efke 820c and IR filter

[coigach]

Hello,

I plan on using Efke 820c with my Pentax 67II in-camera meter and a Heliopan RG695 (equivalent to wratten 89b or Hoya 72) filter. Will use this setup with tripod for landscape shots in bright sun. I think the filter should allow enough light through to allow me to meter in-camera in bright sun.

The Pentax 67 lenses have an IR mark on them. Should I focus using these to take account of IR wavelength or should I use my 'standard' hyperfocal focussing for the aperture I'm using? Am not sure what wavelength the Pentax IR lens markings measure. Help! :confused:

Cheers,
Gavin

 

[Uhner]

Have you read this document? http://www.mahn.net/TA820ce.pdf

 

[coigach]

Thanks for this, very helpful.

 

[Travis Nunn]

This shot was taken with Efke IR and a 89b filter on my RB67... (there was a url link here which no longer exists)

I metered through the lens and did not adjust focus.

 

[ntenny]

I've shot quite a bit of Efke 820c through the equivalent filter and never adjusted the focus. I think it's more of an issue with the far-IR frequencies to which HIE is sensitive.

The one exception was the roll I shot through a Rolleinar, which resulted in some of the worst photos ever. The problem may have been that the focus adjustment became critical at macro distances (but it could have been other things too).

You could shoot a test roll with the same exposures twice, once with normal focus and once adjusted to the mark, and see what you get.

-NT

 

[Toffle]

The one exception was the roll I shot through a Rolleinar, which resulted in some of the worst photos ever. The problem may have been that the focus adjustment became critical at macro distances (but it could have been other things too).

You could shoot a test roll with the same exposures twice, once with normal focus and once adjusted to the mark, and see what you get.

-NT

I've just been experimenting with this over the past week. I took a few shots on a roll of SFX using a Rolleinar 2. While the rest of the roll is accurately in focus, the close-ups are definitely outside of the DOF/COF. As was suggested to me, a simple but fairly accurate test would be to take a shot at a known distance, with a ruler in the frame. By comparing the portion of the ruler that is in focus with the subject that was supposed to be in focus, you should have a pretty good idea how to adjust the focus for future work.

Cheers,

 

[Gary Holliday]

I've shot quite a bit of Efke 820c through the equivalent filter and never adjusted the focus. I think it's more of an issue with the far-IR frequencies to which HIE is sensitive.



-NT

If you are going to use an IR filter I would always adjust the focus. Here is a link with some focus tests for Rollei IR 400 which isn't particulary strong in IR sensitivity.

The filter is an R72.

http://www.digitaltruth.com/products/product_tests/infrared_film_007.php