Black and White photography with digital: to use real colour filters or not?

Discussion in 'Digital SLR' started by default, May 21, 2006.

  1. default

    default Guest

    I sometimes like to take pictures with my Canon 350D as black and whites. I
    always shoot them raw and if I decide a pictures should be b&w, I do the raw
    conversion using one of the two Canon RAW convertors (Digital Photo
    Professional, or Raw Image Task). Often I check how the image looks using
    one of the colour filters in the raw convertor (red, orange, yellow, or
    green) compared to unfiltered. Sometimes one of filter colours is a
    significant improvement.

    Would I get better results using a real colour glass filter on the front of
    the lens? My suspicion is that, for example, without the filter, the red
    exposure might be limited by light of other colours saturating the sensor's
    pixels. A real red filter would prevent this whereas the raw convertor has
    to work with the data that is present and unfiltered before aquisition. The
    exposure may need to be longer however.

    Would using actual colour filters for b&w photography provide an image with
    more dynamic range and less noise than doing the filtering in the raw
    convertor software? Are there other drawbacks or artifacts that would come
    into play due to the bayer filter and demosaicing due to the filtered light?
     
    default, May 21, 2006
    #1
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  2. No.... Black and Whites are not a function of the sensor but your
    post processing. To do good B&W from digital you need a dedicated
    printer with only different carbon based inks in it and use a RIP
    driver rather than the standard driver.

    Setting the Camera to B&W is a waste of time since you can do a far
    better job in Photoshop.

    For more on digital B&W particularly the printing which is the hard
    part to get really good.

    http://home1.gte.net/res0a2zt/photos.html

    http://harrington.com/index.shtml (see the information on Quad Tone
    RIP)


    --

    "I have been a witness, and these pictures are
    my testimony. The events I have recorded should
    not be forgotten and must not be repeated."

    -James Nachtwey-
    http://www.jamesnachtwey.com/
     
    John A. Stovall, May 21, 2006
    #2
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  3. default

    babalooixnay Guest

    You can use colored filters although it isn't necessary with a good
    editing program. I use Photoshop CS2 but there are others much cheaper
    and even some dedicated B&W. Within the editing programs you have an
    amazing ability to manipluate each color channel individually or in
    concert. If you have come from shooting B&W film with the traditional
    filters you will be amazed and you won't have to fiddle with all the
    filters. You can apply the equivalent of colored filters or you can
    manipulate the channels themselves and with various opacity sliders you
    won't have to ask yourself before hand should I use orange or light red
    or dark red as you will be able to non-destructively apply the filter
    or it's equivalent and view the results on screen before printing. You
    will have complete control. That said I still use polarizers, some
    graduated and full ND filters but colored filters don't even live in my
    bag anymore. There are dozens of good tutorials around the web with
    many different approaches to the issue, google "digital B&W tutorials"

    There are also a number of dedicated B&W inksets available, mostly for
    Epson printers printing on all kinds of paper. I use a dedicated
    hextone Epson R220 (that you can get for well under a hundred bucks)
    with MIS UT-R2 inksets that come in both warm and nuetral tones. You
    can do a mix and match with the cartridge positions for different tonal
    levels and there are dedicated blacks for matte and glossy papers. If
    you still want to use Silver papers there are even methods to print
    digital negatives with inkjet printers and do contact printing on
    silver paper. Enjoy!
     
    babalooixnay, May 21, 2006
    #3
  4. Your understanding about these things are correct. A "real" colour
    filter should (at least in theory - I am not sure if this will be
    significant in practice) give you more dynamic range at the point of
    aquisition.

    You should still record in RAW and do the conversion to B&W yourself
    (rather than relying on the JPEG "B&W-mode" your camera might have
    as an option). As long as you convert to B&W in the RAW-converter,
    I don't think demosaicing will produce any adverse effects.
     
    Gisle Hannemyr, May 22, 2006
    #4
  5. default

    w.beckley Guest

    I'll be the voice of dissent here. I'm fairly certain that the use of
    B&W filters will have detrimental effects on your images. Based on my
    experience with using B&W filters on color film (and desaturating
    digitally from scanned negatives) *and* my experience using B&W filters
    in video (desaturating in post), I've observed a number of
    posterization/solarization-type artifacts that are nothing like what I
    observe in using the same filters with B&W film. I've got no technical
    explanation for this, but I've certainly observed it. It is possible
    that I could have worked around the problem, but I'm not sure how, and
    it is also possible that DSLRs work differently in some way that
    prevents the problem, though I doubt it.

    But one thing certainly remains true: black and white filters are
    expensive and their use is an art. They permenantly alter the image in
    ways that are irreversible and in some cases unwanted. I used them for
    years with black and white film, but since my switch to digital, I
    haven't looked back. You can control the B&W tonality of each different
    hue in your image with digital capture! Why sacrifice that control? If
    you used, for example, a red 25 filter, you'd have little to no blue or
    green data to manipulate to finesse tonality with. The same image,
    taken without that filter, could be made to look the same as the one
    taken with the filter very easily, and could then be further doctored
    in the other two channels. Save your money and use it elsewhere... like
    buying Photoshop CS2 or another program with a more rubust feature set
    than Canon's software.

    Will
     
    w.beckley, May 22, 2006
    #5
  6. default

    default Guest

    Thanks for your response. I was concerned that using colour filters may be
    have some detrimental effect. I was hoping someone would have tried it.

    I presently do not own colour filters and I wasn't sure if it was worth the
    cost. I do have Photoshop CS2 and I like it. However Adobe Camera Raw does
    not have the B&W modes like the Canon convertors so I use the Canon programs
    when I want a B&W picture and then finish up in CS2 after raw conversion.
    Canon DPP now has noise reduction in the latest update as well. I do use
    ACR for most of my colour conversions though.

    There is a clear benefit to using no filters, besides the costs savings. I
    can always get a colour version or a differently filtered version by
    reconverting the raw image. A filtered image would not be useful this way.

    However I thought that maybe a better image would be possible with a real
    filter but I haven't tried it so I was asking for other's experiences before
    spending money on filters.
     
    default, May 22, 2006
    #6
  7. default

    default Guest

    Thank you for your response. I'll always record in raw since then I have
    the flexibility to adjust the exposure or even restore the original colour
    image and if it is unfiltered, I can generate images that are filtered
    differently as well.

    I was hoping someone had tried using a red filter and comparing the results
    to capturing in colour and then software filtering. I was expecting a lower
    noise image with more dynamic range captured because of first getting rid of
    the non-red light which can then not saturate the sensor.

    I was also wondering if the potential gains are lost during demosaicing an
    image taken under monochrome light. Since I don't quite understand the
    algorithm used in de-bayerizing an image, I can't really predict if there
    are further losses in this situation.
     
    default, May 22, 2006
    #7
  8. default

    Paul Furman Guest

    If you know what you want, filters will give a real improvement but it's
    true that it will be irreversible. Be sure to set a fixed white balance,
    not auto-WB or the camera will simply correct the filtered light back to
    normal. It is real easy to adjust WB & channels with RAW & photoshop but
    the filters will provide somewhat better data compared to stretching
    digitally. Maybe not worth the hassle for actual gains but I'm sure
    filters will give a real improvement.

    The question partly comes down to whether the RAW file actually is
    different with different WB settings and maybe it is, at least in the
    case of the D2x where they had the proprietary WB code issue. If that's
    the case, you could use a different WB setting to achieve the same
    effect as a physical filter. But there is no question that a filter will
    change the data the sensor recieves so it will give better/different data.
     
    Paul Furman, May 22, 2006
    #8
  9. default

    JPS Guest

    In message <[email protected]>,
    Well, it's certainly possible to get better or special results with real
    filters. A real filter may alter the wavelength response of channels;
    for example, a deep red filter might reduce the ratio of purples to reds
    in the red channel, something you can't do in the color mixer, per se. A
    red filter could also allow you to expose more heavily without blowing
    out the other channels (most digital cameras are least sensitive in
    their red channels).

    This really is all very complicated. There are metering issues,
    different ways of obtaining B&W (I never make B&Ws from JPEGs or RAW
    conversions; I make them directly from the RAW data, which has no
    cross-contamination due to conversion).
    --
     
    JPS, May 23, 2006
    #9
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