Adjustable IR filters

[Sirius Glass]

Thank you for informing us about the dreaded X!

 

[Andrew O'Neill]

Thank you for informing us about the dreaded X!

I'm wondering now if it's brand specific... I got a comment from a subscriber to my channel, and he said that he has not witnessed the dreaded X with two different brands... Of course you know that I will have to investigate this further!

 

[MCB18]

need to load in the dark

I’m so glad I don’t need to worry about this with rollfilm to an extent, I just load Aviphot in my shadow if I’m outside. Haven’t had any issues.

 

[AnselMortensen]

I just processed a test roll of CatLabs 320 (Aviphot 200) 120 that I shot under mixed bright sunlight with a 760nm filter.
I processed the film in Rodinal 1+50, 15 min @ 68°F and got excellent exposure at 1 second @ f8.
There's a bit more room for overexposure for even stronger Wood effect...I'd consider adding another f-stop of exposure and reducing development time to drop the contrast.
Single-band IR filters are the way to go.

 

[Andrew O'Neill]

I just processed a test roll of CatLabs 320 (Aviphot 200) 120 that I shot under mixed bright sunlight with a 760nm filter.
I processed the film in Rodinal 1+50, 15 min @ 68°F and got excellent exposure at 1 second @ f8.
There's a bit more room for overexposure for even stronger Wood effect...I'd consider adding another f-stop of exposure and reducing development time to drop the contrast.
Single-band IR filters are the way to go.

Did you shoot at box speed? How many stops did you give for the 760 filter?

 

[AnselMortensen]

Did you shoot at box speed? How many stops did you give for the 760 filter?

I had previously shot Aviphot 200 with a 720nm filter and come up with an acceptable exposure time of 1 sec @ f16...so EI of 1.
For the lens I used today, only a 760nm filter was available in that size, so I needed to re-test.
I did a bracketing sequence, and
I found that the 760nm filter required 2 more stops of exposure than with a 720nm filter.
This test was all done without metering, just based on experience & sunny 16.
This will be useful for me, since I have some Avi200 on the way in 220, 4x5 & 5x7.

 

[Ivo Stunga]

Please do report how that filter works, because my gut feeling tells me it's fake Chinese dreams.

I don't think it's necessary to disparage a country or people over a filter

China is known to sell non-viable, fake products - they can stop doing so if the opinion of the world matters to them.

Checked out a variable IR filter.. the FOTGA.

Maybe not a disparage, but educated "lol no thanks commie" is warranted, me myself being born in a ex-communist country, having evolved nose for commie bullshit I guess.

 

[Ivo Stunga]

Because no filter is perfect it still makes a lot of sense to use a pol filter with a R72 filter.

Well, when I do, I must bracket some more, it's an additional variable one can do without and tends to introduce even more crushing contrast that's not always beneficial, especially with current IR stock.

I have tested CPL after IR filter and wonder if the other way around wouldn't be the better/logical. Cannot test this due to the sizes of filters I have.

 

[Ivo Stunga]

Hmmm, OK. But I'm pretty certain IR films of yore were responsive out to 800 or even further, the late lamented Efke IR820 for example; Kodak HIE went to nearly 900. Most of the stuff today appears to be already running out of sensitivity at 720. I found about six additional stops exposure needed to go from a 720 to a 760 filter with Rollei Infrared 400 as an example.

I guess it's no point to be lamenting films of yesterday. I would therefore embrace the new stuff and work it.
If I shoot a scene with Aviphot 80 and no filter, I get low latitude high contrast shot. If I put IR 715 filter on, the same scene renders completely differently: haze is cut, skies turn dark and one can see deeper in forest/foliage, differentiate between various foliage and trees, them reflecting IR light at various intensities, IR being used to interperet plant health.

Therefore it's Infrared photography, the data in the filtered shot is physically different/records effects of different wavelength. Sure, sad those 30+ IR films of yesterday are gone, but hey - there's stiill something to play around with.
I'd agree that taking digital shot and converting it to "Infrared" in a software is no IR photography at all, because it's just tone remapping and fakery. But this is different.

Current IR stock is especially fun after removal of AH layers and sticking white paper to the film pressure plate to aid halation - then it sings tune that's quite similar enough to that of the yesterday, and "increases" speed too!

 

[Andrew O'Neill]

I had previously shot Aviphot 200 with a 720nm filter and come up with an acceptable exposure time of 1 sec @ f16...so EI of 1.
For the lens I used today, only a 760nm filter was available in that size, so I needed to re-test.
I did a bracketing sequence, and
I found that the 760nm filter required 2 more stops of exposure than with a 720nm filter.
This test was all done without metering, just based on experience & sunny 16.
This will be useful for me, since I have some Avi200 on the way in 220, 4x5 & 5x7.

Probably EI 1.5. I'm assuming 7 stops more exposure was given to accommodate the 760 filter. Thanks!

 

[Helge]

Well, when I do, I must bracket some more, it's an additional variable one can do without and tends to introduce even more crushing contrast that's not always beneficial, especially with current IR stock.

I have tested CPL after IR filter and wonder if the other way around wouldn't be the better/logical. Cannot test this due to the sizes of filters I have.

The order would matter very little optically. The only possible factor could be inter-filter reflection.
Practically If you need to put the pol-filter back on after direct visual confirmation, then having the pol-filter in front is the only sane choice.

Polarization normally brings down contrast if you go for taking down reflections.

IR is inherently high contrast because shade is lit by the diffuse blue in the sky, which has comparatively little IR content.
All IR film is contrasty.

You can speed the film up and bring down contrast by a minus two stop uniform preflash (not necessarily IR). It’s what HR-50 has done to it.

 

[Helge]

I guess it's no point to be lamenting films of yesterday. I would therefore embrace the new stuff and work it.
If I shoot a scene with Aviphot 80 and no filter, I get low latitude high contrast shot. If I put IR 715 filter on, the same scene renders completely differently: haze is cut, skies turn dark and one can see deeper in forest/foliage, differentiate between various foliage and trees, them reflecting IR light at various intensities, IR being used to interperet plant health.

Therefore it's Infrared photography, the data in the filtered shot is physically different/records effects of different wavelength. Sure, sad those 30+ IR films of yesterday are gone, but hey - there's stiill something to play around with.
I'd agree that taking digital shot and converting it to "Infrared" in a software is no IR photography at all, because it's just tone remapping and fakery. But this is different.

Current IR stock is especially fun after removal of AH layers and sticking white paper to the film pressure plate to aid halation - then it sings tune that's quite similar enough to that of the yesterday, and "increases" speed too!

Films of yesteryear are overrated.
The only thing that would be nice, would be the hole in the spectrum. That is, the green and lower red sensitizers omitted. That would allow not using an expensive IR filter that blocks the view on SLRs.

But it would mean no ability to scale the effect or not use IR on certain frames.

The speed of the film is in fact much the same.
Konica IR had similar speed to Aviphot.
HIE got a speedup and speedup from contrast reduction in lacking AH layer. Real speed of HIE with R72 filter is probably between EI 12 and 25.

 

[Ivo Stunga]

The order would matter very little optically. The only possible factor could be inter-filter reflection.

I was thinking possible IR transmittance issues of CPL material that would suggest selecting light polarization before slicing the spectrum cake via IR filter. But I guess this doesn't apply to NIR.

It's either my TTL metering or something, but all the CPL shots I've taken feature more contrast and err on underexposure... when going for more saturated look/dark skies. YMMV.

HIE got a speedup and speedup from contrast reduction in lacking AH layer

lol - when I remove AH layers from Aviphot 200 and 80, it "gains speed" of about 2 stops. Combine that with less frequent agitation and it's clear to me: I'd buy the version without antihalation layers so I don't have to spend half an hour removing them.

 

[BMbikerider]

(Perhaps it's my aging brain, but) At a quick look, these apparently sandwich a red filter and two polarizers and I can't quite see how the summation of a variable neutral density filter plus a low pass filter is going to move the cut-off frequency. Dunno, maybe the actual polarizers are less effective at longer wavelengths?

At any rate, it appears this topic came up in 2016, and there is an outfit that does IR conversions of digi-cams that didn't sound very enthusiastic about these filters. Of course, it's pointed out that compared with top of the line filters, they are cheap enough to experiment with.

I saw results which may or may not be similar by a fellow photographer, where he was using Tri-x coupled with a 8 times red filter and a circular polariser. The results were quite impressive and not un-similar to the old Kodak High speed infra red without the problem of what to rate the film speed at. If I recall correctly it was always exposed at 400iso and the camera's meter took care of the rest. The only discernible difference being the Kodak film 'halo' was missing.

 

[Helge]

I was thinking possible IR transmittance issues of CPL material that would suggest selecting light polarization before slicing the spectrum cake via IR filter. But I guess this doesn't apply to NIR.

It's either my TTL metering or something, but all the CPL shots I've taken feature more contrast and err on underexposure... when going for more saturated look/dark skies. YMMV.


lol - when I remove AH layers from Aviphot 200 and 80, it "gains speed" of about 2 stops. Combine that with less frequent agitation and it's clear to me: I'd buy the version without antihalation layers so I don't have to spend half an hour removing them.

CPL should be exactly the same as regular PL from an optical PoV. I never observed any difference between CPL and PL with digital IR.

What kind if camera are you using that underexposes with a CPL filter?
Regular film (non IR) can look darker in general when using a red filter, with or without a polariser, but doesn't sound like that's the issue.

 

[Ivo Stunga]

What kind if camera are you using that underexposes with a CPL filter?

OM-1n with diode adapter

 

[Helge]

OM-1n with diode adapter

I might very well be wrong, but I never trusted the electronics in Olympus SLRs.
I've had about seven through my hands and all of them has had problems with something electronic, not counting the the obvious OM-10s which are more often than not borked.
The best Olympus camera I ever used was frankly the IS-3000. What a pleasure of a machine to use. and wonderful optics.

 

[Ivo Stunga]

I might very well be wrong, but I never trusted the electronics in Olympus SLRs.
I've had about seven through my hands and all of them has had problems with something electronic, not counting the the obvious OM-10s which are more often than not borked.
The best Olympus camera I ever used was frankly the IS-3000. What a pleasure of a machine to use. and wonderful optics.

Meter is wonky at times due to funky wiring, but I can pull slides off with my OM-1n, so it isn't that bad. YMMV

And what joy it is for me to shoot it - compact, bright and large finder, ergonomic controls you can adjust without lifting camera from face + nice Zuiko glass

 

[Ivo Stunga]

The only thing that would be nice, would be the hole in the spectrum. That is, the green and lower red sensitizers omitted. That would allow not using an expensive IR filter that blocks the view on SLRs.

I'm wondering if blue wouldn't then overpower any IR response the film could provide. Because I interpret you saying that the blue sensitivity remains, but light at that frequency carries more energy.

 

[Helge]

I'm wondering if blue wouldn't then overpower any IR response the film could provide. Because I interpret you saying that the blue sensitivity remains, but light at that frequency carries more energy.

You’d use a yellow or orange filter as with Konica 750 or HIE.

 

[Sirius Glass]

You’d use a yellow or orange filter as with Konica 750 or HIE.

That is a real waste of hard to find discontinued infrared film, especially since the manufacturers' specify using any of a number of red filters. But what the heck, you know more about how to use their film than any of them did.

 

[Helge]

That is a real waste of hard to find discontinued infrared film, especially since the manufacturers' specify using any of a number of red filters. But what the heck, you know more about how to use their film than any of them did.

Read the data sheets. They suggest using weak filters. It’s “good enough” for Woods and Rayleigh black out effect.
FWIW I haven’t shot either film.

 

[Andrew O'Neill]

With HIE, a yellow Wratten #12 was enough to get Wood Effect. I shot a lot of it in 4x5 in the 90's and early 2000's. I still have a box, expired in '67, that works perfectly fine... albeit a bit of base fog, and a speed loss of three stops... not a waste of time, if you can find this film. I also shot a lot of Konica 750. If you want wood effect, a #25 will get you in the ballpark. #29 is better. 720 filter is the best. There are a lot of similarities to Rollei IR.

 

[Helge]

 

[Sirius Glass]

Read the data sheets. They suggest using weak filters. It’s “good enough” for Woods and Rayleigh black out effect.
FWIW I haven’t shot either film.

I have shot HIE with Red23, Red25, Red29 and 720 and each provides its own rendition. I have not use my stock of Konica 750 yet.