Digital IR

[Audii-Dudii]

I can't offer any higher praise than to say this is a photo I would have taken myself if I had the opportunity ... well done. 8^)

[Ari]

High praise, indeed!
Thanks, Jeff.

[alan_b]

If you are using the IR Chrome filter on the lens with a full spectrum camera is it correct to assume that this is what you see in RAW? If so, that would make it a kind of true color, not the "faux" color usually seen with IR produced by channel swapping and such?

Yes, that's correct. Apart from basic white balancing, color/curves adjustments, color channels are all in the "right" place out of camera.

The main difficulty is that since the filter passes IR and some visible light, it's challenging to find lenses where these two frequency ranges focus close enough together. I haven't found a wide angle lens that performs well enough. (Although my search has been limited to the ones I have on my shelf.) Is there such thing as a wide angle superachromat? I've settled on using an old Nikkor 55/3.5 micro for being close enough at f/11 and having good manual focus feel, stitching for wider views. I'd love to find a usable ~35mm.

[jon.oman]

The main difficulty is that since the filter passes IR and some visible light, it's challenging to find lenses where these two frequency ranges focus close enough together.

Until you mentioned that, I did not realize that this would be a problem! I guess older uncorrected lenses would work better with this filter?

[jon.oman]

Off the top of my head, I couldn't remember, so I went back to the raw files and was surprised to see that I actually photographed it both ways: horizontally and vertically!

Even worse, I photographed each panel seven times, so I could median-blend them into a single photo and reduce the noise level by 2.64 dB. Then I merged all five of the blended panels into a single pano using Photoshop's merge tool.

But to answer your question, this version was made using the horizontally oriented photos and according to RawTherapee, I didn't process the vertically oriented photos. Maybe I should do that now, because to my eyes, the sky is as interesting as the rest of the scene!

I learn something every day! Until now, I had never heard of 'median-blend'. Had to look that one up. Seems to work very well, if rather labor intensive. I also see you can eliminate transient subjects from the images as well. Great way to get rid of the tourists!

[jon.oman]

Very nice image Ari!

[Audii-Dudii]

I learn something every day! Until now, I had never heard of 'median-blend'. Had to look that one up. Seems to work very well, if rather labor intensive. I also see you can eliminate transient subjects from the images as well. Great way to get rid of the tourists!

Median-blending is an essential part of my nighttime photography workflow, because the extra headroom it provides allows me to tease more details from the shadow areas without having to increase exposure in the highlight areas.

It also works very well for daylight IR photography, too. Because it allows me to slightly but meaningfully expand the DR capability of the APS-C format camera I use to better capture the wide range of contrast present when photographing scenes under the midday desert sun.

And not only does it get rid of tourists, but it also removes light trails from airplanes, planets, and stars in the sky and often adds a nice bit of motion blur to tree leaves and clouds, too.

While it does add time and/or complication to my photographic process, it's nevertheless an indispensable tool in my chest...

[Ari]

Until you mentioned that, I did not realize that this would be a problem! I guess older uncorrected lenses would work better with this filter?

Thanks for your kind comment, Jon.
About your focusing issue, Alan, would it be eliminated if you use a mirrorless camera instead of your DSLR?

[alan_b]

I guess older uncorrected lenses would work better with this filter?

I think it's more of a design decision, this use being outside of it's intended application. Newer, more highly corrected lenses might work better, assuming they don't fail on other characteristics (hot spot)?

I chose this lens (Nikkor 55/3.5 micro pre-ai) because:
a) I already had it, b) no hot spot, c) good enough ir-visible f/11 focus at distance, and d) better manual focus than other AF lenses I have.

About your focusing issue, Alan, would it be eliminated if you use a mirrorless camera instead of your DSLR?

No, it's a lens property - how many wavelengths it was designed it to focus simultaneously.

Here's a Wikipedia diagram: https://en.wikipedia.org/wiki/Superachromat

I'd be curious to see how the new Voigtlander 35mm APO-Lanthar works, but they won't work on a Nikon DSLR (Sony E mount).

[Peter De Smidt]

We had some nice clouds today, and so I went to a high location and took a bunch of photos with many of my lenses, both regular color photos and IR ones. I did a few things different. First, I changed the ISO from my normal 100 to 800, and I switched the picture mode to 'monchrome'. The raw files are still in color, but the image on the rear LCD becomes bw. These changes made my exposure times much faster, and the image on the rear screen was easier to view in bw instead of in red. The files did have more noise than my ISO 100 ones, but it wasn't too bad.