Infrared Bandshell

Nice open shadows reflecting the calm and tranquil scene. Can I ask how you arrived at 4 secs? I have no experience of LF but even with 5-6 stops extra exposure for the IR filter 4 secs seems a lot

Thanks

pentaxuser

Nice IR! That is the fanciest band shell I have seen.

pentaxuser said:

Nice open shadows reflecting the calm and tranquil scene. Can I ask how you arrived at 4 secs? I have no experience of LF but even with 5-6 stops extra exposure for the IR filter 4 secs seems a lot

Thanks

pentaxuser

Click to expand...

I got to the exposure experimentally. I'd read I needed a 7-stop filter factor with an IR filter -- thus ISO 3 on ISO 400 film. ISO 3 was way underexposed, ISO 0.75 was still a little thin. You can call it ISO 0.4 but my meter only goes to ISO 3 so I meter at that and give 3 more stops of exposure.

Rollei IR has a spectral sensitivity of 650-750 nm (larger numbers are farther into the infrared). After I bought the 88A filter I learned it blocks visible wavelengths shorter than 700 nm and allows 90% of infrared light with wavelengths of 715 nm or greater to pass through. So it's capturing the more extreme IR range of the film but is only using half that range. An 89B filter would allow more exposure but with slightly less IR effect. Still, I've got the filter and it's the one I'll use.

After buying the 88A, I found this article.

Thanks for the reply I now under stand why it was 4 secs I had no idea that even 7 stops still underexposed things as much as that. For what it is worth I have seen pictures using the Adox HR50 film and an Hoya R72 which came close to opening up shadows nearly as much as yours but at a lot higher EI

Nice architecture, composition and overall feel of the image! One tiny detail is that you may have forgotten to invert the image as the numbers on the building are reversed.

Acere said:

Nice architecture, composition and overall feel of the image! One tiny detail is that you may have forgotten to invert the image as the numbers on the building are reversed.

Click to expand...

You're right! Good catch.