be trusted, but the image in the finder isw a little de-focused when lens focus is correct. What a hassle. Makes manual focusing almost pointless, as when screen image is sharp, captured image is not.

And have you found that with time exposures, the read- time is as long as the exposure time? You know, a 5 minute exposure makes you wait 5 mins for the review pic, meanwhile the camera is locked up processing. This is my experience, enyhow. Do you get the same problem?

Regards,

Jan.
01-05-2010, 04:19 AM   #13
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QuoteOriginally posted by flashcactus Quote
I've found now, that the focus is accurate, red target can be trusted, but the image in the finder isw a little de-focused when lens focus is correct. What a hassle. Makes manual focusing almost pointless, as when screen image is sharp, captured image is not.
Regards,

Jan.
You can fix that issue with the diopter setting.
If the writing at the bottom of the VF is then OOF, it means your focusing screen is badly aligned. Better to have the writing slightly OOF, and the MF works fine.
Or, you can adjust it by adding another shim to the focusing screen inside.
01-07-2010, 03:25 PM   #14
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QuoteOriginally posted by flashcactus Quote
Do you use a K-10D? My 16-45 also provides back focus, as do all the other lenses I use. I don't think the lens is the culprit- it's the positioning of the chip!

To fix this in the K-10D you need to load the v 1.1 firmware and execute a particular series of button presses on startup. This will get you to the debug menu, and by navigation you get to the focus correction bar.- focuses in nanometres. If you have backfocus, move the slider right, and vice versa. then exit, and test, doing careful focus checks at moderate apertures, different zoom lengths etc.

I've found now, that the focus is accurate, red target can be trusted, but the image in the finder isw a little de-focused when lens focus is correct. What a hassle. Makes manual focusing almost pointless, as when screen image is sharp, captured image is not.
I used my K100D Super for these photos. I do have a K20D though that adjusts for back/front focussing.

QuoteQuote:
And have you found that with time exposures, the read- time is as long as the exposure time? You know, a 5 minute exposure makes you wait 5 mins for the review pic, meanwhile the camera is locked up processing. This is my experience, enyhow. Do you get the same problem?

Regards,

Jan.
Dark Frame Subtraction. There are some threads regarding this in this forum. And yes, I do notice it happening with my DSLRs.
03-25-2010, 11:17 PM   #15
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QuoteOriginally posted by RollsUp Quote
Thanks, interested_observer. I guess I just have to watch for fogging when I use this lens in cold temps. But I think the ghosting in the above images are flare as Wheatfield said earlier. I used the same combo earlier today in 10 deg temperatures excluding windchill. I didn't keep it in the bag very long from the time I took it out of the house to taking my first photo and I didn't see any fogging in any of my images.
It wasn't flare as I had thought earlier. It doesn't happen all of the time, and in those times that I started noticing some fogging in the viewfinder I didn't think to look at the front element. I finally took a look at the front element today when I started noticing some fogging in the viewfinder of my K20D and this is what I saw.



It makes me not want to bring it out in cold temps anymore.
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