IR exposure times, ISO and confusion

[danny_rowton]

Hi

 

Ive been reading so much on IR film and the more I read the more confused I get.

 

Firstly, my set up for what will be my first attempt is going to be Nikon F2, Efke 820IR & Cokin 007 (89b)

 

I have read I need to box speed (100) but also that I need to set my ISO at 1 (my lowest setting is 6).

 

I have read that shutter speeds are usually about 1/125 for a standard sunny day (I want to start with sunny weather as it brings the best

results. That much I do know!) Yet if im on a camera ISO of 6, BEFORE I get my filter on, Im looking at about 1/2 second in bright

sumlight with a not particularly small aperture of f8.

 

I appreciate time and experimentation is required but can somebody advise on the above as a good starting place?

 

Many thanks for your time - Danny

[SCL]

<p>If you're using ISO 6, on a sunny day with your aperture at f8 your shutter speed would be 1/25 sec before adding the filter. If you're using ISO 100, on a sunny day with your aperture at f8 your shutter speed would be 1/400 sec before adding the filter. If you know how many stops your filter adds, then adjust your shutter speed and aperture accordingly. Once you've made those calculations, you need to see if you need at add an additional factor for reciprocity (check your film specs - it applies only when you have long exposures on film).</p>

[curt wiler]

<p>The key is NOT to try to measure exposure through the filter. Many older meters have trouble with the strong red color. Therefore, either use a hand-held meter or meter TTL without the filter, and use the lower EI number, which is the effective speed of the film and filter combination.</p>

[lex_jenkins]

<p>Some newer cameras - film and digital - can meter surprisingly accurately through heavy IR filters. My Nikon D2H meters accurately through IR filters, and it'll be interesting to see whether my F3 and FM2N can do the same for SFX 200 sorta-IR film. But as Stephen and Curt noted it's probably a better idea to meter without the filters and use conversion factors to estimate the exposure. True film speed is educated guesswork, and with longer exposure times reciprocity characteristics may affect results.</p>

<p>I just Googled Efke IR 820 and see a few articles from other users, including <a href="http://www.shutterbug.com/content/efke%E2%80%99s-ir-820-infrared-film-unique-ir-option">this 2008 piece by Roger Hicks</a>. I'd include those user experiences as guidelines for exposure and developing.</p>

[lex_jenkins]

<p>Okay, I just compared metering through infrared filters on my Nikon D2H (dSLR), F3 and FM2N. I know the D2H meters accurately through this IR filter. The F3 was a full stop underexposed and the FM2N two full stops underexposed. The difference between the F3 and FM2N didn't surprise me - the F3 can meter accurately with a shifted PC-Nikkor, while the FM2N must be metered with the PC-Nikkor unshifted for accurate exposure. So, again, it's probably safer to meter without the filters and then make the appropriate adjustments.</p>

[glen_h]

<p>Metering through the filter means you are measuring actual IR light.<br>

There is some correlation between visible and IR, but they are enough different that if you might do better to meter IR and correct for the difference.<br>

That is for silicon. For CdS and Selenium meters, they probably don't respond to IR at all.<br>

You should probably compare the sensitivity curve for the film against the transmission for the 89B. The 87 is the traditional IR filter.</p>

[danny_rowton]

<p>OK thanks chaps. <br>

This forum is so useful to me as I'm 'serious amateur' and use film only at the moment but never used IR before. There is a lot of contradiction on previous threads other people have started which really started to drive me a bit crazy because I want to dive in to infrared.<br>

I know I will make mistakes, but I am prepared for that. I just didnt want to plump for any old way of shooting it. <br>

Basically, it seems its not necessarily as confusing as its been made out. Meter without the filter using sunny 16, and as Lex said use conversion factors (which one would use for any other type of film). <br>

I still find a great variance in exposure times from anecdotal contributions online though! Obviously this being the case with no mention of ND filters of course. <br>

I will just use sunny 16 and go from there haha. After all that, I go back to the most basic form of metering there is. <br>

I dont know if Im missing something here but in respect of the camera film speed dial setting, is there a particular reason you might use a low ISO rather than box speeding on this type of film? Its just that of course, you can do either and make the respective amendments to the exposure time, but I just wondered why on IR you'd consider not box speeding?<br>

Thanks, Danny</p>

 

[Mike Gammill]

<p>Agreed, safer without the filters. Although many meters will detect IR even through the filter, they may not provide readings that are best for the E.I. used. Modern meters are certainly a lot more sensitive. My Maxxum 8000i will not only meter through an IR filter, it will even autofocus with it attached, although you can't see an image in the finder. Would I rely on that? No way. I meter through filter and use exposure corrected for filter as a starting point.</p>

[curt wiler]

<p>Meter sensitivity is not the only issue here. The OP has an F2, which used a CdS meter as I recall. These were very non-linear in the red spectrum. I first tried metering through filters for B&W with a Nikon FE, and found that I had to draw up a correction table for the different filters. The meter in the FE is different but similar vintage. The Wratten 29 (dark red) caused the meter to misread about 2 stops, if I remember correctly. Only the K2 had no correction due to the light spectrum. Everyone seems to agree that metering without a filter is recommended, but I have found that using an EI of 3 is the best starting point for this film. It will depend a lot on development, and of course the amount of IR that is actually present in the light because this can be highly variable with the time of day, season, atmospheric conditions, and even with latitude. I always bracket, at least three shots preferably plus/minus 1-1/2 stops.</p>

[lex_jenkins]

<blockquote>

<p>"...I just wondered why on IR you'd consider not box speeding?"</p>

</blockquote>

<p>Probably due to the variables in filters. There are several different ready made IR filters, each with different light transmission characteristics in terms of spectrum and number of "stops" for exposure purposes. It's simpler for the film manufacturer to stick with the ISO standard as a baseline for determining a film's true speed, without filters, in a standard developer.<br>

<br>

I imagine it's tricky for manufacturers to estimate the ISO to determine the true speed by the usual definition: the least measurable density over the film base and fog. Some IR films are extremely vulnerable to fogging, halation and light piping. Manufacturers probably do the best they can to give us a number, but it's educated guesswork in terms of real world applications.</p>

 

[Mike Gammill]

<p>The Kodak HIE was very prone to light piping. Very true about CDS meters and red sensitivity. CDS can respond a little to IR, but not enough to be any use. I can point the IR remote from my television at my Minolta SRT and the meter needle will jump very slightly when I press a button on the remote. Not sure about the Efke 820 IR and light piping. I would just follow the manufacturers recommendations.</p>

[lex_jenkins]

<p>In the <a href="http://www.shutterbug.com/content/efke%E2%80%99s-ir-820-infrared-film-unique-ir-option">article</a> I linked to earlier Roger Hicks described some edge fogging with Efke 820 IR as "light strikes", which I'm assuming is light piping from loading the film in anything other than darkness. Some IR films lack the anti-halation coating and other tricks used to protect most panchromatic b&w films from this.</p>

[danny_rowton]

<p>I've drawn up a colour coded chart for this exercise. The weather looks good for Sunday. Fingers crossed.</p>

[glen_h]

<p>Film box speed gives its sensitivity to visible light. Even more, with a spectrum similar to sunlight. Some films are separately related for tungsten lamps.<br>

If you expose IR film without a filter, then box speed is fine, but the pictures will look pretty much like any other.<br>

With a specified filter, daylight illumination, and some assumptions on the IR reflectivity, you could give an IR box speed, but then again you might as well give shutter speed and aperture.<br>

The interesting cases are other than daylight illumination, or other than average reflectivity. Those are the ones you would want to meter.</p>