Strange lights with long exposures

mtroute · 07-19-2009, 08:22 PM

I tried out some long exposures over the weekend and saw some strange things that seem to me to be hardware problems. Can anyone explain the purple light in the same exact location on 3 separate exposures?

Example one, look along the top of the image.

Aperture: ƒ/4
Shutter Speed: 3.71 mins
ISO: 1600

Example 2, same location in the frame but not quite as severe.

Aperture: ƒ/4
Shutter Speed: 133.4s
ISO: 1600

And the 3rd example:

Aperture: ƒ/5.6
Shutter Speed: 426.5s
ISO: 800

During the star exposures there was NO other light source and this location is in the Willamette national forest far from any city lights. The creek picture was lit with a single 4w fluorescent flashlight located about 20 feet to the right of the camera.

All pictures were taken in Bulb mode with the camera laying on a wooden bridge (not perfectly still however) with me holding the shutter button (even less still) it was an impromptu shoot.

Ideas?

**Ash** · 07-19-2009, 08:36 PM

It does seem these artifacts are sensor or lens dependent. Were all these taken with the same lens? If so, try again with another lens to see if you get the same result. If so, I'd say it's from sensor heat. I've seen similar effects on my K10D, but not always - usually as a result of some extraneous light source trickling through the lens, but I've not yet tried it on my K20D.

Let us know how you go with that.

mtroute · 07-19-2009, 08:48 PM

Yes they were all taken with the DA 18-55mm 3.5-5.6.

captmacq · 07-19-2009, 10:18 PM

could this be light leaking in from the eye veiw finder?

inferno10 · 07-19-2009, 11:32 PM

Originally posted by mtroute

I tried out some long exposures over the weekend and saw some strange things that seem to me to be hardware problems. Can anyone explain the purple light in the same exact location on 3 separate exposures?

Off-camera UFOs!

EDIT: Here's another thing to test. Try making a long exposure with the lens cap and viewfinder cap on in a dark room, and see if you get the purple splotches. If you do, then it's most likely heat from the sensor affecting the image. If not, try without the viewfinder cap; if you get splotches, then it's the viewfinder leaking.

- Jason

Darky · 07-19-2009, 11:51 PM

That noise is called amplifier-noise...
It comes from the amplifier sitting next to the sensor. I got that quite strong on my Nikon CP8800 but on the K10d it is much less of a problem.
I just saw this yesterday after a 1300 seconds exposure at iso 100.

If you increase iso the purple noise will also increase.

jezza323 · 07-20-2009, 12:10 AM

my guess would be heat related noise too, 3 mins + at ISO 1600 is a lot!

nice shot apart from the purple bits though!

rawr · 07-20-2009, 12:50 AM

I've taken a few thousand shots with my K200D and only seen this two times, thankfully.

I took a series of 50 or more night exposures around town the other day using a M series 50mm 1.7 at 800 and lower ISO w. my K200D. Exactly the same sort of purple flare showed up in only one of those photos (3.5 second exposure), in only one spot in the very top left of frame.

One other occassion I saw two of those purple patches in the lower area of a shot @1600 ISo 1/15th of a second using the same 500mm 1.7 wide open.

The lack of consistency in the purple patches showing up makes me suspect light leakage rather than sensor issues. Next time I will take along my viewfinder cover.

LeDave · 07-20-2009, 01:01 AM

I have these a couple of times shooting with my Pentax K-m/K2000. I thought it was my filter problem because I'm using a Hoya UV S-HMC 52mm. The lenses I shoot with is the kit lens DA L 18-55mm AL.

Darky · 07-20-2009, 02:47 AM

Originally posted by rawr

I've taken a few thousand shots with my K200D and only seen this two times, thankfully.

These purple areas seem to be reflections coulered because of the coating not noise like in the TO's pictures.

petercrane · 07-20-2009, 02:53 AM

It's disapointing to hear that there are problems with your Pentax. Aside from the purple streaks the photos look great. Good job.

rawr · 07-20-2009, 03:19 AM

Originally posted by Darky

These purple areas seems to be reflections coulered because of the coating not noise like in the TO's pictures.

You may be right. I will have to try to replicate this behaviour. Probably it is not a sensor issue.

flyer · 07-20-2009, 03:56 AM

I sometimes find the same happening with my K20D at high ISO. Since I more or less know it can happen in some situations, I try to avoid those situations. It's not a cure, but when you're aware of a problem, you can always try to work around it.

kenyee · 07-20-2009, 06:26 AM

Originally posted by Darky

That noise is called amplifier-noise...

ditto. The Nikons have this issue as well.

rawr's shots are something else though. Amp noise happens only at the edges...

mtroute · 07-20-2009, 10:59 AM

So what I am hearing is that there is no fix for the problem and that it is inherent in digital SLR's?

07-19-2009, 08:22 PM	#1
mtroute Veteran Member Join Date: Jun 2009 Location: Portland OR Posts: 533	Strange lights with long exposures I tried out some long exposures over the weekend and saw some strange things that seem to me to be hardware problems. Can anyone explain the purple light in the same exact location on 3 separate exposures? Example one, look along the top of the image. Aperture: ƒ/4 Shutter Speed: 3.71 mins ISO: 1600 Example 2, same location in the frame but not quite as severe. Aperture: ƒ/4 Shutter Speed: 133.4s ISO: 1600 And the 3rd example: Aperture: ƒ/5.6 Shutter Speed: 426.5s ISO: 800 During the star exposures there was NO other light source and this location is in the Willamette national forest far from any city lights. The creek picture was lit with a single 4w fluorescent flashlight located about 20 feet to the right of the camera. All pictures were taken in Bulb mode with the camera laying on a wooden bridge (not perfectly still however) with me holding the shutter button (even less still) it was an impromptu shoot. Ideas?

07-19-2009, 11:32 PM	#5
inferno10 Veteran Member Join Date: Feb 2007 Location: San Francisco, California Posts: 342	Originally posted by mtroute I tried out some long exposures over the weekend and saw some strange things that seem to me to be hardware problems. Can anyone explain the purple light in the same exact location on 3 separate exposures? Off-camera UFOs! EDIT: Here's another thing to test. Try making a long exposure with the lens cap and viewfinder cap on in a dark room, and see if you get the purple splotches. If you do, then it's most likely heat from the sensor affecting the image. If not, try without the viewfinder cap; if you get splotches, then it's the viewfinder leaking. - Jason Last edited by inferno10; 07-19-2009 at 11:37 PM.

07-20-2009, 12:50 AM	#8
rawr Veteran Member Join Date: Jun 2009 Posts: 11,913	I've taken a few thousand shots with my K200D and only seen this two times, thankfully. I took a series of 50 or more night exposures around town the other day using a M series 50mm 1.7 at 800 and lower ISO w. my K200D. Exactly the same sort of purple flare showed up in only one of those photos (3.5 second exposure), in only one spot in the very top left of frame. One other occassion I saw two of those purple patches in the lower area of a shot @1600 ISo 1/15th of a second using the same 500mm 1.7 wide open. The lack of consistency in the purple patches showing up makes me suspect light leakage rather than sensor issues. Next time I will take along my viewfinder cover. Attached Images

07-20-2009, 02:47 AM	#10
Darky New Member Join Date: Dec 2007 Location: Germany Posts: 12	Originally posted by rawr I've taken a few thousand shots with my K200D and only seen this two times, thankfully. These purple areas seem to be reflections coulered because of the coating not noise like in the TO's pictures. Last edited by Darky; 07-20-2009 at 05:59 AM.

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07-19-2009, 08:36 PM	#2
Ash Loyal Site Supporter Join Date: Mar 2007 Location: Toowoomba, Queensland Photos: Gallery \| Albums Posts: 23,920	It does seem these artifacts are sensor or lens dependent. Were all these taken with the same lens? If so, try again with another lens to see if you get the same result. If so, I'd say it's from sensor heat. I've seen similar effects on my K10D, but not always - usually as a result of some extraneous light source trickling through the lens, but I've not yet tried it on my K20D. Let us know how you go with that.

07-19-2009, 08:48 PM	#3
mtroute Veteran Member Join Date: Jun 2009 Location: Portland OR Posts: 533 Original Poster	Yes they were all taken with the DA 18-55mm 3.5-5.6.

07-19-2009, 10:18 PM	#4
captmacq Senior Member Join Date: Jul 2009 Location: fort worth tx Photos: Gallery Posts: 107	could this be light leaking in from the eye veiw finder?

07-19-2009, 11:51 PM	#6
Darky New Member Join Date: Dec 2007 Location: Germany Posts: 12	That noise is called amplifier-noise... It comes from the amplifier sitting next to the sensor. I got that quite strong on my Nikon CP8800 but on the K10d it is much less of a problem. I just saw this yesterday after a 1300 seconds exposure at iso 100. If you increase iso the purple noise will also increase.

07-20-2009, 12:10 AM	#7
jezza323 Veteran Member Join Date: Jan 2009 Location: Brisbane Photos: Gallery Posts: 1,421	my guess would be heat related noise too, 3 mins + at ISO 1600 is a lot! nice shot apart from the purple bits though!

07-20-2009, 01:01 AM	#9
LeDave Veteran Member Join Date: Jun 2009 Location: Minneapolis - St. Paul Photos: Gallery Posts: 3,067	I have these a couple of times shooting with my Pentax K-m/K2000. I thought it was my filter problem because I'm using a Hoya UV S-HMC 52mm. The lenses I shoot with is the kit lens DA L 18-55mm AL.

07-20-2009, 02:53 AM	#11
petercrane Inactive Account Join Date: Jul 2009 Location: Brisbane, Australia Photos: Gallery Posts: 87	It's disapointing to hear that there are problems with your Pentax. Aside from the purple streaks the photos look great. Good job.

07-20-2009, 03:19 AM	#12
rawr Veteran Member Join Date: Jun 2009 Posts: 11,913	Originally posted by Darky These purple areas seems to be reflections coulered because of the coating not noise like in the TO's pictures. You may be right. I will have to try to replicate this behaviour. Probably it is not a sensor issue.

07-20-2009, 03:56 AM	#13
flyer Veteran Member Join Date: Jan 2008 Location: Ste-Anne des Plaines, Qc., Canada Posts: 2,013	I sometimes find the same happening with my K20D at high ISO. Since I more or less know it can happen in some situations, I try to avoid those situations. It's not a cure, but when you're aware of a problem, you can always try to work around it.

07-20-2009, 06:26 AM	#14
kenyee Veteran Member Join Date: Mar 2007 Location: Boston, PRofMA Photos: Albums Posts: 3,026	Originally posted by Darky That noise is called amplifier-noise... ditto. The Nikons have this issue as well. rawr's shots are something else though. Amp noise happens only at the edges...

07-20-2009, 10:59 AM	#15
mtroute Veteran Member Join Date: Jun 2009 Location: Portland OR Posts: 533 Original Poster	So what I am hearing is that there is no fix for the problem and that it is inherent in digital SLR's?