M8 and red filter for BW

[Nocti-Luchs]

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Just tried to use a red filter (8x). Pictures looked good (when not zooming in) on the camera display but the JPEG´s were extremelysoft . On the other hand this could look good with some kind of portraits or nudes. The DNG´s were a bit better but still not usable like converted files. Noise reduction (level 3 or 4) together with some sharpening (around 100-300 in C1LE, depending on subject) helps (might be okay for small prints) but if You want to have really sharp pictures this is not enough. If You sharpen the DNG´s without noise reduction they look like printed on canvas. Would have been nice beeing able to use BW filters and getting the intended effect right on the spot. Does anybody know why it doesn´t work? Is it the IR sensibility of the sensor?

 

Thank You

Joachim

[ho_co]

Joachim--

I think you've guessed the answer. Remember, all the pixels (R, G and have some sensitivity to red and to infrared.

 

The problem (I think) is that the lens doesn't bring IR to the same focus point as the 'standard' colors, so the out-of-focus IR produces a diffuse haze over the image. You might be able to help the situation by making some focus tests for each lens you use, probably over a wide range of focus distances, to see where you get best results. ("Best" results because the IR and the red rays still won't be focusing at the same plane; and remember that since the amount of IR varies, the best results with a particular scene might require a different focus point from the best results with a different scene.)

 

Or the simpler (but less fun ) solution might be to use both the 8x red and the IR-cut filters: Get rid of the IR, and you're dealing only with the effect of the red filter, just as was the case with film.

 

Just my guess, but I think it probably does all arise from the sensor's IR sensitivity, as you said.

 

--HC

[Bob Ross]

One point to consider is that color filters were used with negative B&W film and digital is a positive process like B&W slide film. To make blue skies darker, you need a blue filter. The red filter is cutting out cyan and as you have guessed letting in most of the IR. The IR becomes a large percentage of the color mix. My fooling around with color filters was with a green, yellow and a Cokin Blue acetate from their creative filter package. I expected softness from the last one, but didn't find it. I didn't see enough difference to continue fooling around. Now, that the foliage is back I may try again. I thought of it as a sort of channel mixing and figured that an 81A or B might give an interesting tone shift/B&W look. The trade-off is the filter factor when comparing to conversion.

Bob

[mjh]

One point to consider is that color filters were used with negative B&W film and digital is a positive process like B&W slide film. To make blue skies darker, you need a blue filter.

Not at all. Negative or positive makes no difference. For dark blue skies, you need a red filter, with the M8 as with any other camera, digital or analog. A blue filter would result in bright, washed-out skies.

 

Having said that, I wouldn't use an optical filter, but rather “filter” the RGB image to obtain a B&W version. A real filter may still be useful when dealing with high contrast scenes, but generally it is to be avoided.

[Bob Ross]

Not at all. Negative or positive makes no difference. For dark blue skies, you need a red filter, with the M8 as with any other camera, digital or analog. A blue filter would result in bright, washed-out skies.

 

Having said that, I wouldn't use an optical filter, but rather “filter” the RGB image to obtain a B&W version. A real filter may still be useful when dealing with high contrast scenes, but generally it is to be avoided.

I had to think about that Michael, but I'll agree with you. I was thinking in terms of saturation rather than luminosity.

Bob