Using a dual band filter with a mono camera

[tomato]

Apologies if this notion has been discussed before and I missed it, but is it possible to use a dual band filter designed for a OSC camera with a mono camera?
I presume it would produce a NB “luminance” channel made up of combined Ha and OIII signal. Could this then be combined with data from a dual band/OSC camera to produce a NB colour image?
Not as efficient as separate NB filters and a mono camera, but worth a try?

[ollypenrice]

How would you distinguish between OIII and Ha in the mono capture? You'd get them both but in one channel. If you used this as a luminance channel the Ha and OIII would be applied equally to all three channels, destroying any colour differentiation.

Olly

[vlaiv]

Yes, and I think that it is most suitable use for dual and tri band filters - as a luminance for NB images.

Say you have Ha/OIII dual band filter - then, all you need to shoot is:

1. OIII

2. Dual band filter

Spend more time on OIII if it is fainter of the two (and usually it is). Use Dual band filter as luminance.

Use OIII data as teal component of chrominance and Dual band - OIII as Ha or red component of bicolor image. Just make sure that you have matched exposure lengths for 1 and 2 so you can easily subtract the two. Do subtraction after background removal phase while data is still linear.

[vlaiv]

I just read the original post - and sure, if you already have OSC+dual band for color - just shooting dual band + mono for luminance is excellent option.

It will give you by far the best SNR per unit time of all combinations (much like lum filter does for LRGB).

[tomato]

Thanks, that was how I saw it, the mono camera and dual band filter taking luminance (and the detail) and the OSC camera and dual band filter taking the colour, much in the same way as we take LRGB.