Newt, I have one of these filters and it is a medium-light orange, factor appears to about 2/3 of a stop with my initial tests. I bought it for use with IR film and get minimal results alone, however combined with a #29 dark red it begins to produce some good ir effect.
As to previous comments about light meters not reading IR, I don't think that's true. A 720nm filter placed over the sensor on my Luna Pro meters give readings within about 3 stops of unfiltered readings, so i expect that like digital sensors there is some IR sensitivity. At least that's been my experience.
I suspect you're correct and I also suspect it may vary a lot between different types of meters. The latest generation of IR films have such limited bandwidth that they are almost looking at visible wavelengths anyway.
Originally Posted by scheimfluger_77
As far as I know, most "alternate technology" cameras have IR attenuation filters on the sensors because the basic sensor has high IR sensitivity. I would expect to see different characteristics between selenium, CdS and silicon cell meters too. But in my opinion, there are so many variables working with IR -- first and foremost, we can't see it, so the "usual" intuitive adjustments are unavailable, and the amount of IR varies by season and time of day -- I don't see how a bit of testing and bracketing (at least in the first couple of passes) can be avoided. The suggestion of taking one shot unfiltered, on at least the first roll, to verify the basic workflow is also a worthy use of one frame!
Indeed I realized that I pretty much have to try a few tests esp with the tip of stacking two ir filters. I have a spot meter and I'll also test that as well with the filter over that and report my results, mine is from Polaris. I just need some sun here!
If it is of any help. I just finished five rolls of the Konica 750. I rated it at EI3 with the 89b filter, and bracketed one below and above. D76 1+1 at 70 for 11m.
I have not contacted everything yet, but generally the frames with additional exposure were closer to the mark. Of course everything has to do with the quality of the light, but it appears that EI3 is a good starting point. You will get workable negatives.
I do not know about the other films you mentioned.
Yes, you are right of course. I should have said that they are not calibrated for infrared.
Originally Posted by scheimfluger_77
This could probably be done however, if someone were so inclined, so that you could read through an optically opaque IR filter and get a useful reading.
How does the filter type chosen effect the exposure with Efke 820? I have an 850nm filter, should i be using 720? I did get some good results with this filter, just checked the details and the best were 1sec @ f16, though other shots at same exposure were not as good.All were shot within 4 hours on the same day but at different locations and aspects.
We had a loooong thread about IR film exposure before.
I recommend to soup it in XTol 1:1 or Diafine to get a little more than 3 ASA. XTol results show less grain than Diafine results with this film.
Then it all comes down to use 6 or 12 ASA with the Efke. Meter without the filter. If your lightmeter does not allow 3, 6 or 12 ASA just set it to 100 ASA and add 4 stops (12 ASA), 5 stops (6 ASA) or 6 stops (3 ASA).
- Photograph on bright sunny days. IR photography is possible on dull days, too, but results have a tendency to be, well, dull.
- Motifs in front light might look boring, sidelight and backlighting render more interesting results.
Based on my limited experience, the 850nm filter should be OK with the EFKE film - you might need one stop more exposure for the 850 than the 720. If you run the cutoff that high with the Rollei material, you'll be looking at another 5 or 6 stops over the exposure with a 720.
Originally Posted by Craig Swensson
Points to consider....
1) Look for a couple of rolls of SFX (ILFORD) in your local store. It works well and will be likely sold where ever they sell ilford films. If you order online, go get the real stuff. The first one to experiment, and the second to do it right.
2) Choose a lens that has a red dot, just left of the focus line on your lens. This will be your IR offset for this lens. These marks were provided years ago, not so much now. Look at your older lens.
3) You develop your film at box speed. IE: SFX gets developed at 200 iso. The EFKE at it's box speed. Exposure (EI) is to compensate for the massive (usually -4 stops) light loss of the filter. So....IS0 200 - 4 stops is EI 12. Take one shot on the roll with out your IR filter. When you develop, that will be your reference image for proper development. IR film witll still develop as any pan film.
4) Try to load your film in as much darkness as possible. This stuff is more sensitive than other films.
5) Keep it fresh. IR sensitivity drops fast with age. It will turn into normal pan film, and can be shot that way when it gets old.
6) Best time of day are opposite. High noon is awsome. You want heat from the sun, winter or summer.
So what I do.....
1) Find a scene.
2) Meter for the box speed of your film. If using the one in your camera, take the filter off your lens to do this.
3) Put your camera in manual mode and take the reading from above and adjust for -4 (or -5) stops. If this is the first time you have used your filter, try both.
4) Focus without the IR filter. If you have a marked lens, adjust accordingly. If not, you will need to braket to find where your sweet spot is. Take notes.
5) Put the filter on and shoot.
You should try to stop down as much as possible until you have worked out the focus on your lens. Develop with the developer you are used to. You do not want to introduce too many variables until you get the basics worked out.
I got my B+W 099 filter in today, just a bit before. It is a light orange, darker yellow color filter. First thing I did was test it with my spot meter, with it over the lens, and off. Its only about ~2/3 stop. I suspect it will act exactly like a orange filter on both Pan and IR films lol. The literature indicated its supposed to be used with color IR films. I will try some film with it this weekend. The same seller had the 092 which I totally didnt see which sold for really cheap too. Kinda kicking myself for that one, Alas I will keep using a cheapo 720nm IR filter I have.