Tips on processing low-light image...

Discussion in 'Image Processing' started by Wab, May 16, 2016.

  1. Wab

    Wab Mu-43 Regular

    126
    May 27, 2015
    This is the image straight out of the camera:

    [​IMG]

    This is the exif:

    [​IMG]

    This is what it looks like after I'd 'crayoned' on it. I used Dfine2 (first time I used it) to try and help with the noise and did the rest of the tweaks in Lightroom.

    [​IMG]

    If anyone can give me some suggestions or pointers on how to improve (improve in general; not just this image which is just really an example), I'd love to hear them.
     
  2. gryphon1911

    gryphon1911 Mu-43 Hall of Famer

    Mar 13, 2014
    Central Ohio, USA
    Andrew
    1) Always nail the exposure to the best of your ability in camera (or a smidge of over exposure is better than under)
    2) Shoot in RAW and use Oly Viewer 3.
    3) Use a third party post processing tool. I find that the 3rd party tools have a better algorithm than Lightroom. I use Topax DeNoise, but others like Noise Ninja, Nik Dfine, amongst others.
    4) Keep the ISO as low as possible, any extra light is helpful. Don't be afraid to use external flashes.
    5) (This image) The main subject is most important, so trying to pull the shadows from the background is not really that important. I'd have let them be darker.
     
  3. David A

    David A Mu-43 All-Pro

    Sep 30, 2011
    Brisbane, Australia
    Andrew's comments about avoiding underexposure and not trying to pull the shadows from the background are important because underexposure and lifting shadows too much both increase noise. The less noise you have to start with, the better the result will be. I'll add that I have a personal aversion to shooting a low light scene which doesn't have bright highlights and does have a lot of shadow areas and then processing it so that the final image looks like the scene was much better lit than it actually was. I think that sort of approach destroys the mood of the scene. I think if you want a result that looks well lit you're better off using flash or some other form of additional lighting to get the results. I much prefer my low light shots to look like there was low light.

    What i've found with dealing with noise in low light shots in Lightroom/ACR is that the sharpening you apply plays a big part in your result. Sharpening for high detail, i.e. using a radius of less than 1.0 and a high detail setting, makes the noise much worse. In any event, in a low light situation there are going to be a lot of shadow areas so there isn't going to be a lot of detail visible to you in the first place and visible fine detail is the first detail to disappear when the light drops,. You're also going to be shooting with the lens wide open or close to wide open so your depth of field is going to be shallower than it often is and that means less sharp detail and definitely no fine detail outside the zone where depth of field keeps things looking sharp. That means that sharpening for fine detail doesn't make a lot of sense so avoid low radius/high detail settings for your sharpening. Start off by using the Sharpen Faces preset or a radius of 1.4 or so and a Detail setting of 15 or so, but less than 25. The image will look sharper, especially if you aren't trying to lift the shadows too much, and the noise won't be accentuated as much. The more you try to bring out detail, the more you are going to accentuate the noise that is present. If you don't sharpen in ways that accentuate noise, then noise reduction becomes easier, more effective, and the image looks a lot better.

    I won't argue about whether LR is a good choice for sharpening/noise reduction for low light shots or any other sort of shot, or about which application is the best. I will say that LR is capable of better results than those a lot of people complain about and the problem with bad results in more than a few cases is not LR but simply the fact that it isn't being used in the most appropriate way for the image.
     
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  4. Klorenzo

    Klorenzo Mu-43 All-Pro

    Mar 10, 2014
    Lorenzo
    I agree with the others in general, but in this specific case the SS was already 1/15s, so there was not much space for a brighter exposure involving a "moving" subject (unless you were doing a proper photoshoot in that case just bring more light or find a better location/time of the day). You could have tried to use the pop-up flash but in my experience it takes a little practice/a few attempts to get good results.
    WB is off, so again shoot RAW (or RAW+jpeg) when the situation is complex so you have one less thing to fix later.

    First I did a coarse exposure (half stop), levels (stretch the histogram) and WB correction.
    I think you have mixed light here: some artificial light bulb from above that turned all the scene to yellow and some natural light from the bottom left that casts a blue halo on the right side of the subject. So I killed as much blue as possible from the whole scene (with LAB curves) and smaller color corrections for the skin with a different curve. I'm not completely happy but it's reasonable.
    I would not do a uniform exposure correction here: the sweater is black, I suppose(?), no need to turn it to gray. The upper/lower and left/right parts of the subject are also lit in a different way so it makes sense to do a different correction. I used one tone curve for the whole scene and a different one for the face, trying to brighten it as much as possible before it starts to look unnatural.
    I did no shadows recovery, just highlights on the back wall.
    I did a little denoise even if denoise on an already denoised/sharpened jpeg is not ideal. I used a tone mask to denoise only the darkest parts: the front and chins are already good, I would only remove skin details that are clearly visible. And noise is already good, there is no real reason to remove it much further.

    This is what I got: Lorenzo z has shared 1 photo with you!

    I looked at your editing: the noise is extremely amplified, I think you applied a lot of sharpening with a threshold too low. In this way you sharpened the noise and the jpeg artifacts too (this is where working on RAW makes a big difference). I would also sharpen the subject only, sharpening the background remove some of the out-of-focus separation. You cropped a lot: cropping makes noise more visible. You could have gone tighter (with a different lens or moving closer). Now I think you did work on the RAW file: it was impossible for me to recover the eyes color from the jpeg.
    Here you also tried to change the exposure of the scene: it was quite dark and you want it to be bright. I mean that if you used an external exposure meter or a gray target to have a "natural" exposure (for the skin) you would probably get an image just a little brighter then the starting one. So you are not only dealing with ISO 1600 noise and I think a little underexposure but you are also changing the scene brightness. Nothing wrong here per se, it just makes things harder.
     
  5. GBarrington

    GBarrington Mu-43 Veteran

    As others have pointed out, your exposure isn't very good. You need to work on that, and I think a lot of your problems will resolve themselves.

    However, I have been experimenting with HDR lately for problem exposures (on my E-M10), and I am learning that a fusion HDR technique, as opposed to tone mapping can result in VERY natural looking photos, and what those composite images can do to improve noise and detail issues is pretty cool.

    You still want the best possible initial exposure, HDR is not a workaround for bad metering techniques, but then a 3 or 5 burst sequence varying the exposure by an EV of 2 or 3, in both a darker and lighter versions can provide a sort of insurance for exposure problems.

    I should think a photo like this, where the subject is relatively still, would lend itself to fusion HDR techniques pretty easily.
     
  6. dwig

    dwig Mu-43 Top Veteran

    624
    Jun 26, 2010
    Key West FL
    Also, the Masking slider is very very very useful in such situations. Hold down the Alt/Option key when adjusting this to get a preview of the mask as you adjust the slider. The Mask controls where the sharpening is done. My adjusted the slider so that there is no sharpening anywhere except important edges avoids have the sharpening accentuate the noise is smooth areas.

    Another point about exposure: While overexposing a bit to lift the shadows away from the noise can help the shadows, it runs the risk of clipping the highlights. When the highlights clip there is a total lost of data and nothing can be done to recover them. In general, it is better to lower the ISO than to "overexpose" to increase the shadows.
     
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  7. gryphon1911

    gryphon1911 Mu-43 Hall of Famer

    Mar 13, 2014
    Central Ohio, USA
    Andrew
    Given the on screen histograms and real time preview in an EVF with the ability to turn on the clipping highlights should give just about everyone the tools they need to get better exposures with much less guesswork than using a camera with only an OVF.

    To summarize my points in a more basic way.

    1) Always get the best possible file to start with - which means getting the best in camera exposure possible.
    2) Use extra light to help your exposures. There are some pretty small speedlights out there and even on camera flash that can be bounced to aid in keeping the subject exposure in a low ISO range.
    2) Shoot in a way that gives you the most latitude for post processing - RAW
     
  8. Speedliner

    Speedliner Mu-43 All-Pro

    Mar 2, 2015
    Southern NJ, USA
    Rob
    I turn sharpening off, then maximize the mask in LR before adding it back. Usually no point in sharpening the background which just elevates overall noise.
     
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  9. David A

    David A Mu-43 All-Pro

    Sep 30, 2011
    Brisbane, Australia
    I agree with Rob's comment but as an alternative if you don't want to mask strongly you can always use a local adjustment on the background and even in darker areas of the subject and increase the noise reduction there. That can give you a bit more sharpening in the areas which are important and minimise the noise in areas which aren't as important. There's often more way than one to skin a cat.