Third Stop Increments: Full, Half, and Third Stops

Third stop increments are the small steps, each one third of a stop, that most cameras use for aperture, shutter speed, ISO and exposure compensation. Three clicks make one full stop, which doubles or halves the light, so each click changes brightness by about 26 percent. You can switch the steps to half or full stops in the camera menu.

Why It Matters

If you do not know the step size, camera dials seem to give odd numbers such as f/3.5, 1/320 and ISO 125, and you may not realize how small or large each click is. Then you either make changes too tiny to see or lose track of how much brighter the photo will be.

Understanding the steps lets you make precise, repeatable adjustments, such as brightening a photo by exactly two thirds of a stop, and lets you choose the step size that suits your way of working.

Beginner Third Stop Increments On Your Dials

A stop is a doubling or halving of light. The lesson on stops of light covers it in full. Early cameras only had full-stop settings, such as f/4 then f/5.6. Modern cameras divide each stop into smaller steps so you can fine-tune brightness. The most common choice is one third of a stop: two extra settings fit between each pair of full stops.

That is why you see values like these as you turn a dial:

Exposure compensation shows +0.3 and +0.7 on many cameras because those are the rounded forms of one third and two thirds. Each click of a dial, on any of these controls, changes the brightness by the same amount: one third of a stop. Three clicks is one full stop.

Why Not Just Use Full Stops?

Full stops are a big jump. A single stop of error means a picture is twice as bright or half as bright as you intended, which is a clearly visible difference. One third of a stop is a gentle adjustment you can barely see, so thirds let you aim exactly at the brightness you want, especially when shooting raw files where small highlight changes matter.

Full stops are easier to count and need fewer clicks, which some shooters prefer for fast action. Half stops sit in the middle. The choice is personal.

How To Change The Step Size

1. Open the camera menu and look in the custom or shooting settings section.
2. Find the option for exposure steps. The wording varies: Canon uses “Exposure level increments”, Nikon uses “EV steps for exposure control” on many models, and Sony uses “Exposure Step”. Menu names and positions differ by model, so check your manual if you cannot find it.
3. Choose 1/3 stop, 1/2 stop or, if offered, a full stop.
4. Turn the aperture, shutter and exposure compensation dials and confirm that the number of clicks per stop has changed.

The same settings usually live in the same part of the menu as the other shooting options covered in camera menu settings.

When a Nest Helps a Beginner

Nest when a section is finished and you want it out of the way, such as an intro with a logo, a title and a music sting. Nest when several clips must move as one, such as a picture-in-picture with a border. Do not nest just to feel organized. If you only need to find things, markers, track colors and labels are lighter tools. A good rule is to nest groups of three or more items that you will treat as a unit, and to leave single clips alone.

Common Mistakes

• Assuming a single click is a full stop. With thirds, you need three clicks.
• Changing the step size on one control and forgetting that others may follow it. On many cameras, exposure steps affect aperture, shutter speed and compensation together, but ISO may follow a separate setting.
• Reading +0.7 as nearly a full stop. It is two thirds, about 1.6 times the light.
• Trying to fine-tune with the wrong step size and finding that the dial jumps past the value you wanted.

Advanced Mapping Thirds Across Every Dial

The Exact Numbers

A third of a stop is a factor of 2 raised to the power one third, about 1.26 in light. Two thirds is 2 to the power two thirds, about 1.59. Because the f-number scales with the square root of the light, one third of a stop in aperture multiplies the f-number by 2 to the one sixth, about 1.12. Printed values are rounded, which is why the sequence is f/2.8, 3.2, 3.5, 4, 4.5, 5, 5.6, 6.3, 7.1, 8, 9, 10, 11, 13, 14, 16.

Shutter speeds multiply by 1.26 per step: 1/125, 1/160, 1/200, 1/250, 1/320, 1/400, 1/500. ISO follows the same ratio: 100, 125, 160, 200, 250, 320, 400, 500, 640, 800. The numbers are nominal. Real cameras may calculate with unrounded values, and some lenses can set the aperture in finer steps than the display shows. Half stops, for comparison, multiply light by about 1.41 and the f-number by about 1.19: f/2.8, 3.3, 4, 4.8, 5.6, 6.7, 8.

One Click, One Third, Any Dial

The practical benefit is a shared unit. One click on any dial is one third of a stop of brightness, so you can reason in clicks instead of numbers. To brighten an image by two thirds of a stop, you can add two clicks of exposure compensation, two clicks of ISO, two clicks of slower shutter or two clicks wider aperture. You pick the one with the side effect you can afford: aperture changes depth of field, shutter speed changes blur and ISO changes noise.

Swapping Between Settings

To keep brightness constant while changing another setting, count clicks. If you move the shutter from 1/250 to 1/125 (3 clicks slower), close the aperture by 3 clicks, from f/4 to f/5.6. Mixed adjustments are also easy: raise the aperture by 2 clicks and compensate with 2 clicks of shutter. This is the working method behind equivalent exposures.

Precision Techniques

• Exposing for raw files. When protecting highlights, many photographers watch the histogram and back off by 1/3 or 2/3 stop from the point of clipping. Raw files allow recovery of shadows more easily than blown highlights. See expose to the right.
• Bracketing. Bracketed sets can be built at one stop or one third of a stop intervals. Narrow spacing suits a single tonal range; wide spacing suits a high-contrast scene. See exposure bracketing.
• Flash compensation. Flash exposure compensation often uses the same increments, so a +2/3 flash correction is two clicks.
• Consistency across a series. Setting the camera to full stops for a tripod landscape makes each change large and deliberate. Setting thirds for portraits with changing light gives smooth corrections.

Limits Of The Display

Automatic modes can pick values between the printed ones, and some cameras let electronic shutters set arbitrary speeds. The displayed numbers are good approximations, not a complete description of what the sensor actually receives.

Try It

1. Open your camera menu and find the exposure step setting. Note the current value and set it to 1/3 stop.
2. In Manual mode, point at a plain surface and center the exposure meter. Note the aperture, shutter speed and ISO.
3. Take four photos: the first at the metered setting, then three more, turning only the shutter dial one click toward slower each time.
4. Compare the images on a computer. Each should be about 26 percent brighter than the one before, and the fourth should be exactly one full stop (twice as bright) compared with the first.

Common Questions

How many clicks make one stop?

With third stop increments, three clicks equal one full stop. With half stop increments, two clicks equal one stop. With full stop increments, each click is one stop.

Why does my ISO go 100, 125, 160, 200?

Those are third stop increments. Each value is about 1.26 times the last, and after three steps the ISO has doubled. If you set the camera to full stops, the sequence becomes 100, 200, 400.

Which step size is best?

Thirds suit most photographers because they give fine control, and most cameras default to them. Use full stops if you want quick, large changes, such as when shooting action, or half stops as a compromise.

Does the step size change image quality?

No. The step size only changes how far each click moves a setting. The resulting image depends on the final aperture, shutter speed and ISO you choose, not on how you reached them.

Related Lessons

• Stops of Light to see why every step is a doubling or halving.
• Exposure Compensation Guide to apply thirds when the camera misjudges the scene.
• Equivalent Exposures to swap clicks between aperture, shutter and ISO.
• Exposure Bracketing to shoot a series at set step sizes.
• Exposure Triangle Explained to review the three controls these steps adjust.