Dark Current Enable Tool

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Re: Dark Current Enable Tool

Postby astronomer » Mon Sep 15, 2014 7:22 pm

Oknoder wrote:Astro,
I downloaded and installed the true dark script to try out with the D800e&810 and the embedded patch for the D7000. I have not tried it yet for the D7k or 810 but played with it on the D800e and I must say I am stunned.


It won't work for D810. Nothing has been done on such a new model.

Oknoder wrote:Now all that is left is to debayer the sensor, strip off all the excess and properly cool it, then I believe it will easily compete with some of the scientific instruments of similar size.


Personally I oppose stripping the sensor bayer layer. It will strip all the microlens as well so you lose at lease 3 fold of quantum efficiency at any wavelength. It won't be comparable to dedicated scientific monochromatic CCD or sCMOS with microlense or even back-thinned. The mod is also dangerous as the success rate is around 50% or less from what I heard.

Oknoder wrote:I do have a couple of questions though, just to see if I understand what is going on properly. With this patch/program once I tether my camera to my PC and load the script onto the camera's rom, it no longer needs to be tethered, at least until the camera goes to sleep or is shut off, which is why you suggest extending the meter shut off time to keep this from happening. This is because it is not actually injected into the firmware but resides in the rom of the camera, which is flushed when the camera hibernates/sleeps or powers down correct? Or does the script exist only in the PC so the camera needs to be kept tethered when in use. Hmm I wonder if I can write a script to start this patch whenever the PC syncs with the camera, probably not worth the effort though

It resides on RAM and every time camera waken up it will reload the data from ROM in flash.

Oknoder wrote:Kudos guys, I do have to say I had no interest in the video mods that have been done since I have never used any of my DSLRs for video, but I do understand the very high demand for it. You guys have done an increasingly great job doing what many have no clue how to implement. I see a lot of people posting on here begging for certain features or to have their camera supported, and so often I have wanted to answer that they should get to work then and share with the rest of us when they figure it out.


Me neither. These sensor is not designed for video. It's line skipping and rolling shutter, not to mention the bottleneck of data transfer downstream.
And I doubt a lot people actually are capable of RAW video workflow. Most of them just want it because Magic Lantern has it. For serious video, get a Black magic and it's not expensive compared to dslr.
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Re: Dark Current Enable Tool

Postby Iliah Borg » Sun Sep 21, 2014 4:43 am

I was under impression D810 does not subtract the black level, as the black is around 600, also listed in Makernotes tag 0x3d.
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Re: Dark Current Enable Tool

Postby astronomer » Sun Sep 21, 2014 7:27 am

Iliah Borg wrote:I was under impression D810 does not subtract the black level, as the black is around 600, also listed in Makernotes tag 0x3d.


Can you send me a D810 dark image if you have one?

I downloaded a RAW sample from imaging resource and the black point is still at zero.

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Re: Dark Current Enable Tool

Postby Iliah Borg » Mon Sep 22, 2014 8:10 am

The black frame http://s3.amazonaws.com/IliahBorg/Nikon ... C_1261.NEF
Also, you can check the black level with RawDigger or exiftool (we reported the tag to Phil, and it is processed by exiftool since we discovered it in D5300/D3300). The tag value is to be divided by 4 if the file is in 12-bit mode (not applicable to Nikon's sRAW).
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Re: Dark Current Enable Tool

Postby astronomer » Mon Sep 22, 2014 2:00 pm

Iliah Borg wrote:Also, you can check the black level with RawDigger or exiftool (we reported the tag to Phil, and it is processed by exiftool since we discovered it in D5300/D3300). The tag value is to be divided by 4 if the file is in 12-bit mode (not applicable to Nikon's sRAW).


Hi Iliah,

Thanks for the link. And yes, the image looks like Canon now. But I would like to see a dark frame with long exposure, say 5 minutes. Right now I could still observe gaps in color channel. It's also important that dark current gets accumulated in the bias level. Otherwise it will still not be good for accurate dark subtraction in a scientific imaging situation.

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Re: Dark Current Enable Tool

Postby Iliah Borg » Mon Sep 22, 2014 2:17 pm

> I would like to see a dark frame with long exposure, say 5 minutes

I will try to arrange for one.

Gaps in colour channels
Image
- Looks to me like Nikon's white balance pre-conditioning, same as on a regular shot
Image

What you have achieved is a major breakthrough.
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Re: Dark Current Enable Tool

Postby astronomer » Mon Sep 22, 2014 2:55 pm

Iliah Borg wrote:> I would like to see a dark frame with long exposure, say 5 minutes

I will try to arrange for one.

Thanks!

Iliah Borg wrote:Gaps in colour channels
Image
- Looks to me like Nikon's white balance pre-conditioning, same as on a regular shot
Image

What you have achieved is a major breakthrough.


Also visible is the digital scaling related to aperture value, which is really annoying. It appears D4s has black level as well.
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Re: Dark Current Enable Tool

Postby Iliah Borg » Mon Sep 22, 2014 3:29 pm

> Also visible is the digital scaling related to aperture value, which is really annoying.

I tend to use lenses that have manual aperture control, like enlarger lenses (they have wider spectral transmittance anyway)

> It appears D4s has black level as well.

True, and any expeed 4 -based camera would be a good candidate to check black level.
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Re: Dark Current Enable Tool

Postby Simeon » Mon Sep 22, 2014 9:02 pm

Iliah Borg wrote:> Also visible is the digital scaling related to aperture value, which is really annoying.
I tend to use lenses that have manual aperture control, like enlarger lenses (they have wider spectral transmittance anyway)

What astronomer was meaning is the gaps in the data seen in above picture in the red and blue channel. The gaps are because the R/B channels are scaled in integer space, and the scaling is a function of the aperture/shutter/ISO setting of the camera, not related to your actual awesome glass.
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Re: Dark Current Enable Tool

Postby Iliah Borg » Tue Sep 23, 2014 5:05 am

Simeon wrote:
Iliah Borg wrote:> Also visible is the digital scaling related to aperture value, which is really annoying.
I tend to use lenses that have manual aperture control, like enlarger lenses (they have wider spectral transmittance anyway)

What astronomer was meaning is the gaps in the data seen in above picture in the red and blue channel. The gaps are because the R/B channels are scaled in integer space, and the scaling is a function of the aperture/shutter/ISO setting of the camera, not related to your actual awesome glass.


Lenses that I use when doing these experiments do not transfer aperture values to the camera. This switches off aperture-related scaling effects. I never saw shutter speed affecting gaps, but maybe I'm missing something. Gaps, as I saw, depend on particular camera sensor calibration (what Nikon are calling WB pre-conditioning), and yes, it is an operation over integers. I saw digital scaling depending on ISO setting on, say, Canons; but not on Nikons within the calibrated ISO range.
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