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Can an Ra be used for infra-red landscape photography?

Started Sep 13, 2020 | Discussions thread
Barry Pearson
OP Barry Pearson Veteran Member • Posts: 9,625
Re: Can an Ra be used for infra-red landscape photography?

Barry Pearson wrote:

klausd wrote:

No. The Ra is just enhaned until the Ha line. But IR is still cut. It would look similar to the Baader line of the following. (Canon is non modified, Baader modified like the Ra)

https://s12.directupload.net/images/200913/wibcf977.png

I now accept that an Ra wouldn't have a full IR spectrum, for the reasons you identify.

But would it have significantly more of the spectrum than the R?

I've just put a Hoya R72 infra-red filter on my RF 70-200mm f/2.8 lens on my (unmodified!) R. And shot (hand-held!) some trees, in and around my garden.

These are the results after significant (minutes!) work in Photoshop.
(No cropping, though).
There is some IR remaining after the R72.
(I realise the R72 probably isn't a perfect visible-light filter).

The R72 filter does appear to be a near-perfect filter.
See Hoya diagram in red below.

Its cut-off excludes visibility of the H-alpha line.
So my Canon R (not Ra) must be accepting infra-red light well beyond the H-alpha line.

Since my Canon R is doing that, what is the upper-spectrum-limit of the Ra?
Does the Ra simply have a very narrow pass around H-alpha?
Or does its variation from the R extend well beyond the R's own limit?

In other words:
Would the Ra make a good camera for infra-red landscape photography?

 Barry Pearson's gear list:Barry Pearson's gear list
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