Full-spectrum Infrared

Hi all,

I shoot a lot of daylight infrared with a full-spectrum camera (Fujifilm GFX50S). I have heard over the years that one can do astrophotography with it as well, using a hotmirror (IR block) that is H-Alpha pass.

So I bought one. A lot of them are pretty pricey, but I found this relatively affordable one from Kolarivision:


Any tips or advice? I'm not shooting DSOs (no scope), but I would like to try my hand and some Milky Way with wide-angles (while there's still a bit left of galactic core season left).

How about Auroras? Will I get some enhanced light with the northern lights using the h-alpha pass filter?

Thanks for any feedback,

Chris

The filter you linked to turns your camera into what is known as an Ha mod. Ha is not in the IR but is at the far end of the visual range and right at the fringes of most manufactures preinstalled cut filters which tend to block some to most of the Ha. It can be very effective to emphasize Ha emission regions in the Milky Way, but will not be of any additional value for aurora photography.

NotASpeckOfCereal said:

Hi all,

I shoot a lot of daylight infrared with a full-spectrum camera (Fujifilm GFX50S). I have heard over the years that one can do astrophotography with it as well, using a hotmirror (IR block) that is H-Alpha pass.

So I bought one. A lot of them are pretty pricey, but I found this relatively affordable one from Kolarivision:

https://kolarivision.com/product/uvir-cut-h-a-pass-lens-filter

Any tips or advice? I'm not shooting DSOs (no scope), but I would like to try my hand and some Milky Way with wide-angles (while there's still a bit left of galactic core season left).

Click to expand...

Experiment. Try some with the H-alpha filter and even full spectrum, at different exposures. The unfiltered full spectrum camera may let in nearly 2x the amount of light as the H-alpha filter. The dark areas in the Milky way apparently let through some IR, so they are not very dark when shot with full spectrum, but can appear reddish

NotASpeckOfCereal said:

How about Auroras? Will I get some enhanced light with the northern lights using the h-alpha pass filter?

Click to expand...

If the aurora is mostly greenish then the filter might not make much of a difference, as the green aurora emission is around 550 nm which unmodded cameras pass very well. If the aurora is reddish, or has reddish areas, the H-alpha filter will definitely show a lot more red as that emission is around 630 nm (not far from the H-alpha 650 nm) which standard camera filters are already reducing somewhat.

NotASpeckOfCereal said:

Thanks for any feedback,

Chris

Click to expand...

Larry Rexley said:

Larry Rexley said:

Any tips or advice? I'm not shooting DSOs (no scope), but I would like to try my hand and some Milky Way with wide-angles (while there's still a bit left of galactic core season left).

Click to expand...

Experiment. Try some with the H-alpha filter and even full spectrum, at different exposures. The unfiltered full spectrum camera may let in nearly 2x the amount of light as the H-alpha filter. The dark areas in the Milky way apparently let through some IR, so they are not very dark when shot with full spectrum, but can appear reddish

Click to expand...

Cool, thanks. I probably will experiment.

But the reason I got the filter rather than try with just the open full-spectrum was because of the following article, which has this excerpt:

"However, the colors produced by a Full Spectrum camera [with no filter] are clearly "off" due to the mixture of various wavelengths and require extensive post-processing if no additional filters are used"


(I was going to add this article to the OP but forgot.)

Larry Rexley said:

If the aurora is mostly greenish then the filter might not make much of a difference, as the green aurora emission is around 550 nm which unmodded cameras pass very well. If the aurora is reddish, or has reddish areas, the H-alpha filter will definitely show a lot more red as that emission is around 630 nm (not far from the H-alpha 650 nm) which standard camera filters are already reducing somewhat.

Click to expand...

The last one I did (a KP6/G2) definitely had a lot of reddish area, so I'll try it with the h-alpha filter.

The following were shot from an unmodified D850. (Note: this is not Iceland or the Yukon, but I thought was a fair first effort from central Washington State):


Chris

NotASpeckOfCereal said:

Larry Rexley said:

NotASpeckOfCereal said:

Any tips or advice? I'm not shooting DSOs (no scope), but I would like to try my hand and some Milky Way with wide-angles (while there's still a bit left of galactic core season left).

Click to expand...

Experiment. Try some with the H-alpha filter and even full spectrum, at different exposures. The unfiltered full spectrum camera may let in nearly 2x the amount of light as the H-alpha filter. The dark areas in the Milky way apparently let through some IR, so they are not very dark when shot with full spectrum, but can appear reddish

Click to expand...

Cool, thanks. I probably will experiment.

But the reason I got the filter rather than try with just the open full-spectrum was because of the following article, which has this excerpt:

"However, the colors produced by a Full Spectrum camera [with no filter] are clearly "off" due to the mixture of various wavelengths and require extensive post-processing if no additional filters are used"

https://irrecams.de/en/astro-filter-photographing-stars-at-night-with-a-modified-camera/

(I was going to add this article to the OP but forgot.)

Click to expand...

From a photographic point of view where everyone wants 'normal' colors, that makes sense. My guess is that article was written by someone who was a photographer, or possibly even associated with an IR conversion servicem, and not an astronomer by background. The text there looks awfully famliiar and I don't think I've visited that site before.

I come from an astronomy background where the sky is typically imaged at a very wide variety of wavelengths with different telescopes using different wavelength filters. Objects appear different, and different 'temperature' stars are more prominent, in different wavelength ranges even with a full-spectrum camera using the various filters available to you. Who's to say what is the 'right' range? There's a lot to be learned by expanding your horizons and shooting with more of the options available to you as a full-spectrum camera user and modifying the results to your taste.

It all depends on what you're trying to image. Shoot RAW if possible, and white balance the background sky (where there is no millky way) to a neutral color or slightly blue (my preference). and then adjust the saturation to your taste. If you have light pollution, you generally get much better results using a light pollution filter. I have a K&F concept Clear natural Night filter which does a pretty good jon, however it shows a color cast in the corner of very wide angle photos (12mm on APS-C sensor).

I've shot the Milky way full spectrum, with a Spencer Visible+ H-alpha filter, and with a Tiffen Hot mirror filter which is a UV/IR cut filter but the cut is much deeper in the IR than the Spencer filter is. It is interesting to compare the various images.

NotASpeckOfCereal said:

NotASpeckOfCereal said:

If the aurora is mostly greenish then the filter might not make much of a difference, as the green aurora emission is around 550 nm which unmodded cameras pass very well. If the aurora is reddish, or has reddish areas, the H-alpha filter will definitely show a lot more red as that emission is around 630 nm (not far from the H-alpha 650 nm) which standard camera filters are already reducing somewhat.

Click to expand...

The last one I did (a KP6/G2) definitely had a lot of reddish area, so I'll try it with the h-alpha filter.

The following were shot from an unmodified D850. (Note: this is not Iceland or the Yukon, but I thought was a fair first effort from central Washington State):

https://www.chrissherwoodphotography.com/Astrophotography/Auroras/Big-Hill-Aurora/

Click to expand...

Lovely images! You definitely know what you're doing.

NotASpeckOfCereal said:

Chris

Click to expand...

Thanks Larry,

I'm certainly not afraid of post-processing to taste, beyond the realm where some purists must remain. I also have a full hot-mirror filter, so I'll be able to shoot all three (no filter, h-alpha pass hot-filter, and full hot-filter) to compare and learn from.

Cheers, Chris

NotASpeckOfCereal said:

Thanks Larry,

I'm certainly not afraid of post-processing to taste, beyond the realm where some purists must remain. I also have a full hot-mirror filter, so I'll be able to shoot all three (no filter, h-alpha pass hot-filter, and full hot-filter) to compare and learn from.

Cheers, Chris

Click to expand...

Nice... an experimenter, like me! Infrared is great for exploring and experimenting, there are so many possibilities with filters. What is the hot mirror filter you have.... Tiffen, Kolari? it's possible its response is similar to a Visible + H-alpha filter, depending on the brand and generation of the filter.

If you're curious to see the effect of Tiffen hot mirror vs. Visible + H-alpha vs. full spectrum vs. unconverted camera for daylight photography, I created a monster comparison post which does those, plus the 'standard' IR filters, and then some, both on a full-spectrum camera and on an identical unconverted camera!

https://www.dpreview.com/forums/post/66445185

In that thread I also posted some astro images, wide-field shots with the H-alpha filter + light pollution filter, and some others:

Larry Rexley said:

NotASpeckOfCereal said:

Thanks Larry,

I'm certainly not afraid of post-processing to taste, beyond the realm where some purists must remain. I also have a full hot-mirror filter, so I'll be able to shoot all three (no filter, h-alpha pass hot-filter, and full hot-filter) to compare and learn from.

Cheers, Chris

Click to expand...

Nice... an experimenter, like me! Infrared is great for exploring and experimenting, there are so many possibilities with filters. What is the hot mirror filter you have.... Tiffen, Kolari? it's possible its response is similar to a Visible + H-alpha filter, depending on the brand and generation of the filter.

Click to expand...

The Ha pass hot-filter and the full hot-filter are both Kolari. I've had the full for a long while, so when I recently purchased the Ha, I made sure they were different pages / part numbers, and they also look different.

Larry Rexley said:

If you're curious to see the effect of Tiffen hot mirror vs. Visible + H-alpha vs. full spectrum vs. unconverted camera for daylight photography, I created a monster comparison post which does those, plus the 'standard' IR filters, and then some, both on a full-spectrum camera and on an identical unconverted camera!

https://www.dpreview.com/forums/post/66445185

In that thread I also posted some astro images, wide-field shots with the H-alpha filter + light pollution filter, and some others:

https://www.dpreview.com/forums/post/66358186

Click to expand...

Cool. I've been doing experiments with a bunch of filters lately, the Hoya X0 yellow/green and X1 green and Red #25A, B+W KB12 (can't find a reasonably priced KB20), a 80A and a strange Chinese QB2 (that is much like the KB12) and mixing them with infrared filters. I got started after someone posted some "Candy Pink Photography", which I have yet to achieve, but have found some interesting stuff meanwhile.

Chris

Side question: are hot-spots still an issue with astro?

For daylight infrared photography, certain lenses perform better than others regarding hot-spots (caused by light reflecting on the lens inner elements). The lenses that do not perform as well do just fine in normal/visible-light photography—the hot-spots with infrared photography.

But that's in daylight infrared. Is it a non-issue with astro?

Chris

NotASpeckOfCereal said:

Larry Rexley said:

NotASpeckOfCereal said:

Thanks Larry,

I'm certainly not afraid of post-processing to taste, beyond the realm where some purists must remain. I also have a full hot-mirror filter, so I'll be able to shoot all three (no filter, h-alpha pass hot-filter, and full hot-filter) to compare and learn from.

Cheers, Chris

Click to expand...

Nice... an experimenter, like me! Infrared is great for exploring and experimenting, there are so many possibilities with filters. What is the hot mirror filter you have.... Tiffen, Kolari? it's possible its response is similar to a Visible + H-alpha filter, depending on the brand and generation of the filter.

Click to expand...

The Ha pass hot-filter and the full hot-filter are both Kolari. I've had the full for a long while, so when I recently purchased the Ha, I made sure they were different pages / part numbers, and they also look different.

NotASpeckOfCereal said:

If you're curious to see the effect of Tiffen hot mirror vs. Visible + H-alpha vs. full spectrum vs. unconverted camera for daylight photography, I created a monster comparison post which does those, plus the 'standard' IR filters, and then some, both on a full-spectrum camera and on an identical unconverted camera!

https://www.dpreview.com/forums/post/66445185

In that thread I also posted some astro images, wide-field shots with the H-alpha filter + light pollution filter, and some others:

https://www.dpreview.com/forums/post/66358186

Click to expand...

Cool. I've been doing experiments with a bunch of filters lately, the Hoya X0 yellow/green and X1 green and Red #25A, B+W KB12 (can't find a reasonably priced KB20), a 80A and a strange Chinese QB2 (that is much like the KB12) and mixing them with infrared filters. I got started after someone posted some "Candy Pink Photography", which I have yet to achieve, but have found some interesting stuff meanwhile.

Chris

Click to expand...

Funny you should mention that - I've been looking at those 'candy pink' threads for a little while too! For reference, here are some links:

https://www.dpreview.com/forums/thread/4585259

https://www.dpreview.com/forums/thread/4619006

https://www.dpreview.com/forums/thread/4639879

I got a Hoya Green X1 filter about a week ago, and today got a Hoya Green X0 filter. I did a little experimenting.... the X0 and a Tiffen 47 filter look like they might work for candy pink in some way.... I'll experiment in the coming days and probably reply in one of the candy pink threads.

Earlier today I managed to find and order a B+W KB20 off eBay in 55mm size for less than $12 shipped, and a 77mm 80A for the same price. I'll use the 55 with a step-up ring and stack it with larger filters.

NotASpeckOfCereal said:

Side question: are hot-spots still an issue with astro?

For daylight infrared photography, certain lenses perform better than others regarding hot-spots (caused by light reflecting on the lens inner elements). The lenses that do not perform as well do just fine in normal/visible-light photography—the hot-spots with infrared photography.

But that's in daylight infrared. Is it a non-issue with astro?

Chris

Click to expand...

What I've found is that hot spots seem to be worse as you stop the lens down. For astro you are using the lenses at widest apertures... so for the lenses I am using, hot spots aren't really an issue. Also for me I am dealing with light pollution and apply DxO PL5 'control point' masks in places to even out the sky, so I may be correcting for hot spots.

Also I find hot spots worst with the deepest IR filters like 850 nm and 950 nm. Not as noticeable with 'super color' 590 nm or Red 25A filters. Since you usually shoot astro in the very near IR close to the H-alpha emission wavelength of 650 nm I don't think you'd really notice them in astro shots unless the lens had a really bad hot spot at wide aperture.

As I suspected. thanks.

Chris