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In response to recent posts about Aerochrome simulation I'm sharing a few images I've taken recently. All where shot with the my now usual filter stack for this : - Midopt TB550/660/850 (behind the lens) - Lee Flesh pink gel - GRB3 This time all images are taken on a Sony a6300. I used the internal Jpegs as working files so all the color science happen in camera. I used the "Still" gamma curve and gamut with the saturation lowered to -10. Noise reduction is abled in camera (usefull because of chroma noise that can happen very fast after the channel swap even at low isos). The channel swap is performed in Darktable with no need for any color substraction. Contrast and film grain are set in Lightroom.

I've been experimenting on aerochrome emulation for the last 8-9 months using a lot of information from all over the web (a lot of which I found on here). The main thing that I have found is that in order to get very distinct variations in foliage, the amount of incoming infrared light needs to be cut. It seems as though pretty much every species of tree and plant reflects the same amount of infrared (which makes sense as chlorophyll a is highly conserved between all land plant species). To this end, the triple bandpass 550/660/850 from MidOpt is attached to the rear of my lens and the HOYA X1 to the front. This leaves me with images that are extremely green, but have the correct amount of red and IR light for a successful conversion. My workflow then generally involves desaturating the greens in lightroom and then performing the standard channel swap in Photoshop. Even with somewhere between -60 and -80 saturation applied to the greens in lightroom there's is still plenty of colour left to give the deep blue sky with white fluffy clouds that I'm after so much, without having to worry about the magenta cast that I've seen mentioned before. I'll keep iterating through, and I have seen Fandy's post about using a linear colour space so I may try that out on some existing files. I also need to try out a circular polariser to see if I can get the sharp drop off in the skies that I've also seen from some film photos.

I've been using my new Aerochrome filter set a lot these past weeks. It produces really articulate colors. At a point that I don't think the original film necessarily did better. (plus digital offers a completely different dynamic range, making digital IRG photos very disctinct from the OG) Until now I haven't noticed any plant health information that isn't distinguishable with the naked eye : young leaves and show pink, older leaves red and the more they wither the more the lean toward orange brown and yellow until it is completely dry and shows grey. My guess is that aerochrome is not intended to be properly white balanced like I do with my photos, and that therefore it shows a strong dichotomy beetween cyan dead plants and pink healthy plants. It is maybe easier to tell the different beetween cyan and pink that beetween grey and green. So yes from what I've seen nothing special is reavealed, it's just way more beautiful than the usual boring green. So to recap my setup for these pictures is : filters : Midopt TB550/650/850 + Lee "Flesh Pink" + GRB3 (+Cokin diffusion filter on some shots) Camera : full spectrum Canon 1200D The channels are swapped in darktable, no IR substraction is needed. I work from sRGB jpegs. No color edits at all. I edit the contasts in Lightroom.

The following experiments are inspired by the findings of @Christoph Here is a series of pictures with my full spectrum canon 1200D and a stack of these three filters : Midopt Triple bandpass 550/660/850nm Lee "Flesh pink" gel GRB3 from Tangsinuo The transmission curve of the three filters combined should look something like this : Both the green and the IR spike are heavily filtered. When the TB is used alone, it seems to suffer from a very weak red transmission : without the GRB3 the red channel records as much (if not more) IR than red, requiring IR subtraction of 100%. The green spike transmission to the contrary is very powerful. To the eye (at least mine) the filter is green. I'm not sure how bright humans are able to percieve red at 660nm, its pretty deep already. I then decided to reduce the transmission of IR and green equally to give room for the red transmission. The GRB3 is used to minimise IR contamination in the RED channel and the Lee gel is used minimise green contamination in the blue/IR channel and to make it more or less match the level of output of the red channel. The blue channel stays very underexposed compared to the two others, and is brought back in white balance (pretty extreme : lower than 1900Kelvin). The exposure value with these filters ranges from 1/50s to 1/100s in sunlight at f5.6, 200iso. It's a very dark combo. All the pictures are channel swapped in Resolve from the camera Jpegs, the process is video ready. No saturation was added and zero IR substraction is needed. The fact that IR transmission is cut by 90% by the GRB3 causes some green leaks to be percieved in the Blue/IR channel. This leads to the need to apply a hue correction to the sky in order to make it look properly blue and not purple-ish. This process is simple and non-destructive. The original color of the sky after channel swap : Important notice : The channel swap causes a significant decrease in contrast and micro-contrast. For a moment I thought this was due to the Jpeg compression but it is not. Do you remember this law ? Y = 0.1 Blue + 0.6 Green + 0.3 Red It is actually crucial in understanding why the images look better unswapped. It describes how the human eye is sensitive to luminosity. The green value is far more decisive in the percieved brightness of an object than the red and blue values. A quick exemple Unswapped image : Swapped image : it looks less detailed and dynamic. The contrast beetween the bright grass and the dark trees is lessened Swapped image but with the "preserve luminance" box ticked : the image is sharper and more alive. (Click on the image and use the viewer to compare both instantaneously.) Explanation : The grass in the unswapped image appears turquoise. Let's make it cyan for the sake of clarity. The trees appear blue. Cyan RGB values are (0; 255; 255) Blue RGB values are (0; 0; 255) The minimum luminance(Y) is 0 and the maximum luminance is 1. Y(cyan grass) = 0.1x Blue(255/255) + 0.6x Green(255/255) + 0.3x Red(0/255) = 0.7 Y(blue trees) = 0.1 x B(255/255) + 0.6 x G(0/255) + 0.3 x R(0/255) = 0.1 in the unswapped image the contrast beetween the brightness of the trees and the grass is important : Y=0.1 versus Y=0.7. Now, let's do the same for the swapped image where the grass is magenta and the trees are red. Y(magenta grass) = 0.1 x B(255/255) + 0.6 x G(0/255) + 0.3 x R(255/255) = 0.4 Y(red trees) = 0.1 x B(0/255) + 0.6 x G(0/255) 0.3 x R (255/255) = 0.3 in the swapped image the contrast beetween the brightness of the trees and grass is less important than in the original image (Y=0.3 versus Y=0.4) In this chart the colors are ranked by luminance. white Y=1, yellow Y=0.9, cyan Y=0.7, green Y=0.6, magenta Y=0.4, red Y=0.3, blue Y=0.1, black Y=0 As you can see here the brightness of Magenta and Red is very close as opposed to cyan and blue that are very far apart. So that's why channel swapping sometimes makes the image lose quality. A solution to this is to tick the box "preserve luminance" in the channel mixer. It doesn't work in every situation since it makes the yellow objects turn way darker, leading to an unnatural look. Ticking the box also makes the sky way brighter. It's a tradeoff that has to be made for each individual picture. In the selection I posted above, a few have the box ticked and most don't.

I have been taking a lot of photos lately. This time I decided to investigate a pair of cucumbers. I illuminated them with a halogen spotlight, which emits enough light for IR, visible and UV. IR tri color is using my GRB3 method UV is taken with a ZWB2+QB39 stack (which surprisingly does not leak significantly, even with halogen) I will also be including the individual pictures if anyone else wanted to take a shot at processing them (please, do post). I'd especially appreciate if someone managed to stack all 7 channels continually. I only could stack them by binning the visible and the IR part of the spectrum together. The pictures are in full hd so if you still have a 1080p display, you might want to enlarge. visible IR tri color 850nm+720nm+red Aerochrome simulation GBUV full spectrum individual color channels: 950nm longpass ~850nm band ~720nm band red band green band blue band UV band (400-350nm) I also decided to stack the images in Photoshop and pick the range stack mode, I got interesting results. All of the bands stacked: All of the bands except for UV stacked: IR only stacked: IR only stacked (normalized): Bonus: IR stacked, normalized and processed with Topaz Denoise AI: Here's the IR range mapped on the visible image: Here's the range between 720 and 850 bands mapped on the visible image:

Hello, There was a nice opportunity to take pictures a morning during Ascension's Week End last May. The shots were done in Aerochrome emulation using @Christoph's combination of Hoya X1 Green + Tiffen #16 Orange filters. The amount of IR is more reduced compared to using a Tiffen #12 only, but with the advantage of not saturating the images too much. Processing was done using Rawtherapee. Photographs were taken using a Canon EOS 6D Full Spectrum paired with a Nikon 50 mm F/1.8D : 1. ISO 160, 1/250s, F/5.6 or 8. These buildings seem straight out of one of Philip K. Dick's novels (Ubik). 10-15 years ago it was tall grass and abandoned factories. 2. ISO 160, 1/250s, F/5.6 or 8 3. ISO 160, 1/250s, F/5.6 or 8. The tower's construction started in October 2021 and is nearing completion now. 4. ISO 160, 1/250s, F/5.6 or 8. 5. ISO 160, 1/250s, F/5.6 or 8. This metallic sculpture is an homage to Gustave Eiffel, who was born here (Dijon, France). 6. ISO 160, 1/250s, F/5.6 or 8.

Emulating Aerochrome is a long and winding road. Anyone who has read my previous posts on Aerochrome has probably seen my frustration in achieving an authentic look. Now I am back with the Foveon (Sigma SD1 Merrill) and have tested with the Triple Bandpass. And suddenly I achieved an in-camera look that is actually not bad at all. The magic phrase is FOV Classic Blue. This is an in-camera preset that exists in the Sigma SD1, like “neutral”, “landscape” and so on. What it does? I don’t know. Like much else about Sigma’s Foveon sensor cameras, it’s a black box. But in any case, it results in getting red-pink trees and green-blue skies right out of the camera with the Triple Bandpass filter from Midwest Optics. The color changes were unfortunately not there yet, with the exception of yellow to white. But red was still reddish, or let’s say at least orange. But if you install an additional filter that flattens the transmission curve of green (in the 550nm range), then it becomes good. Why? I do not know. The best result I got so far was with magenta/pink filters from Lee. Here are some results. Unfortunately I did not get a Custom White Balance with both filters together. That would be necessary to get a convincing result. It's not perfect yet, the color changes aren't optimal yet, as well as the coloration in the vegetation, but I think that's a big step forward towards authentic Aerochrome SOOC.

LINK: https://mike-makes.com/2021/08/09/aerochrome-a-year-long-journey/ At that link there are (digitally scanned) film photos shown made with Kodak Aerochrome III Infrared Film 1443 which the photographer sourced from Russia. The $100 film was of course expired as would be any most Aerochrome film still in existence. The shots were made with an orange 056 filter. He cross-processed with C-41 rather than the suggested E-6. The photos are weirdly cool. For many photos the original digital scan is shown together with a slightly edited alternate color version. Enjoy!

Hi everybody. I realy like taking images of nature, especially creeks and rivers. In the last years I have been doing a lot of panoramas using conventional cameras. Last week I went to beautiful Slovenia. As I still have not progressed further on the topic of wetplate emulation, I have been taking my full-spectrum camera with me while visiting Slovenias Triglav Nationalpark to try taking my first infrared panoramas. Fuji X-E1, Full-Spectrum, Fujinon XF 14 2.8 F 8/10, ISO 100. KolariVision IR Chrome 58 mm Filter. Tripod with single row nodal-point-adapter. 2s self timer. Stitched using Kolor Autopano Giga 4.4 - Panini Projection (a mix of planar and cylindrical I think). What I really struggle with is white balance. Is there a proper way to do it? Kind regards, Jon

Aye up lads! I have been attending this forum for a while as a reader, and following your discussions on how to imitate Aerochrome film in digital. This is clearly not what this post is about, although it put me on the right way to find out how to obtain a DIY version of Kolarivision IR Chrome filter. I would say it has been a mix of trial and error plus some rudimentary investigation on colour wavelengths. The filters tested are the chinese QB2, QB3 and QB19. A chinese factory was selling QB2 as the cheap version of IR Chrome, but QB2 is far from any resemblance by itself. They even stole Kolarivision photo from the website to promote the QB2. The QB2 toghether with a GRB3 or KG3 from the same retailer made some difference, but still not good enough. The leakage of IR was still too strong. The tests I did with only visible light showed too much red and yellow overall. So the amount of light transmited around 500nm to 700nm was still too much compared to IR Chrome. On the images below you can see the original colour pattern I created followed by Kolari vs. QB2 vs. QB3. All photos taken with a non-sensible NIR camera. So there is no possible NIR leakage in them. QB3, as you can imagine, is far from any resemblance with Kolari's. The final image is too blueish. Although its wavelength is quite similar to Lee 729, I couldn't manage any similar results. I must say, my QB3 is just 1mm, I will come back to this later. I saw this QB19 filter after a while, which looked somehow in between QB2 and QB19. QB19 filter is really similar to QB2, but cuts blues at 325nm aproximately. Also, does not allow that much light from 500nm to 700nm as QB2 does. I will let experts from this place to debate on it. I am not a physicist, so I am afraid I'd say some stupid stuff. My QB19 filters are 1mm and 1.5mm. Toghether with them, I tried GBR3 or KGB3 from the same retailer. These are 1mm and 2mm thick. Right now I am using 1:1 ratio. So same thickness on both filters. The good thing about using 1mm filters is that I can use one single ring for my super wideangle lenses. Below you can see the results SOOC from a Fuji XT10 with 10-24mm and 15-45mm lenses. The order is as follows: Original scene (no NIR). Kolari IR Chrome. QB19 + KG3 (True Color SR). 1:1mm QB2 + KG3 (True Color 550nm). 2:2mm QB3 + KG3 (True Color SB). 1:2mm The slight difference you can see between QB19 + KG3 and Kolari's is due to adjusts made on camera white balance. I did not have a WB card, so I had to do it by visual approximation. A bit more green on the camera would solve the problem. QB2, as you can see has a bit too much red, this bothers a bit when editing and makes it hard to preserve the warm-orange-red tones from the vegetation. This combination, QB2 + KG3 is really nice to make golden vegetation. The following images are in the same order, but the WB preset is a bit different. I will keep posting some more images to compare True Color SR and Kolari's filter. Disclaimer: I really appreciate Yann's work on IR Chrome, and this post is not by any means trying to discredit his work. In fact, I got inspired by his dedication to IR light and this is what took me here! ;)

After messing around with a Sony Nex-3N for 2 years I finally got to modify my Sony A7 to full spectrum. It was pretty easy but it was still my back up camera for wedding shoots I used to do with my ex partner so I couldn't risk ruining it. Now that I'm alone again I didn't need it for that anymore so I finally got the chance to take it apart. I'm very happy now that I finally have a full frame camera dedicated for IR. First day results look promising. #1 is Sony A7 with Samyang AF 45mm f/1.8 FE and Lee 115 + GRB3 stack #2 is Sony A7 with Tamron 17-28mm f/2.8 Di III RXD and a Zomei 850nm filter

Some of us have been experimenting with the Lee Scuba Blue 729 filter combined with KG3 or GRB3 which gives almost identical results to the Kolari IR Chrome filter. However, it would be nice to have both filters made of glass instead of having to use the Lee 729 I was surprised to see that a seller on AliExpress is now selling a stack of 2 glass filters: QB3 & GRB3 https://www.aliexpress.com/item/1005004024273274.html QB3 is a Chinese equivalent for Schott BG3 Has anyone here tried that combination? The last product picture even shows a camera with the IR Chrome filter on it so it's obviously intended to serve the same purpose. The transmission charts for QB3 and Schott BG3 show they're quite a bit lower in the spectrum though, peaking below 400nm.

Hi. First shot with the Lee #172 lagoon blue + chinese GRB3 at the end of the day with a weak sunlight. SOOC (panasonic Gf3 full spect conversion by myself)...WB to auto but corrected to yellow/reds. For me it was surprisingly good....what´s your opinion?

Hello. In the first tests with the Lee #729 I didn't get the aerochrome sooc effect :( ....I don't know why! maybe it has to do with the white balance of the camera (I've tried many wb settings without success). So I decided to combine the #729, which I placed between the sensor and the lens mount, with other color filters. Using Kenko ya3 I got this beautiful and vibrant goldie effect by messing with the channel mixer and switching channels.... The day is cloudy and dusty from North Africa

Pentax K-1 full spectrum converted by Kolari Vision with chrome Nikon EL-Nikkor 80mm enlarging lens and Kolari Vision Ir Chrome filter. This required a small hike in the woods, on my only day off. It was windy and took many shots to get a sharp shot. Lightly processed in Silkypix and PSE 11. No channel swapping with this filter. Comments welcomed. Thanks for looking, Doug A

Well, here it is, the fabled filter from Midwest Optical that seems to be great for Aerochrome-style photos: The Triple Bandpass TB550/660/850. You can't buy it from any store or online store, unfortunately, but only directly from Midwest Optical. Or, and this is how I did it, from a dealer on Ebay. That also comes out a lot cheaper. Originally, I inquired with Midwest Optical. They only seem to sell to companies, colleges, and so on. And the prices are very high. Filter size 77mm costs around 1100 Swiss francs (is about the same in US dollars right now). Even filter size 37.5mm - which I have now - still costs around 600 Swiss francs new. Unbelievable. I paid around 50 francs/dollar for a 37.5mm at the Ebay dealer (including delivery costs). Actually, I wanted to test today, but the Sahara dust, which is currently blown over all of Europe, currently leads to heavy cloud formation. The sun glitters only in between from behind the gray ceiling. Nevertheless, I was outside and took some pictures. Here is one of them, which shows very well the Aerochrome color change. The car is actually red, as is the hydrant. Preliminary assessment: The filter seems to work very well, possibly with better results than with the green-orange combination. It is greenish-yellow (thus reminiscent of my combi), but reflects strangely. What does it do exactly? It lets only green, red and near infrared (NIR) pass. By simply switching color channels (NIR is imaged in the blue channel, so you make blue -> red, red -> green, and green -> blue), you get a false-color IR image that strongly resembles Aerochrome. Because the process is so simple, I see great potential in it for video projects. The Orange-Green method is not very suitable for filming, because the processing is rather tedious and artifacts occur. I think and hope that this will be much easier with the triple bandpass filter. The blue vegetation (before the channel swap) is already there, the white balance also fits very well (with 2500 Kelvin). Am curious how the results will look in sunshine.

Today I had to break new ground (for me) to get a bit closer to my goal - to reproduce Kodak Aerochrome film authentically. My experiments with Sigma, especially with regard to details like the color change from red to yellow, were disappointing recently. So I grabbed my Nikon and went out. The vegetation is anything but super at the moment. But I was pleasantly surprised. Here is the equipment for the experiment: Nikon D7100 Full spectrum Hoya X1 Green Tiffen 16 Orange (or yellow) Hot Mirror Kolari B+W 830nm filter Polarizer (Neewer) First I tried the two-photo method with one image with visible light only, and one image with IR only. For this I used the Hot Mirror and the B+W filter. This was OK for me. Here is the result. Yes, yellow taillights, red vegetation, but the red car in the background was caramel colored (maybe it's the perspective though). These images were just processed with the color channel method, no additional reworking... Then with only orange filter and polarizer - very disappointing. Again, no reworking, just the channels: Finally I tried what was my greatest hope: the combination of green filter and orange filter (plus polarizer). I am quite happy with it. The red car is bright yellow, the vegetation is already good (for the season). The following are also straight out of the channel mixing, no reworking: Those were reworked minimally via raw converter (red and orange hues both more red/magenta (-40) and vintage preset filter): Probably a good method, because the X1 is known for differentiating vegetation very well, and it does a cutoff in the infrared spectrum...

This is a rainbow shot with my "single shot IRG" method using a Tiffen#12 + DB850 filter. The combination transmits roughly 550-650nm + 800-900nm, without the 700-800nm region which otherwise contaminates the IRG since that part of the IR contributes unequally to the three channels (unlike the 800-900nm band) and so cannot be subtracted off by removing the blue channel without supplying unknown multipliers. Here is my estimate of the spectrum based on the Tiffen#12 data and DB-850 data supplied by the manufacturers: The processing has been documented by me extensively already on this board, so I will just present the final image. (Unfortunately I did not record shooting data, and in any case this is a panorama, so I can't give the exposure.) Lens was the metal EL-Nikkor 80mm/5.6. Interestingly, some inner bows can be seen. Now compare to the visible photo, taken by iPhone XS Max:

A software company that has been unknown to me released a plugin for Adobe CC and Lighroom that simulates the rendition of Aerochrome. https://reallyniceim...-lightroom.html While the landscapes looks really like the images shot with Aerochrome or the skilful simulations posted to this forum, the skin tones seem to be rendered normally. I'm not sure if some AI engine recognizes human beings and masks them out. Unfortunately, they don't seem to offer a trial version. How do you think?

As many here know, the SIgma Foveon sensor makes it possible to get a Full spectrum look which is reminiscent of the old Aerochome films. Two methods have been promoted and explored already: 1. "Rich" Full spectrum: Remove the Hot mirror, get a custom white balance on grey/white card, almost no post-processing is needed. This will get you a wide variety of red/yellow and magenta hues in the vegetation and blue skies. 2. With additional green filter, for example Hoya X1 Green: Remove hot mirror, choose light bulb as WB preset, install the filter and shoot. This will get you magenta tones and more accentuated, cyanish skies. I always had my problems with both these methods: 1. The "Rich Full spectrum" method just lacks the magic and mood of old Aerochrome. It's hard to pinpoint to a specific trait. For me, it lacks the stark contrasts, the dark skies and the surreal lighting of scenery. It just looks too natural/normal for my taste. 2. The Green filter method gives you more of that Aerochrome charm, but it has greenish/cyanish skies, and the magenta tones are quite uniform and too pinkish for my taste. So yesterday, I spent an afternoon in my atelier and just tried out different filters with my SD1, in the hopes of achieving other ways to a more authentic Aerochrome-style emulation. I was trying to get good custom white balance, which is soo difficult with Sigma cameras. I tried a classic Red Filter from Tiffen, the 25... Custom white balance whitout filter on, because I just couldn't get a CWB with the filter on the camera. I got a very yellowish image with red trees in it. I thought that this would never work out in post-processing. But I was wrong. So here's what I did in SPP and the final result with additional WB optimization in Photoshop Raw Converter: I also tried a combination of filters: Red and Green (Hoya X1). Unfortunately the lighting conditions were very poor. But in post, I also came up with a very good solution. So now I will try to test both methods in clear sunlight, hoping to see if these methods produce more "Aerochrome" like dark skies and colorations. Recommendations, Comments are very welcome..

These were all taken with the Sigma sdQH + 70mm Art lens + KG3 filter. Quite different results than the IR Chrome filter, that I had been using. Surprised that I was able to add some yellow to the mix, with the KG3. Poppy Cornflowers Viburnum Leaves Iris and ferns

Sigma recently added a new "Teal&Orange" toning mode to the sdQ-H firmware, so I thought I'd try it out with my Kolarivision IR Chrome filter, which I haven't used in while. For this set, the sdQH is CWBal on neutral gray, then I switched from Standard to T&O mode. Some brightness, contrast editing, but basically SOOC colors. Sigma sdQ-H (T&O mode) + 70mm Macro DG Art + IR Chrome filter

I haven't used my Kolari Vision IR Chrome filter in a while, and decided to try it out on my newly acquired Sigma sd Quattro H. Instead of the usual orange tones, the sdQh seems to produce a vivid range of magenta/reds SOOC. Not much greenery this time of year, but here are a few test shots. Snowdrops "Cine" color mode Snowdrops "Standard" color mode Steet scene "Standard" color mode

Just a summery and a few reminders about the Lee 729 + KG3 2mm (Hrommagicus = Chrome Magic) stack. https://www.leefilte...=cf&sort=number First, let's start with the history: If you want to see the origin of all this, David Twede's original examples and explanation about the 729 + KG3 stack. David's instructions are exactly what I use when I shoot with the 729 + KG3 2mm stack. I think it was David that invented this, as far as I know, so go there first if you want to see how it all started: https://next-eyes.bl...tal-ir.html?m=1 Now a few graphs showing Lee 729. This first one is their online example, which excludes anything above 700nm. This second one is the graph they include in their swatch book, it has an extended data range up to 800nm. Everyone should get the Lee numeric swatch book, which contains hundreds of 3.5" x 1.5" polyester film filter samples, with an extended graph for each filter. This third one is just an overlay of the Lee 729 and Schott KG3 This forth one has Lee 729 data entered into the Schott filter program, the line is more jerky because the data was only entered for about every 10nm from the Lee 729 graph. Reminder, somewhere around this site, is a spectrometer scan of Lee 729 that goes up much higher than 800nm, which Ulf made, I don't know where, maybe you can find it. Now for a comparison showing the 729 stack with and without IR removed by stacking it with S8612. (you might also try this test using Baader UV/IR-Cut filter for your visual/IR barrier (instead of the S8612 2mm), I forget how much 700nm range the Baader UV/IR-Cut filter leaks or not) Lee 729 + Schott KG3 stack Lee 729 + Schott KG3 2mm + Schott S8612 2mm NOTE: although the barn and pump house are red in real life visual, they are colorless when shot with the visual range of the 729 filter, which suppresses all visual red transmission, thus all of the red you see on the barn and pump house with the full range of the 729 + KG3 stack is derived from IR, not from any visual red. Lee 729 + Schott KG3 stack (close up crop) Lee 729 + Schott KG3 2mm + Schott S8612 2mm (close up crop)

What is the raw color of the Hrommagicus filter? I like to determine this for my filters by photographing an UV/Vis/IR white standard which has broad uniform, diffuse reflectivity such as the 5x5 inch Spectralon square shown in the photo. The Hrommagicus filter is a cyan filter having a bit more blue than green as you can see from the raw histograms. Cyan is at 180° on the color wheel. The Hromaggicus is at approximately 189°. Just call it 10° toward the blue away from cyan. I made a white balance on the Spectralon in Photo Ninja. The screen shot shows that the Temperature = 15000 and the Tint = 59. I saved this white balance in Photo Ninja for use on a later test scene. When photographing the Spectralon, the blue channel was the first to blow out. The shot is actually somewhat underexposed to prevent hitting the wall in the blue channel because Photo Ninja will not white balance on a blown out area. This is probably a correct approach. Interpolation is good for dealing with highlights, but not so useful for a correct white balance which should not be based on guessing. The raw histogram in log format shows that I got fairly close to the right hand wall in the blue channel. That is not obvious in the linear version. The raw histogram was created from only the cyan area. The left-hand side of the photo was excluded. Hrommagicus Test Scene I photographed some sky and a dark green juniper. There are a bunch of dried grasses in the foreground. OK, maybe not the greatest shot ever, but it was cold out there! I made an in-camera white balance against the scene just as seen in the photo. When attempting an in-camera UV or IR WB with a Nikon, remember Bob Friedman's advice to first set a proper exposure in manual mode. Under a colored filter the metering will not always show the correct exposure. For this Hrommagicus a good exposure was about 2 stops longer than what the meter was showing. At the metered exposure, the D610 could not make the WB measurement. This in-camera WB turned out to be the one having the foliage colour closest to red (as either 0° or 359° on the color wheel.) That has been important for some members here who are working on achieving the Aerochrome "look". But the outcome here was a pure surprise to me. And I'm not sure you would necessarily get pure red foliage for a different scene. The version you are seeing here is the extracted JPG. No formal conversion was done. No edits were made. Resizing and labeling was done in Photo Mechanic. The in-camera sharpening was preserved as well as the Vivid picture control. (Resizing may have dulled the sharpening, of course.) Here is the test scene in all its raw cyan glory, as shot. The red, green and blue channels are also shown. (The two green channels were averaged by Raw Digger.) The blue channel is the brightest. The raw histograms are as expected - blue leads green just a bit. Two Test Scene Variations This version of the test scene was converted in Photo Ninja. The white balance made from the Spectralon was applied to the file. No camera color profile was added. The color of the foliage has shifted about 10 degrees away from pure red (0°/359°) back towards blue. This produces more of a cerise (cherry red) colour. Is this a more valid colour version of the test scene? Who can say? We are dealing with false colour here. Anything goes! Using a Spectralon white balance made just prior to shooting any scene is a good way to standardize false colour outcomes when needed. But feel free to push your false colour in whatever direction pleases you best. [side Note: It is good practice to photograph a white standard for every scene. Our cameras do not always measure white balance correctly under UV, IR or color filters even when you are measuring WB against the white standard itself. If you make documentary photographs, this step is mandatory indoors or out. Outdoors maybe more so because sunlight is changing composition and colour every second. ] This conversion does not have the same amount of saturation in the sky colour as does the extracted JPG above because I was only making simple conversions. But you can see from the sampled sky colour (pushed to 100% brightness and 100% saturation) that a richer sky colour can be easily attained. This version was also converted in Photo Ninja. The preceding Spectralon WB was again applied to the file. Then I added a Nikon D610 visible color profile made in sunlight for my converted D610. The red foliage shifts a few degrees more. And the sky colour moves also - away from cyan towards blue. Combining a standard WB with a colour profile is another legitimate approach for standardization of false colour results, when desired. Just Playing Around I wondered what would happen if I photographed a Color Checker Card under the Hrommagicus Filter and used it to create a Hrommagicus false-colour profile. Mind you now, this makes absolutely no sense. I just thought it would be fun! The result produced a very rich, deep colours for the test scene. The CC Card is shown in its raw colours first. Here is the profiling step in Photo Ninja. This is the Hrommagicus false-colour profile applied to the CC Card photo. [side Note: This photo also illustrates why we do NOT use a visible colour card for white balance under our UV or IR or other filters. The Spectralon white balance was applied to this photo, but you can see that the top row of visible neutral patches are not at all neutral because the CC Card is designed for visible reflectivity only.] Now the Hrommagicus false-colour profile is applied to the test scene. This is not the Aerochrome look, but it is quite beautiful.