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

dchew

Well-known member
I agree Ken.

Here is the test I'm in the process of running:

1. Shoot a dark-ish room @ f/5.6, 30 sec, std mode normal latency. Change to Aerial mode, zero latency
2. Take another shot @ f/32, 16 min.
3. Take another shot @ f/32, 16 min.

The first image is just for reference. Hopefully my 5-stop math is correct...

Based on Doug's comment regarding forcing the back to use the dark frame from the first exposure, it makes a lot of sense to shoot that first frame at an exposure close to what the subsequent shots would be. Even if your exposure was going to be 1 hr, it would be prudent to take a generic dark frame first at that exposure time while you were setting up or driving to the site or whatever.

Doing it this way eliminates any cast from ND filters, etc. Sure the second and third images will be soft because of f/32, but we don't care about that for this test.

Dave
 

Paul2660

Well-known member
Dave's results will be most interesting from this last test.

I have a feeling personally, that Voidshatter's type of shot was never tested by P1. For them Aerial mode is for use by the Aerial cameras, and none of them would be shooting for 20minutes on a single exposure would they? Thus the back is in spec.

On the XF, you have to use the LE mode and wait out the same amount of time via the dark frame, (so again more than likely most shooters wanting this type of shot are back on 645z or 35mm) as waiting for 20 extra minutes for the LE mode to finish is just too much of a cost in time and possibly missed opportunities, not to mention added heat build up as the back is working the entire extra 20 minutes.

Very well may have been just overlooked and is a problem with heat build up or something similar.

It also may be why there is no video recording possibilities, again due to heat build up? Most Live View via HDMI session would not be anywhere near this long.

Might very well be just a limitation of 100MP CMOS. At least this generation.

Paul C
 

dchew

Well-known member
You obviously didn't read this thread. There have been 3 copies of IQ3 100MP involved so far.
Yunli,
I don't think you can count my back in this. Here are my tests.

Two things of note. First, everything has a green cast because there are windows off to the right and a bunch of very green leaves on trees. Second, there is a reddish tint in the shelves because I had a small light on.

First, 30 sec f/5.6 shot in normal mode as a reference:


Second image, 14 min f/32 in normal mode:


Third image, 15 min f/32 in Aerial mode:


Note in the third image the sun started to come out so I turned off the light (you don't see the red cast in the shelf). Still I had to reduce the exposure in C1 1/2 stop because there was more light.

Neither of the images have any WB applied. They are all "as shot". So I see no issues anywhere. Two caveats: First, these are close to "correct" exposures. I'm not pushing exposure or shadows in C1. Second, there are no filters except for the 60xl center filter. I wondered if there is some association with the ND filter on these long exposures, so I am also going to try a shot at f/5.6 but with my HOYA proND64.

Dave

PS: It was an overcast day that is now partly cloudy. The variability in filtered light is driving me batty.
 
Thanks for the tests Dave! It appears that your images are not affected as you described for your darkframe test shot. What would happen if you attempt to push the shadow for both of your 16 minute shots?
 

dchew

Well-known member
Not much other than that wonderful grunge look.
:facesmack:

Here is the aerial image pushed 100 shadow:


And here are the images with the ND64. ~15 min @ f/5.6. Left is normal, right is aerial mode. I dropped the exposure on the "normal" shot. Damn clouds keep changing. But the aerial shot is SOOC:
 

dchew

Well-known member
Off topic, but I think this test shows that HOYA filter is pretty darn neutral!
:clap:
 

vjbelle

Well-known member
Thought I would throw this into the mix..... two images - first taken in normal mode around 15 minutes, second arial mode 15 minutes. As you can see I do not have a red cast issue. No white balance for either image although the first image was about 1.5EV overexposed and I compensated for that.

Victor
 

Attachments

dchew

Well-known member
Thank you Victor.

A few uneducated comments about all this. I think there are at least one and probably two things I did differently in my test that diverge from Yunli’s instructions and the images he included in the first post.

First, based on Doug’s comment about the back using the dark frame from the initial capture, I took the first shot at a shutter speed that was the same order of magnitude as I planned for the test images. I did not simply take a 1/60 sec frame once in Aerial mode. Don’t know how much this matters, but (as Miska posted) it seems to me the prudent thing to do. By the way, at 100% I do see stuck pixels in the Aerial-mode shots, so I’m pretty sure I did all this correctly.

Second, it appears to me that the images in Yunli’s first post are dramatically pushed. Both shadows and the image overall. Mine are not. If anything mine are a tiny bit overexposed. On the hottest image, RD shows 0.2% pixels overexposed in the green channel. Not bad if I may say so myself, but I think very different from the images in Yunli’s first post. Yunli, if you have access to the original images, could you please post what they looked like without any post processing?

The third, obvious thing I did differently was I used my DB, not the one in question. So of course this could be a problem with that back.

Here’s the thing (and I’m going way in the weeds here). All this could be because somewhere in the pipeline, very dark areas get a magenta twist when there is a very long exposure. I could continue to investigate some things to figure out which of the above is the issue, but it just takes too long and I don’t really see a benefit. What I mean is, we might have a situation where under very long exposures, and the photographer turns off LENR(maybe/maybe not), and then the subsequent image is pushed dramatically because it is underexposed, the shadows look bad.

Well, if I had an image that was underexposed, I would kick myself and do it right the next time. But I get that some people thrive on these types of images and rely in the ability to do this type of processing. Not me though. I think I’ve shown that a properly-exposed shot is fine out to at least 15-20 minutes, regardless of whether you use Aerial mode or not. That was really all I was interested in. I did learn some things so I am happy for that!

Dave

Note: I sent Yunli my three raw files. If anyone else wants to see them pm me and I will send you the link.
 
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Arjuna

Active member
Dave

It seems that in your test you did:
1. a short exposure,
2. a long exposure, normal mode (no dark frame?),
3. a long exposure, Aerial mode.

However your plan was:
"1. Shoot a dark-ish room @ f/5.6, 30 sec, std mode normal latency. Change to Aerial mode, zero latency
2. Take another shot @ f/32, 16 min.
3. Take another shot @ f/32, 16 min."

My understanding of Doug Peterson's post, was that his hypothesis was that the (automatically generated) dark frame from the first, short exposure, was being used, inappropriately, on the subsequent Aerial mode exposure(s). I think that your stated plan would have tested this, but I am not sure if that is what you did.

Note: on re-reading Doug's post, it says "forcing the back to reuse the dark frame made in the first capture executed after enabling the aerial mode", emphasis added. I wouldn't have thought that dark frames were made in Aerial mode? I (mis?)understood it as 'reuse the dark frame made in the last capture executed before enabling Aerial mode'. Perhaps a short, normal exposure after the Aerial mode shot needs to be added to the test? Or another test with a short, normal exposure in Aerial mode, before the long exposure?

Plainly I am confused.

Ross
 

vjbelle

Well-known member
I should have expanded as to how I took my LE shots. I simply turned the camera on and shot the first exposure at 'Normal' mode for 15 minutes - it just happened to be a tad over exposed. I then put the back in Arial mode and shot the second image but with a slightly smaller F stop to compensate for the overexposure but also at 15ish minutes. My back is always set to '0' latency.

Hope this clarifies things...... Just happy I didn't see any RED!

Victor
 
Dave, thanks for the raw files! I have looked into them and there is no problem at all. It appears that a darkframe test shot alone isn't sufficient to conclude any problem. It seems that you could use your back without worrying about anything for now.

My current guess is that if there are parts of the image close to overexposure then C1 and the firmware can properly white balance the shadow as well. It may work in other way but I need to do more tests myself and figure out how to reproduce this.
 
I should have expanded as to how I took my LE shots. I simply turned the camera on and shot the first exposure at 'Normal' mode for 15 minutes - it just happened to be a tad over exposed. I then put the back in Arial mode and shot the second image but with a slightly smaller F stop to compensate for the overexposure but also at 15ish minutes. My back is always set to '0' latency.

Hope this clarifies things...... Just happy I didn't see any RED!

Victor
Thanks for the tests Victor!

I'm curious what would happen if you underexpose both images :)
 

vjbelle

Well-known member
Thank you Victor.

The third, obvious thing I did differently was I used my DB, not the one in question. So of course this could be a problem with that back.


I think I’ve shown that a properly-exposed shot is fine out to at least 15-20 minutes, regardless of whether you use Aerial mode or not. That was really all I was interested in. I did learn some things so I am happy for that!
You are dead right that this is an issue with someone else's back and not yours or mine..... a very good thing.

You are also right that a properly exposed shot is fine out to at least 15 to 20 minutes. This is not stuff I normally do so its a moot point for me but I did want to establish that my IQ3-100 doesn't exhibit those issues and to post my results.

Victor
 
Thanks to everyone who participated!

To make it less confusing, I sum up all current observations:

Digital back Firmware Darkframe with LENR Darkframe without LENRUnderexposed lightframe with LENRUnderexposed lightframe without LENRLightframe with LENR Lightframe without LENR
Demo unit3.05.1? Red cast????
Jazz's4.01.2?Red castRed cast in shadowRed cast in shadow??
Dave's4.01.2?Red cast??NormalNormal
Victor's?????NormalNormal
IQ2501.05.1?Normal?Normal?Normal

Hopefully more tests can shed some light.
 

dchew

Well-known member
Ross,
I apologize for the confusion.

Here is what I did:

1. A short exposure in std mode (w/dark frame). This was just for reference.

2. Switch to Aerial mode and take a long ~15 min exposure. Since this is the first exposure after switching, it does a dark frame on this shot. Per Doug, this dark frame will be used for all subsequent photos while in Aerial mode.

3. Take another, identical ~15 min exposure, but this one will not have its own dark frame.

I did not test for what happens if you take a short exposure and try to use that dark frame for a long exposure. I don't see why someone would do that. Presumably a photographer knows when she/he is going to do long exposures, so in preparation, with the knowledge that the first dark frame in Aerial mode will be used for all subsequent shots, the photographer would take a "typical" long exposure frame as the first frame so a roughly relevant dark frame would be used. This is one of the things I learned (thanks Doug!). If I ever go out shooting long exposures, and don't want to wait for a dark frame, then my first image in Aerial mode will be a long exposure. I could do that while driving to the site!

Remember though, when I did the first lens cap shot (manual dark frame), I did not go through the above process. So my initial black lens cap shot I posted and discussed did not have a long-exposure dark frame created when switching to Aerial mode. It had a relatively short dark frame exposure, about 10 sec if I remember right.

Boy you're right; this is confusing.

Dave

Dave

It seems that in your test you did:
1. a short exposure,
2. a long exposure, normal mode (no dark frame?),
3. a long exposure, Aerial mode.

However your plan was:
"1. Shoot a dark-ish room @ f/5.6, 30 sec, std mode normal latency. Change to Aerial mode, zero latency
2. Take another shot @ f/32, 16 min.
3. Take another shot @ f/32, 16 min."

My understanding of Doug Peterson's post, was that his hypothesis was that the (automatically generated) dark frame from the first, short exposure, was being used, inappropriately, on the subsequent Aerial mode exposure(s). I think that your stated plan would have tested this, but I am not sure if that is what you did.

Note: on re-reading Doug's post, it says "forcing the back to reuse the dark frame made in the first capture executed after enabling the aerial mode", emphasis added. I wouldn't have thought that dark frames were made in Aerial mode? I (mis?)understood it as 'reuse the dark frame made in the last capture executed before enabling Aerial mode'. Perhaps a short, normal exposure after the Aerial mode shot needs to be added to the test? Or another test with a short, normal exposure in Aerial mode, before the long exposure?

Plainly I am confused.

Ross
 
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