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IQ3 100MP long exposure issue - shadow filled with red color cast

I haven't received my IQ3 100MP yet due to the earthquake, but a friend of mine found a problem with it:

If darkframe noise reduction is disabled with "Aerial Mode", the IQ3 100MP gradually fills up shadow with red color cast if the exposure time is over 2 minutes.

Below is an example:

IQ3 100MP + Rodenstock 50mm HR-W, 32 minutes:

27.JPG

Note that it's not a white balance problem. Adjusting white balance does not fix the red color cast in shadow.

Here is another example:

IQ3 100MP + Rodenstock 23mm HR-S, 2 minutes vs 7 minutes:

26.JPG

Note that this is not a lens color cast issue, because LCC has been applied and the 2 minute exposure does not suffer from this red shadow problem.

After I looked into these examples, I recalled that when I first tested the IQ3 100MP about 6 months ago I did notice that the darkframe of the 20 minute long exposure looked red.

22.JPG

For comparison, the IQ250 does not have this issue at all.

Here is a real world picture I made with the IQ250:

IQ250 + Rodenstock 40mm HR-W, 8 minutes:

28.JPG

There is no red color cast in the shadow at all.

Then I looked into the darkframe files with RawDigger:

23.JPG

24.JPG

It appears that there is no red color cast of shadow in RawDigger, and there are no higher values of the red channel reported. To me it looks like a bug in Capture One. Hopefully this issue can be fixed in the next version of Capture One.
 

Paul2660

Well-known member
Did you take a 20min shot with LE ON? Just curious if the LE has that much effect? LE should be after standard noise and stuck pixels at least in my experience.

I have not taken anything longer than 5 minutes with the IQ100 but that was with the XF, where LE is on and can't be turned off.

Phase may also not see this as a bug, as their official response is that that all exposures at 1 sec or longer should have LE turned on.

It would be interesting to open the problem files in LR if they ever get support for the back, or raw therapee?

Thanks for posting, interesting issue as I agree any CMOS back should be able to run for 20 minutes with a flood of red noise.

Paul C
 
Did you take a 20min shot with LE ON? Just curious if the LE has that much effect? LE should be after standard noise and stuck pixels at least in my experience.

I have not taken anything longer than 5 minutes with the IQ100 but that was with the XF, where LE is on and can't be turned off.

Phase may also not see this as a bug, as their official response is that that all exposures at 1 sec or longer should have LE turned on.

It would be interesting to open the problem files in LR if they ever get support for the back, or raw therapee?

Thanks for posting, interesting issue as I agree any CMOS back should be able to run for 20 minutes with a flood of red noise.

Paul C
Hi Paul, when I tested the IQ3 100MP I did not specifically test exposures longer than 5 minutes and the only test I made longer than 5 minutes was that 20-minute darkframe alone without LENR. RawDigger reported very low numbers for standard deviation (on the contrary to the histograms I didn't pay attention to) which gave me very high expectation of the digital back.

My Photoshop is still CS6 with ACR 9.1.1 so I am unable to try these problematic raw files. I don't use Lightroom either.

Currently I have no access to the IQ3 100MP so I am unable to do further tests regarding LENR. I can certainly ask my friend to disable Aerial Mode to enable LENR and try again but I have no idea when I can get the feedback.

Maybe currently you are the best person to test this, if you still have a technical camera to use Aerial Mode to disable LENR?

If it's confirmed that this red shadow is a problem without LENR, and that Phase One isn't going to fix it, then it would become extremely difficult for me to justify this upgrade.
 
Any idea of the FW # on the red problem images?
According to EXIF data found in the 100MP IIQ files, firmware versions are:

3.05.1 for the darkframe, and 4.01.2 for the realworld pictures.

I don't think it's a firmware problem, but it would be helpful if someone else could post results of 4.03.2.
 
Update: I have just received another file *with* long exposure noise reduction (i.e. *not* Aerial Mode). There is still a red color cast in the shadow, even with RawDigger.

31.JPG
 

Paul2660

Well-known member
This 2nd example is with LE on? Normal latency with a tech camera?

If so then it would seem there is a problem with the particular back or the heat where the back is being shot is too high ambient temp?

So far the longest I have done is about 5 or 10 minutes but I had the dark frame in use. It's way to hot now I'm my local area to try a 20 minute shoot 105 degree daytime 97 night.

Paul C
 

miska

Member
This could be dark current creeping up.

If the effect happens only with LE noise reduction OFF (but not with noise reduction ON), you could record 10-20 (!) dark frames (images with lens cap on, same length as your image). Average those, and subtract from your image. IF temperature is about the same, that should solve the problem. IF temperature has changed, you probably need new darks.
You need many darks to reduce photon noise on the darks. If you can do only a few (because it takes a while...) it should still improve the situation.

It could also be that in aerial mode, a "standard" dark is still subtracted, but it is not good enough ? Or it is noise from the on-chip dark current suppression.

In astrophotography, where LE noise reduction is usually off for efficiency reasons, the standard procedure is:
- Take all images
- Take 10-20 darks, average them to get master dark
- Subtract master dark from image
That work pretty well, as long as temperature is mostly constant. Some people have libraries of darks at different temperatures.

Hope this helps...
 

Paul2660

Well-known member
The problem is your darks are normally to remove stuck pixels and other excessive noise. These images need something like an LCC applied to remove the color cast. The files don't seem overly full of noise to me.

Quick other note.

When I had my first P45+ and took it past 15 minutes I had the exact same problem. Strong magenta color cast on the file. Phase fixed this with a firmware later on in the life of the P45+. Some early P45+ backs bricked when this firmware was applied and needed new control boards. Sure hope this is not the case with the IQ100.

And I also hope if this is a problem with early backs that a fix will be applied retro to those affected.

Paul C
 
This 2nd example is with LE on? Normal latency with a tech camera?

If so then it would seem there is a problem with the particular back or the heat where the back is being shot is too high ambient temp?

So far the longest I have done is about 5 or 10 minutes but I had the dark frame in use. It's way to hot now I'm my local area to try a 20 minute shoot 105 degree daytime 97 night.

Paul C
EXIF data:

Sensor Temperature
34.25 C
Sensor Temperature 2
33.75 C

Pretty much normal temperature for a CMOS back.

I did mention that LCC has already been applied.

Also I don't think it's a problem with the particular copy of back because the demo unit also showed the same problem.
 
This could be dark current creeping up.

If the effect happens only with LE noise reduction OFF (but not with noise reduction ON), you could record 10-20 (!) dark frames (images with lens cap on, same length as your image). Average those, and subtract from your image. IF temperature is about the same, that should solve the problem. IF temperature has changed, you probably need new darks.
You need many darks to reduce photon noise on the darks. If you can do only a few (because it takes a while...) it should still improve the situation.

It could also be that in aerial mode, a "standard" dark is still subtracted, but it is not good enough ? Or it is noise from the on-chip dark current suppression.

In astrophotography, where LE noise reduction is usually off for efficiency reasons, the standard procedure is:
- Take all images
- Take 10-20 darks, average them to get master dark
- Subtract master dark from image
That work pretty well, as long as temperature is mostly constant. Some people have libraries of darks at different temperatures.

Hope this helps...
These are pretty standard procedure for astrophotography. There is no excuse that the IQ3 100MP has to rely on these while the IQ250 does not have to rely on these.
 

dchew

Well-known member
Any chance this is a light leak problem with the 23hr? The pattern sure looks lens related.

Dave
 

dchew

Well-known member
The sun is coming up here but I could try something tonight. Someone would have to help me with how to set this up since I've never tried shots longer than 1 min.

I have a 6x ND and a polarizer. Should I use both at dusk at F/22 and 50 ISO? I guess I have a light meter somewhere. Have to put batteries in it. :loco:

Dave
 
Any chance this is a light leak problem with the 23hr? The pattern sure looks lens related.

Dave
The 23HR images are without center filter. Correcting lens vignetting in post processing means pushing shadow.

I don't think it's light leakage as the 50HR image also has this issue, as well as the dark frame image (with lens cap on).
 
The sun is coming up here but I could try something tonight. Someone would have to help me with how to set this up since I've never tried shots longer than 1 min.

I have a 6x ND and a polarizer. Should I use both at dusk at F/22 and 50 ISO? I guess I have a light meter somewhere. Have to put batteries in it. :loco:

Dave
One Singh-Ray 15-mor-slo would do the job. Otherwise just put the lens cap on and shoot a dark frame. A dark frame should look dark (as for the IQ250 one), not red (as for the IQ3 100MP one).
 

dchew

Well-known member
I just did a 20 min lens cap image in Aerial mode and it is still doing its own dark frame.

How do I turn it off? Sorry long exposure newbie.
 

dchew

Well-known member
Firmware 4.01.2

I am trying again. Cycled the back on/off with it in aerial mode before taking this one. We will see...
 

dchew

Well-known member
Still doing it. Do I have to have it in zero latency?
ISO 50
Normal latency
Aerial mode
??
 
Still doing it. Do I have to have it in zero latency?
ISO 50
Normal latency
Aerial mode
??
The following three conditions together will disable darkframe NR:

a) Aerial mode;
b) Zero latency;
c) Not the first image since power on (i.e. since the second image and on).

So if you want to trigger a long exposure without darkframe NR: just power on, switch to aerial mode and zero latency, shoot one image at 1/60s or any fast shutter speed, and then do the long exposure.
 
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