Changes in latitudes, changes in IR exposure?
Been shooting some Maco 820, and now Kodak HIE, so I have these (sorta) figured out as far as metering and development. But I'm up here in the Great Northwest, and I'm going to Tampa FL next week with some HIE. I assume being more equatorial means more IR, but about how much? Half stop? Full stop? Is this even something to worry about? Thanks, ya'll.
The sun is the sun. I wouldn't worry about it too much. The thing that changes, and perhaps more so throughout the day, is of the light measured, how much of it is IR. As the sun rises and sets, the amount of IR that makes up the total light can change due to the atmosphere.
As you change latitude, I wouldn't think that it changes all that much.
I live at 38 degrees latitude and what works for me here with Kodak high Speed IR film, is different when I head closer to, or further away from the equator.
Using a black infrared filter
Clear sun summer 1/125 f16
Clear sun winter 1/125 f11
Cloudy bright 1/60 f11
Overcast 1/30 f11
I don't meter at all, I use these figures and I get very, very good negatives.
D76 neat 11 minutes @ 20C
If you are using a red filter the film is getting about a stop more light, so you need to change the settings to:-
Clear sun summer 1/250 f16
Clear sun winter 1/125 f11
Cloudy bright 1/125 f11
Overcast 1/60 f11
Keeping the aperture smaller than f8 is a great help in obtaining reasonably good focus.
I use mainly my 35, 28 and 24mm lenses with IR film.
When I visited Germany and used this film at 48 degrees latitude in Stuttgart I gave the film about 1/2 a stop more as a test, developed the film and this was about right.
In my own country I have been as close as 20 degrees from the equator and I gave the film 1/2 a stop less which is close to what is required.
I assume that whatever the latitude of Rochester is would be the latitude that most tests of this film has been done at and which most recommendations would be based on.
One interesting thing that you can do if you have a genuine IR filter is this. Take the filter off the camera, hold it between your thumb and forefinger, then using both hands and one eye, hold the filter so you block out all light except that coming through the IR filter. You will be able to see what IR rays are around. You'll be amazed at some of the scenes that have virtually no IR rays whilst others are overloaded with IR rays.
Shooting with IR film is terrific because you don't have to carry a meter, just pull out the chart and set your camera then fire away. The downside is that you have to have a black room or cavity, to change film.
Hey Mick, that's good stuff. Thank you. Going by the Kodak manual, I'm metering about 1/125 at f16 in bright sun here near the Canadian border. That's with a red 29. Robert, is IR transmission higher at low sun angles?
Ah, I'm asking q's about light that I cannot see, while I don't fully understand that light that I can!
Ritch, my experience is that the amount of IR light is dependent pretty much, on the clarity of the atmosphere.
If you are closer to the equator the sunlight is coming in slightly straighter, therefore stronger.
If there are clouds or dirty atmosphere, then less IR light gets through.
You will have a far better idea of how much IR light is around if you have an IR filter and use it to look through.
You could also do a search on this forum for the subject, there have been previous discussions regarding IR film.
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Infrared doesn't change much with latitude or time of day. Nowhere near as much as UV, at least!
It's easy to get overexposed IR film when sunset is coming up if you meter without the filter and compensate, since visible light changes a lot more than IR.
-- Ole Tjugen, Luddite Elitist