Rollie IR - Kodak #88A or Heliopan RG715

[Jeff Canes]

I have a few 120 rolls of Rollei IR, the spec sheet recommends 400iso without a filter and 25iso with either the Kodak #88A or Heliopan RG715, big difference, I cannot find either of those filter in any size, did find IR filter but none are labeled as 88A or RG715 are they the same, would a 4x ND work, the last problem is the camera will be either a Rollie TRL or Hassy, so I will like shot out with the filter first

 

[Alpha]

The 88A and RG715 are opaque filters, and their spectral sensitivity is closest to an 89B.

 

[Helen B]

From a previous post of mine:

Here, for reference, are the 50% transmission wavelengths for some common filters, to the nearest 5 nm. Heliopan filters are given their Schott RG numbers, which correspond to the 50% transmission wavelength.

Wratten # 25 (Old designation: A): 600 nm
Wratten # 29 (Old designation: F): 620 nm
B+W 091 (Schott RG630): 630 nm
B+W 092 (Schott RG695): 695 nm
Wratten # 89B: 715 nm
Hoya R72: 720 nm
Wratten # 88A: 745 nm
Wratten # 87: 795 nm
B+W 093 (Schott RG830): 830 nm
Wratten 87C: 850 nm

Best,
Helen

Edit, when I wasn't in such a rush:
A 4x ND will not work as well. Many ND filters cut infrared less than they cut light, so they can be used to alter the balance between infrared and light, but it depends a lot on the type of ND filter (there are dye filters and carbon particle filters for use in the image path, and silver particle filters intended for non-imaging use - all of which have different spectral properties) and the effect is nowhere near as drastic as true IR-pass filters.

It's going to be a lot easier to use your TLR than the Hssy, because you won't be looking through the filtered lens. You could use polyester or gelatin filter material cut into a circle and held in place by a normal filter. If you stick to small apertures you could also put the polyester of gelatin filter behind the lens, or in the case of the Hassy even try to fix it in front of the film, behind the mirror. Scotch ATG tape ('snot tape') is useful for this kind of thing.

Filters behind the lens affect the position of the plane of focus, but only by an amount roughly equal to a third of the thickness of the filter. In the case of a Wratten gelatin filter the thickness is about 0.3 mm, or 0.1 mm focus shift.

 

[Jeff Canes]

Found a Lee 87C gelatin/polyester at Freestyle, hopefully I can get that to work without to much trouble