Author Topic: Dual ISO- Green and dark spots- Canon 5D mark II  (Read 6050 times)

chrfrad

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Dual ISO- Green and dark spots- Canon 5D mark II
« on: December 20, 2014, 06:39:16 PM »
 :-\ I wonder if somebody have experienced the following problems when taking photos with Dual Iso and may have a solution for the problem.
I use a Canon 5D mark ii and the 24-105mm for the photos I ask help for.
In ML I activated the modules Auto ETTR with the link to Dual Iso "on" and the Dual Iso also activated. If i remember well i had chosen the iso 100/800 alternative. The camera was on A (aperture), iso 100 and WB on sunny. Photos are taken with a tripod and exposition time is 30 seconds.
I then develop CR2 files in cr2hdr and the DNG files in photoshop. The photos show a great amount of green and dark spots, i call them spots as i cannot find a better definition. These spots were also visible in the Dual Iso original CR2 file. I run a new development in cr2hdr-20bit in case but the result was the same. Before the photo session I had done a manually cleaning of the sensor for both dust and dead pixels. I have also taken several photos from ISO 100 to iso 3600 in the "normal" way without ML installed and the photos are clean from spots of any nature. I did a new trial today and Dual Iso photos show the same type of spots.
Here you can find  a link to photos, No PP is done as i wanted to keep them as identical as DNG as possible
_MG_8039-spots-Dual Iso by chrfrad, on Flickr

_MG_8025 by chrfrad, on Flickr

 Please note that I am not a pixel peeper. Download and review the photos for better understanding of the problem. i appreciate very much is somebody can read this message and maybe help me. Thank you in davance. :)

dmilligan

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Re: Dual ISO- Green and dark spots- Canon 5D mark II
« Reply #1 on: December 20, 2014, 07:30:03 PM »
Have you tried using the 'fix bad pixels' option in cr2hdr?

I have also taken several photos from ISO 100 to iso 3600 in the "normal" way without ML installed and the photos are clean from spots of any nature.
They are probably still actually there, just being automatically removed. The dual ISO lines are probably confusing the hotpixel removal algorithm, so they remain.

chrfrad

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Re: Dual ISO- Green and dark spots- Canon 5D mark II
« Reply #2 on: December 21, 2014, 06:09:07 AM »
Thank you for your reply.
 I have tried the fix pixel option in cr2hdr with bad, really bad and black-bad-pix. The <really bad > option washed out a lot spots and details as it was mentioned in the plugin documentation. I am not sure that I will go that way.
 I could not see a great difference between using the bad pixel option and the previous development without bad pixel alternative chosen. I have done at least 8 dead pixel cleaning with the dust sensor cleaning,and have had the long exp.noise reduction on for every shot, for every exposure time.
To check the sensor I also did single shots with the lens cap on, noise reduction on at different ISO settings. Then I proceed the photos in photoshop and in an HDR program with quite high settings. I could detect some "spots" which may be dead pixels. The thing is that i could not see as many spots on the "normal photos" even in terrible HDR state as on the dual iso shots taken earlier. I understand that if i had taken dual iso photos these dead pixels could confuse the hotpixel removal algorithm. I will now try to take photos in the daylight with shadows areas to check if the spots are coming from long exposures or not.
Thank you for your help.

dmilligan

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Re: Dual ISO- Green and dark spots- Canon 5D mark II
« Reply #3 on: December 21, 2014, 02:47:50 PM »
Long exposures make hot pixels worse (the longer the gates are open, the more likely they are to overflow or exhibit non-linear behavior causing hot pixels). Try viewing your normal CR2s in an editor that doesn't automatically remove them or has an option not to (photoshop/ACR does automatically remove them and there's no way to disable it). Also use the same ISO and shutter speed as a dual ISO photo. You should see basically the same hot pixels.

Or you can upload some samples (the original CR2s)

chrfrad

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Re: Dual ISO- Green and dark spots- Canon 5D mark II
« Reply #4 on: December 21, 2014, 06:00:11 PM »
Thank you again for replying. I have only DPP and Adobe clouds as editors so i have uploaded CR2 files om my google drive.

https://drive.google.com/folderview?id=0B_x5LY06_X9zY0RuTmtaRG9iZFE&usp=sharing

I hope the link is working. I have included:
2 of CR2 files taken at same aperture and same ISO as the dual iso image also included.
2 of CR2 files taken at same shutter speed and same ISO as the dual iso image also included.

I can  clearly see some spots (dead pixels?) on the normal CR2 and I definitely see spots on CR2 the dual iso photos.
It is raining so the photos are taken outside home just for a test purpose but I tried to have enough range between shadows and higlights. Noise reduction was off.
Have a nice evening.

Levas

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Re: Dual ISO- Green and dark spots- Canon 5D mark II
« Reply #5 on: December 22, 2014, 12:26:32 PM »
Downloaded one of you pics and those spots are definitely hot pixels caused by long exposure times.
If you do a normal shot (non dual iso) and activate long exposure noise reduction in Canon menu, the colored dots are probably gone...
Long exposure noise reduction automatically takes a second picture with the same exposure time, but with a closed shutter, this second picture is used to extract from the first picture and removes most of the hot pixels.

I don't know if long exposure noise reduction can be used with dual iso pictures...I'm not sure if the second picture get's extracted from the first raw file  :-\

If not, you can process you dual iso pictures the normal way, but in the end use a different raw editor to process the DNG.
RawTherapee is free, open source software, that has hot pixel remover build in, as wel as different debayering options, my opinion is that it works better for dual iso DNG's then Lightroom.
But there are probably a lot more free/open source options available

chrfrad

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Re: Dual ISO- Green and dark spots- Canon 5D mark II
« Reply #6 on: December 22, 2014, 10:54:16 PM »
Thank you for taking time locking at my spot issue.
 I will in future use more often the noise reduction that i disabled  for the session of evening photography i did with dual iso. I think it is interesting to see if noise reduction will apply with dual iso alternative. Look forward to it . For years i did use Raw therapee which is an exellent editor and the options you mentionned are well convincing me for a new download of RT.
I wish you, mr Milligan and the ML team a merry christmas and a happy new year

a1ex

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Re: Dual ISO- Green and dark spots- Canon 5D mark II
« Reply #7 on: February 28, 2015, 10:39:56 PM »
https://drive.google.com/folderview?id=0B_x5LY06_X9zY0RuTmtaRG9iZFE&usp=sharing

Can you upload the images again? It says "Empty folder". I noticed this thread a bit too late...

HondaATC

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Re: Dual ISO- Green and dark spots- Canon 5D mark II
« Reply #8 on: March 01, 2015, 12:47:18 AM »
Anything similar to my two posts here;

http://magiclantern.fm/forum/index.php?topic=7139.2325

?

a1ex

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Re: Dual ISO- Green and dark spots- Canon 5D mark II
« Reply #9 on: March 01, 2015, 08:42:08 AM »
Nope, your issue is aliasing.

SpcCb

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Re: Dual ISO- Green and dark spots- Canon 5D mark II
« Reply #10 on: March 02, 2015, 03:23:46 AM »
Maybe ISO 3200 was defined as the high value of the Dual ISO (?).
In this case it generates a lot of _big (macro-blocks)_ hot pixels. I don't know why, maybe a question of pixel value or something who loose the link with the internal hot pixel removing feature, but with the 5D2 the maximum ISO to use should be 1600 in Dual ISO mode to not get this issue.
Note: it appends with short exposures too, long exposure does not matter in this case, even if it's not help (hot pixels are just more 'brighter').

a1ex

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Re: Dual ISO- Green and dark spots- Canon 5D mark II
« Reply #11 on: March 02, 2015, 08:14:55 AM »
Do you have some samples with these macro blocks? I don't remember seeing them.

SpcCb

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Re: Dual ISO- Green and dark spots- Canon 5D mark II
« Reply #12 on: March 02, 2015, 03:55:37 PM »
I send you a sample by PM, as I don't use this setup I just have in stock private pictures where we can see these hot pixels macro blocks.
If I get times next days I could try to make fresh ones with and without Dual ISO in the same conditions, if need.