400D Custom White Balance woes with CLS filter...

[Vega]

Hi

I've just discoverd that people with CLS filters use custom white balance in their DSLR to counteract the false colouring caused by the filter.

I've taken my blank white/grey image with my Canon 400D with CLS filter clip insterted and uploaded it to the cameras custom white balance feature. It seems to be correcting the white balance fine when I did a few test jpg shots. However... when shooting in RAW mode it does not make any amendments and I still get a green tinge. Im kinda thinking this would be true otherwise it wouldn't be a RAW image (untouched) right ? . Im using ImagesPlus for image capture.

Does anyone know how I go about implementing custom white balance when shooting in RAW mode or does it have to be done afterwards when processing your final image?

Cheers

A very confused Matt

[jgs001]

The white balance sets the default setting for a raw, but it's so easy to edit. Although I've found that with DSS, the combining process when processed using the RGB channels calibration (and the developer says the same) carries out a custom white balance on the image, largely removing the tint from the filter..

Here's a single unedited raw image from last week with the CLS

and the stack

I didn't have to process out a green tint, that was all done for me.

[Aza]

I also use DSS to fix the colour balance, here is how:

After clicking 'Stack checked pictures' in DSS, click recommended settings.

In that section you can scroll down and ensure you use the option that says:

"If the colour balance in the resulting image is hard to fix......."

[George]

Shooting in RAW ignores any CW balance you may have.

[samtheeagle]

Vega, I was worried about this issue myself, albeit with a different camera an LP filter, but the principle is the same... I shot in RAW and left DSS to sort out the white balance for me, and it appears to have done a very good job. The setting is in the "RAW/FITS DDP Settings..."

[Vega]

Thanks all for the advice. So im guessing when shooting in RAW, it best just to leave the WB on auto. I use ImagesPlus for my calibration, aligning and stacking. Anyone know the best option to use in that software for editing the WB?

Matt

[brendant]

It's worth looking into using Deep Sky Stacker if using a modded 400D, it makes very easy work of correcting the colour automatically as Arran (Aza) says. I use a 400D modded and DSS, image calibration and stacking is much easier than in Images Plus which is a good program but there are easier ways to achieve the same result.

Shooting in RAW on a modded 400D, I would suggest setting the camera WB to Daylight, in any case custom white balance is completely ignored in RAW and colour correction must be manually corrected in an image editing program such as Photoshop, Pixinsight or similar. DSS does the best job by far if you let it then subsequent processing and stretching of the image is much easier.

Brendan

[Vega]

I've found the setting in ImagesPlus for editing the cameras custom white balance. Its done when converting the RAW to a fit. Glad I dont have to learn a whole new software (DSS) as im used to ImagesPlus. All makes sense now, cheers all

Cheers

Matt

[Vega]

Screenshot for anyone who uses IP....

[Roger B]

Hi, sorry to bring this back up but I'm experiencing the same thing here with my modded 350d & clip but no matter what i try to do the resulting stacked image from DSS always has green/cyan stars. ( only on the smaller ones) Can anyone explain what settings they use in DSS as i just cannot see in DSS what you are saying.

Roger

[philj]

Shooting in RAW ignores any CW balance you may have.

Thats interesting, the 1000d will use the CWB in raw but switch to auto and it defaults to AWB, the oppossite from the 400d it would seem.

[jgs001]

Shooting in RAW, sets the white balance to a certain value, but you can redefine it easily as you look in processing... however, if you set DSS up, so the White balance settings are off in the RAW processing, and to use RGB background calibration, DSS will calculate a WB for the image, in fact, this works well enough, so that if you do a series of images over different nights with different filters, all colour casts are removed... Here's the settings as I use them...

The setting at the bottom of the lights stacking options box.

I got this information from the DSS Yahoo group and the author of DSS. It works well for me.

[Roger B]

Thanks for that John,

How ever i have run a image of the double cluster through DSS & i cannot see any difference at all the smaller stars are still cyan/green. I'm having to reduce the saturation in photoshop on the cyan/green channel by nearly 100% to get rid of it.

Although the filter is good for light polution it's not to good for me with my processing skills for imaging.

Roger

[jgs001]

Roger, rather than reduce the saturation, try adjusting the colour balance instead... You could do a selection by colour, click on the offending stars... create a new adjustment layer for colour balance, and tweak them back into line...

[michaelmorris]

Roger, rather than reduce the saturation, try adjusting the colour balance instead... You could do a selection by colour, click on the offending stars... create a new adjustment layer for colour balance, and tweak them back into line...

Is their some way of clicking on an off-colour star and getting DSS, Photoshop or another program to automatically alter the colour balance of the whole picture so as to set the star to white?

[simon hicks]

Is their some way of clicking on an off-colour star and getting DSS, Photoshop or another program to automatically alter the colour balance of the whole picture so as to set the star to white?

PixInsight does that. It lets you first neutralise the background. Then you select areas of the background, and then areas that should represent white....a nearby galaxy (i.e. unredshifted) is a good target. It then does a complete colour calibration for you. I use it on a modded 400D with an UHC filter and it does actually seem to work wonders.

[michaelmorris]

PixInsight does that. It lets you first neutralise the background. Then you select areas of the background, and then areas that should represent white....a nearby galaxy (i.e. unredshifted) is a good target. It then does a complete colour calibration for you. I use it on a modded 400D with an UHC filter and it does actually seem to work wonders.

Unfortunately I don't have pixInsight . Is this function available on Photoshop?

[Roger B]

Roger, rather than reduce the saturation, try adjusting the colour balance instead... You could do a selection by colour, click on the offending stars... create a new adjustment layer for colour balance, and tweak them back into line...

Anychance of explaining how you do this step by step. My processing skill are limited.

I have attached a example of the type of problem i have. This has come from DSS into Cs2, changed from 32bit to 16 once through Noels actions to increase star colour.

Roger

[jgs001]

I've just discovered something interesting about DSS and the stacking algorithms... The custom white balance settings I've been describing appear not to make any difference with an Average stack. Only the more complicated ones. I normally use Kappa Sigma, Median Kappa Sigma, or Auto Adaptive Weighted Average and the stacking process sorts out the colour cast using the settings described. I found this with my M45 image I've been trying to get more subs on. With any of those stacking mechanisms I got well aligned colour channels, and no colour cast to deal with. With average stacking, I got a big peak of red to the right of the other colour channels, that's using the SW LPR which gives a pinkish tinge.

What stacking mechanism have you been using ?