486 for B&W- a dissenting view

[steve_l]

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I've decided to use 486's for B&W (I respect Sean's reasons for not using them, but have my reasons for using them.) Here's my (still somewhat conjectural) reasons. I've only had the M8 for a couple of days, so this all may be totally dumb, in which case I apologise in advance....

 

Pro:

Using the 486 cancels out the bump that IR-heavy materials get. In a wedding, the blacks are black, and in a landscape the greens are just green, not glowing. As Sean points out, the shadows (if IR heavy) get a bump. However, that is at the expense of compressing the delicate midtones by swamping them with IR-heavy light, for a contrast loss in midtones and highlights. I'd rather see some of the shadows go to stay dim and preserve the range in the midtones and highlights, which the M8 is not very good at (at least theoretically, according the the 8-bit encoding scheme for the DNG's, I haven't tested this yet, although the extensive testing I've done with Canon gear showed that reducing contrast did lose info in the mids). The M8 encoding scheme is aimed at pulling detail out of shadows.

 

Using the 486 eliminates the fuzzy landscapes due to focus shift of the IR. Actually, I've tested this and have been unable to see any loss of resolution in bright grass due to this (should be most obvious here, the color and intensity shift is obvious).

 

Con:

The cyan drift should appear as vignetting in a B&W image - loss of the reds should just show up as a loss of intensity. But I've been unable to see this in images. The color shift is obvious, the intensity shift is not.

 

Conclusion:

Use the 486 in normal contrast scenes to preserve the full range and avoid compression of mids and highs. Consider removing it in high contrast scenes to make the lens into a lower contrast lens.

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[steve_l]

Oh, of course I forgot the typical con for the filter - reflections and flare (contrast loss). Which is why my Leicas haven't worn a filter for 25 years. But somehow, I've let go of that and prefer the more "realistic" filtered image for the M8.