Pentax...fix the Magenta Bug...please?

MJKoski · 04-27-2017, 01:17 PM

I just wasted 1100 shutter actuations for 2 in-camera multiexposure images. First one had 500 exposures in it, the second one here 600. Both plagued by extreme magenta cast which is not fixable in post. Linear curve conversion straight from lightroom:

This is just wrong. I reported it last autumn few times. Get your act together and fix this please as the multiexposure function is perfect for replacing ND filters.

hooverfocus · 04-27-2017, 01:40 PM

What file format?
Have you tried with another image processor?

LensBeginner · 04-27-2017, 01:45 PM

Have you considered RAW as a workaround? not very practical I know... but it would give you greater control.

**newmikey** · 04-27-2017, 02:02 PM - **1 Like**

I'd just save the exposures to a computer and apply a median filter to them with the output redirecting to one new image file which you can then deal with in an editor. Have a look here: Pat David: Faking an ND Filter for Long Exposure Photography

That way you can finetune the result and are not dependent on camera firmware.

MJKoski · 04-27-2017, 02:21 PM

I used 1/60th shutter speed without any filters and Zeiss 28/2 Distagon @ f/5.6. I have managed to get at least two successful images by averaging hundreds of image in-camera. The output is a .PEF RAW file and it is not only Lightroom which does this. It is liike that with SilkyPix as well. This can be replicated, anything over 500 will almost surely fail.

But if it works, the output can be pushed and twisted in post without anything breaking. +8EV boost? Check.

This one here equals roughly 10 minute exposure.

stevebrot · 04-27-2017, 02:31 PM

Originally posted by LensBeginner

Have you considered RAW as a workaround? not very practical I know... but it would give you greater control.

I don't know what part is impractical. I frequently use the multi-exposure feature with RAW.

Originally posted by MJKoski

Linear curve conversion straight from lightroom:

Are you using a custom profile of some type? A strictly linear conversion (no curves applied) from RAW should look pretty dull with potential for color cast. That aside, I suspect you may be seeing a side-effect of the composite method used. Are you willing to share your settings including how you were managing exposure and the composite mode being used?

Are you seeing similar results from an in-camera JPEG or using Pentax DCU?

Steve

**newmikey** · 04-27-2017, 02:32 PM - **1 Like**

Originally posted by MJKoski

I used 1/60th shutter speed without any filters and Zeiss 28/2 Distagon @ f/5.6. I have managed to get at least two successful images by averaging hundreds of image in-camera. The output is a .PEF RAW file and it is not only Lightroom which does this. It is liike that with SilkyPix as well. This can be replicated, anything over 500 will almost surely fail.

But if it works, the output can be pushed and twisted in post without anything breaking. +8EV boost? Check.

This one here equals roughly 10 minute exposure.

Certainly a great technique and a downer if it doesn't work because of some bug in the camera. I'd still think you'll get better mileage shooting on-camera and averaging in software afterwards but I suppose that's just a personal opinion.

**jatrax** · 04-27-2017, 02:34 PM - **3 Likes**

Just a thought, did you have the view finder covered? I have seen similar magenta casts on long exposures when the view finder was not covered. Covering it removed the cast. I have no explanation as to why it happens but I proved it through testing myself.

What is the purpose of a 600 exposure image? I would have used an ND filter in this case so I am curious what this method does that the ND filter does not?

hooverfocus · 04-27-2017, 02:45 PM

Originally posted by hooverfocus

What file format?
Have you tried with another image processor?

Originally posted by MJKoski

I used 1/60th shutter speed without any filters and Zeiss 28/2 Distagon @ f/5.6. I have managed to get at least two successful images by averaging hundreds of image in-camera. The output is a .PEF RAW file and it is not only Lightroom which does this. It is liike that with SilkyPix as well. This can be replicated, anything over 500 will almost surely fail.

But if it works, the output can be pushed and twisted in post without anything breaking. +8EV boost? Check.

This one here equals roughly 10 minute exposure.

Reason I was asking is because I found a random thread mentioning .dng as taking care of the issue (with a D800 to boot). This was for RawTherapee, though, so YMMV.

stevebrot · 04-27-2017, 02:51 PM

Originally posted by MJKoski

I used 1/60th shutter speed without any filters and Zeiss 28/2 Distagon @ f/5.6. I have managed to get at least two successful images by averaging hundreds of image in-camera. The output is a .PEF RAW file and it is not only Lightroom which does this. It is liike that with SilkyPix as well. This can be replicated, anything over 500 will almost surely fail.

But if it works, the output can be pushed and twisted in post without anything breaking. +8EV boost? Check.

This one here equals roughly 10 minute exposure.

OK...it appears you must be using "Average" as the composite mode.* Was the light changing significantly during the exposure series? If so, one might expect that the spectral contribution might change significantly from start to finish, particularly if done at dusk. Without knowing the algorithm for how the "Average" mode actually works, it is difficult to predict how a spectra shift might translate to the final image.

Sadly, the only way to certify this as a bug, rather than a known and expected behavior, is to shoot an neutral gray target with the same settings and compare to a single 1/60s shot.

Steve

* I have typically used "Additive" as the composite mode when attempting ND filter emulation. "Average" uses some kind of running average and I can imagine many strange things happening.

MJKoski · 04-27-2017, 02:56 PM

600 exposures were used to create cloud trailing. Not possible with such short exposures otherwise. Stacking in Photoshop works but not going to waste disk space with 600 sequential RAW files if in-camera gives one very malleable file. Sure it is extreme but I have some 30x multiexposures with exact same problem. And yes, the viewfinder was TAPED shut with the plastic eyepiece also in place. I have not used the OVF since last september.

Light was stable. And yes, average blending mode.

lightbox · 04-27-2017, 02:58 PM

I've seen this technique used by Tony Northrup and was also pitched as a means to go without ND filters (or at least a polarizer). Though in his example I think the frames were averaged in post, not on camera, and there were not as many.

Side thought: would ND filters not be cheaper in the long run, considering the heavy burden this puts on the shutter? You can only expect to take a few hundred photos like this before the body is kaput.

rechmbrs · 04-27-2017, 03:02 PM

Originally posted by MJKoski

I just wasted 1100 shutter actuations for 2 in-camera multiexposure images. First one had 500 exposures in it, the second one here 600. Both plagued by extreme magenta cast which is not fixable in post. Linear curve conversion straight from lightroom:

This is just wrong. I reported it last autumn few times. Get your act together and fix this please as the multiexposure function is perfect for replacing ND filters.

Matti,
First off, I really like your Brass Maiden series. The sculpture is so real and your light treatment nails it.

Where did you come up with the number of frames per output? That is maybe ten times what I have ever thought of for this method. Main reason is that the output is an 8 bit jpg file and the summing buffer is 14-16 bits. I would expect that you have exceeded the camera's hardware and then jpg didn't have much to play with. Why don't you try 10 - 60 frame exposures and sum the ten in a computer.

Cheers,
RONC

**Schraubstock** · 04-27-2017, 08:43 PM - **1 Like**

Wow
600 shots to take one picture

And I thought Kim Jong-un using an anti aircraft rocket to kill his uncle was an overkill. (pun intended)

**shardulm** · 04-27-2017, 09:23 PM - **1 Like**

Start bashing me please.... for what I am going to say about this.

I think this is purple fringing on around the cloud lines averaged across the cloud shift OR a white balance issue since the scene is turning from warmer to colder in about 10 mins.

Read above and begin bashing me please. I need some light in the tunnel.

04-27-2017, 01:17 PM	#1
MJKoski Veteran Member Join Date: Aug 2016 Posts: 1,784	Pentax...fix the Magenta Bug...please? I just wasted 1100 shutter actuations for 2 in-camera multiexposure images. First one had 500 exposures in it, the second one here 600. Both plagued by extreme magenta cast which is not fixable in post. Linear curve conversion straight from lightroom: This is just wrong. I reported it last autumn few times. Get your act together and fix this please as the multiexposure function is perfect for replacing ND filters.

04-27-2017, 02:51 PM	#10
stevebrot Otis Memorial Pentaxian Join Date: Mar 2007 Location: Vancouver (USA) Photos: Gallery \| Albums Posts: 42,007	Originally posted by MJKoski I used 1/60th shutter speed without any filters and Zeiss 28/2 Distagon @ f/5.6. I have managed to get at least two successful images by averaging hundreds of image in-camera. The output is a .PEF RAW file and it is not only Lightroom which does this. It is liike that with SilkyPix as well. This can be replicated, anything over 500 will almost surely fail. But if it works, the output can be pushed and twisted in post without anything breaking. +8EV boost? Check. This one here equals roughly 10 minute exposure. OK...it appears you must be using "Average" as the composite mode.* Was the light changing significantly during the exposure series? If so, one might expect that the spectral contribution might change significantly from start to finish, particularly if done at dusk. Without knowing the algorithm for how the "Average" mode actually works, it is difficult to predict how a spectra shift might translate to the final image. Sadly, the only way to certify this as a bug, rather than a known and expected behavior, is to shoot an neutral gray target with the same settings and compare to a single 1/60s shot. Steve * I have typically used "Additive" as the composite mode when attempting ND filter emulation. "Average" uses some kind of running average and I can imagine many strange things happening. Last edited by stevebrot; 04-27-2017 at 02:59 PM.

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04-27-2017, 01:40 PM	#2
hooverfocus Senior Member Join Date: Aug 2010 Posts: 210	What file format? Have you tried with another image processor?

04-27-2017, 01:45 PM	#3
LensBeginner Veteran Member Join Date: Sep 2014 Photos: Albums Posts: 4,696	Have you considered RAW as a workaround? not very practical I know... but it would give you greater control.

04-27-2017, 02:02 PM - 1 Like	#4
newmikey Site Supporter Join Date: May 2007 Photos: Gallery Posts: 2,289	I'd just save the exposures to a computer and apply a median filter to them with the output redirecting to one new image file which you can then deal with in an editor. Have a look here: Pat David: Faking an ND Filter for Long Exposure Photography That way you can finetune the result and are not dependent on camera firmware.

04-27-2017, 02:21 PM	#5
MJKoski Veteran Member Join Date: Aug 2016 Posts: 1,784 Original Poster	I used 1/60th shutter speed without any filters and Zeiss 28/2 Distagon @ f/5.6. I have managed to get at least two successful images by averaging hundreds of image in-camera. The output is a .PEF RAW file and it is not only Lightroom which does this. It is liike that with SilkyPix as well. This can be replicated, anything over 500 will almost surely fail. But if it works, the output can be pushed and twisted in post without anything breaking. +8EV boost? Check. This one here equals roughly 10 minute exposure.

04-27-2017, 02:31 PM	#6
stevebrot Otis Memorial Pentaxian Join Date: Mar 2007 Location: Vancouver (USA) Photos: Gallery \| Albums Posts: 42,007	Originally posted by LensBeginner Have you considered RAW as a workaround? not very practical I know... but it would give you greater control. I don't know what part is impractical. I frequently use the multi-exposure feature with RAW. Originally posted by MJKoski Linear curve conversion straight from lightroom: Are you using a custom profile of some type? A strictly linear conversion (no curves applied) from RAW should look pretty dull with potential for color cast. That aside, I suspect you may be seeing a side-effect of the composite method used. Are you willing to share your settings including how you were managing exposure and the composite mode being used? Are you seeing similar results from an in-camera JPEG or using Pentax DCU? Steve

04-27-2017, 02:32 PM - 1 Like	#7
newmikey Site Supporter Join Date: May 2007 Photos: Gallery Posts: 2,289	Originally posted by MJKoski I used 1/60th shutter speed without any filters and Zeiss 28/2 Distagon @ f/5.6. I have managed to get at least two successful images by averaging hundreds of image in-camera. The output is a .PEF RAW file and it is not only Lightroom which does this. It is liike that with SilkyPix as well. This can be replicated, anything over 500 will almost surely fail. But if it works, the output can be pushed and twisted in post without anything breaking. +8EV boost? Check. This one here equals roughly 10 minute exposure. Certainly a great technique and a downer if it doesn't work because of some bug in the camera. I'd still think you'll get better mileage shooting on-camera and averaging in software afterwards but I suppose that's just a personal opinion.

04-27-2017, 02:34 PM - 3 Likes	#8
jatrax Site Supporter Join Date: May 2010 Location: Washington Cascades Photos: Gallery \| Albums Posts: 12,991	Just a thought, did you have the view finder covered? I have seen similar magenta casts on long exposures when the view finder was not covered. Covering it removed the cast. I have no explanation as to why it happens but I proved it through testing myself. What is the purpose of a 600 exposure image? I would have used an ND filter in this case so I am curious what this method does that the ND filter does not?

04-27-2017, 02:45 PM	#9
hooverfocus Senior Member Join Date: Aug 2010 Posts: 210	Originally posted by hooverfocus What file format? Have you tried with another image processor? Originally posted by MJKoski I used 1/60th shutter speed without any filters and Zeiss 28/2 Distagon @ f/5.6. I have managed to get at least two successful images by averaging hundreds of image in-camera. The output is a .PEF RAW file and it is not only Lightroom which does this. It is liike that with SilkyPix as well. This can be replicated, anything over 500 will almost surely fail. But if it works, the output can be pushed and twisted in post without anything breaking. +8EV boost? Check. This one here equals roughly 10 minute exposure. Reason I was asking is because I found a random thread mentioning .dng as taking care of the issue (with a D800 to boot). This was for RawTherapee, though, so YMMV.

04-27-2017, 02:56 PM	#11
MJKoski Veteran Member Join Date: Aug 2016 Posts: 1,784 Original Poster	600 exposures were used to create cloud trailing. Not possible with such short exposures otherwise. Stacking in Photoshop works but not going to waste disk space with 600 sequential RAW files if in-camera gives one very malleable file. Sure it is extreme but I have some 30x multiexposures with exact same problem. And yes, the viewfinder was TAPED shut with the plastic eyepiece also in place. I have not used the OVF since last september. Light was stable. And yes, average blending mode.

04-27-2017, 02:58 PM	#12
lightbox Veteran Member Join Date: Mar 2015 Posts: 599	I've seen this technique used by Tony Northrup and was also pitched as a means to go without ND filters (or at least a polarizer). Though in his example I think the frames were averaged in post, not on camera, and there were not as many. Side thought: would ND filters not be cheaper in the long run, considering the heavy burden this puts on the shutter? You can only expect to take a few hundred photos like this before the body is kaput.

04-27-2017, 03:02 PM	#13
rechmbrs Veteran Member Join Date: Jan 2007 Location: Conroe, TX USA Posts: 423	Originally posted by MJKoski I just wasted 1100 shutter actuations for 2 in-camera multiexposure images. First one had 500 exposures in it, the second one here 600. Both plagued by extreme magenta cast which is not fixable in post. Linear curve conversion straight from lightroom: This is just wrong. I reported it last autumn few times. Get your act together and fix this please as the multiexposure function is perfect for replacing ND filters. Matti, First off, I really like your Brass Maiden series. The sculpture is so real and your light treatment nails it. Where did you come up with the number of frames per output? That is maybe ten times what I have ever thought of for this method. Main reason is that the output is an 8 bit jpg file and the summing buffer is 14-16 bits. I would expect that you have exceeded the camera's hardware and then jpg didn't have much to play with. Why don't you try 10 - 60 frame exposures and sum the ten in a computer. Cheers, RONC

04-27-2017, 08:43 PM - 1 Like	#14
Schraubstock Site Supporter Join Date: Oct 2010 Location: Melbourne Photos: Gallery Posts: 3,386	Wow 600 shots to take one picture And I thought Kim Jong-un using an anti aircraft rocket to kill his uncle was an overkill. (pun intended)

04-27-2017, 09:23 PM - 1 Like	#15
shardulm Loyal Site Supporter Join Date: Jul 2013 Location: Cumming, GA Posts: 793	Start bashing me please.... for what I am going to say about this. I think this is purple fringing on around the cloud lines averaged across the cloud shift OR a white balance issue since the scene is turning from warmer to colder in about 10 mins. Read above and begin bashing me please. I need some light in the tunnel.