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Astrophotography and Sketching >> DSLR & Digital Camera Astro Imaging & Processing

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WhitenerJ
professor emeritus


Reged: 02/06/12

Loc: Waxahachie, Texas
Confused again!!
      #5559714 - 12/07/12 06:05 PM

Ok just when I think I got the white balance, IDAS filter, and my modded T2i figured out, I get confused again. I'm trying to figure out when imaging using BackyardEOS how to use the histogram when different white balance settings affect the hisogram. Some setting shift the colors all over so. Before I modded my T2i I was able to get a fairly stable histogram in BYEOS to guide me on exposing. I would always aim for 1/3 to 1/2 of my histogram for the correct exposure. So now how do I know where to aim and which white balance setting to use. Should I use Auto or do a custom white balance or what? Help me out guys!!

Thanks, Jason


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mmalik
Postmaster
*****

Reged: 01/13/12

Loc: USA
Re: Confused again!! new [Re: WhitenerJ]
      #5559889 - 12/07/12 08:02 PM Attachment (11 downloads)

Here is what I use (leave custom default); complete settings at the end of this... doc.

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WhitenerJ
professor emeritus


Reged: 02/06/12

Loc: Waxahachie, Texas
Re: Confused again!! new [Re: mmalik]
      #5559909 - 12/07/12 08:18 PM

So daylight, right? Do you have a sub I could look at to see your histogram?


Jason


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mmalik
Postmaster
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Reged: 01/13/12

Loc: USA
Re: Confused again!! new [Re: WhitenerJ]
      #5559920 - 12/07/12 08:26 PM

Yes, daylight; one sub here... (10min, ISO1600)

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fco_star
Carpal Tunnel
*****

Reged: 12/13/10

Loc: Texas, Midland
Re: Confused again!! new [Re: mmalik]
      #5560165 - 12/07/12 11:34 PM

mmalik.... if the camera is modded + CLS-CCD filter don't you have to use custom balance to fight the (green/bluish) color?

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mmalik
Postmaster
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Reged: 01/13/12

Loc: USA
Re: Confused again!! new [Re: fco_star]
      #5560174 - 12/07/12 11:41 PM

Quote:

mmalik.... if the camera is modded + CLS-CCD filter don't you have to use custom balance to fight the (green/bluish) color?




Yes, that's what I meant; may be didn't say it right. Thx


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pfile
Post Laureate


Reged: 06/14/09

Re: Confused again!! new [Re: mmalik]
      #5561058 - 12/08/12 03:25 PM

you don't *have* to use a custom white balance. all the white balance data is is 2 multipliers stored in the EXIF header of the CR2 file. some programs read the white balance data and automatically scale the channels. some don't. some can be configured to ignore or pay attention to the white balance data.

if you are serious about it you need to do color calibration on your images anyway, either G2V or something like PixInsight's ColorCalibration. assuming your stars or galaxy core are not blown out, color calibration can fix your color casts.

having said that, usually simply balancing the histogram channels in PI or PS gets you most of the way to proper color balance. of course if the DSO is Ha-rich or something then this won't yield good results.


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nofxrx
Vendor (HyperCams & Mods)
*****

Reged: 07/12/05

Loc: Palm Bay,Florida
Re: Confused again!! new [Re: pfile]
      #5562856 - 12/09/12 05:49 PM

It doesnt matter what WB setting you use for capture.
But I prefer to use the same CWB setting I use for daytime...it just seems to make post processing/color balance later easier..

However, for using the BOC histo to judge what exposure settings you should be shooting for..
If your channels are separated, like you showed me before, Jason, just shoot so that however far apart your channels are try and find the center of the channels(combined channels, not each separate channel's center, know what I mean?) and use that as your "line" for determining 1/3-1/2 on BOC Histo..

Atleast, that is what I do..

Maybe someone with a bit more experience will chime in..

EDIT, pfile has beaten me to it lol


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WhitenerJ
professor emeritus


Reged: 02/06/12

Loc: Waxahachie, Texas
Re: Confused again!! new [Re: nofxrx]
      #5562906 - 12/09/12 06:24 PM

So in this sample image I would aim for the blue peak as my guide for the 1/3 histogram exposure?



Jason


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nofxrx
Vendor (HyperCams & Mods)
*****

Reged: 07/12/05

Loc: Palm Bay,Florida
Re: Confused again!! new [Re: WhitenerJ]
      #5563018 - 12/09/12 07:26 PM Attachment (3 downloads)

Yep.
Since you are looking at the individual channels Histo, this is pretty normal AFAIK...I think if you switched to a Luminance view, it MIGHT show you one single peak/curve...IDK..
But, that looks perfect to me as is. The R channel being the most dominant, obviously being modified..and B being more dominant than G due to the LP in your area, and the 'color' of the sky itself..

This is from my UNmodified D800..not much, but you can clearly see that the channels do not line up perfectly..and is more of a result of the WB used(AWB in this case)..
Once modified the result will be VERY similar to yours.

I would like to see if others chime in and show a histo of a single exp..


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nofxrx
Vendor (HyperCams & Mods)
*****

Reged: 07/12/05

Loc: Palm Bay,Florida
Re: Confused again!! new [Re: nofxrx]
      #5563023 - 12/09/12 07:29 PM

Oh, that was not an actual AP attempt..it was a stationary tripod. I was catching some lightening storms out east HERE on the coast, and above the clouds was a perfect sky, so I just pointed up and snapped a pic...so this is NOT what I would consider a "set up/planned" exp..just F/4 ISO 400 and 20sec..I would probably double that exp length, or double the ISO for a "proper" image..

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