Rollei RPX25 extended red sensitivity example

[lassethomas]

I'm in the process of developing sheets from this summer.
I read that Rollei RPX25 had extended red sensitivity, but never thought more about it.
But then I shot some subjects on my trip to the mountains on both RPX25 and Fomapan 400 or HP5+.
And the difference is obvious.
And interesting for the different creative options it opens up.

So I thought I'd share.

207084
RPX25

207085
Fomapan400

Same setup on my Chamonix 45H-1 with red filter. Both shoot with a few minutes in-between. Developed in Xtol 1+1.

[Jim Noel]

In this case, I prefer the Fomapan.

[Kiwi7475]

This is interesting because at least per the respective specs, the difference is not huge, I mean, Foma starts rolling off at 680nm and Rpx at 700nm, both about as sharply.
Of course by using a red filter you effectively amplify this because you're only letting red go through (I assume you mean a #25, which usually passes above ~580nm, of course the number depends on the brand, etc.). So if the incident light was spectrally uniformly distributed, then Rpx would get 20% more "light" in.

It's just interesting how much difference there is in the trees. I am not an expert in spectrometry but I thought chlorophyll absorbs red light (creating a low right around the ~680 nm in fact), but probably it also depends on the type and state of vegetation...

All this assumes that film linearity, development process and exposure have no significant say in the difference.

[lassethomas]

In this case, I prefer the Fomapan.

Me too actually :)

[lassethomas]

This is interesting because at least per the respective specs, the difference is not huge, I mean, Foma starts rolling off at 680nm and Rpx at 700nm, both about as sharply.
Of course by using a red filter you effectively amplify this because you're only letting red go through (I assume you mean a #25, which usually passes above ~580nm, of course the number depends on the brand, etc.). So if the incident light was spectrally uniformly distributed, then Rpx would get 20% more "light" in.

It's just interesting how much difference there is in the trees. I am not an expert in spectrometry but I thought chlorophyll absorbs red light (creating a low right around the ~680 nm in fact), but probably it also depends on the type and state of vegetation...

All this assumes that film linearity, development process and exposure have no significant say in the difference.

Well, the Rpx rolls off from 700 to 750, and Foma from 680 to 690 so there is a definite difference (a bit uncertain in comparison since the scales are not equal). And as you say the red filter would only amplify this.
I have another example that show the same thing. Sunny foliage with large difference i tone.

I'm temped to try a few sheets with a R72 infrared filter. It should be possible to get an exposure at least.

[Dugan]

I prefer the Foma image, but it is good to have that extended red sensitivity option available.
Thanks for doing the side-by-side test, that's the best way for a fair comparison.

[Dugan]

I'm temped to try a few sheets with a R72 infrared filter. It should be possible to get an exposure at least.

Please post your results, that would be interesting & useful info!

[revdoc]

RPX25 is Agfa Aviphot 80, the same film as Retro 80s. An R72 filter will produce pretty good IR images.

[lassethomas]

Please post your results, that would be interesting & useful info!

If I do, I will!.

Have to remember on a really sunny day.

[Kiwi7475]

If I do, I will!.

Have to remember on a really sunny day.

If you’re shooting with the Chamonix be mindful that at least a few years back their bellows were not IR proof.

This may have changed or not, since then, I don’t know.

Just mentioning this is if you haven’t shot IR with it before. There are solutions out there if you search, like covering with some specific dark cloths over the bellows, etc.

[revdoc]

This shows what the film can do with an R72 filter. (Apologies for posting a 35mm image, but it's all I have for this film.)

This was at 80 ISO, but 50 ISO is closer to the mark.

207105

[Ironage]

Very dramatic!


Sent from my iPad using Tapatalk

[revdoc]

Thanks! I got lucky with a very clear sky that day.