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D80 RAW format problem-- making a dark flat for astrophotography not working

Dr Garry

AU
3 posts

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Dr Garry Registered since 11th Sep 2012
Tue 11-Sep-12 11:19 AM

Hi All:

I'm a noobie tinkering with astrophotography. One of the things you do is to make a series of dark flat images, which are 1/4000 ISO 100 exposures with lens cap and eyepiece cover on. The idea is to capture wonky sensor elements (I think). You take these in NEF/RAW format.

A dark flat should look completely black with the odd wacky pixel. But my dark flat RAW images are cacophonies of coloured "snow". My understanding is that just ain't right.

When I make a dark flat using JPEG/Fine/Large it looks just like it's supposed to: entirely black with some wonky pixels. But you can't use jpegs for astrophotography.. they have to be RAW.

Any ideas? I open my images in Paint Shop Pro X2 just to see what they look like, and process them with DeepSkyStacker. My only thoughts are:

* Paint Shop Pro X2 does not open the Nikon D80 RAW format correctly.
* I should convert Nikon NEF to some normative RAW format.
* There's a tiny elf in my camera lighting a firecracker when I take the image.

Thanks for your time
Garry

elec164

US
2238 posts

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#1. "RE: D80 RAW format problem-- making a dark flat for astrophotography not working" | In response to Reply # 0

elec164 Silver Member Nikonian since 15th Jan 2009
Tue 11-Sep-12 12:56 PM | edited Tue 11-Sep-12 01:00 PM by elec164

Welcome to Nikonians Garry.

Perhaps you haven't noticed, but an Astrophotography Forum was just recently created. You would most likely get the best response posting this question over there. Perhaps one of the moderators would move it there for you.

>One of the
>things you do is to make a series of dark flat images, which
>are 1/4000 ISO 100 exposures with lens cap and eyepiece cover
>on.

I believe you are referring to a dark frame subtraction, if so it should be taken at the same ISO and shutter speed the regular frames are captured at in the same ambient conditions. But something sounds amiss. At ISO 100 and 1/4000th, the D80 should have provided a black frame. Could you put up an example somewhere for us to analyze?


>* Paint Shop Pro X2 does not open the Nikon D80 RAW format
>correctly.

Perhaps, the NEF is a proprietary format that third party software companies reverse engineer. So all raw converters are not created equal. Another thing that makes the D80 less than desirable is that it suffered from considerable amp noise plus most Nikon DSLR's are known as star eaters requiring the Mode 3 work-around to eliminate the median blur filtering of the NEF long exposure.

>* I should convert Nikon NEF to some normative RAW format.

In MHO, not really. The only real reason most give is to convert to a more universally supported standard to insure you will always have software that will open them. Trouble is there really isn't an industry wide standard yet. Adobe has been pushing its DNG, but it's not been adopted as Universal yet.
>* There's a tiny elf in my camera lighting a firecracker when
>I take the image.

I hate those tiny elves when they get into the camera, the should stick to making cookies!!

Pete

Pete

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gkaiseril

Chicago, US
6739 posts

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#2. "RE: D80 RAW format problem-- making a dark flat for astrophotography not working" | In response to Reply # 1

gkaiseril Gold Member Nikonian since 28th Oct 2005
Tue 11-Sep-12 08:48 PM

>* Paint Shop Pro X2 does not open the Nikon D80 RAW format
>correctly.

If the program is updated and recognizes the camera, then the NEF can be opened. Then the question becomes does Paint Shop Pro X2 process the camera data included in the NEF file.

The short answer is only the White Balance camera setting from within the main body of the EXIF data is used by programs other than the Nikon products. All the other camera settings recorded in the MakerNote section is ignored. Nikon View NX2 and Nikon Capture NX2 read and process the date within the MakerNote but can not process the RAW foramts of other cameras.

The MakerNote section includes data tags and values as designed by the manufacturer of the camera. The tags and values are not standardized and do vary by manufacturer and camera model. Because there are so many possible combinations or location, size, and value it becomes very difficult for software programmers to program for all of these items in a reasonable amount of time. So the approach of 3rd party products including Adobe, is to ignore this data and provide a preset set of processing values to simulate a possible set of camera settings.

You can open the NEF with Nikon Veiw NX2 or Capture NX2 and have MakerNote settings applied to the NEF and then either transfer the processed image to another program, "Open with..." or save as a Tiff file and then open the saved Tiff file with another program.

George
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aolander

Nevis, US
3492 posts

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#3. "RE: D80 RAW format problem-- making a dark flat for astrophotography not working" | In response to Reply # 0

aolander Silver Member Nikonian since 15th Sep 2006
Tue 11-Sep-12 10:13 PM

It's noise from underexposure. The JPEG has noise reduction applied probably.

Alan

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Dr Garry

AU
3 posts

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#4. "RE: D80 RAW format problem-- making a dark flat for astrophotography not working" | In response to Reply # 1

Dr Garry Registered since 11th Sep 2012
Tue 11-Sep-12 11:58 PM

Many thanks for your reply, Pete. I'll re-ask the question in the astro forum.

On the terminology, I think I meant a "dark" as opposed to a "dark flat", which is indeed as you describe.

FYI, I've put two images here, one a dark taken as a RAW/NEF (whihc looks terrible) and one taken as a jpg, which looks the way I think it should look:

downloads.archsoc.com

User name: Friends
Password friends

Click the links to download.

Thanks for your time,
Garry

elec164

US
2238 posts

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#5. "RE: D80 RAW format problem-- making a dark flat for astrophotography not working" | In response to Reply # 4

elec164 Silver Member Nikonian since 15th Jan 2009
Wed 12-Sep-12 03:00 PM

>On the terminology, I think I meant a "dark" as
>opposed to a "dark flat", which is indeed as you
>describe.
>

OK, just wanted to be sure. There is a flat field correction, but that is generally not used for astrophotography I would think.


>FYI, I've put two images here, one a dark taken as a RAW/NEF
>(whihc looks terrible) and one taken as a jpg, which looks the
>way I think it should look:
>

I downloaded the NEF and opened it in Photoshop CS3 and it appeared black as I expected it to be. I then adjusted levels to bring out any possible sensel variation and a few pixels appeared, but nowhere near what you described. So it appears that it is possibly PSP X2 that is giving you a false rendering.

Pete

Pete

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Dr Garry

AU
3 posts

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#6. "RE: D80 RAW format problem-- making a dark flat for astrophotography not working" | In response to Reply # 5

Dr Garry Registered since 11th Sep 2012
Thu 13-Sep-12 12:34 AM

>>
>
>I downloaded the NEF and opened it in Photoshop CS3 and it
>appeared black as I expected it to be. I then adjusted levels
>to bring out any possible sensel variation and a few pixels
>appeared, but nowhere near what you described. So it appears
>that it is possibly PSP X2 that is giving you a false
>rendering.
>
>Pete
>

Huzzah! You are absolutely correct. I DL'd PSP X5 to open the file and it shows a nice black image with a few wonky pixels, as opposed to the Jackson Pollock painting that PSP X2 displays. For a while I was thinking I had the noisiest camera in all of creation.

Many thanks,
Garry

G