I've got an NII and IR72 filter; if it's any help I could point my camera out the window now and take a meter reading with and without the filter, though the weather is terrible so I don't know how much actual IR light is about.
I've got an NII and IR72 filter; if it's any help I could point my camera out the window now and take a meter reading with and without the filter, though the weather is terrible so I don't know how much actual IR light is about.I wonder how we find out what the P65N or even I suspect the older P645 in-camera meter is in terms of the graphs. Do the graphs indicate that any of the three sets of spectral sensitivities will do the job of giving the four stops required for extended red sensitivity films?
You would also think that such in-camera meters would not be confined to Pentax and thus you'd expect other camera users to report that R72 give them the right the exposure as well. Maybe they just have bothered to report this. The problem is that we get almost no threads which report good news in an exchange of information. By this I mean most users who find that that there is no problem with their in-camera meters for IR photography are unlikely to share this information. We tend to be a "problem" forum only and any exchange of information stems for a problem not a desire to exchange information for its own sake
Anyway there are probably too few of us here on Photrio who have P645n or P645s and a R72 filter to test and report on this but it would certainly be helpful if those who can report do so
Unfortunately as I reported i do not have a R72 to test.
pentaxuser
Thanks Paul.That's a great offer as there are I suspect do few of us here with both any of the combos of the P645 and the more info the better but don't worry for a few days until the weather turns reasonable again. Where I live I am busy building an arkI've got an NII and IR72 filter; if it's any help I could point my camera out the window now and take a meter reading with and without the filter, though the weather is terrible so I don't know how much actual IR light is about.
One wonders why they aren’t just marketed as Agfa film?Aviphot Pan 200 seems to be a current product according to Agfa's website. Over the years, Rollei's repurposed films from Agfa's stocks may have changed. Aviphot Pan 400 might have been used in the past, but it's no longer available, so Rollei IR could have been the 400 variant, whereas today it's converted from the 200. Generally speaking, Maco aren't very upfront about the source of their films, but nevertheless, I'm glad that they make the effort to make some interesting aerial films available to us. And yes, all repurposed Agfa film stocks with the clear polyester base make spectacular slides. They also dry dead flat, which is another bonus.
Thought I might as well just try it, despite the weather. Ok, this is what I got: pointed camera at grass that was lit by a brief appearance of the sun between clouds, aperture set to f11. Unfiltered reading was 1/250, filtered reading was 1/10. So what's that, a 4 1/2 stop difference? Hope that's of some use.Thanks Paul.That's a great offer as there are I suspect do few of us here with both any of the combos of the P645 and the more info the better but don't worry for a few days until the weather turns reasonable again. Where I live I am busy building an ark
pentaxuser
Thanks Paul. Can you send that brief spell of sunshine towards me now its done its job ?Thought I might as well just try it, despite the weather. Ok, this is what I got: pointed camera at grass that was lit by a brief appearance of the sun between clouds, aperture set to f11. Unfiltered reading was 1/250, filtered reading was 1/10. So what's that, a 4 1/2 stop difference? Hope that's of some use.
Yeah, it really surprised me to get that reading tbh. And the 4 1/2 stops overexposure ties in with when I shot 2 rolls of Ilford SFX200 a couple of years ago and manually set 4 stops over what the non filtered reading was before attaching the IR72 filter. I've definitely learned something new today cos I'd never have considered shooting the films taking the readings with the filter in place.Thanks Paul. Can you send that brief spell of sunshine towards me now its done its job ?
While 2 swallows( yours and fs999) do not make a summer. It is pointing towards the P645Nii and I think this probably includes the P645 and P645N all having in-camera meters that do meter correctly for an IR filter
pentaxuser
Yes I may be premature in saying this but it looks as if you, I and fs999 and indeed anyone else fortunate to own one on these three models have cameras that meter correctly with an IR filter. Sounds like the P645 and both Ns had a feature that maybe few other cameras have.Yeah, it really surprised me to get that reading tbh. And the 4 1/2 stops overexposure ties in with when I shot 2 rolls of Ilford SFX200 a couple of years ago and manually set 4 stops over what the non filtered reading was before attaching the IR72 filter. I've definitely learned something new today
In those particular conditionsYes I may be premature in saying this but it looks as if you, I and fs999 and indeed anyone else fortunate to own one on these three models have cameras that meter correctly with an IR filter.
I know the Agfa name has be whored out and everybody and their father has had their way with it (same with Rollei), but it’s still weird, that what is arguably the last real part of what could really be called the original Agfa, can not put their own name on the film.@Helge Maco may not have the right to sell Agfa films as Agfa.
I haven't read fs999's post, but today was really cloudy (the horrible grey kind, not the summery fluffy white ones) and I took my readings as the sun briefly shone through a gap.Matt I can'be sure but I strongly suspect that Paul's light conditions today in the U.K were likely to be quite different from those experienced by fs999
pentaxuser
I'm sure.Matt I can'be sure but I strongly suspect that Paul's light conditions today in the U.K were likely to be quite different from those experienced by fs999
pentaxuser
HIE had quite a different spectral curve (rising and plateauing between 750 and 850).Photographic filters are commonly specified in terms of where they hit 50% of their peak transmission, so a Hoya-type R72 filter might have 50% transmission around 720nm, while that 87 filter has a peak transmission around 90%, and hits 45% at around 800 nm. While that filter transmits some light at say 710-720 nm, it's not very much. and it would probably take a really long exposure with an extended-red sensitivity film like the current Rollei or Ilford films.
For scientific purposes the tail of the transmission curve sometimes matters, so filter manufacturers may tell you "blocks all light above XXX nm," but that may be the 1-5% point on the transmission curve, not the half-power wavelength.
If you're doing pictorial work the exact transmission curve isn't super critical. I have had good luck with digital IR and cheap 720 or 760 nm import filters bought on ebay. These are nearly opaque to the eye, and I don't have an IR modified camera so I have to do long exposures of ~ 0.5 sec. When I used Kodak High Speed IR back in the 90s and it was much less easy to find IR filters, I used a plain 25 red filter and could handhold the camera, and get a strong "IR" effect on a clear, low-humidity day.
Understanding the sources of red/IR light and the weather is important, you can't just take a IR film out on a hazy day and expect to get dramatic black skies.
Photographic filters are commonly specified in terms of where they hit 50% of their peak transmission, so a Hoya-type R72 filter might have 50% transmission around 720nm, while that 87 filter has a peak transmission around 90%, and hits 45% at around 800 nm. While that filter transmits some light at say 710-720 nm, it's not very much. and it would probably take a really long exposure with an extended-red sensitivity film like the current Rollei or Ilford films.
For scientific purposes the tail of the transmission curve sometimes matters, so filter manufacturers may tell you "blocks all light above XXX nm," but that may be the 1-5% point on the transmission curve, not the half-power wavelength.
If you're doing pictorial work the exact transmission curve isn't super critical. I have had good luck with digital IR and cheap 720 or 760 nm import filters bought on ebay. These are nearly opaque to the eye, and I don't have an IR modified camera so I have to do long exposures of ~ 0.5 sec. When I used Kodak High Speed IR back in the 90s and it was much less easy to find IR filters, I used a plain 25 red filter and could handhold the camera, and get a strong "IR" effect on a clear, low-humidity day.
Understanding the sources of red/IR light and the weather is important, you can't just take a IR film out on a hazy day and expect to get dramatic black skies.
I used to joke that I is an engineer. I guess I can also joke that IR a photographer.
HIE had quite a different spectral curve (rising and plateauing between 750 and 850).
No analog filter has an absolute cutoff, but judging from the datasheet, the Hoya R72 has a pretty abrupt transmission onset.
Guess I’ll just go with a Zomei filter.
I’d still like some kind of gel or resin (with 720nm pass) that I’d be able to cut and shape to fit in filter holder for folder cameras and flash, that isn’t worth it’s weight in gold.
Yeah, I know. I don’t want to shoot digital.Very nicely summarized in layman terms. Thank you.
One of my areas of expertise is an IR systems engineer. And I can ever spell it.
All digital cameras come with a built in filter [called a "hot filter"] which removes IR light. Digital cameras can be modified by having the built-in IF filter removed thus making a digital camera that takes IR photographs.
Yeah, know. I don’t want to shoot digital.
This thread is about IR or NIR film.
It’s fine to use digital as an example, but I believe we are all familiar with it.
Film still retains many of its advantages here, even if the sensitivity and spectrum of current film leaves something to be desired.
Why do you assume my age?Life is just so much better with film. Too bad the young waste their youth with digital. Sad. So sad. So very very sad.
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