Here's The Thing:
The main exposure modes on our cameras are not always practical for fast changing lighting situations. Above, sunlight on the bald eagle dimmed behind fog, and I was photographing from a moving boat. If I had to change my ISO, I would have missed getting this photograph. I set a fast shutter speed to ensure a sharp image, and even when the light changed, the shutter speed and aperture did not, as the ISO changed automatically.
We may need to get creative with subject focus, depth, blurring motion and over or under exposure by using selected apertures and specific shutter speeds. The camera modes of Aperture Priority, Shutter Priority, and Manual (PASM) are usually used with a set ISO. But AUTO-ISO is a more forgiving and flexible choice for wildlife photography.
You will get better exposures by learning to combine Auto ISO with Manual Mode, so you can set specific shutter speeds and apertures.
HOW TO SET AUTO ISO Combined with Manual Exposure Mode (M) :
Setting the three elements of exposure (shutter, aperture, and ISO), we lock in two of them and then change the third element to let it “float.” For instance, in Manual Mode, choose your F-stop (aperture) first. It won't change. You could set F/2.8, for instance. Then, dial in your creative Shutter Speed. I like to use 1/2000th and faster for sport and nature. Remember, in the camera's Manual Mode, a shutter speed of 1/4000 of a second appears as 4000. For example, for the parasailing image below, I used a telephoto lens and set a fast 1/4000th of a second, and an F/5.6 Aperture to ensure I could hold the heavy lens steady for a sharp photograph. The ISO was set to AUTO ISO.
Your camera's Menu will have an Auto ISO setting. Let's see how to set Manual and AUTO ISO on a mirrorless camera.
EXAMPLES: Setting Manual Mode and Auto ISO with a mirrorless camera. First, an example from Nikon. Then, a mention of the Canon (R3) mirrorless Auto ISO.
Easy Steps to Set Auto ISO:
START STEP #1: Look in your camera menu, and find AUTO ISO. Nikon, for example, calls this ISO Sensitivity Settings. Almost all camera makers now offer this feature in the menu. Auto ISO can be fine-tuned for maximum or minimum sensitivity. Newest camera models allow fine tuning for flash pictures as well.
Set the maximum Auto ISO sensitivity that you will accept. This is subjective because the number you choose affects the amount of noise and grain you’ll see – and can live within your photographs. Since I have my maximum ISO set to ISO 6400 as a maximum value, that means my camera will not shoot at ISO 12,500 or higher ISO numbers until I adjust Maximum ISO.
STEP #2: Next, set the lowest or minimum ISO you want in your camera ISO settings menu. Pick the lowest ISO the camera has, like ISO 25, 50 or 100. If set to 100, the camera will not use a lower setting like ISO 50.
FINISH #3: Last, set the minimum (slowest) shutter speed that you want the shutter to be faster than. This might range, for instance, from 1/250th of a second for nature shots on a tripod to 1/8000th of a second for sports or fast-action imagery. When you set 1/250th of a second, the camera will not use shutter speeds slower than this speed, and will only shoot 1/250th, 1/500th, 1/1000th and faster.
MORE ON CANON MIRRORLESS: Canon makes it easy to set AUTO ISO. For the R3 mirrorless camera: there are 3 steps:
What Does it Mean? Better Exposures and Ergonomics:
Using AUTO ISO means the camera changes (floats) the ISO to get the exposure correct even when light, camera F/stop and other conditions vary. For example, when you photograph in fog or dim conditions in the winter, AUTO ISO adjusts the sensitivity of the sensor. The ISO might change, automatically, to ISO 2000 as it did for the photograph of a shearwater above. If I had chosen Aperture Priority for the shearwater, the picture might have had motion blur from the camera automatically using a slower shutter speed. Manually setting a fast Shutter Speed of 1/8000th ensured the image would be sharp with no motion blur.
MANUAL EXPOSURE MODE:
Using your camera's AUTO-ISO feature in combination with Manual (M) exposure mode, you can smoothly and quickly make changes to your exposure settings. How? Simply by adjusting a single dial with your index finger or thumb. Whether you change shutter speed, or F/Stop with your hands, your eyes are still focused on the subject through the viewfinder. We need to learn to use Manual Exposure Mode so that using it becomes second nature, and this comes with practice. With Manual, what you set is what you get. Turn your Mode Dial to M for Manual. Let’s say you are in low light. Pick a shutter speed of 1/60th with Optical Stabilization (OS) or Vibration Reduction (VR), and set your aperture to F/2.8. You control both the aperture and the shutter when you choose Manual exposure mode.
IN THE CAMERA:
Modern digital cameras have the ability to combine AUTO ISO with Manual Exposure Mode, but check your menu for AUTO ISO. Here are two examples, and your camera may be set up similarly. In a Nikon DSLR, Nikon's ISO setting is in the Shooting Menu. On a Canon 5D, the AUTO ISO can be changed with the Info Button on the back of the camera.
Why Use AUTO-ISO Plus Manual?
Setting Auto ISO and Manual Mode together frees your attention and lets you operate the controls smoothly. Canon, Nikon, Leica, Fuji, Sony and other makers let you first set Auto-ISO, then easily change shutter and aperture with just a single dial in front or behind the shutter release button. For creative compositions, it helps to focus your attention and keep your eyes in the finder. Without taking your eye from the viewfinder, you can easily rotate the dial to move from 1/125th of a second to 1/4000th of a second. Or, you can quickly change your aperture for more depth of field.
Delightfully, AUTO-ISO + M lets you choose shutter to control motion, AND set an F-stop to control creative depth of field, with the camera automatically on a range of ISO values you’ve set up in its menu. AUTO ISO plus M is the most flexible of all exposure modes. Dialing in AUTO-ISO plus Manual exposure mode works well for wildlife photography of birds landing, mammals on the run, and large fast wildlife in changing conditions. Why? You are concentrating on the subject and not fiddling around with exposure modes. As we saw above, Shutter Priority mode is an effective choice to control motion within the frame. Slow shutter speeds allow motion blurs. Fast shutter speeds let us stop action, as with birds in flight. As you know, Aperture Priority is a way to control the plane of focus and depth of field. Therefore, setting your camera for Auto-ISO + Manual gives the advantages of controlling depth of field and stop-motion control for sharpness or motion blur.
Better Ergonomics and Exposures:
Using your camera's AUTO-ISO feature in combination with Manual (M) exposure mode, you can smoothly and quickly make changes to your exposure settings. How? Simply by adjusting a single dial with your index finger or thumb as in the image above where the command dial on a Canon camera body is turned to change any setting from exposure compensation, to F/stop or even Shutter Speed. When you change settings with a single index finger, you can keep your eyes focused on the subject through the viewfinder, and this gives DSLR's and mirrorless cameras a big advantage over cell phone cameras, by the way.
What Does It Mean?:
When you set AUTO ISO, this means your camera changes (floats) the ISO to get the exposure correct even when the light, subject motion, F/stop and other settings vary or change. For example, when you photograph in a dim room with a digital camera, and then go outside in the bright sun, AUTO ISO adjusts the sensitivity of the sensor. The ISO might change, automatically, from ISO 2000 inside to ISO 200 outside.
Modern digital cameras have the ability to combine AUTO ISO with Manual Exposure Mode, but check your menu for AUTO ISO. We need to learn to use Manual Exposure Mode so that using it becomes second nature, and this comes with practice. With Manual, what you set is what you get. Turn your Mode Dial to M for Manual. Let’s say you are in low light. Pick a shutter speed of 1/60th with Optical Stabilization (OS) or Vibration Reduction (VR), and set your aperture to F/2.8. You are in control of both the aperture and the shutter when you choose Manual exposure mode. If you have not used Manual Mode, grab your digital camera now and go practice!
Advantages For Photographing With AUTO ISO Combined with Manual Exposure Mode:
1. You can keep your eyes in the viewfinder.
2. You can get sharper photographs. Blurred photographs happen at times when the camera chooses too slow a shutter speed. This can happen with Aperture Mode (A). When photographing wildlife with a long focal length telephoto lens like 400 or longer, and the light changes, the shutter speed will slow down in Aperture Priority Mode.
3. You can get more depth in your photographs. WIth AUTO ISO and Manua, you can set small F-stops like F/11 or F/16. (Yes, there is diffraction, but the newest mirroless cameras as of 2022 have diffraction control) . This lets you be creative with getting deeper Depth of Field and varying the bokeh or the quality of the blurred areas around the subject. Or, should you desire a shallow plane of focus, dial in a wider aperture like F/2 and F/1.4 and set the lowest ISO possible when photographing still subjects.
For instance, photographing for blurred background for a perched bird, I open the F-stop to f/2.8 or f/4, which is near the widest lens opening. Then, I use the lowest possible ISO (50, 100, 200, or whatever is native to the camera) when I want to reduce noise in the image file. The payoff is efficiency: there’s no time spent searching the camera’s menu or fiddling with buttons.