Sigma Aerochrome via Red & Green filters

[Christoph]

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..

[OlDoinyo]

There is, of course, the venerable two-exposure method with a Sigma:

 

 

In this case I used an SD14. The internal hot-mirror was taken out and the IR frame was shot with a black-IR filter. Rather than bothering to put the camera's own hot-mirror back in, I just slapped a deconverting filter on the lens for the visible exposure. The workup to a final IRG image is simple and presumably self-evident; this method produces fairly accurate IRG images although it is on the clunky side.

[colinbm]

All good & interesting Christoph

Glad to see you experimenting.

I gave the term "Rich" Full spectrum to describe when a CPL is added to the full spectrum Sigma camera with the hot mirror removed.

Different brands of CPL give varying results too.

Cheers

Col

[Andrea B.]

Good experiments, Christoph. Thanks for posting. Let's see what you get with good sunlight, OK?

[Christoph]

Here are some test shots with the red filter (on SD1), with CWB on white card (without filter on) and the settings in SPP which produce this result:

 

 

 

 

[Christoph]

"Rich" Full spectrum (above) vs Red filter:

 

 

[Christoph]

"Rich" Full spectrum (above, cloudy) vs red filter (full sunlight):

 

 

[colinbm]

Are you using a CPL with these ?

[Christoph]

Yes

[colinbm]

Which brand please ?

[Christoph]

Hoya CIR-PL Slim

[colinbm]

Good, keep it up.

[Christoph]

Ok, so here are some more... the thing is: WB/Color adjustments are tricky... one way to really get blue skies is to go into the "red" areas of your color matrix... how to get there? Trying. I know it sounds silly... Choose very dark green areas... if someone knows how to export the profile, I'll be happy to share it here... there must be a repeatable workflow that does make sense... any suggestions are welcome...

 

 

 

 

 

[colinbm]

Looks really good

[Christoph]

Thanks!

[colinbm]

I got one of my favorite CPL's out today for a play, after having a rest from photography for the past few years & found that it has started to de-laminate....:-(

[Christoph]

Red filter also allows yellow vegetation via channel mixer in Photoshop

 

 

 

[dabateman]

I really like those yellows.

 

I will have to play around with my SD14 more.

[Christoph]

These are shots from today (around noon) which were processed via the method described above. The only difference: I used a Hoya Red 25A instead of a Tiffen Red 25A. The results are (in my opinion) exactly the same. I also used a Hoya CPL. Please note that no additional color optimization was done, just the raw SPP workflow plus further white balancing in Photoshop raw converter. I'm very happy with the result. I really achieved what I wanted: pure red vegetation and dark blueish skies...

 

 

[colinbm]

Very striking Christoph

[Andy Perrin]

Yes, I love the skies here.

[Christoph]

White vegetation, the classic (720nm) look is absolutely possible with a Sigma Foveon sensor. Here's the proof. I used a red filter, processed the image in SPP, then channel mix in Photoshop...

 

[Christoph]

Here's another one with sky...

[colinbm]

Looks great Christoph

[Christoph]

Here's an interesting filter combination: Hoya Green X1 and Tiffen Yellow 8 - will give you blue skies, some great contrasts and a wide palette of red/magenta/yellow tones...