Choices for IR film?

[Pentode]

I don't know. I suppose it depends on the opacity of the filter.

I think what pentaxuser was asking was what filter factor did you use for the R72 filter? I would love to know as well.

 

[MattKing]

It sounds like fs999 didn't use a filter factor but instead metered through the filter with the meter set to box speed.

 

[Pentode]

It sounds like fs999 didn't use a filter factor but instead metered through the filter with the meter set to box speed.

I suspect you're right.

 

[pentaxuser]

With R72. I used the meter of my Pentax 645N through the lens.

.

Thanks, fs999. I now understand why you cannot give an answer. I would not be able to give an answer either if it was through my lens with a filter on it. Indeed for a long time, like you, I assumed that the camera's meter would properly compensate for any filter so that I had the right exposure without bothering about filter factors

Recently after reading an article from the IlfordPhoto site about filters I began to wonder. I had also seen other articles and the general consensus of opinion was that while a low factor filter such as a yellow will give about the same exposure through the camera's meter as applying the filter factor the darker filters need more compensation than the meter says they do. So for instance it is usually advised that for a red you need to add at least one stop to the camera's meter reading. The R72 used with near infra-red films has the added complication of infra-red light

I too have a P654N and found that a red R25 on the camera gives a reading of two stops less but the filter factor for this red filter is 3 stops so according to that I need to add one stop to my exposure through the meter which is in line with the Ilford article as well. However the strange thing is that with its own near infra-red film the use of the red 25 only requires one and a half stops via the filter factor and suggests that maybe with a red filter and a SFX film the P645N 's meter gets it about right

The specification sheet on SFX does however suggest that with a R72 it is 4 stops so I doubt if the meter does give the right exposure. I have never had a R72 on my P654N but I doubt very much if the meters suddenly changes its reading by 2 more stops

What has this got to do with Rollei Retro 80S? Well it is a different film from Ilford SFX but both films' reactions to infra-red light might be be very similar and the P645N meter will clearly see the same amount of light through R72 irrespective of the film

So why is it that your shots look right and there is no sign of the shadows being underexposed as should be the case if the meter has not added an extra 2 stops. Everything looks right to me and if the shadows are underexposed then it is so slight as to be unimportant - at least to me.

Is there a way to explain this? I think there might be. In reality Retro 80S Rollei IR 400 etc are all the same film which a Aviphot 200. This has a real speed of 200 but in your case Rollei says that it is ISO 80 which is what you placed on the film speed setting. So in effect the meter reduced the exposure by say 2 stops from 80 down to 20 whereas if the real speed of the film is 200 like SFX then the application of the correct 4 stops reduces it from 200 to 12 which in fact is probably close enough to what you meter gave you to make your meter read close to the correct exposure if you use the real speed of the film Aviphot 200 and apply the filter factors

That's a long way of trying to say that in practical terms you and I, if I use my P645N or my 35 mm Pentax whose meter agrees with the P645N meter, can just use the speed on my film speed setting that Rollei says the film is and allow the meter to do the rest

pentaxuser

 

[Pentode]

So why is it that your shots look right and there is no sign of the shadows being underexposed as should be the case if the meter has not added an extra 2 stops.... ....Is there a way to explain this? I think there might be.

I think your assessment is pretty close to right. There are several factors at play: One is that different meters respond differently to the infrared spectrum; Some appear to be pretty accurate in that range (that Pentax meter, for instance) while others won't respond to IR at all. Another is that the film's sensitivity itself varies depending upon the wavelength so a film's "true" speed only applies to the film's speed as its being used. This is why a film such as IR400 can be 400 or 200 or 100 or even less depending upon how it's being used. Lastly, and seldom talked about is the fact that filter factors themselves are dependent upon wavelength. As Laurie White points out in her (excellent) book on IR photography, IR filters attenuate less and less as the wavelength gets longer. This makes perfect sense, and it seems obvious when we look at a filter's graph, but we seldom think about it in terms of real-life applications. In reality, an IR filter will have a lower filter factor when photographing scenes with more IR radiation than they will when photographing scenes with less. That means shooting in the morning or late afternoon could require a very different exposure than shooting at noon but we may not realize it unless our meter is sensitive enough to IR to recognize the difference. I'm explaining it poorly but I think you get the idea.

 

[pentaxuser]

Thanks Pentode and no, you are not explaining it poorly as far as I can see. What you said makes sense to me.

I have her book. Time I read it again

pentaxuser

 

[Athiril]

Is there a way to explain this? I think there might be. In reality Retro 80S Rollei IR 400 etc are all the same film which a Aviphot 200. This has a real speed of 200 but in your case Rollei says that it is ISO 80 which is what you placed on the film speed setting.

Ive used these films as normal films, not as IR. Rollei Retro 80S. 80S is as sharp or sharper than T-Max 100 with significantly finer grain. Retro 400S/IR 400 on the other hand has quite rough grain. I would not say they are the same film.

https://www.agfa.com/specialty-products/wp-content/uploads/sites/8/2017/06/AVIPHOT-PAN-80.pdf

 

[OrientPoint]

I've been told by multiple people who should know that they're the same film – Aviphot 200. The difference is in processing. Which makes sense I guess... pulling an ISO 200 film to 80 vs. pushing it to 400 would be expected to result in different grain.

 

[Athiril]

I've been told by multiple people who should know that they're the same film – Aviphot 200. The difference is in processing. Which makes sense I guess... pulling an ISO 200 film to 80 vs. pushing it to 400 would be expected to result in different grain.

Pulling a film, faster T-Max 100, less than 2 stops, thats normally a rough grained lower sharpness film cannot make it finer and sharper than T-Max 100. 80S is also quiet contrasty at 80S. The grain of 80S in Rodinal is finer than the grain of T-Max 100 in Xtol, and unlike other films (including T-Max 100) the graininess doesnt change a lot between Rodinal and Xtol. I have some samples here Ill get around to posting.

Also looked in Rollei's PDF, and the developing time using RLS 1+4 for 80s is 13.5 minutes for EI50 at 24c, and 400S is 1+4 for 14.5 minutes at 24c for EI200.

Also for 80S you need about +5 stops of exposure for shooting IR if I recall too.

Here is what it looks like (as a normal film), the crop is an 8000 dpi crop from a Flextight 949, it is exceptionally fine grained. This is also in Rodinal of all things. EI of 64, and it struggles with shadow detail. It isnt pulled Retro 400S, Retro 400S pulled to 64 would have more shadow detail.

 

[Sirius Glass]

I have found that I can trust the published literature as listed below:

R23 => 2 f/stops
R25 => 3 f/stops
R29 => 4 f/stops
R72 [720] => 5 f/stops​

I use Kodak HIE and Rollei IR 400 at box speed, use a light meter and then adjust for the filter and never had a problem.

 

[Paul Manuell]

To all the posters above, asking about filter factors and metering: if it helps, my working method when shooting with SFX200 (I know, not a true infrared film) was as follows:
Set camera on tripod and frame up the shot
Take meter reading with no filter in place
Screw IR72 to the lens
Manually set shutter speed to 4 stops over original reading
Take shot

This is an example of one of my shots

 

[pentaxuser]

Looks good Paul. My explanation of why fs999's exposure looks about right depends to a large extent on the allegation that Rolliei 80S is the Aviphot 200. If it isn't then i'd be interested in what it is as well as what the other Rollei films are but I cannot state for definite that it is Aviphot 200. However if we assume for a moment that it is, then fs999's reading from his P645N in-camera meter which he had set to ISO80 and allowing for the two stops that the Pentax in-camera meter shows would closely match the 4 stops required for a known similar ISO 200 film, namely SFX and does help explain why fs999's reliance on his meter took him close to the same reading that applying 4 stops to a similar near infra-red film, namely the Aviphot 200

If fs999's shots are seriously underexposed for a R72 filter then that kind of underexposure will do for me.

pentaxuser

 

[Athiril]

Can you share some examples with the Adox HR-50, I have not heard of that film yet.

HR50 is just Rollei 80s, which is Agfa AviPhot 80, but with a preflash base fog.

 

[Athiril]

Looks good Paul. My explanation of why fs999's exposure looks about right depends to a large extent on the allegation that Rolliei 80S is the Aviphot 200. If it isn't then i'd be interested in what it is as well as what the other Rollei films are but I cannot state for definite that it is Aviphot 200. However if we assume for a moment that it is, then fs999's reading from his P645N in-camera meter which he had set to ISO80 and allowing for the two stops that the Pentax in-camera meter shows would closely match the 4 stops required for a known similar ISO 200 film, namely SFX and does help explain why fs999's reliance on his meter took him close to the same reading that applying 4 stops to a similar near infra-red film, namely the Aviphot 200

If fs999's shots are seriously underexposed for a R72 filter then that kind of underexposure will do for me.

pentaxuser

EI 3-6 is 4-5 stops from ISO 80, not ISO 200.
I havent seen anyone else claim that 80s is AviPhot 200. You can see another persons finding here.
http://www.martinzimelka.com/pages/Rollei_Retro80s.htmla
also http://www.martinzimelka.com/pages/Rollei_Infrared_400.html
"The recommended EI of 25 is simply not enough, even if using highly compensating developers. The usable EI is 3 to 12, but obviously with matching developing times." (for IR 400), thats obviously past 4 stops. While 80S appears good often at EI of 6.

The films can have different IR sensitivities, its entirely possible for the 200 speed film to have lower IR sensitivity but higher overall film speed from larger grain which can put the IR sensitivity in same area as 80S. Also the fact it is appears to lose IR sensitivity "the more base fog they develop, and the less sensitive they become to IR"

 

[MattKing]

It isn't just that films have different IR sensitivities.
It is that your meters don't really read the light that the film is sensitive to (much).
Two scenes which meter the same may need different exposures, because the proportion of IR and near IR mixed into the visible light that the meter can read varies with the conditions.
Your meter reading, plus experience, informs your exposure guess.

 

[revdoc]

Just to be clear on what film is what: Rollei RPX25, Rollei Retro 80S and Adox HR50 are all Agfa Aviphot 80. The 80 refers to aerial film speed; the ISO speed is about 50 for all three.

Rollei IR is Aviphot 200, which is closer to ISO 125.

I've used all of them, except for the Adox. Generally for IR, I use an R72 filter and TTL metering on my Nikon, and so far I haven't had to think much about exposure... I just do what the meter recommends.

 

[fs999]

In reality Retro 80S Rollei IR 400 etc are all the same film which a Aviphot 200.

No it is Agfa-Gevaert Aviphot Pan 80 as stated on Wikipedia...

I must say that I used a cheap chinese filter not my Heliopan which seems to be darker...

 

[pentaxuser]

Thanks that's helpful info. So Rollei 80S which was the film used is Aviphot Pan 80. The point I was trying to make and unsuccessfully it would seem is that fs999 treated it as film speed 80 and put this speed into his P645N My P645N has the same meter and mine with a red filter on increases the shutter speed by 2 stops Unless the Pentax in-camera meter distinguishes the R72 from a normal Hoya red 25 and has the ability to render a R72 filter with the correct 4 stops increase in shutter speed and based on everything I have read on filters this and the ability of in-camera meters to render such filters's factors correctly would seem unlikely, then fs999 shot his pics at two stops more than 80 which is 20

This speed of 20 appears to have produced excellent pictures. Could EI 6 have produced better pics? I don't know but what I do know is that the speed he used does appear to have been enough. There was nothing in his pics that screamed "underexposure" and when he posted them some 4 months ago I would have expected a response to the effect these were seriously underexposed. I saw no such reaction so I assume that most posters' eyes rendered these pics as good as did my eyes

pentaxuser

 

[fs999]

Thanks that's helpful info. So Rollei 80S which was the film used is Aviphot Pan 80. The point I was trying to make and unsuccessfully it would seem is that fs999 treated it as film speed 80 and put this speed into his P645N My P645N has the same meter and mine with a red filter on it increases the shutter speed by 2 stops Unless the Pentax in-camera meter distinguishes the R72 from a normal Hoya red 25 and has the ability to render a R72 filter with the correct 4 stops increase in shutter speed and based on everything I have read on filters this and the ability of in-camera meters to render such filters's factors correctly then fs999 shot his pics at two stops more than 80 which is 20

This speed of 20 appears to have produced excellent pictures. Could EI 6 have produced better pics? I don't know but what I do know is that the speed he used does appear to have been enough. There was nothing in his pics that screamed "underexposure" and when he posted them some 4 months ago I would have expected a response to the effect these were seriously underexposed. I saw no such reaction so I assume that most posters' eyes rendered these pics as good and did my eyes

pentaxuser

I will look this evening how much this filter increases the shutter speed...

Here some more...

Pentax 645N • Pentax FA 645 45mm f:2.8 ED • Infrared R72 filter
Rollei Retro 80S developed in Caffenol CL 50min stand @ 20°C


PENTAX 645N • Pentax FA 645 75mm f:2.8 ED with IR72 filter
Rollei Retro 80S developed in Caffenol CL 50min stand @ 20°C

 

[pentaxuser]

Thanks for this further set of prints. Again I see no signs of underexposure but to at least establish what your in-camera meter is doing with a R72 on it it will be helpful if you can check and report what is is doing so we can all see.

What is clear to me is that whatever you in-camera meter is doing, it is doing it right with the Rollei 80S which is either Aviphot 200 or Aviphot 80 or Aviphot Pan 80.

It would be helpful if this bit of controversy could be settled as well by those who have stated the two different film names of Aviphot films. Someone has to be wrong by definition or so it seems to me

pentaxuser

 

[fs999]

I have made following tests with my Voigtländer VC meter II and my Pentax 645N with the no-name filter and the Heliopan Infrarot 780

vc II : No Filter : 1/60 IR72 : 1/8 Heliopan : 1/4
645n : No Filter : 1/10 IR72 : 2 " Heliopan : 4 "

 

[pentaxuser]

Thanks fs999 So the P645N in-camera meter does reduce the exposure to slightly more than the 4 stops which the likes of Ilford suggests as the correct factor for R72. Thus you were exposing Rollei 80S at the EI that appears to be the consensus for this film which of course does explain why I see no sign of underexposure in your pictures.

Athiril, you were right about the need for the EI range you mentioned and surprisingly, at least for me, is that the P645N in-camera meter does meter correctly for a R72.

The meter presumably cannot know what the film is so it meters according to the darkness of the filter and flies in the face of the usual consensus that once filters get beyond mid-yellow and successively darker, camera meters under-estimate the exposure required.

pentaxuser.

 

[Athiril]

Thanks fs999 So the P645N in-camera meter does reduce the exposure to slightly more than the 4 stops which the likes of Ilford suggests as the correct factor for R72. Thus you were exposing Rollei 80S at the EI that appears to be the consensus for this film which of course does explain why I see no sign of underexposure in your pictures.

Athiril, you were right about the need for the EI range you mentioned and surprisingly, at least for me, is that the P645N in-camera meter does meter correctly for a R72.

The meter presumably cannot know what the film is so it meters according to the darkness of the filter and flies in the face of the usual consensus that once filters get beyond mid-yellow and successively darker, camera meters under-estimate the exposure required.

pentaxuser.

It would have to do with the meter's spectral sensitivity as well, none of them would be using an IR blocking filter etc in front of the meter sensor. Electronics are sensitive to and digital cameras require an IR blocking filter to capture normal images. Much like colour film has a yellow filter layer to block blue light from the other colour layers.

 

[pentaxuser]

Thanks Athiril. Given that the in-camera meter on the P64N works nearly perfectly. I wonder if the meter's spectral sensitivity was set with that in mind or might it be just a happy coincidence?

My 654N gives just over 2 stops with a red 25 which Ilford says is about correct in its article so while I cannot be sure that my in-camera meter reads as does the camera of fs999 it would seem to be right according to Ilford although the filter factor for my red 25 is 8 so 3 stops.

I cannot guarantee that my meter is correct but based on taking shots with yellow, orange and red the exposures seem to produce darkroom prints that look OK .I need to obtain a R72 and see if I get the same result as fs999

pentaxuser

 

[MattKing]

Are you sure that the 645N's meter is within its sensitivity range when you stich an R72 filter on the front of the lens?
That filter is substantially opaque to a lot of visible light.