Use of IR Filters for M8 B&W Photography

[lanetomlane]

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Tom, take some test photos and see what you think for your type of shooting.

 

Yes, I intend to do this when I get chance but I'm away for the next couple of weeks.

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Regards, Tom

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[Bob Ross]

Well, strangely enough it even depends on the lens, as the amount of misfocus with IR light varies with the lens. The basic premisse is that the M8 will record an IR image that is basically about 4-5 stops underexposed compared with the visible light image, but in a different focal plane. It will lighten up foliage and some shadows to a certain extent, reason a number of B&W shooters prefer it.

If the lens has an IR hotspot, one will even add vignetting.

 

However, being out of focus, there will be a slight deterioration of contrast edges, thus of sharpness. Certainly not enough to really spoil a photograph, but still I can see a more crisp image when I use an IR filter.

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Add to that that shadow density can be manipulated in Photoshop, I feel there is a case to be made for using IR filters on the M8 even for Black and White..

And to add to the potential spoilers, I saw a post on another forum that addressed diffraction across the light spectrum. Diffraction occurs more on the red end of the spectrun than the blue.....more for IR than UV. A diffraction limited photo was looked at in the red and blue channels and it showed true. I haven't researched this, but diffraction may set in at wider apertures at the IR end and when we cut that off with a filter, we might be errasing diffraction, too. Probably not the only factor, but a contributory one, to the crispness of the filtered images.

Bob