Ilford sfx 200 focusing with filter

[steve_lynam]

Hi There,

Ive just got hold of a pack of sfx 200 and a special filter that comes with it, ive searched the forum and cant seem

to

figure out are you supposed to focus then put the filter on? as when i put the filter on I might as well have the

lens

cap on...cant see a thing! my camera has ttl metering will this suffice or will I have to increase exposure?

Thanks in advance,

 

Steve

[carbon_dragon]

That's the only way if you have an SLR. The alternates are -- use a rangefinder camera, or you could put an accessory viewfinder on your accessory shoe if you have one and look through that. Focusing is still a problem, but you could conceivably scale focus with a wide angle lens (using the depth of field scale on your lens if you have one or a printed table if you do not). Whether your meter works through the filter depends on the camera. You can probably get a filter factor from the manufacturer (probably on the film box if that is an SFX filter) and then compare the meter results to an external light meter adjusted for the filter factor. Of course an additional problem is that infrared film is sensitive to light the external meter cannot see (SFX isn't so bad in this respect)

 

I handle this sort of thing with a Leica M2 and an external light meter. I can see through the viewfinder fine (I'm not looking through the lens), focus fine, and my external meter tells me how to set the camera. Any rangefinder would do, it doesn't have to be a Leica. Or you can just suffer.

[randall ellis]

Here's the fact sheet on that film. It has exposure factors for the various filters, including the one you are using.

 

http://www.ilfordphoto.com/Webfiles/2007651134552223.pdf

 

Meter without the filter, put the filter on and then adjust your exposure based on what your readings were. i.e. add 4 stops to that reading for the SFX filter.

 

Focusing is a bit more interesting, so try to use at something like f/16 or f/22 to boost your depth of field to compensate for the focus difference of IR light from the visible spectrum. The fact sheet says that APO lenses may not experience focus differences, but I can't speak to that. Only experience will say for certain with your lenses.

 

- Randy

[randall ellis]

Sorry, obviously focus first before adding the filter...

 

- R

[tom_overton]

I meter SFX at ISO 6 and have had really good results to date. I've used both TTL and hand-held metering (35mm and 120) and notice little if any difference. Of course, the 120 shows a much finer grain when enlarged, but that is to be expected. As for focusing, I try to focus about 5% closer than my subject. I don't know if this is technically correct, but as I shoot at f16-22 I'm still pretty well within the acceptable DOF.

 

Cheers,

Tom

[jay_jay12]

I focus, put camera lens on manual focus, apply filter, click shutter button.

[steve_lynam]

Thanks Guys,

 

Steve