Sensor stains detection and lens lenght.

**Porga** · 10-08-2011, 11:47 PM

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.

pxpaulx · 10-08-2011, 11:59 PM

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.

**Porga** · 10-09-2011, 03:27 AM

Originally posted by pxpaulx

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?

Ole · 10-09-2011, 06:37 AM

Focal length doesn't matter. The aperture matters. Use f/16 ot thereabout.

JeffJS · 10-09-2011, 07:06 AM

Originally posted by Porga

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

Ailuropoda · 10-09-2011, 09:27 AM

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.

**Porga** · 10-09-2011, 11:25 AM

Originally posted by JeffJS

28mm

Thanks.

JeffJS · 10-09-2011, 06:55 PM

Originally posted by Ailuropoda

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

10-08-2011, 11:47 PM	#1
Porga Site Supporter Join Date: Dec 2009 Photos: Albums Posts: 476	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.

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10-08-2011, 11:59 PM	#2
pxpaulx Veteran Member Join Date: May 2009 Location: Twin Cities, MN Posts: 2,867	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
Porga Site Supporter Join Date: Dec 2009 Photos: Albums Posts: 476 Original Poster	Originally posted by pxpaulx 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
Ole Administrator Join Date: Sep 2006 Location: Copenhagen, Denmark Photos: Gallery \| Albums Posts: 4,408	Focal length doesn't matter. The aperture matters. Use f/16 ot thereabout.

10-09-2011, 07:06 AM	#5
JeffJS Inactive Account Join Date: Aug 2008 Location: Michigan, USA Photos: Gallery \| Albums Posts: 7,484	Originally posted by Porga 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
Ailuropoda Forum Member Join Date: Jul 2011 Posts: 71	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
Porga Site Supporter Join Date: Dec 2009 Photos: Albums Posts: 476 Original Poster	Originally posted by JeffJS 28mm Thanks.

10-09-2011, 06:55 PM	#8
JeffJS Inactive Account Join Date: Aug 2008 Location: Michigan, USA Photos: Gallery \| Albums Posts: 7,484	Originally posted by Ailuropoda 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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