metering with IR stock

Hi all,

Been a looooong time since I posted on photo.net.

 

I'm going to embark on an effort to eat up my remaining IR stock. HIE and EIR in 135, Konica, Efke, and Ilford in 120. My question is on metering. My notes on my technique are not clear from when I was last shooting IR a few years ago, and searches give me confusing answers. I'll try to keep my question direct.

 

Let's take Konica 750. What do I set the meter at, when metering without a filter? I will be using a Hoya R72 filter, but the camera I'm using at least for medium format has no meter, so I'll be using a spot meter, probably (just what I have handy - I might pick up an incident meter). I know I have to bracket. Suggestions? I have EI "30-50" in my notes but that has to be before the filter factor, yeah? So I'd drop 5 stops to account for the filter? I've read of Konica being in the single digits so that actually makes sense.

 

Hope that makes some sense. Appreciate the help.

Back in the day (early 70's) I used Kodak Infrared film for landscape photos. At that time it was not recommend to use a light meter since the meters did not "see" infrared light and the amount of infrared light varied greatly depending on clouds, haze angle of sun, time of year. Clouds actually don't stop that much infrared so if you used a meter you could greatly overexpose your film. I followed the suggested exposure sheet that came with the film. The suggested times included using the 25A red filter, other filters ( 29A, #15 orange) had filter factors to add or subtract from the base exposure. I suggest you bracket your exposures. It takes a lot of practice to be able to nail the infrared exposure. Good luck.

The earlier IR is blue and IR sensitive, so red filters work fine.

 

Later there is HIE which is panchromatic + IR, so you want a real IR filter.

 

Silicon is sensitive pretty far down in the IR, but then meters have to block that.

 

You could make a meter with a silicon phototransistor, then put an IR pass filter in

front, and make your own IR light meter.

 

Otherwise, as above, use a regular light meter, then adjust for the supposed IR content

relative to visible light.

SFH310-3.pdf

 

shows the peak sensitivity between about 700nm and 900nm.

I still have some unused rolls of Kodak Ektachrome Infrared, but I gave some to somebody to try out, and it seems to be "most sincerely dead" - perhaps not surprising given the type and age of the film

develop before JUL 1972

 

With normal films, especially B&W, film does get fogged with age, but lasts an astonishingly long time.

Edited March 18, 2021 by JDMvW

Normal light meters do not measure NIR so for film all the many sources I've got state you must bracket widely.

So much easier with my converted digital cameras - the meter with the same sensor that takes the image so it's nice & consistent.

Based on the expiration date the Ektachrome infrared would be E4 process which might be difficult to obtain. I actually shot a couple of rolls of this film in the mid 1970's. I never tried the later E6 version.

I agree with the strategy to bracket widely with the black & white infrared.

Based on the expiration date the Ektachrome infrared would be E4 process which might be difficult to obtain.

 

I think the accurate word is closer to "impossible to obtain", but my associate here was trying B&W processing, as I recall.

As far as I know, you can use E6 chemistry at E4 temperatures. The exact times are less obvious.

(Also cool C-41 for C-22 films.)

 

Note that even when it works right, everything is the wrong color, so color shifts are likely not noticed.

 

Infrared films, and presumably the infra-red layer on this one, are much more sensitive to heat and age.

The other layers likely work as well as usual for color films.

 

As was explained to me 50 years ago, aging of a color film is about like a black and white film two stops faster.

That makes some sense with three layers, each sensitive to one color.

Also, as well as I remember, there isn't a big difference between E2, E3, and E4 films,

and that it is change in chemistry, not film. So, E4 films should work in E2 chemistry.

My experience with the Ilford in 120 format with the IR720 filter was to expose at ISO 3 . Anything higher and

there was no "Wood Effect " ( that lovely glow to people and trees) . Peter

@peter_fowler you mean set the meter at ISO3, right? I'm shooting with a camera that doesn't have TTL metering so I'd use a handheld meter. Just confirming. With an R72 filter which is 5 stops I believe.

The sensitivity curve for the Ilford film peaks at 720nm and is already on halfway down at 750nm, so, yes, the result will be very low speed.

 

Microsoft Word - SFX_281118.doc - https://www.ilfordphoto.com/amfile/file/download/file/1907/product/701/

 

But as they always say, the IR reflectance of scenes, and of daylight, can be very different.

 

There will be a big difference between a 719nm filter and a 721nm filter. I suspect that for

the first try, one should bracket by large factors!

 

I suspect no meters have the exact sensitivity to meter that combination.

Thanks for the information, all. I know the speeds will be low, and that of course meters are not metering for IR. I know I'll have to bracket. But I have to start somewhere. I appreciate the guidance.

 

Allan

I'd tried to get the "wood" effect by exposing at ISO 25 , then 12 and 6 , still no glow . This was all

done during nice bright days , by ISO 3 , the effect was suddenly what I was hoping for . I didn't go

any lower . I'll see if I can find the pics ( hard drive crash , means a lot of searching through old negatives .

Peter

ps; these iso sttings were taken with a little Sekonic Twinmate meter

Thansk @peter_fowler . That helps a lot. I'm using a Sekonic 308. Again, I know bracketing is key.

Years ago I used a Leitz or Zeiss blackish infa red filter for Kodak bw infamous red film, not a red filter. Must have followed instructions from Kodak, of Morgan&Morgan book. IR was kind of trendy at the time. I do understand the OP's desire of not wanting his IR film not to go to waste.

It took me forever to find the Infra red pics , but here's one from my Mamiya 7 with the IR720 filter and shot at ISO 3 , ISO 6 was close

but that IR glow ( or Wood effect ) was quite noticeably improved with the ISO 3 setting . Bright daylight and I still needed a tripod ! Peter

 

Yashica MAT 124G with bay1 Heliopan RG715, Rollei IR-400 iso 12.

https://www.l3harrisgeospatial.com/portals/0/images/Vegetation_Spectrum_Detail.png

 

The important point is called the red edge, where the absorption drops close to 700nm.

 

Since these films don't go so far into the near-IR, barely past 720nm, I wasn't so sure

that you would see the white foliage, but yes, it is close to 700nm, so plenty of IR

just past 720nm.