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Underexposure and RAW

bradkbradk Member
edited October 2011 in general photography
On a photo shoot last week end I under exposed a number of images. I was shooting in RAW. So my first question is what is the general consensus on how much you can increase the exposure with a RAW image on Lightroom or Photoshop without damaging the image?

And secondly, the issue I had over the week end was with back lit trees or sky that I wanted to blow out a bit. I did have an off camera soft box so I had lots of latitude but the "histogram alone" technique wasn't very useful in those situations. I mostly used Photovision's pocket digital calibration target, which has an area of black, gray and white so I could see how they looked on the histogram taken zoomed in without the blown out areas. Of course it sounds like a great plan but in practice, outside during dynamic lighting conditions, downtown Portland, I certainly didn't nail the exposure every time. And of course, out of the 638 shots I took, even though most were exposed within 1/3 stop correctly, some of my favorites were off by more.
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  • TrevTrev Moderator
    edited October 2011
    bradk,

    You can easily bring up the image in RAW even up to 2 stops under, however, you will suffer some exposure noise in the shadows, to what extent that affects the image depends on how much shadow is in the image, but certainly it's not a hopeless situation in that circumstance.

    Just make sure you get the exposure pretty good *before* you try to adjust color settings, as under-exposing makes the colors muddy and trying to adjust first, then exposure, will have you going back anyway to do colors again.

    As to the 'histogram method' you do need to remember to take a shot fairly close with only the 'relevant' highlights in the image, none of the background that you did not care about, meaning a close up of bride's dress before settling on your settings, even a bit under on that as you said you had the off camera softbox flash to lift them up to proper exposure, or, setting that correctly and only using the softbox for a touch of fill light, then ignoring the rest if you were happy with the background blowing a bit.

    It's actually better to slightly overexpose an image, [in raw] depending on subject content if there are lots of shadows in the composition, as that brings up the shadows reducing noise, and bring down the exposure when manipulating, even masking if need be, the shadows.

    The fact you said you were happy with the vast majority of the 638 shots you took, speaks volumes in terms of how you achieved that, so a few under or over is to be totally expected. Guarantee you no one gets exposure dead on each and every shot.

    You can download one of these actions for 'Shadow Range' listed here:

    http://neilvn.com/tangents/2011/08/31/photoshop-actions-to-help-with-post-processing-after-raw-conversion/

    Run, and adjust the layer opacity and you will be amazed at how much you can open it back up, without blowing highlights, layer opacity of around 20-30% normally suffices.

    Trev.



  • Thanks Trev! After thinking more about the shoot on Sat the other thing that was disconcerting was the fact that I often had a dark background and the model was wearing dark clothes. I would use the gray/white card to expose the image close up then take a series of pictures. It was hard for me to trust my exposure because of course my histogram had nothing in the fifth column.
  • Also, typically when I was using the softbox I always took an exposure with my gray/white card with the flash firing at the manual exposure that I set and at the distance my assistant was holding it. After metering for the ambient light.
  • bradk,
    If the scene is predominantly dark tones, your histogram will often be left-leaning. If you had a "perfect histogram" in that situation, your darks would have been likely overexposed.
  • A flash meter is so invaluable in these situations.
  • TrevTrev Moderator
    edited October 2011
    bradk,

    Yes, as Stephen said, in that case you would have wanted the histogram to be left orientated without showing a lot of clipping [jammed up to left too far] and that way you would also have obtained a much better exposure.

    As in the case of what you said the subject was wearing dark clothes, and you did have the grey/white card, then using that as a guide is a way to go; also using a light meter if you have one.

    What you need to do is practice with what your camera 'shows' and what the results look like when image downloaded to computer.

    Experience is the only way to gauge an estimate setting straight off the bat.

    eg: The moment I step into outside shade I immediately open up my camera by 2 stops, aperture, ISO or both. Inside a room, 3-4 stops, and then work from there, it comes down to just 'knowing' where to start.

    Here is a little trick that I learned a loooong time ago in film days. IF you have a patch of green grass, point the camera at that making sure you fill the frame, and that you aim at same lighting conditions you wish to expose for [sun or shade], then, using ISO or aperture or shutter/combo zero your camera's meter out.

    Take a shot, and look at the histogram, you should have it like a mountain peak, rising up equally from left/right to having it placed smack dab in the middle of the histogram. Green grass is almost a perfect 18% reflective grey card, [EDIT: I mean exposure wise as in 18% reflective grey, not color balance] at least that will get you off to somewhere to start from.

    Trev.
  • Thanks Trevor - I do have a flash meter which is how I calibrated my grey/white card with my camera meter. I practiced dentistry for 30 years so if you know anything about dentists we are gadget lovers. As I have pursued portrait photography more seriously i started to get bogged down with a lot of technical stuff (which i love) and found that with the on location shoots i often do they can get in the way, I'm just trying to sort out the best approach for me without getting obsessive about it. I appreciate the practical advise form someone who has a lot of experience. I am trying to enjoy the process recognizes that the learning never ends. Which is one of the things I love about portrait photography
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