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05-21-2012, 09:44 AM   #1
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I think I have a problem, Please advise.

Hello,

How are you?

I have recently upgraded from a K-r to K-5........

I hope this is the right place for my questions.

I also use Pentax 18-250.

I have a few questions:

1. I think I have a stain on my mirror, looks like a red stain. on the bottom right. what is it? is that normal? can I do anything about it? from the look of it, I think it does not effect the pictures, but i am not sure. Can you advise? (I have added pictures of it).


2. I have the Pentax 18-250, It seems to AF slowly compered to 18-55DAL or 55-200DAL, and in low light conditions it's worse. I think it is normal considering the zoom? what do you think?




Thank you.

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05-21-2012, 10:07 AM   #2
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I can't help with the sensor mirror, sorry. But I know my DA18-250 (450g) focuses slightly more slowly than my DA18-55 (250g). I expect that is because it's a heavier and much longer lens. My Lil'Bigma DG 170-500 (1270g) focuses even more slowly. These and others like my DA100-300 (silver, 380g) are all optically slow lenses toward their long ends, and will give the AF system difficulty in low light. It's not really reasonable to expect instaneous performance from these lenses, driven by in-body AF. Longer lenses with HSM or similar internal AF will focus faster -- and cost much more.

Last edited by RioRico; 05-21-2012 at 10:53 AM.
05-21-2012, 10:51 AM   #3
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QuoteOriginally posted by RioRico Quote
I can't help with the sensor, sorry.
The OP was asking about a stain on the mirror, not the sensor

A stain on the mirror won't affect picture quality at all, only your view through the viewfinder. It should be possible to clean it.
05-21-2012, 10:53 AM   #4
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Regarding your #1: Whatever is on the mirror will not affect the image. The mirror flips out of the way when the image is captured.

Do not attempt to wipe it of, the mirror is very delicate.

05-21-2012, 10:55 AM   #5
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QuoteOriginally posted by boriscleto Quote
The OP was asking about a stain on the mirror, not the sensor
Fixed. Duh, I'll blame it on having just awoken partially. Need more depresso (decaf esspresso). Yeah, don't take Windex to the mirror. Just learn to ignore it (and me).
05-21-2012, 10:57 AM   #6
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A stain on the mirror shouldn't hurt image quality. It's just there to route light to your viewfinder and then gets out of the way when the shutter trips. Is this a used K-5? If so, I'm guessing someone tried to clean the mirror at one point. If it's a new one, I'd send/take it back and get a replacement, if it were mine. Does the stain distract you when looking through the viewfinder?
05-21-2012, 11:21 AM   #7
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No It is not.

Thank you all.

I just want to be sure.

that's a great forum!!!!!!
05-21-2012, 11:34 AM   #8
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I can verify the 18-250 will focus a bit slower than some others, especially on the long end. This is mainly due to the slowness of the lens (the aperture -- you're simply letting in less light than with other lenses, and lesser still when it is zoomed towards 250) rather than the focus throw, which isn't that long (actual amount of travel the the focus ring does from minimum distance to infinity). It tends to hunt a bit in low light on the long end.

05-21-2012, 12:45 PM   #9
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Thank you.

Do you have the rubber ring for the zoom creep?
you know what it called and where I can buy it?
05-21-2012, 01:15 PM   #10
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QuoteOriginally posted by karelson Quote
Do you have the rubber ring for the zoom creep?
you know what it called and where I can buy it?
Mine is called a "wide rubber band" and I usually buy it with a stalk of celery at the grocer's.
05-21-2012, 01:18 PM   #11
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Moved to Beginner's Q&A.
05-21-2012, 03:00 PM   #12
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Yeah, the LensBand. Big silicone rubber band. Or get the one from the grocery store with the celery.
05-21-2012, 09:19 PM   #13
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New kid here :-) so sorry if this is a silly question - but how does the rubber band thing work? If you just place it around the lens does it not interfere with the function of the lens? Is the zoom creep what happens when you point the lens down & it extends all by itself?

Thanks
05-21-2012, 09:38 PM   #14
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QuoteOriginally posted by Augustine Quote
Is the zoom creep what happens when you point the lens down & it extends all by itself?
Yes.

QuoteQuote:
New kid here :-) so sorry if this is a silly question - but how does the rubber band thing work? If you just place it around the lens does it not interfere with the function of the lens?
Put half of the band on zoom ring (that rotates when zooming) and half off the zoom ring onto a part of the lens that doesn't move. The zoom can't creep without the zoom ring turning, so you want to stop it from turning but without impeding your ability to turn it manually -- the band just adds some non-abrasive friction. Whether this will be at the front or rear edge of the zoom ring depends on the lens.

See here:
LensBand images

(If you scroll down to the Pentax 18-250, that's actually me. I got the band for free by submitting the pic. See "free lens band" under the buy section.)
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