ETTR, uni-WB, and Nikon's new cameras

Discussion in 'Nikon' started by tonybeach, May 10, 2007.

  1. To begin with, the most common mistake I see when people are trying to ETTR
    (expose to the right) is that they are applying WB gain to the equation and
    stop when one of the channels appears to be clipping based on the embedded
    JPEG. Usually this is the red channel, and you read it all the time when
    someone warns "watch the red channel on the histogram". If you are shooting
    JPEG, then this is good advice; but ETTR is for shooting in RAW and not
    suitable for shooting JPEG.

    To better understand how your camera is actually exposing the scene, WB gain
    needs to be ignored. Consider the BFA (Bayer filter array), with its 2 green
    photosites for every blue and red photosite; this means the sensor is twice as
    sensitive to the green channel as it is to the red and blue channels.
    Therefore, the red and blue channels have to be amplified by the camera's ASIC
    for OOC (out of camera) JPEGs or by software as a part of converting the RAW
    data. This is why noise comes primarily from the red and blue channels,
    because they are often underexposed.

    One solution is to only look at the green channel in the histogram being read
    from the embedded JPEG. The problem is that sometimes you will end up
    overexposing one of the channels and not even realize it. Now there's
    something I bet you weren't expecting. As many of you already know, BFA is a
    composite of the light reaching the photosite filtered to respond to one
    color, but it is then blended with light from the neighboring photosites to
    arrive at a value for that pixel that has all three color channels. Take a
    picture of a deep blue sky in the afternoon and the composite value that makes
    up the blue channel in the embedded JPEG will look good; but if you only look
    at the blue channel without applying any red channel gain to the composite
    pixels in the sky, you will see that the blue channel there has been
    overexposed. Overexposing a color channel means that even though the
    histogram says you have an accurate exposure, you have actually ended up with
    a color shift (not enough blue in those pixels relative to red and green).
    The problem is that there is no way to view the data accurately without
    removing the WB gain.

    To accurately see what your camera is doing therefore requires that you start
    with a neutral WB, which is called a uni-WB. I am indebted to Julia Borg for
    here graciousness in making the uni-WB available to me and everyone else who
    has asked for it. I have some versions of the uni-WB for the D200 and D70
    here: http://imageevent.com/tonybeach/mypicturesfolder/junk and they can be
    installed directly onto those cameras by saving the original file and copying
    it to a folder being used by the camera (e.g., DCIM > 105ND200) and then
    accessing the image through the custom WB setting in the camera and applying
    it. For those with other cameras that can use Nikon Capture, if you have
    Nikon Capture, you can get the custom WB here:
    http://www.pochtar.com/UniWB.zip and install it using Nikon Capture.

    Some other image optimization settings and the selected colorspace and color
    mode will also affect the embedded JPEG. Therefore, the most accurate display
    needs to have the following settings applied:

    aRGB

    Color Mode II

    Linear custom contrast curve

    Saturation Normal

    Sharpening Off

    Once you are seeing what your camera is really doing, it becomes apparent that
    some attenuation of the color channels is desirable for optimal exposure, that
    way you keep the more sensitive color channels from overexposing while you get
    adequate saturation in the less sensitive ones. This is accomplished by using
    a CC (color correction) filter in front of your lens. The amount of color
    correction is largely dependent on the camera and the lighting, but for a D2x
    Julia Borg recommends CC40M and for a D200 she recommends CC30M.

    Here's the problem, and the reason I mentioned Nikon's new cameras in the
    subject line of this thread -- Nikon's new cameras cannot have custom WB
    installed. Camera Control Pro is now required to access and upload settings
    to any camera after the D200, and it doesn't do what could be done with Nikon
    Capture's camera control module. This means that the D2xs, D80, D40, and D40x
    do not have this capability. It gets worse, since Nikon is not supporting
    NC's camera control module anymore, the feature is lost in Vista and any
    future OS upgrades as well.

    Recently I was unfairly called a "Nikon fanboy" for not conceeding that my
    D200 was a piece of junk. Well, I think Nikon could improve their products
    and I'm confident that they will, that seems like a reasonable stance on my
    part. However, I am very upset with what Nikon is doing right now with NX and
    Camera Control Pro; they have taken a $100 item that worked reasonably well
    and replaced it with a $140 and a $70 item that for my purposes don't work as
    well. I don't think it's unreasonable of my to implore Nikon to restore
    custom WB settings to Camera Control Pro so that we can benefit from using uni-
    WB in the future and make accurate ETTRs.
     
  2. God, it makes me want to hug my Nikon F3, Anthony.
     
  3. Well, this is a discussion about three issues related to digital photography; but every one of them applies in some way to film also.

    First, there is the question of exposure and density. Understanding that is the critical first step to getting optimal results. With film we could have a lengthy discussion about emulsions and darkroom techniques to address this.

    Second, we could take about color accuracy. Digital is easier in this regard than film since balancing lighting, emulsion and filters is replaced by relatively straightforward WB gain.

    Finally, there is an issue of support. I have a gripe about custom WB settings in Camera Control Pro; I wish Nikon would address this, but I am not hopeful. On the other hand, I find it increasingly difficult to buy and develop film -- and for a time Velvia 50 had ceased being available and had to be reformulated by Fuji before it could be reintroduced.

    The future for 35mm film actually looks pretty grim to me; which is regrettable. I feel that profit hungry companies are pandering to mass consumer markets at the expense of serious photographers.
     
  4. "I feel that profit hungry companies are pandering to mass consumer markets at the expense of serious photographers."

    I certainly share your frustration in that respect; it is all about the bottom line.

    The age of digital imaging can enable anyone to think they are a great photographer. "Anyone", is obviously the target market for Nikon.

    A small part of the reason I retired from photography is because of statments like, "Its so easy! Why should I pay so much money for a professional when my 9 year old daughter can take pictures like this?"
     
  5. "The age of digital imaging can enable anyone to think they are a great photographer. "Anyone", is obviously the target market for Nikon."

    Well, what you have Nikon do? I've heard these same statements made about desktop publishing as well. "Well, why should I hire a design agency when I can buy Quark (or heaven forbid MS Publisher) and make my own brochures?" Or, why should I hire an illustrator when I can buy clip art.

    Nikon is responding to market demands. They're a corporation first and foremost. I guess they should refuse on principle to sell nice cameras to amateurs who blabber on about themselves being artists.

    Most people can tell the difference - just like they can tell the difference between a professionally-designed brochure, and something done by a wannabe.
     
  6. The above put me too far into the forest to find an individual tree. There may be a few photographers who want to take tuning to that level but most don't--especially folks shooting with the lower end of the DSLR line.

    We can get so involved in the detail whe forget to take the picture.
     
  7. Vince,

    I don't fault Nikon for attempting to take advantage of a needy market. I just wish they
    were doing a better job of it. I find their inability to keep up with market demand and
    failure to maintain quality control very annoying.

    I'm also an old man lamenting change and the passage of time. ;)

    Wayne,

    I avoid out of camera manipulation and post processing as much as possible because I do
    not have the patience
    to spend hours in front of the computer. That's why I'm glad I have years of film
    experience behind me. The more tweaking I am able to do in camera, the happier I am.
     
  8. Wayne, I'm not trying to baffle you here; just giving you a useful tool that can improve your photographs.

    The technicalities of photography are as important as the subjects we choose to shoot. You can choose to ignore the technical parts of photography and instead rely on intuition, good luck, and some small degree of exposure latitude to get an optimal image from your Nikon DSLR; but not paying attention to the technical parts does not mean they are not there, they are lurking whether you choose to understand them or not.

    I would suggest that it is best to master the technicalities of photography so that you can be in control of the outcome of your photographic efforts. Only by immersing yourself in the small details, can you actually attain a skill level where those details are truly unimportant; not because you are ignorant of them, but because they have become second nature.
     
  9. Anthony:

    I post process everything with NX (RAW files), then sometimes touch up a little more in PS. One reason is I'm working with a D100 so I don't have as much of a "fudge factor." I'll admit, however, that I'm more of a "adjust until it looks right to me" guy than getting into the technical aspects.

    It's no different now than in the film days when some folks could go on at great length about the alleged superiority of Rodinal v. D-76, HC-110, etc. (Rodinal negs always looked grainy rather than sharp to me).There's nothing wrong with focusing on technical aspects but I would disagree that the technicalities are as important as what we shoot. I don't claim to be a master photographer but I do know that a technically perfect photograph isn't worth much unless the content has "soul" on some level. On the other hand, sometimes a photo that sucks from a technical standpoint can have a powerful message. Photography at its best is when a photo has at least some of both attributes.
     
  10. Wayne wrote:

    I'll admit, however, that I'm more of a "adjust until it looks right to me" guy than getting into the technical aspects.

    My reply:

    Where do you perform the adjustments? If you "adjust until it looks right" in the field while shooting using auto-WB, then you are often underexposing your shots.

    Wayne wrote:

    There's nothing wrong with focusing on technical aspects but I would disagree that the technicalities are as important as what we shoot.


    My reply:


    Perspective, angles, composition, lighting, etc. are also technical aspects of a photography. You may prefer a snapshot of your young daughter that ignores all the technical stuff to a polished photo of a supermodel, and many men would prefer the snapshot of the model to your young daughter's well crafted photo; but most neutral observers would prefer the well taken photo of your young daughter to the snapshot of her or of the supermodel.
     
  11. I understand your point that the histogram seen after white balance adjustments is not quite as accurate, but do you have any evidence that the difference given by your method is routinely significant? All camera processes lead to abstractions, approximations and representations of the real world; all can be improved, but some improvements offer better returns on effort invested than others. How many situations are there in which this refined exposure technique produces an exposure setting (shutter and aperture) materially different from the slightly lower one that a non-neutral white balance would produce? After all, shutter and aperture are usually set only in increments of 1/3 stop. Everyone already knows to compensate exposure a bit on studio shots dominated by a single strong colour, and this amounts to very little more than an obsessive way to measure that adjustment.

    Most amateur photographers could achieve more significant improvements in the results their equipment gives them by investing their efforts in other technical aspects, such as lighting. Most professionals put a fairly high premium on efficiency, reliability, and minimising fiddle - and would rather spend their effort on developing their business than on minute quality improvements. That leaves a very small proportion of users to whom the lack of this feature is a meaningful omission. One can hardly blame Nikon for concentrating on other, more relevant factors.

    (I am purely amateur in the digital age but used to freelance on film, so I freely admit that I have plenty of room for technique improvements but retain a lack of patience for minutiae that get in the way of other aspects of the work... worst of both worlds :)
     
  12. Anthony:

    My experience with super models is very limited (40 years of marriage);) But when I take pictures of my granddaughter I often--but not always--try to consider technical aspects into account, too. I do not make my living with a camera (although I did for a time back in the B&W film days). The only critics I have to please in most cases are myself and friends and family. Photography always has been a very subjective art form. What trips on person's trigger may leave the next viewer cold.

    If you feel I was belittling your efforts, I apologize. That was not my intent. There is always room for photographers to improve their techniques and your research is, I'm sure, helpful to some. But I have never heard of anyone winning a Pulitzer Prize for photography because of perfect white balance. In fact the 1954 Pulitzer winner was shot by a little girl using a Kodak Brownie box camera.
     
  13. Lester, the advantage typically is about 1/3 of a stop; but with images containing strong reds it is more often a full stop; and that's significant. As to Nikon not making room for loading custome WB into Camera Control Pro, there is absolutely no good reason not to. Personally, I make it a point to master all minutia precisely so that it doesn't get in the way of my photography.

    Wayne, Pulitzer Prizes are specifically given to journalists; not to photographers per se. AFAIK, none of the greatest photographers who weren't actually journalists ever won a Pulitzer Prize.

    Anyway, the topic of obtaining accurate exposure has come up more than once in these forums and I was specifically asked to address this issue. Things have been slow around here, so I did; for me it beats the endlessly repetitive and pointless questions about what consumer camera or lens to buy next.
     
  14. Why Not Make your custom WB in the field with the EXPODISC and forget about downloading custom WB alltogether. make a custom WB every shoot with an expodisc and have it perfect every time all the time in just a sec.
     
  15. "Things have been slow around here, so I did; for me it beats the endlessly repetitive and pointless questions about what consumer camera or lens to buy next."

    Good point.

    I think, however there a some pretty big names in the photographic world who considered themselves photographers first and journalists second.
     
  16. Kendall, you missed the point completely. In bad lighting, especially in bad lighting, determining exposure with WB applied will lead to dramatic underexposure because of the significant amount of gain applied to the red and blue channels (often 3 to 4 times the original amount).
     
  17. "The amount of color correction is largely dependent on the camera and the lighting, but for a D2x Julia Borg recommends CC40M and for a D200 she recommends CC30M."

    For a D200 what lighting is the CC30M recommended for, and are there filter recommendations for other types of lighting?
     
  18. Sorry William, I really need to select the "Notify me of Responses" option at the bottom of the page so I'm alerted to questions that arrive months later. The short answer to your question is to use the CC30M or CC40M for daylight and strobes, use CC40C (Cyan) for tungsten and fluorescent lighting.
     
  19. Thanks Anthony.

    I'm especially interested in lighting for indoor sports with the goal of reducing noise without blowing out skin - I think I'll give the CC40C type a try. I've read as much as I can find on this from you and Julia and do appreciate you sharing your knowledge.
     
  20. Hi William,

    One thing to keep in mind with indoor sports is that these filters block some light from getting to the sensor. That's fine if you want to give an underexposed blue channel a chance to catch up with overexposed red and green channels, you can just raise your ISO to maintain a decent shutter speed and you'll probably still end up with less noise than you would have without the filter (although you can see it starts to become a trade-off). The problem though may become one of AF performance, as the more light that reaches your AF sensors the better they will perform; if you are using an f/2.8 zoom it would effectively become an f/3.5 zoom using a CC40 filter (the difference is 2/3 of a stop).
     
  21. Hi Anthony,

    Thanks for noting the level of light loss and potential affect on AF performance. I may be able to afford the loss because sometimes the most off-color lighting is in the brightest gyms. For indoor sports I'm normally using 1.4 or 1.8 aperture primes.

    If nothing else I'm sure I'll learn something through the experience.
     
  22. Hi Anthony,

    I was able to load into my D300 the linear.ntc file into Camera Control Pro 2.1 Trial and save
    it as a preset but I thought Saturation should be Neutral rather than Normal. Any thoughts?

    Also, which CC filter did you use to give you the closest UniWB for use in NX?

    James
     
  23. "I thought Saturation should be Neutral rather than Normal. Any thoughts?"

    > Hi James,

    Set Saturation, Brightness, Contrast, and Sharpening to "-".

    "Also, which CC filter did you use to give you the closest UniWB for use in NX?"

    > CC40M with some tweaking of the WB settings (A6, G2; but do not consider these settings absolute as they may be filter and WB target related) to get the numbers to line-up with what I saw using the Rawnalyze program to determine when channels clipped.

    I have been playing with Iliah Borg's recommendations for setting WB, the results are slightly different but essentially consistent. I may be updating the uni-WB file after further testing, I need some bright skies to come to any conclusions (hint: blue channel is more difficult to overexpose than it appears).
     

Share This Page