Daytime IR cut filter to compensate for astromoding?

[Sedna]

Hi everyone, I astromoded my Canon 70D a couple years ago and let's just say that my wife, who shares the camera with me (okay, it is technically HER camera), has never been very pleased since then 😅 For those of you who do daytime terrestrial photography in addition to astrophotography, I'm guessing it must be common to also have an IR cut filter that can be screwed on the lens as needed?

For Xmas, I was thinking of getting my wife one so she can finally feel comfortable using our DSLR for daytime photography. I see there are a number of options out there: https://www.bhphotov...ilters/ci/16886 ... so I'm wondering if anyone can offer recommendations? In particular, I don't want a filter that will overcompensate and also block visible red wavelengths, if the filter roll off isn't steep enough ...

Most of our are lenses have a 58 mm diameter, though our best lens is 77 mm.

What do you all use or recommend?

Thanks in advance 🙏

[almcl]

Can't answer your question directly, but when Juan Fierros sold me an Astro modded Canon 700d some years ago, he fitted a replacement filter, I think a Baader BCF1, in place of the Canon original.  This lets through a lot more IR but, with a custom white balance means the camera is still good for day time terrestrial use. In fact it has now retired from Astro in favour of a 2600MC but is still much in use for terrestrial.  

Unfortunately, I don't think Juan is still doing this work, and not sure if a screw-in filter of the same transmission characteristics is available, but if you're up for a re-mod?

There are a couple of example images  about three quarters of the way down the thread here which show how the filter performs

[vlaiv]

How did you mod your DSLR?

There are two types of modifications: one is removal of IR/UV cut filter and other is replacement.

UV/IR cut filter that comes with camera has particular response that is crafted so that camera produces correct colors (or to be easier for it to produce correct colors).

Here is comparison:

Blue curve belongs to Canon stock filter, and red to Baader astronomical filter replacement. This modification is performed mainly due to emission type nebulae astrophotography - as you can see the difference in Ha line sensitivity (green vertical dashed line).

In either case you have two options - get regular UV/IR cut filter that is front mounted - but this is redundant if you did second type of astro mod - replacement of UV/IR cut filter. In this case - you need to look up ways to calibrate your images for new response (derive new color correction matrix and so on).

Alternative is to find front mounted UV/IR cut filter that has curve like Canon's one in above image - and I'm not sure you'll easily find such one.

[Louis D]

Why not just buy an Astronomik OWB Type 3 Clip-Filter EOS APS-C?  It seems like the most reasonable solution for you.

Here's the tech info:

[michael8554]

Hi Sedna

1) If you did a Ha Mod, by removing only the LPF-2 filter, the LPF-1 filter remains and blocks unwanted IR.

So you don't need an external UV/IR filter, which in any case won't give you a daytime spectral response.

You can get a good Ha response AND a good daytime response by installing a Baader filter in the LPF-2 position - see vliav's graph.

Or get a pretty-close to correct spectral response by using a Custom White Balance.

 

2) If you did a Full Spectrum Mod, by removing both LPF filters, you will need at least an IR/UV filter, to prevent bloated stars in the case of lens or refractor use.

But again, an UV/IR filter will not fix the daytime spectral response.

Michael