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A beginners low-light exposure question (sorry!)

Discussion in 'Panasonic Cameras' started by nickfromlondon, Jan 23, 2012.

  1. nickfromlondon

    nickfromlondon Mu-43 Regular

    27
    Dec 4, 2011
    Good afternoon,

    So, I am really get used to my G2 now. As I have said before, it is my first "proper" camera. I have bought the 20mm lens, specifically to use in low light.

    One of the big puzzles to me is low light exposure. This is not a question about WYSIWG, I know I can see the true light of what I am actually photographing on the LCD by pressing the DOF button and then display.

    What really perplexes me is that when I take a relatively dark picture (in RAW), it can very often be brought back to normal in Lightroom (using the auto tone button for example). When using auto tone control, the light brightens, the colours come out and the photo is no longer dark.

    What I don't understand is, if the camera has all the necessary information to create a relatively bright picture, why doesn't it do so in the first place? Why wait until we "unlock" the detail in a photo editing suite?

    This also leads to the question of how do you know, when taking a shot, if a dim shot is going to be rescuable? I mean, if I take a dim shot, do I have any way of knowing how manipulable the shot will be in lightroom?

    Or do you always make sure you have good light in your picture, no matter what? (i.e. if the DOF/Display buttons show a potentially dark photo, do you just not take the photo using those settings?).

    And as an aside, do any of you ever use the flash? So many people have said in articles I have read online that a flash should never be used!

    Thanks a lot for taking the time to read this

    Nick
     
  2. dhazeghi

    dhazeghi Mu-43 Hall of Famer

    Aug 6, 2010
    San Jose, CA
    Dara
    The short answer is that it doesn't have all the detail that a properly exposed shot would. In many cases, the result is still good enough for casual use, but in other cases, it's not.

    The less light the sensor gets, the less actual information gets captured, and that means noise, as photoreceptors falsely report information that isn't there.

    If you take two shots, one with 'correct' exposure, and with a shutter speed 1/4 of the original shot's, then correct the second shot in Lightroom to look like the first, and then view both at 100% or 50% magnification, I bet you'll be able to tell the difference quite easily.

    DH
     
  3. DDBazooka

    DDBazooka Mu-43 Veteran

    211
    Sep 3, 2011
    Editing the picture like that selectively changes the exposure in the picture. Matrix metering has to average out the exposure and lighten/darken certain areas to achieve the "average".

    Maybe one day we'll have a magic metering mode where we can set different quadrants of a picture to different shutter speeds or fstop.
     
  4. Ned

    Ned Mu-43 Legend

    Jul 18, 2010
    Alberta, Canada
    A photo "recovered" in post by increasing the exposure value does not have the same detail of information as a photo which was fully exposed in the capture. This is NOT a method you should be using by choice, but only as a very last resort if you mess up in the field.

    How a camera meters for exposure is all dependent on you, the photographer. There are three main methods of metering, which vary slightly in name from camera to camera but otherwise serve the same function - spot, center weighted, and matrix. Matrix metering averages out the entire scene to get a meter reading, center weighted does the same over a small central area, and spot metering takes a reading off a small spot. Spot meter is of course the most accurate, but can also be thrown off drastically by an isolated shadow or highlight. That's where Center Weighted comes in to give you a balance of manual control and a consistent area reading. This is my choice for "general purpose" photography. Center weighted and spot both give you manual control over your metering subject, though they vary on how specific. If you meter on a piece of dark clothing for instance, then the camera will brighten the exposure to reveal the details of the fabric. If you meter on a light patch of skin, then the camera will darken the exposure to retain the details in the skin. Proper exposure is determined by the PHOTOGRAPHER'S evaluation of the scene, not the camera. The camera can't distinguish between a subject and background for instance, so don't let the camera make all the decisions for you.

    Next function you have to control exposure is Exposure Compensation or "Program Shift", in every shooting mode but Manual. This will simply change your camera settings to brighten or darken the exposure over or under your initial meter reading. So if you meter off your desired subject but it still looks underexposed, then increase the Exposure Compensation. It's that simple. :)

    What Exposure Comp actually does is determined by your shooting mode. There are three factors that determine exposure - Aperture size, Shutter speed, and ISO sensitivity. The wider the aperture (lower f-stop), the slower the shutter speed, or the higher the ISO value, the brighter the image and vice versa. If you are in Aperture Priority then you set the aperture and the camera picks the shutter speed depending on your meter reading. If you are in Shutter Priority then you set the shutter speed and the camera decides the aperture size depending on your meter reading. So Exposure Compensation will change the non-priority value, be it aperture or shutter. In Program mode it's called "Program Shift" because it changes both Aperture and Shutter. In Manual mode you choose both factors yourself so there is no Exposure Compensation. ISO is normally set yourself, but can also be set to Auto in any mode. The camera will normally leave it at the lowest ISO unless your camera reaches its limits in aperture and/or shutter speed and needs to bump the ISO to brighten the image further. Bumping ISO should normally be a last resort to gain more exposure when the other two factors are too slow, as a lower ISO (at least, closer to base ISO, which is the lowest ISO on most cameras but not all) will give you a higher quality image (less noise, more detail, higher dynamic range).

    When people say flash should never be used, they are talking about using the pop-up flash on the camera. This is a very direct flash and will give a very flat look that's full of shadows, and it is not very easy to diffuse the pop-up. Professional photography often involves all sorts of strobes (speedlights are a type of strobe) in order to control your lighting and produce the image you want. Photography is all about capture of light, so being able to artificially control that light is what will guarantee the right image. We do not use the flash on the camera though, and we rarely shoot bare lights with no modifiers to soften or manipulate them.

    If you want to shoot with "ambient light" (aka, what light is available in the scene), then you should invest in a fast lens. This will allow you to capture a full exposure without bumping up the ISO, by providing a wide aperture to capture more light. Look for a lens which provides a smaller f-number (marked on the lens like 1:1.4, 1:2.8, or 1:2.8-3.5, etc.).
     
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  5. mumu

    mumu New to Mu-43

    4
    Jan 16, 2012
    Hi Nick. dhazeghi already answered your question but I thought I'd jump in as well. When you're bringing an image "back to normal" in Lightroom, you're basically raising levels on an underexposed image. So the noise in the underexposed areas is being amplified and becomes more noticeable when you increase the levels in Lightroom.

    And yes, the camera can do this too. That's why images shot at higher ISOs have more noise.

    As for your particular example when the camera undexposed, well, basically, the metering algorithm mis-read the scene and chose the wrong exposure. Even with today's fancy exposure systems, it's still possible for the system to be fooled.

    Generally speaking, the meter will get the exposure right, so dim exposures are usually the result of some limitation that prevents you from using the idea exposure. In low light shooting, this is usually a limitation in shutter speed, where you want to use a minimum shutter speed to reduce either camera shake, or subject movement blur. In that case, I would typically expect that I could get away with underexposing by about 1-stop. Or, if I only want to use a small version of the final image (eg: I'm just going to use it on a web page), then I could get away with 2-3 stops worth of underexposure since the artifacts caused by the boosting of the exposure in post processing might not be as noticeable.

    Of course, you also have to consider the tonal range of the image. If you need detail from the shadows, then under exposing is not going to be nearly as salvageable since the shadow areas might be so dark as to be 100% black and therefore it will contain no detail at all.

    If I really need to take the photo, then I will take the shot even though I know it's underexposed. But if I can improve the light, then I will. Oh, another thing: not all photos require lots of light to have good light. Some photos are purposely underexposed to achieve the look that the photographer is looking for.

    IMO, most people who say that flash should never be used either don't know how to use flash. Either that, or they're not being very precise in their wording, and are only referring to direct, on-camera flash, pointing at the subject. There's a whole world of flash lighting techniques that can produce jaw-dropping results.

    But even direct, on-camera flash can provide decent results, particularly when used as a fill-flash. Plus, imo, it's still better to get the shot than not, even though the lighting isn't as perfect as you'd like it to be.
     
  6. drewbot

    drewbot Mu-43 Top Veteran

    702
    Oct 21, 2011
    Toronto, ON
    I think that yes, on-board flash should be avoided if you can.

    However, there are multiple options for nicer flash.

    A cheap option would be installing a simple flash diffuser for your on-board flash. A Gary Fong hotshoe attachment comes to mind. A DIY solution can be added right to the flash on your G2, with some tape.

    Of course, the next option would be to add a hotshoe flash. You could bounce light from different angles to create dramatic effects.
     
  7. nickfromlondon

    nickfromlondon Mu-43 Regular

    27
    Dec 4, 2011
    Seriously, THANK YOU for such brilliant replies. I cannot tell you how useful they are...

    I think my problem is I am trying to use a high shutter speed in low-ish light as I am taking photos of my kids inside our house. As they move faster than a speeding bullet, I find I have to have the shutter speed set to at least 1/100th.

    I bought the 20mm/ f1.7 lens to compensate for this, but even this lens cannot "cope" with shutter speeds of 1/100th in indoor light...

    Out of interest, what do you think my best workflow for this kind of shooting would be (beyond investing in proper flashes)? Am I trying to square an impossible circle by shooting moving objects (kids) in low indoor light?

    And another question out of curiosity, would I be having these same questions with any camera? I mean, let's say any camera below $700? Or is this problem more apparent in the G2, compared to say a G3 or EOS 600D?

    At least I won't be relying on Lightroom now to rescue me. All your answers point to me needing to ensure good exposure at source rather than rely on post production.

    Thanks again, really fascinating replies for me...
     
  8. RichDesmond

    RichDesmond Mu-43 Veteran

    356
    Nov 18, 2011
    Nick, what is your ISO set to? If it's at a low value, like 100 or 200, you will definitely have problems. Bumping it up to 800 or even 1600 will help. The images will be slightly noisier, but for the type of shots you're describing I don't think it would be a problem.
     
  9. DDBazooka

    DDBazooka Mu-43 Veteran

    211
    Sep 3, 2011
    Great post. The only thing I want to point out is that Program Shift doesn't actually affect the exposure, it just cycles through the combination of aperture/shutter speeds while maintaining the original metered amount of light.
     
  10. sprinke

    sprinke Mu-43 All-Pro

    Apr 5, 2011
    Pasadena, CA
    Debi
    I was in your same situation. I ended up buying a hotshoe flash (Metz 50). Now I do a lot of bounce flash in the house and the results look SO much better. It's not really that hard, and all of the walls and ceilings in our house are white anyway so it works for me.
     
  11. speltrong

    speltrong Mu-43 Veteran

    338
    May 8, 2011
    Northern California
    You could also up the lighting in your house - Install higher wattage or more efficient types of bulbs. Poor quality low-light sensitivity is one of the (very few, IMO) drawbacks to the Micro 4/3 sensor, which I believe is mostly to do with the physical size of it. Larger sensors like APS-C and Full-frame have much better light-gathering capabilities, therefore giving you better results indoors. It's gotten better over time - the new GX1 seems to do noticeably better than my GF1, but neither of them still compare to a Canon 5D or a Nikon D4 ;). For now, your only option is to get more light on the kids indoors. Get a flash and learn to bounce so you don't wash everything out.
     
  12. leonberdi

    leonberdi Mu-43 Regular

    133
    Apr 15, 2011
    Montreal
    I'm in the same boat with my toddler... On top of exposure, focus is a problem indoors. Some recomednations:
    1) Try continous shooting mode. There will be lots of throw-aways, but you can get a gem once in awhile
    2) diffuse the onboard flash with something, anything, even paper-towel (I use an old plastic film container)
    3) Use exposure/focus lock. The 20mm is a 'fast' lens, but relatively slow at focussing.
    4) as has been mentioned before, increase the ISO to a point that you find you are still gettiing acceptable results.

    Good luck!
     
  13. 13Promet

    13Promet Mu-43 Regular

    84
    Dec 11, 2011
    Milano
    Even if it's "just" taking pictures of your kids, getting 1/100'' in dim indoor light without using a flash is quite demanding from the techinical standpoint.
    A very expensive fast lens will give you about double light compared to the 20 1.7, where "double" is not as much more as it sounds: basically, you'd be stuck again at the same point. Wich a much emptier wallet :biggrin:
    You can verify this point easilly: if in lightroom you raise the exposition by more than one EV in order to compensate the underexposure when using the 20/1.7 , it means that you'd get underexposed pictures even with an f/1:1 lens in the same shooting conditions.

    High-end SLRs allow much better IQ at high ISO, but that comes for a price and for a bulk...

    The most cost-effective solution of your case, in my opinion, would be a flash to be used bounced by the ceiling :thumbup:
     
  14. nickfromlondon

    nickfromlondon Mu-43 Regular

    27
    Dec 4, 2011
    Thanks everyone, again, for all your detailed replies. I am not sure I have come across a more helpful forum before...

    Two quick questions do come to mind: Re ISO - I have read so many articles saying to never shoot above 800. How high do you go? Should I not worry about going to, say, 1600?

    Also (@13promet) when you talk about the higher IQ in bulkier and more expensive kit, are you talking about the >£1000 cameras? Or would I have got significantly better results with a 600D/ 3100 or even G3. I guess I am asking this because I felt I was better off getting a cheap G2 body, plus the 20mm lens, for less than the price of a 600D. I'm just hoping that I didn't make a bad judgement call!

    Thanks again...
     
  15. crsnydertx

    crsnydertx Mu-43 Top Veteran

    995
    Dec 31, 2010
    Houston, TX
    Chuck
    A 600D would arguably be a better low-light performer, but would need to be paired with a fast prime. Canon has several choices, one (50mm f/1.8) quite attractively priced at around $105 US. The others are significantly more expensive. The kit zoom for the 600D is much slower and I don't believe it would compete with the G2 with 20/1.7.
     
  16. dhazeghi

    dhazeghi Mu-43 Hall of Famer

    Aug 6, 2010
    San Jose, CA
    Dara
    Max. ISO depends on the lighting and what you do with the images. It's a personal choice. I stick to 800 or below on the E-PM1 (same sensor to the GF1), but you may find 1600 suitable for your purposes.

    Regarding alternatives, a G3 with will get you perhaps 1/2 stop better high ISO performance (so 1100 is as good as 800 on what you have now). A faster lens like the 25/1.4 will also give you half a stop. A kit like the Nikon D5100 + 35/1.8 will get you a bit more 1.3 stops or thereabouts (so 1600+ like 800 on the GF1).

    Brighter indoor lighting is a more cost-effective approach. Flash can be helpful, but it's still a fair bit of work to set up properly.

    DH
     
  17. RichDesmond

    RichDesmond Mu-43 Veteran

    356
    Nov 18, 2011
    Definitely try the 1600 setting, or even higher. Doesn't cost anything but a bit of time to see how it works for you. :smile: I took a bunch of shots the other night with my GF1 in a dimly lit concert venue at 1600, and was surprised at how well they came out. Probably won't want to make 16x20 prints out of them, but for normal prints and viewing on the computer they're great.
    Another thing that can help is to shoot in burst mode, just to improve the odds of getting that random instant when the kids aren't moving quite so fast.
     
  18. fin azvandi

    fin azvandi Mu-43 All-Pro

    Mar 12, 2011
    South Bend, IN
    I try to keep the ISO as low as possible, but if the choice is between not taking a photo and bumping it up past 800-1600 then bump it up!

    Here's one from a friend's New Year's party taken at ISO 3200, wide open (20/1.7) at 1/40s, straight OOC Jpeg - it was fairly dim in the room and I didn't use flash but you could get a faster shutter speed by improving the light. Sure it's noisy and a bit blurry but IMHO still okay for viewing on the computer.
     

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  19. 13Promet

    13Promet Mu-43 Regular

    84
    Dec 11, 2011
    Milano
    Yes, I was referring to >£1000 cameras.
    I probably did not point out clearly enough that 1 or 2 or even 3 stops of ISO IQ advantage (which you can get by a low-end SLR like the D3100 or the 600D over your m4/3 by using a same speed lens) won't lead you much farther in field.

    Our eyes and brain compensate very efficiently the lighting differences whithin the scene.
    That's why the sky in the pictures out of camera always looks whashed out (as long as you don't use filters): it actually IS whashed out compared to the rest of the scene, but human view employs a very advanced "dynamic range management" :biggrin:
    This to say that those two stops are a really neglibile advantage in actual ability of taking or not taking pictures, if you're not a pro who must achieve up to date perfection.

    Cameras with significant ISO/quality ratio advantage, basically the FF ones, are quite expensive and so are their lenses.
    And when you've soon reached their limit and got used to it, there will be several situations when they're not enough, either.
    Basically, you'll be endlessly running after sensor's HI-ISO technology, because there will always be a new camera one stop faster than yours.


    In other words, IMO the cheapest way to grab the shots you want is not to make your equipment able to shoot in lower light, rather to increase the level of the lighting so that your current equipment can get good pictures :smile:

    Indoors, this can be done either by improving the room's lighting, as suggested by other users, or by using a speedlight.


    The third option would be accepting that low light photograpy is a very narrow and expensive option which would be better to keep down to the strict necessary, unless you're really artistically in love with it or technically forced to it.
    How many of the most beautiful pictures you've ever seen are shot in low-light? 1% or more? :wink:


    If I where you, I would bring my kids to the park before sunset and exploit the warm, soft, natural light from the Sun while they're freely playing in a beautiful environment :smile:
    This could be done at low-med ISO and optimal aperture to get 100% IQ both from sensor and lens.

    And when I really wanted to have an acceptable shot indoors of a situation that I can't miss, I'd used bounced external flash with diffuser. Which is cheap, simple and effective.


    My 2c