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Lightmeter Vs. in camera exposure/histogram....

Discussion in 'Lighting Forum' started by shanguli, Jul 4, 2015.

  1. shanguli

    shanguli Mu-43 Regular

    89
    Sep 16, 2014
    canada
    Check this link out:
    My cam is GH3, but if your camera has features as seen in the above video, then I wonder, how would a lightmeter like the Sekonic L-358 be of use to you?

    Reason why I mentioned L-358, is because I've heared good things about it, and found one that I'm thinking of buying, but wanted to hear about your experience & thoughts... Thanks very much!
     
  2. David A

    David A Mu-43 All-Pro

    Sep 30, 2011
    Brisbane, Australia
    I have an L-358D and an E-M1 and E-M5. The L-358D is a good meter but I tend to use the camera meter most of the time.

    I find using the L-358D very different to using the camera's meter. You have no histogram or highlight and shadow clipping indication, both of which are available on the camera. What you get is simply the recommended exposure so, on the face of it, the camera provides more information. Even so, the L-358D gives you several things the camera's meter doesn't. The first is a 1 degree spot meter which is a much smaller spot than the camera provides unless you're using a long lens. That means you can get a more precise spot meter reading with it than you can with the camera but spot meter readings are tricky unless you can identify an 18% reflectance area by sight for measurement, or unless you have a good idea of just how bright you want the area you're measuring to appear in your image so that you can work out the correct amount of exposure compensation to apply to the reading. Spot meter readings can be very useful but you need to know what you're doing when you choose to use spot metering. If you don't know how to use a spot meter you're going to be a lot better off using one of the camera's average metering modes and the L-358 series do not have an averaging meter mode for reflected light. What you can do is use it to take and store a number of spot meter readings from different parts of your subject and then have the meter average them for you but, once again, that takes knowledge and experience for best results.

    The next thing the L-358 series meters do that you can't do with the camera's meter is take an incident light meter reading. You place the meter at or on the subject with the incident meter dome pointing towards your shooting position and measure the light falling on the subject, not the light it reflects toward the subject. The meter will then provide a recommendation that should provide you with the correct exposure but that reading will give you no indication of whether the brightness range of your subject will exceed the range the sensor can capture. If it does exceed the sensor range then you're going to end up with clipped highlights or shadows, or both. The histogram and highlight and shadow clipping indications the camera's meter provide help you avoid that problem.

    The good thing about incident light readings is that they aren't influenced by the colour or reflectivity of your subject. If you take several shots of your scene using the camera's meter and you recompose for each shot so that you get a bit more shadow area in one shot and more highlight area in another, the camera's meter will give you different results even though you're shooting the same subject and the light hasn't changed. That's because it averages the range of brightnesses you include in the frame and if you have more shadow area in one frame the camera's meter will recommend more exposure and if you have more highlight area in another frame it will indicate less exposure, simply because you're changing the mix of dark and light areas in the frame whenever you recompose but the problem with that is that whatever is common to both frames, say a person's face, is going to be darker in one frame and lighter in another. Incident light meter readings aren't influenced by the mix of dark and light tones in the frame because they're based on the amount of light falling on the subject. That can be very handy for portraiture but it's a bit harder to take an incident light reading if you're shooting a landscape and the mountains you're interested in are 10 miles away. By the time you take the meter to the mountains, take the reading, and get back to your camera the light is likely to have changed and the reading will no longer be of use.

    The L-358 series also provide a range of measurement options for flash photography and shooting movies that the camera's meter doesn't. I haven't used any of those options so I can't tell you anything about them.

    I'd view the L-358 series of meters as specialist tools for photographers who know how to use them and who have a special need for those sorts of measurement. If you have a need for those sorts of measurement and you know how to make and use them, they're very useful meters. I bought mine for the more precise spot metering occasionally and also to experiment with trying incident light readings in some situations. What I learnt was that for most situations I'm just as well off using the camera's meter and that is a lot quicker and more "user friendly" in some ways than my L-358D. The other thing I found out about it is that the battery it uses is expensive, it's not a re-chargeable battery, and it's easy to let it run flat so batteries can end up being expensive. I end up removing the battery after I use it because if I don't I'm likely to find I've got a flat battery the next time I decide to use it.

    My advice would be to learn how to use your camera's meter and how to get the best results from it, especially how to use the histogram and/or the highlight and shadow clipping indication. Only consider the L-358 if you have a specific need for the sorts of measurement options it offers that your camera doesn't. For most general photography the camera's meter is simple and reliable once you learn how to use it to best advantage and the L-358 isn't going to recommend a different exposure if you use it properly. It's also simpler to use and you don't have to set your camera to manual mode and transfer the L-358's recommended shutter speed and aperture to the camera. There's a big convenience factor to using the camera's meter. On the other hand the L-358 series of meters do offer options your camera doesn't have and if you need those options it could be invaluable. The question you need to consider is whether or not you need those options.
     
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  3. shanguli

    shanguli Mu-43 Regular

    89
    Sep 16, 2014
    canada
    Thanks very much David for explaining this and giving me your thoughts....
    You pointed out that when I use the L-358, to measure the incident light, the meter will suggest a correct exposure "but that reading will give you no indication of whether the brightness range of your subject will exceed the range [... that my camera] sensor can capture."
    1-The question is how do I determine "the range" that GH3 sensor can capture?

    2-What you say about using the L-358 light meter to shoot landscape and mountain makes total sense, but my goal is to do headshot/portrait photography & am wondering if L-358 would provide some advantage over the in camera metering and histogram?
    3-You did mention spot metering (as opposed to evaluative/matrix....). If my goal is portrait and headshot photography, is it better to choose spot as opposed to say center weighted/matrix metering...?
    Thanks very much!
     
  4. oldracer

    oldracer Mu-43 All-Pro

    Oct 1, 2010
    USA
    shanguil, David's reply is thorough and thoughtful. I don't disagree with him at all, but I will try to add a little:

    For most ambient-light situations it is entirely feasible to take a test shot, look at the resulting histogram, and adjust as necessary there is no reason to fool with a hand-held light meter of any kind. Your in-camera, center-weighted, meter will probably get you within one stop of where you need to be. Portraits and landscapes fall into this category. Unusually contrasty situations might benefit from a little spot-metering or incident-light metering but these are not common.

    One place where a hand-held meter can be useful is in flash photography where you are balancing ambient and flash. Experimentation in this area is entirely feasible too, but is more time consuming than experimentation with ambient only. The reason is that you are not only adjusting ambient exposure in the camera, you are adjusting the flash power/ratio of ambient to flash. So, two things to fool with = longer experiments. If you do not know this place: http://strobist.blogspot.com/2006/03/lighting-101.html you should spend a little time there.

    Another place where a hand held meter can be valuable is for flash photography in the studio. With a hand held flash meter you can easily, for example, adjust a second front (aka fill) strobe to be 1.5 stops lower than your primary strobe or soft box. Same story for a back hair light or a backdrop light. Once you meter your primary source, all of the other sources can be metered separately and set according to your taste. The in-camera meter cannot help with any of this.

    In the end it is only the captured image that matters, not the tools used to get it. Learn what your camera histograms look like when your RAW results are good and use that as your standard. One more thing: If you are not familiar with the phrase "expose to the right" that is a concept that you should study a bit, too.
     
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  5. Bif

    Bif Mu-43 Veteran

    380
    May 28, 2012
    San Angelo TX
    Bruce Foreman
    Well, here's my "take" on it. I have an old Sekonic L328 purchased in 1970 on the way back from VietNam, kind of as a "gift" for having survived a combat tour. Used it with film for several decades and was never disappointed in the results I got with it. I always used it in incident mode.

    But we have decent tools built into the cameras nowadays, I used to have to wait a few days to see processed film images so we learned to "read" the light characteristics with eyeballs and integrate that with what we expected from the exposure reading.

    But the tools in today's cameras help us do that. We can evaluate the LCD image or EVF image in playback mode, see the image just taken with histogram, and make judgements from there. Or if there is time put the just taken test image on computer and judge from there.

    One of the most useful accessories you can have with you is a "loupe" that excludes ambient light so you can really "see" what's on the lCD. However I tend to review in the EVF and once you learn to interpret what your camera shows you, you can get along fine.

    Remember, the histogram is NOT an exposure meter. But it will show an indication of highlight clipping or shadow clipping by where the "spikes" are, so by visually evaluating the image highlights and shadow areas while understanding what the histogram is showing it's a great tool. And the built in meter is surprisingly accurate.

    I haven't used my Sekonic in a couple of decades.
     
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  6. Gerard

    Gerard Mu-43 All-Pro

    May 12, 2015
    Vleuten, Utrecht
    Thanks for the explanation, I have always been curious about the purpose of lightmeters.
     
  7. David A

    David A Mu-43 All-Pro

    Sep 30, 2011
    Brisbane, Australia
    That's tricky with any camera and it comes down a fair bit to experience.

    First, are you shooting RAW or JPEG? Camera meters use the image generated for display and that is based on JPEG conversion. RAW files capture a wider range so if you're shooting RAW, the camera's histogram and highlight and shadow clipping indicators will show clipping of highlights and shadows that really aren't clipped and will reveal detail when you process the RAW image. The general rule, regardless of what you shoot, is that you should not clip highlights containing detail you want because you can't recover that detail. If it is genuinely clipped, it's lost. What you can do to get a feel for how the meter display relates to where your highlights will genuinely clip is to get something to use as a target which is very light in colour and place it in a brightly lit area. You want it to be brighter/lighter than its surroundings. I tend to place a piece of white paper on the grass in my yard. Start taking photos of it using your preferred meter option and including a fair area of the surroundings in the frame and dial in increasing amounts of exposure compensation in order to increase the exposure. Note at what amount of exposure compensation the histogram or highlight clipping display starts to show highlight clipping but keep taking more shots until you reach the camera's limit for positive exposure compensation. Then go and process the images. Find out at what exposure the light coloured target actually clips in your processing software and compare that to where your camera started to show clipping. With RAW files you'll find that you have recoverable highlight detail from the target for some amount above where the camera starts to show clipping. That tells you how much you can expose to the right after the camera starts showing clipping in its display. Now go and start shooting some normal scenes and see how well you can recover the amount of detail you want from real life highlights when you expose to the right that much. The target exercise is an unnatural situation but it will give you a general idea. Shooting real scenes starts to tell you what you can do in real life and those results may vary a little for different types of scenes. Different processing applications may give you more or less leeway with the highlights.

    Note that I've talked about clipping of highlights you want to keep detail in. There are some things you can't avoid clipping like actual light sources which are in the frame, and reflections from surfaces like glass, water, or chromed metal. If you've got those sort of things in the frame, let them clip because if you try to reduce exposure to stop them clipping you will either not be able to do so or you will end up with the rest of the frame, which is what you are really interested in, so underexposed that you won't be able to get good results from it.

    As far as determining the other end of the scale, I wouldn't worry about that. If you're exposing so that you give as much exposure as you can without losing highlight detail that you want, then there's nothing you can do about shadow detail which clips. You're already capturing as wide a range as the sensor can capture. If you want more detail in the darker areas of the scene you're going to have to do HDR.


    What incident metering with the L-358 will do in that kind of situation is give you an exposure in which the face should look pretty good when you open the file in your application but if the brightest highlight area you're interested in is not much brighter than the face, then you may be able to do a bit better if you expose to the right. Once again you're going to have to try taking some shots and adding progressive amounts of exposure compensation in order to find out just how much you can add, but then you're also going to have to reduce the exposure a little in processing in order to bring the face back to the right level of brightness in the finished image. You may get less noise in the shadow areas doing that than if you just use the recommended exposure.

    Where the L-358 could be handy to you in that sort of shooting is if you're shooting a lot of portraits and the model is changing outfits between shots, or you're including more or less of their body and clothing in different shots. Those sort of changes will give different recommendations with a meter which reads the reflected light from the subject which is what the camera's meter does. Provided you shoot from basically the same shooting direction and don't change the lighting between shots, the incident light meter reading will be the same from shot to shot and will deliver consistently good (or bad) exposures across all of them. The face will have the same tonality from shot to shot no matter how the average brightness of what you include in the frame changes. If you find that a bit of exposure compensation over the incident meter recommendation helps get the result you want, you just include the same amount of compensation for each shot so basically you set the camera's exposure settings manually at the start and just keep shooting without changing exposure unless you change the lighting, either by adjusting the lighting or shooting from a different angle so the subject is lit differently. If you have a studio setup and you use the same lighting setup, model location, and shooting angle on a regular basis, you just keep using the same exposure all the time and you will get consistent results. That can simplify your processing considerably because you can set up a preset for the basic processing you apply and just apply that preset to every image, then just do whatever "retouching" you want to do for each image. That's the kind of situation that incident light meters excel with.


    Is it better? Yes/no/maybe. In relatively even light it probably isn't. If you're aiming for dramatic results with strong differences between highly and shadow areas on the face, then spot metering may be better but you're going to have to know how you want the shot to look before you start shooting and measure the right areas of the face and then adjust the lighting to suit. You'd spot measure a highly area and adjust lighting so you're not clipping that area, and then adjust the lighting further to control the shadow areas of the face to make sure that the contrast between them isn't to great so the shadow areas get so dark that you end up with noise there or losing detail you want. There are photographers who work that way and take a lot of time setting up the shot before they make the exposure but if you're shooting a more evenly exposed face then there's little or no advantage to spot metering.

    Basically I'll put it this way. Light meters are dumb, by which I mean they have no idea what you want. They just measure brightness and they tell you how bright the subject is. What they tell you is how much exposure to give if you want the area that you're measuring, whether that is the whole frame or just a spot within the frame, to come out with the same level of brightness as a standard exposure target like a grey card which reflects 18% of the light which falls upon it. What you're shooting isn't a grey card, and some parts of it reflect more than 18%, some less. That's why some parts are bright (they reflect more than 18%) and some are dark (they reflect less than 18%). If you want the face in your final image to look like it's brightly lit, so it looks a bit lighter than in a normal setting, you need to give more exposure than if you want it to look like it's in shadow in which case you would give less exposure so it looks darker than it would in a normal setting. You control how the final image looks by how you expose, and by how you process the image. You can get very different final results using exactly the same setup and lighting level simply by varying exposure and processing but all the meter can do is measure the light that's falling on the subject (incident meter reading) or reflecting from it (reflected meter reading) and that may not be changing. The meter is telling you something useful, how much light there is on the subject, but you have to interpret that information in order to give the exposure which will best produce the final result you want. Meters tell you something you really need to know, but that doesn't mean that they're telling you what exposure you need to give in order to get the result you want. You may need to adjust the exposure from what the meter suggests in order to get that result. Learning how to use what the meter tells you is a big part of getting the result you want. There are a lot of different ways to meter the subject and they can give different exposure recommendations but if you understand how the meter reading you're getting relates to the result you want, you can get the result you want and different people may very well prefer to use a different metering approach to the same scene. You have to find a way of working that's comfortable for you and learn how to use that to get the result you want. You may find you like working with a spot meter, or an incident light meter, or an averaging meter. It doesn't matter which way you prefer working if you know what to do with the meter reading you get in order to get the resulting image you want, and you may even find that you prefer one way of metering in one sort of situation and another way of metering in a different situation. It's a matter of building your own personal experience.
     
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