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10-08-2011, 11:47 PM   #1
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Sensor stains detection and lens lenght.

How important is lenght of lens for detecting sensor stains?

Longest lense I have is FA 135mm, and while checking my k-5, i got these.
100% crop, center of the frame, f32, focused to infinity K-5 serial 40xxx..



I can barely see it, but what concernes me is the " line" spots are aligned to.
To be honest, I had more visible dust spots on my k-x at f22 that I did not bother to clean, but if focal lenght is factor - i.e. longer lens will pronounce more those spots - I might reconsider my actions.

So, is 135mm too short for stains check up, or should I already see the stains more clearer at this focal length, than I see it on my example?

If there is more appropriate thread for my question, mods feel free to move it.

Thank you.

10-08-2011, 11:59 PM   #2
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focal length and shutter speed, nor iso factor into the equation, they will only be visible at high f stop numbers. Because they are on the sensor itself only a small aperture makes them visible. You could wave the camera around for a 3 second exposure against a white background and they will still show up the same....if your camera has them.
10-09-2011, 03:27 AM   #3
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QuoteOriginally posted by pxpaulx Quote
focal length and shutter speed, nor iso factor into the equation, they will only be visible at high f stop numbers. Because they are on the sensor itself only a small aperture makes them visible. You could wave the camera around for a 3 second exposure against a white background and they will still show up the same....if your camera has them.

I know that, but advice is that you use your longest lens possible to make them show better.
That is why I asked is 135mm enough to see them?
10-09-2011, 06:37 AM   #4
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Focal length doesn't matter. The aperture matters. Use f/16 ot thereabout.

10-09-2011, 07:06 AM   #5
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QuoteOriginally posted by Porga Quote
I know that, but advice is that you use your longest lens possible to make them show better.
That is why I asked is 135mm enough to see them?
28mm



10-09-2011, 09:27 AM   #6
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Is that just a sample picture of stuff that's on the sensor? I have similar spots on my K-r that bug me when I do macros. I'm still hoping to get rid of them somehow. Please don't tell me that's related to the K-5 sensor stain issue.
10-09-2011, 11:25 AM   #7
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QuoteOriginally posted by JeffJS Quote
28mm



Thanks.
10-09-2011, 06:55 PM   #8
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QuoteOriginally posted by Ailuropoda Quote
Is that just a sample picture of stuff that's on the sensor? I have similar spots on my K-r that bug me when I do macros. I'm still hoping to get rid of them somehow. Please don't tell me that's related to the K-5 sensor stain issue.
Show us a picture with what you are talking about. I doubt you have sensor stains, you would be the first I've heard of having them on a K-r (that doesn't mean a whole lot though). Stains were caused by some manufacturing glitch during the production of the K5 sensors. They are on the Anti Alias filter between the filter and the sensor so one cannot get to them to clean them. They typically would not show up until several thousand exposures had been made (the photo I show was something like 3600 shutter count). To my knowledge, the K-r does not share the same sensor in any way shape or form. Odds are better, it's stubborn dust in your case. Stain spots have a distinct look to them where they typically will have a halo around each spot. If you Think you Have stains, contact Pentax for warranty support. First however, make sure it's not just stubborn Dust.

https://www.pentaxforums.com/forums/pentax-dslr-camera-articles/121739-those-...ml#post1259109



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