How to Spot Meter Successfully
/
Minolta Spotmeter M - Yes it is very old and it is still an incredible tool
Hello folks. You can thank reader Dave C, for this article as he is the person who asked that I take the time to cover this subject.
What is Spot Metering
Spot Metering takes your in camera light meter and restricts the data gathering portion of the scene to a single spot area. Unlike matrix, centre weighted or other metering models it is highly restrictive in what it reads.
Does It Meter Differently?
This is a key point for review. All meters take all their data input and based on algorithms programmed into the light meter portion of the camera, average the values to produce an EV level that will render out to middle grey. The EV number can then be used for a variety of combinations of shutter speed, aperture and ISO based on an EV table. This is automated the more that you use automation in taking the picture.
So All Meter Readings Deliver Middle Grey?
All meter readings by default take all their inputs whether weighted or unweighted and use an averaging algorithm to produce an EV value that delivers middle grey. The metering mode in use only determines which inputs and where they are in the scene that go into the calculation of the recommended EV.
Is a Spot Meter Doing Reflected or Incident Light Metering?
A spot meter by design is reading reflected light. Spot meters are not built to do incident light.
Why Would I Use Spot Metering?
The simple reason to use spot metering is that you want to determine where you will set your exposure settings in order to place middle grey, where you want it to be, not just where the camera proposes. Spot metering comes to us from the days of large film format cameras, and initially from the Zone System. While the Zone System was created for black and white photography, it works for colour photography and still works in the digital realm.
Give An Example of How One Would Use Spot Metering
Ok, here’s a pretty straightforward approach that I use. It is a deliberate set of actions, and not meant to be speedy. It is meant to allow me to decide where I want the different luminance values to fall inside the dynamic range band of my sensor. You are going to NEED a physical notebook and writing implement. This is a developed discipline. Get the right habits first. I recommend Moleskin style notebooks because the paper is thicker and the covers are harder. I like the flip type like police detectives use, you can choose whatever works for you, BUT you have to USE it. If you are not willing to follow proper practice, the rest of this article is not for you.
First you want to at least know what the dynamic range of your sensor is. This should be easy to find, but it is often buried under the detritus of meaningless junk. DXOmark.com is a good source.
Now look at the scene that you are going to photograph, but not through the camera. Create your composition in your mind’s eye
Inside that mental composition, find the brightest area. Point your spotmeter at that area, take a reading and then write it down. I cannot overestimate the importance of note taking when spot metering and when noting it, use an EV value. If you use the spot meter in your camera, it may not tell you the EV value, only providing you a shutter speed, ISO and aperture. If that is all that your camera does, download an EV chart from the Internet, print it off and tape it inside the cover of your notebook.
Find the darkest point in your mental composition and write down its EV value
Now close your eyes for a few seconds and look again for the brightest and darkest areas. Your goals is to determine the widest separation between the lights and the darks.
Subtract the dark EV value from the light EV value. If the number you get is equal to or less than your sensor dynamic range, you are in great shape, if not, come back to the second sequence found after this one.
Halfway between the lightest and darkest EV reading is middle grey, That is the EV setting to use if you want a general exposure. If that is all you wanted, you did not need to go through this exercise, although I like it because it reminds us that ALL meter readings produce middle grey.
Wait What?
We step outside the example process for a second here for a metering review. If I set the camera to the EV value for any point in the scene that I spot metered, what luminance value will I get? If you said middle grey you are correct. So if I spot metered the inside of a dark cave, and exposed for that, the inside of the cave would render as middle grey and not look like what was there. Similarly if I spot meter off a bright white snow field and made that exposure, the snow field would end up middle grey, not white. Until you can accept this, rinse and repeat until you do. An exercise I give my beginning students is to meter off a matte card under flat light that is black on one side and white on the other and exactly set the meter reading for each. They are regularly surprised to see that the final images are pretty much identical.
Back to the Process
Now that you know where your lights and darks are in the range, you now need to decide where you want the exposure on your singular subject to fall. Take a spot meter reading off it. Is it mid way between the lightest and the darkest? Where do you want it to fall? If it fell midway, that’s middle grey, but if you want it to be darker, you now need to experiment with under exposure options to place it darker. If you want it to be lighter, you now need to experiment with overexposure to place it lighter.
Remember that your total image is going to follow where you place your subject. If you push the exposure on your subject to the right and overexpose, you are going to get more shadow detail and your lying histogram is going to tell you that you are blowing out all your highlights. If you pull the exposure to the left to make your primary subject darker, you are going to clump up your shadow detail but expand your highlight detail and you may lose anything that appeared white to you. That’s fine. The only exposure point that actually matters is what exposure you choose for your subject and there is only one subject. If you think that there are more, you are mistaken.
What About If My Subject Wasn’t in the Middle of the EV Range?
I hope that by now, you have seen that where your subject falls when metered doesn’t matter. If you expose for that reading, your subject will fall in the output level of middle grey. If you want it darker, underexpose. If you want it lighter, overexpose. Whatever you choose, by spot metering well, you know what your subject is and where you are going to place it in terms of your sensor’s dynamic range and you also know what’s going to happen to the rest of scene.
What If the Dynamic Range of the Scene is Greater Than My Sensor Can Handle?
Welcome to what we film photographers dealt with all the time. Film had maybe 6.5 stops of dynamic range on its best day. You now, and we did then have to decide which end of the dynamic range spectrum you are willing to sacrifice. You could try using the process of HDR, which may or may not work, depending on the effectiveness of the HDR software that you use, or you could use the proven method of taking control of your work and making a conscious decision on what is not going to render properly in the final image. There’s no such thing as a free lunch.
You May Not Be Done
Just as the great film photographers who spot metered got the exposure that they wanted for their subject on the film sheet, so have you done in the digital realm. However, you may still want to lighten some areas, and darken others before your final output whether as a print, or a social media post. In film we called this dodging (lightening) and burning (darkening) You can do this in any photo editor worth using. Use a brush of appropriate size and hardness/softness and go to town. If you do it on a layer in Photoshop, you can toss the layer if it all goes wrong with no change to your original. Virtual copies in Lightroom Classic provide the same safety margin. Dodging and burning have been forgotten in the leap into pseudo AI and all the other new stuff, but they are critical tools for success in true exposure control. You should learn both. A further method to really dive into this is via Luminosity Masking. That’s a separate conversation entirely.
Wrap Up
Learning to spot meter properly and then applying that learning is a major step in making better images. You move from taking pictures to making photographs. It’s a journey, not an end.
You can support the channel by making a donation through the SUPPORT THE CHANNEL button on the main page. Please submit comments and questions, I read and respond to all. If you shop at B&H Photo Video, please do so through the link on the home page which pays us a small commission and costs you nothing. Until next time, I wish you peace and good health.
