Ilford SFX 200

[benoit_sauzier1]

<p>I have two questions about exposing Ilford SFX 200 correctly:<br /> 1. Does anybody know if it is ok to apply Ilford's standard reciprocity curve to SFX 200? Ilford's spec sheet does not mention anything about reciprocity failure for this film, and if I contact them, I feel that I am likely to get a vague answer like "bracket + - 2 stops".<br /> 2. I am planning to use this film with a deep red 89B filter. From Ilford's spec sheet, the applicable filter factor is four stops. Fine! Elsewhere in the spec sheet they state that the correct exposure under bright sunshine is 1/30 s at f5.6 with the 89B filter. Now, if I "remove" the filter, and add four stops, I come up with an exposure of 1/250s at f8.0, and yet sunny 16 rule for a 200 iso film is 1/250 at f16. So basically the film would be over-exposed by two stops. What am I missing? Can someone enlighten me about this please? I intend to use an external meter and add the filter factor afterwards, no ttl metering involved here.<br /> Thank you!</p>

[jonathan_kleinfeldt1]

Shooting a roll should answer all of these questions ; )

[nickc1]

<p>Sunny 16 is an approximation only, and works for visible light - so if you want a shot using 'normal' film or SFX without a filter it will apply.</p>

<p>When you exclude most visible light with your filter you are relying on the IR to make your image, and there is often less IR in proportion to the visable light - hence the need to break the sunny 16 rule. This is especially true when a film with only a bit of IR sensitivity like SFX is used - in effect you are excluding the light that the film is mainly sensitive to, and the film cannot record much of what is left (IR)</p>

<p>The advice to test a roll is sound as only you can decide what effect you want from this film, and when working with IR 'box speed' for a film is a matter for even more opinion than usual! You may also find that the EFKE or Rollei IR films, which are sensitive far more into the IR region are another option worth testing.</p>