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01-22-2009, 09:58 PM   #1
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flawed lens?

All,

I have a new K200d and a Pentax 18-250, both about 1 month old. I noticed today the upper-right corner of some images seems darker than the other corners.

See attached images. Bigger versions of the first two images can be viewed here and here.

This uneven vignetting does not appear on my SMC Takumar 50mm.

Do I have a bad lens?

If so, what do I do?

Thanks for your help,

Reid

Attached Images
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PENTAX K200D  Photo 
View Picture EXIF
PENTAX K200D  Photo 
View Picture EXIF
PENTAX K200D  Photo 

Last edited by rpriedhorsky; 01-22-2009 at 10:03 PM.
01-22-2009, 10:43 PM   #2
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Reid,
Is your lens hood mounted with the proper orientation?
Is it seated properly?
Is it possible that it is bent or warped just a little?
Does the vignetting occur when you leave the lens hood off?
Do you use a skylight/haze/UV filter? Is it correctly mounted and screwed down all the way? Is it spotless?

Mickey
01-22-2009, 10:57 PM   #3
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QuoteOriginally posted by mickeyobe Quote
Is your lens hood mounted with the proper orientation?
Yes.

QuoteOriginally posted by mickeyobe Quote
Is it seated properly? Is it possible that it is bent or warped just a little?
Seems to be. It looks pretty darn straight to me.

QuoteOriginally posted by mickeyobe Quote
Does the vignetting occur when you leave the lens hood off?
Yes.

QuoteOriginally posted by mickeyobe Quote
Do you use a skylight/haze/UV filter? Is it correctly mounted and screwed down all the way? Is it spotless?
No filters.

FWIW, the two "real" images were taken at f/8.

Thanks for your help.
01-22-2009, 11:42 PM   #4
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I have the same thing with my DA18-55 @ 18mm (upper left corner), only it takes up more space (slowly fading). Haven't tested, as it does not bothers me, but i suspect its only visible @ F3.5..~4.5, might be the hood as well.

01-23-2009, 12:38 AM   #5
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Normal.

Unfortunately, the slight vignetting you see is normal for this 18-250 lens. I own this lens and notice the same thing as well as have read much about this lens and by all accounts, it is a normal characteristic. This doesn't mean ALL 18-250's share this, just a normal thing for this lens.

Jason
01-23-2009, 01:08 AM   #6
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The vignette is present both top and bottom right on image #3.

I would suggest that the lens might have a centering defect or an issue with the iris diaphragm. Vignette, if present and not caused by a hood, filter, strap, or errant coat sleeve, is generally symmetrical to all four corners. If your lens is new, this should be covered by warranty.

Steve
01-23-2009, 10:11 AM   #7
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QuoteOriginally posted by stevebrot Quote
The vignette is present both top and bottom right on image #3.

I would suggest that the lens might have a centering defect or an issue with the iris diaphragm. Vignette, if present and not caused by a hood, filter, strap, or errant coat sleeve, is generally symmetrical to all four corners. If your lens is new, this should be covered by warranty.
That was my feeling..... some vignette is fine and expected, but it's distracting if it's not symmetric. I think I'll pursue a warranty claim.
01-23-2009, 10:45 AM   #8
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dumb idea time

does the vignetting remain constant if you rotate the camera 90 degrees, or if you shoot upside down?

the reason I am asking is that I have found as things moved from MF to AF the front group on many lenses seems to be a little more wobbly, and can move back and forth a little. THis, I am sure is to reduce the drag on the focusing motor.

it may be a normal level of misallignment or a front group that has a little play in it. It would be interesting to see if the vignetting moves with camera orientation

01-30-2009, 06:04 PM   #9
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QuoteOriginally posted by Lowell Goudge Quote
does the vignetting remain constant if you rotate the camera 90 degrees, or if you shoot upside down?
Interesting idea. I tried, and it's the same regardless of orientation.

In other interestingly, it's pretty symmetric at 18mm, much stronger in the upper-right at 30-55mm (as pictured above), but modestly stronger on the left at 250mm.

I'd like to send it in for warranty. Do I need an RMA or something from first? Or can I just put together the information listed here and send it off? (Pentax hasn't responded to my web inquiry from that page, and now I'm bugging you all because customer service is closed for the weekend.... )

Thanks,

Reid
03-23-2009, 07:52 PM   #10
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Update.

I received the lens back from Pentax this evening, after 6 weeks in the shop. Fail. The asymmetric vignette is asymmetric in a slightly different way, but still present and obvious (e.g., at 55mm and f/5.6).

I guess I'll be calling Pentax customer service in the morning.
03-23-2009, 11:32 PM   #11
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QuoteQuote:
Update.

I received the lens back from Pentax this evening, after 6 weeks in the shop. Fail. The asymmetric vignette is asymmetric in a slightly different way, but still present and obvious (e.g., at 55mm and f/5.6).

I guess I'll be calling Pentax customer service in the morning
Sorry to hear this, but thank you for the update. Please, keep us posted of further developments. Best of luck!
03-23-2009, 11:42 PM   #12
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Lousy news! I hope tamron does better with the sticky aperture 70-200/2.8 I just sent 'em... Good luck.
03-24-2009, 07:14 PM   #13
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QuoteOriginally posted by heliphoto Quote
Good luck.
QuoteOriginally posted by Jewelltrail Quote
Sorry to hear this, but thank you for the update. Please, keep us posted of further developments. Best of luck!
Such comments mean a lot to me! Thank you.

I spoke with a Pentax rep on the phone this morning. She was supportive and seemed genuinely sympathetic, so +1 for that. I have a trip coming up that I hoped to use the lens on, and she said that "surely there's something we can do" to get it back in time and noted something to that effect in their file.

So, it's going back, hopefully tomorrow.

The other +1 is that the zoom ring had been tightened, completely eliminating creep, which had been a problem (common on this lens).

I also developed a strategy for appropriate lens equipment for the trip (it's 9 days in the Utah backcountry... I hope to get some great photos and will post a pointer to them here), in the event that the 18-250 doesn't come back in time.
  1. Buy polarizing filter for the kit lens, which will do fine if everything else falls through.
  2. New Sigma 17-70 f/2.8 with polarizing filter.
Pure coincidence that the plan involved a new lens purchase, eh?
03-24-2009, 07:26 PM   #14
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I would be surprised if they don't get a replacement lens sent to you.
03-24-2009, 08:30 PM   #15
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Normal for my Tamron 18-250

I most often seen it at the upper right corner in landscape, but when i rotate the camera vertical for a portrait configuration, the upper right corner follows the rotation and ends up in the upper left corner.

Funny how the pentax and Tamron of this lens both show the same characteristic.

Sometimes also see it in the lower right. Most often at the wide end, 18 to 20mm to F8.

I bought this lens in 2007 Fall, please let me know if you get any warranty satisfaction,

thanks,
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