MAGNAchrom Launches!

[Kirk Keyes]

Overall nicely done.

But I don't get the point of page 6 (Genesis 1: something). At least tell us what Zone He placed the light on when he separated it from the darkness...

[MJSfoto1956]

Overall nicely done.

But I don't get the point of page 6 (Genesis 1: something). At least tell us what Zone He placed the light on when he separated it from the darkness...

Who am I to guess what His intention was!?

[Kirk Keyes]

Your description of how IR photography works is incorect - see page 55.

"Trees and other types of foliage are particulary good candidates for infrared; they are alive and readily absorb heat energy from the sun. When that energy is released, it shows up in the image lighter than the surrounding areas."

For the kind of infrared photography we are talking about here, it does not record light at the wavelengths that we commonly refer to as "heat". At least not unless the object is quite hot -much more than everyday objects, especially one that are still alive. You need thermographic imaging for that.

My understanding is that the Better Light backs are sensitive out to about 900 nm. This range comprises what is typically called "Near IR". Room temperature items, do emit infrared radiation, but this radiation is often called "Long IR" and is in the 8,000 to 12,000 nm region. This is far outside the range of infrared films or the Better Light back.

Since we've determined that "heat", absorbed or reflected, has nothing to do with infrared photography, you might want to update the article (and the one at the Better Light web site) to reflect the real cause of this phenomena:

It;s the simple fact that green foliage reflects near infrared light very strongly. While the tissue of foliage internally scatters near IR that is absorbed by the foliage, it's chlorophyll contained in green foliage that is very reflective to near IR. (http://msp.rmit.edu.au/Article_03/02.html) This means that much of the near IR light that falls on the foliage is reflected back out of it.

When you talk about "energy being released", you may be confusing this with how phosphorescence or fluoresence works, as these processes both absorb light from a lower wavelength, and then reemit it at a higher wavelength. (The difference between them is how long the energy is retained before it is reemitted.) Like a fluorescent poster under a black light - the UV light (less than 400 nm) is abosrbed by the paint, and then the energy is retained very, very briefly for flourescence, and it is reemitted at a longer wavelength, this time in the visible range of 400-700 nm to create that far-out poster of Jimi. While Chlorophyll does fluoresce slightly, it's not really visible in daylight and will not be recorded by IR film or a scanning back like the Better Light.

Anyway - nice magazine - and keep up the work.

Kirk

PS - how about some articles on people that shoot film and not expensive scanning backs.

[MJSfoto1956]

how about some articles on people that shoot film and not expensive scanning backs.

Thanx for the feedback Kirk. Yes of course, every mention of infrared should ideally be replaced with "near infrared" -- look for an update in the next build.

As for film, the second issue of MAGNAchrom is devoted to analog processes: A stunning porfolio and interview of large format color neg work from a long time APUG member, a darkroom methodology article, an apples-to-apples print comparison of all digital vs all analog prints (unlike the tainted results from Michael Reichman et al), a film-based medium format camera review, etc.

Keep the comments coming!