Measuring Light and Achieving the Correct Exposure

Get the measure of light with this simple class.

How do you measure the power of the light from your studio lighting to ensure perfect results? Do you apply visual, theoretical, histogram or light meter readings to achieve the best results?

Karl discusses the best ways to measure light and achieve the desired exposure as well as the limitations of the above methods and why it’s important to truly understand light if you want complete creative control.

In this class:

  • Different methods for measuring light
  • Light meters — what use are they in digital photography?
  • Assessing exposure visually
  • Combining aperture and shutter speed to achieve desired exposure
  • Reading histograms
  • Correctly exposing for different textures

Questions? Please post them below.

Comments

  1. I get the premise of this but don’t entirely agree as the light meter can speed things up a little by requiring less test shots – some can also adjust lights from the metered position. But I guess you are right there would need to be a specific need to invest in a light meter and that it is not entirely necessary.

  2. Steven Lan

    Hi Karl,
    The camera I’m using currently is a Canon R6 and my older model is a Sony a73. I can’t shoot tethered for the lack of proper equipment in the company I work in. One thing I discovered is that Canon does have better screen compared with Sony, however even I darkened the screen darkness, the photo always looks underexposed on computer while it looks okay on the camera. This issue often forces me to grab a light meter for safety.
    I see you use a lot of Canons in your videos, does this problem ever bother you?
    Thank you for reading my questions.

    1. Hi, thank you for your question. For the first part I would ask why can’t you shoot tethered? You said that ‘for lack of proper equipment’ There isn’t much to shooting tethered, you need a cable and some software, most cameras come with their own basic software to do this and if you need something more advanced then independent software is also available (such as Capture One). With regards your second issue we have to work through step by step. First of all is it the camera screen that’s wrong or is it your computer screen that’s wrong. The easiest thing to do would be to see if you can look at the images on a friends screen to see if they are different to your screen. It may be that your computer screen is set incorrectly and that also needs adjusting but you won’t be able to ascertain that until you have checked some of the things I mentioned above. Often there is a small difference between the camera screen and a computer screen but it’s not usually a huge difference. There are also other things that it may be such as the ‘colour space’ you’re shooting images in, for example Adobe RGB or Srgb etc and also if you’re shooting jpeg or RAW. First of all though you need to check the items I’ve mentioned above before we move on.

      1. Steven Lan

        Thanks for the kind reply Karl. It’s a bit embarrassing to say that the computer I usually use to do some editing isn’t in the same place I take photos. For the method you mentioned, double check with different monitor, unfortunately they’re both underexposed. I shoot in JPG with the color space set in sRGB, the Photoshop software is set to RGB mode (color profile is sRGB IEC61966-2.1 to be more precise ), 8-bit.

        There is one thing I forgot to mention earlier is that the underexposed issue happened when I follow the light meter’s aperture number. It’s pretty weird to have this kind of result when you follow the instruction of such device.

        When considering the correct exposure without light meter, is it appropriate to take both the histogram readings and my own thoughts into consideration? To become more creative, I am willing to toss the light meter away.

        Sorry for the late reply, it was weekend and the place I work are not not open.

        1. Hi, no problem. First of all if your camera has the option to use Adobe RGB colour space then I would switch to that. Also it is better to shoot RAW files than jpegs because you can make much greater adjustments to things like exposure and contrast on a RAW file than you can on a jpeg. The camera’s built in lightmeter is never 100% accurate, I think of them more as a guide. The histograms are very useful though if you understand how to read them. We have a class on that somewhere! If what you’re seeing on the camera screen doesn’t match the histogram then you might have a problem with the camera screen or it needs further adjustment but the only way you will know for sure is if you can access a proper colour calibrated monitor such as an Eizo Colour Edge or something similar. Many of the photo retouchers or printing labs use these screens, it may be possible for you to take your camera into them and then compare the photo on your camera screen to a copy of it that they display on their colour calibrated screen, only then will you know for sure if your camera screen is too dark or too light etc.

          1. Steven Lan

            Hi Karl, just finished the course you talked about color spaces and histogram, they are super helpful to me. I did some research online and found out that the Canon LCD sometimes are set too high which misleads us thinking the photo is overexposed or underexposed . In addition, I tried different color space and found that the color space in this case seems not to be the major reason. I’ll do more test shots and stick with the histogram to figure out the correct LCD brightness further.

            For the underexposed photo we talked earlier, I discovered my own mistake, which is that I set the shutter speed too high(1/250) without having high speed sync, causing a subtle stripe at the bottom edge of the image and probably elimiunating the light from the strobe, what a dumb move I made !

            Anyways, thank you for covering my questions and guiding the correct path to solution. I still got a lot of things to learn, I am tuning in more of your courses.

            Have a good day and wish you a happy new year!

          2. Thank you and I’m happy this is helping you make progress, enjoy the rest of our content!

  3. I love the classes, and I see arguments for both ways. I bought a flash meter to get me to “right” faster since I tend to beg friends and family to let me photograph them. Once it is “right,” I switch to the method shown in the video to adjust how I want.

    I felt one point was missed. In the scenario, the meter reading is f/5.6 when I want f/11. I’m not forced to use f/5.6. This information tells me I need to increase the lighting by two stops (or, I guess, modify the ISO if I had to) to get to f/11.

    Thanks for the amazing content. I wish I had found this sooner.

    1. Hi, thank you and I’m glad you are enjoying the classes. I have no problem with light meters when working with film (I used one for 15 years with film) but I would encourage you to try this on your next shoot as it makes you think about an understand lighting more quickly by training your eyes to see in fstops and half stops and ultimately knowing when to adjust by even a 10th of an fstop visually. So on your next shoot, set your lights up. For each light put them half way between their maximum and minimum power (that way you know you can go equally up or down). Then just test your background light first and decide visually if you need to go up or down and take a guess whether that is by one or two stops etc and do each test until you get it right, then your next light and your next light. As you do this you’ll also realise that the second and third lights added some light to the background and so on so you’ll be making a mental note of how each light affects the next. And finally after doing this a dozen times you’ll start to know visually when a light is two stops under or one stop over etc etc and you will build your lighting setup within just 3 tests or so. You’ll also start to see how much a light changes in exposure when you move it even a few inches from where it was etc etc. and the whole process of working will become more fluid.

  4. Hello
    How are you?
    With respect I disagree very strongly. Surprised by your wild comments about light meter users.
    Competence and experience determines where to place the exposure. Not blindly follow what a meter tells you.
    Any competent photographer properly trained knows that a light meter must always be used with a 18% grey card. No excuses. No exceptions. This gives you proper exposure for Zone 5.
    With film (b&w or colour) we always work between zone 2 (-3 strops) and zone 8 (+3 stops) to retain details in shadows and highlights.
    Gossen Lunasix F handheld meter has the zone scale clearly marked. Digi meters like you are using dont.
    Competence and experience determines where to place the exposure. Some may argue artistic interpretation may play a role in “high key” and “low key” photographs.

    1. Hi I’m confused as to your comment as my argument in this class was that competence and experience was what determines where to place the correct exposure? Also this class was aimed at those taking incident flash readings not reflected off a grey card?

  5. John

    Hi Karl. Loving your video lessons! I came across an old Sekonic L-28c2 light meter at a thrift shop. Is this something that I can still use for my photgraphy or do you recommend a newer, digital one? I’m having a hard time finding a video on how to use this particular model for still photography.

    Many Thanks!

    1. Hi John, for the way I work I wouldn’t even worry about it. Sekonic are a good brand and as long as it’s still on point at the correct exposure (check it compared to the result) then I’m sure it will do all you need.

      1. John

        Thanks Karl. I actually just found your video on not using light meters hehe. I’ve been learning your methods thus far and while I may use this just to learn how to use them, I’ll probably stick to your setup methods with being tethered and use the meter for getting a baseline in filmmaking.

        Thanks so much for all you do!

        1. Cheers, John. I don’t think there is anything wrong with using a lightmeter in general, especially if shooting on film, it’s just that the way we shoot these days and the other tools we have at our disposal mean that there are alternatives that I think help the creative process of decision making based on what we see rather than what we are told it should be. All the best Karl.

  7. I want to start by saying your course is excellent. I started loving sports and land scape photography but your style and teaching has gotten me really excited about portrait photography. I may know the answer but i wanted your opinion on aperture setting. Do you determine what F stop you are going to use by how you want the image to look, or is there a sweet spot you like to use personally? I know you set the F stop and shutter speed and adjust the light to that, just curious on how you go about determining what F stop you will use. Thank you

    1. Hi, thank you. Yes I determine the aperture I’m going to use based on the DOF I require for the creative look. For example in softer portraiture this will be shallower DOF but in fashion/beauty head shots it will be greater DOF, so it is always based on that creative decision and then I match the lighting to suit.

  8. Hi Karl, loving your work and your course. However, like CharClarPhoto said, I am going to have to disagree with you on this chapter. I have to agree with all that he said, and I am adding that you measured the reflected light, not the incident light (you should had pointed the lightmeter to the light, not to the camera) and if you want to underexpose the subject you could do it easealy and based on the right exposition.
    And yes we can use the histogram and our eye, of course, but I have to mention the usefulness of the lightmeter about the ratios of light.
    That said, I am happy to learn with you and your courses. (Sorry for my english).

    1. I have to agree with Barrento, used correctly the light meter can speed up your workflow & achieve consistent reliable results (under studio conditions). It’s how we were taught in BA Photography, as I say to achieve repeatable consistent results. It’s how many of the Universities/colleges teach getting studio lighting ratios correct.

      As you well know clients looking at your work often want similar/ identical results to portfolio work. And you can speedily achieve this taking extensive notes of your lighting set ups & ratios. To achieve consistent results

      Also inbuilt camera light meters are not as accurate, every single camera/model can & will give different results. However properly calibrated light meter will give accurate results. Yes we often have to compensate slightly, but that’s down to the cameras not the light meters.

      Like Barrento I do enjoy your courses but I have to disagree with your theory & the way you used the light meter

  9. Vic Peralta

    You suggest using a Color Checker in lieu of using a light meter. I have a X-rite Color Checker. If I am careful with the color checker (don’t touch the color pads, I store it in a bookcase and so on.) My question is do these color checker expire or loose potency?

    1. Hi, the Passport version is good because it comes in a protective case that keeps it in the dark, but if you look after a normal X-rite card it would last you 10 years.

    1. Hi, my understanding is that strobe light and speedlite are the same thing? A small unit that bursts out a brief blast of flash? I believe in the USA they use either term? A studio flash as I was using in this class is essentially a bigger more powerful version of the same thing. A continuous light such as LED is different as it doesn’t have the burst of flash but even with those I’d use the same technique for measuring and assessing light.

  11. Hi Karl,

    You mention shooting tethered…
    Is that subject covered in another section of the course?

    Cheers
    Nick

  12. Hi Karl, loving your course. However, I am going to have to disagree with you on this chapter. You are so adamant about not using a light meter that you are not fully honestly representing the use of a light meter. First, the light meter I have allows me to set the aperture I want to use and then it shows me the shutter speed and/or ISO I want it to calculate ( or any combination of aperture, shutter speed and ISO that I want to select). Second, I don’t think a serious photographer is going to follow a light meter settings blindly (just like you don’t follow your in camera meter/histogram blindly when shooting weddings where the bride is in white and the groom is in black), they will add their creativity to the final setting they will use. Today’s light meters calculate ratios and other things. I think a light meter can be a fine tool for outdoor creative photography, whether it be a model/senior/environmental shoot, or doing black and white zone system shooting. We cannot always be tethered, nor can we always rely on the histogram. However, if you are only referring to “in studio” shoots, then perhaps the title of this chapter could include the “Studio” in the title or in your presentation. And to say someone does not understand light or is trying to justify their purchase, just because they use a light meter, is not true.

    That being said, I still love your courses and your expert and professional presentation of the material. Moving on to the next course, see you there.

    1. Just realize the “Overall Course Title” says “…use studio lighting”, by bad! Continue on sir!

      1. Hi CharClarPhoto, yes the information in this class was relating purely to measuring the output of studio flash lighting and where I see the fallibility in doing so compared to analysing the results visually (which is also using a light meter, just your eyes and brain instead). For me and many other professionals the ethos of good studio lighting is about creating mood and emotion through the choice of modifiers and the look and feeling of the light – this is something that doesn’t need a light meter it simply needs an artists eye. Additionally in such a studio lighting environment the aperture, the ISO and the shutter speed should already have been predetermined so the only thing left is to decide on the amount of light which can simply be turned up or down like a volume control until the desired result is achieved.

    2. AGREED!

      I have a light meter that works with aperture priority or shutter priority. It has an incident meter, flash meter, and spot meter along with the ability to store multiple ISO’s and be programed for your digital camera’s sensor…. I can obviously get the photo I need with a raw file and the ability to see if I’m clipping shadows and highlights on a modern digital camera, but I still shoot film and trusting the in camera meter isn’t an option.

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