Struggling to get colour files in IRIS

[billyharris72]

Hi all:

I've been experimenting with IRIS as an alternative to DSS (which I really don't seem to get on with) and am having issues with getting colour images from my Nikon D3300. Files load in monochrome, which I assumed was okay, but when I run CFA conversion to get colour the image turns green. I don't mean that the colour balance is off, rather there only seems to be one channel. Running split_CFA seems to bear this out, as shown.

I'm assuming that the problem might be at the debayering stage (the D3300 does not appear as a camera option, and I have tried with all the Nikon options - all but one is green, the other magenta). Has anyone else had a similar problem, or am I doing something wrong? Any thoughts much appreciated.

Billy.

[Oddsocks]

Hi Billy.

Go to the IRIS website, download the latest libdcraw.zip file and extract (Unzip) the libdcraw.dll file, (it is linked to in the first paragraph at the top of the IRIS web page). Delete the old version libdcraw.dll in the IRIS program folder and put the latest file in its place.

 

http://www.astrosurf.com/buil/us/iris/iris.htm

 

Open IRIS and from the top menu bar select "File" "Settings" and select file type "Pic"

Click the camera symbol on the top tool bar to access the debayer settings and select the Nikon D100/D200/D3/D300 series camera.

Select "Linear" for the RAW interpolation mode.

 

For setting up recommend you use a daytime sample image from a photo web site that provides reference RAWS, I used this site, scroll down the page to find the RAW Nikon D3300 images and use an ISO 800 sample for setting up.

http://www.photographyblog.com/reviews/nikon_d3300_review/sample_images/

 

From the File menu select "Load a RAW file" and open the test image.

In the Digital Photo menu select "Convert a CFA image"

The image will convert and display as a linear image and will appear with a green hue (because there are twice as many green pixels than red and blue pixels on a DSLR bayer matrix).

 

 

In the Digital Photo menu select "RGB balance" and set R:1.000 G:0.650 B:1.000 and then "OK"

The image should appear balanced with roughly the right colour:

 

The colours should not be saturated with these settings but if you want to you can use values above 1:000 in any channel to increase saturation but remember once balanced you have to add the same number to each channel to keep balanced, i.e to increase saturation and remain balanced you can add 0.1 to each channel making R:1.100 G:0.750 B:1.100 and then balance a freshly opened image, the resulting image will still be balanced but with increased saturation.

Do not attempt to apply to an existing balanced image as this results in an overcorrected image, you can only balance once....to redo open the raw image afresh and start again.

IRIS is not that user friendly and takes some time to get right, unfortunately there is no "Go Back" or "Undo" function so if the colour is wrong you have to stop and reload the image, convert the CFA image and make a small adjustment to the RGB balance and assess the results, the green channel is the one to play with.

Make a note of your RGB balance settings and you should be close for the astro images unless you are using a LP filter in which case take a daytime image with the LP filter and use RGB Balance to get a normal looking image.

There is a bug in the current IRIS program and placing a check mark in the "Apply" box of the "White balance" section of the Camera settings menu has no effect when carrying out the CFA conversion even though it does read your manually entered values from the RGB balance menu, at least this is the case when running on Windows 7 and 10, I don't have a copy of XP running anymore to see if this is the case with older Windows OS's.

There hasn't been any maintenance or updates of IRIS for a while and it seems to be rather neglected these days.

I guess you are looking for free alternatives to DSS but there aren't that many, if you are looking for a good, easy to use image processing package that can calibrate and process as well as manage cameras, mounts, plate solve etc then have a look at Astroart, you can download a free trial that does everything but save:

http://www.msb-astroart.com/default.htm

Astroart has all the functions of more expensive programs such as Maxim DL but at a reasonable cost.

H.T.H.

William.

 

[billyharris72]

Thanks for the help and advice on this William. It does indeed work, though oddly stars in my astro images gain a faint pinkish hue that goes away when I slightly increase the saturation. I also tried Astroart, and have to say I'm very impressed - very intuitive and easy to use. Think I might have to get my wallet out!

Billy.

[Oddsocks]

2 hours ago, billyharris72 said:

stars in my astro images gain a faint pinkish hue that goes away when I slightly increase the saturation

That's not unusual, when you calibrate IRIS using a daytime image the colour balance of the astro image will be skewed slightly by IR and the type of telescope, mirrors, lens coatings, light pollution etc.

You have to play around a little with the colour balance settings to find the correct ratios to use and in IRIS this can take a long time and require a lot of patience to get right but they won't be that far from the settings used for the daytime image. In Astroart (and other processing packages) the camera white balance settings can be read automatically (if wanted) from the raw NEF file and this makes the post processing much simpler.

You might find with a DSLR and IRIS it may be easier to set up the colour ratios using a moon image rather than stars or deep space as you are presented with a large disk to see the effects of changing ratios and once you have the numbers they will be consistent for all astro images with the same camera and telescope or lens.

Astroart was the first astro imaging package I ever bought (version 2.0) and it would still be my first choice, unfortunately my observatory control software can only interface with Maxim DL but Maxim is now overpriced for what it offers and has some annoying bugs in the guiding module that have not been resolved for many years though they have finally admitted there are problems and are rewriting the guiding code at this time. If not for the need to run Maxim I would be using Astroart.

Watch the £-€ exchange rate over the coming weeks/months, things are very volatile at the moment and will remain so for some time ahead because of the leave the EU situation, if you buy the Astroart licence direct you may be able to save a bit when the exchange rate is favourable.

William.