What is exposure on iPhone camera?

Exposure refers to the amount of light that reaches the camera sensor when taking a photograph. It determines how bright or dark an image will appear. The iPhone camera automatically sets exposure based on the lighting conditions, but you can also manually control exposure through some simple adjustments for creative effects.

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What controls exposure on iPhone camera?

There are three main camera settings that control exposure on iPhone:

ISO: This determines how sensitive the camera sensor is to light. Higher ISO settings make the sensor more sensitive to light, so the image will be brighter, but can also make it noisier or grainy.

Shutter speed: This is how long the camera sensor is exposed to light. Slow shutter speeds let in more light for brighter images, but can lead to blur from camera shake.
Aperture: This is how wide the lens opening is for light to pass through. Wider apertures (lower f-stop numbers) let in more light.

By adjusting these three settings, you can control the overall exposure and create different creative effects. The iPhone camera app allows you to adjust exposure through exposure compensation, adjusting ISO, and Live Photos long exposure.

What is exposure compensation on iPhone?

Exposure compensation allows you to override the iPhone camera’s auto exposure setting to make an image brighter or darker. To use exposure compensation:

Open the Camera app and tap the screen to set focus.
Swipe up or down on the screen to adjust exposure. Swiping up increases exposure to make the image brighter. Swiping down decreases exposure to darken the image.

Take the photo once you’ve adjusted exposure to your desired brightness.

Exposure compensation is measured in EV units, from -2 to +2. Negative values will darken exposure while positive values brighten it. Start with adjustments of -0.5 EV or +0.5 EV to subtly darken or brighten the image.

How does ISO affect exposure on iPhone?

ISO determines the sensitivity of the iPhone camera sensor to light. The higher the ISO number, the more sensitive the sensor, and the brighter the image will be. However, higher ISO settings also add noise or grain to the image. To adjust ISO on iPhone:

Open the Camera app and swipe left to open Photo mode. Tap the arrow above the shutter button.
Tap the ISO icon, then drag the slider right or left to increase or decrease ISO.
The default setting is Auto, which lets the iPhone choose the ISO. You can also select ISO values from 50 to 3200.

Some tips for using ISO:

Use lower ISO like 50 or 100 in bright light to get clean, smooth images.
Increase ISO in low light to brighten exposure without using slow shutter speeds.

Higher ISOs above 800 will add noticeable noise.
Use a tripod at high ISOs to avoid blur from camera shake.

How to adjust shutter speed on iPhone

The iPhone doesn’t directly let you pick a shutter speed, but you can adjust it through these methods:

Long exposure Live Photos: Take a Live Photo, then tap Edit and drag the shutter speed slider to set exposures up to 30 seconds.
Third-party camera apps: Some advanced camera apps like ProCamera and Halide give full manual shutter speed control.
Attach a ND filter: Blocking light with a neutral density (ND) lens filter allows you to use slow shutter speeds.

Some creative effects you can achieve with shutter speed:

Long exposures (1+ seconds) – Smooth-looking waterfalls, light trails at night
Fast shutter speeds (1/500s+) – Freeze fast action like sports

Panning shots – Blurred background with sharp subject

How does aperture affect exposure?

Aperture refers to the size of the opening in the lens that light passes through. The aperture is measured in f-stops – lower f-stop numbers indicate a wider aperture. Wider apertures let in more light, decreasing exposure time.

Since aperture is a property of the lens, it can’t be directly changed in the iPhone camera app. However, the following factors influence effective aperture on iPhone:

Focal length – The iPhone has a fixed aperture, so shorter focal lengths let in more light (equivalent to a wider aperture). The wide lens on iPhone has an effective aperture around f/1.8 while the 2x telephoto is around f/2.8.
Portrait mode – Simulates a wide aperture blurry background. Software creates this bokeh effect so it’s not a true aperture adjustment.
Third party lenses – Attachable lenses like Moment provide actual aperture controls since they have adjustable physical apertures.

A wider aperture not only lets in more light for exposure, but also creates beautiful background blur (bokeh) for artistic portraits. Aperture gives you creative control over focus and depth of field.

How does the iPhone meter light for exposure?

The iPhone camera determines exposure automatically using a process called metering. Based on lighting conditions, it calculates the optimal combination of ISO, aperture, and shutter speed needed for a proper exposure.

Your iPhone uses advanced multi-zone metering, meaning it splits the image frame into hundreds of zones and analyzes light in each zone. It balances the readings to determine the best overall exposure.

Some key points about metering on iPhone:

Defaults to evaluative metering for the whole scene.
Gives priority to properly exposing faces and subjects.

Automatic HDR activates in high contrast lighting.
Tap the screen on a specific spot to meter just a portion of the scene.

Overall, the iPhone’s metering system works very reliably in most lighting scenarios. But in tricky high contrast lighting, it’s a good idea to tap the screen on your main subject to get it properly exposed.

When to override the default iPhone exposure

While the iPhone camera app meters exposures well automatically, there are certain situations where it’s a good idea to override the defaults using exposure compensation, ISO, or shutter speed adjustments:

Backlit/silhouetted subjects – Increase exposure compensation 1-2 EV to brighten.
Bright backgrounds – Decrease exposure 1 EV so background isn’t overexposed.

Sunrise/sunsets – Increase exposure +1-2 EV to capture colors.
Portraits – Lower ISO for clean, smooth skin tones.
Minimal noise – Use ISO 100 or lower when lighting is abundant.

Motion blur – Slow the shutter with Live Photo edits or ND filters.

Get to know how your iPhone tends to meter in different lighting, and override exposures when needed for the best results.

Use manual exposure for long exposures

The default iPhone camera app doesn’t provide direct control over shutter speed, which can make it difficult to take creatively blurred long exposure photos. Here are some workarounds that allow manual exposure times from 1 second to 30 seconds or longer:

Long Exposure Live Photos – Takes a Live Photo, then edit to change shutter speed from 1-30 seconds.
Third party camera apps – ProCamera, Slow Shutter, and other apps offer manual control over exposure time.
Attach a neutral density (ND) filter – Physical ND filters block light, allowing shutter to stay open longer.

Extremely low light – iPhone automatically uses a 1-2 second exposure if it’s dark enough, no app required.

Some creative long exposure techniques to try on iPhone:

Rivers/waterfalls – Blurred, misty water.

Light trails – Light streaks from cars at night.
Beach/ocean – Blurred clouds and water.
Zoom during exposure – Create a warp speed effect.

Use Auto Exposure Lock (AE Lock)

Auto Exposure Lock (AE Lock) is useful in situations with tricky or unusual lighting where you want to control the exposure settings manually. It locks the exposure so it won’t change between shots.

To use AE Lock on iPhone:

Tap and hold an area you want properly exposed. The “AE/AF Lock” message appears.

With exposure locked, you can reframe and take the shot.
Tap and hold again to unlock exposure.

Scenarios where AE Lock is handy:

Subject in spotlight with dark background.
Bright backlit subject with silhouette effect.
Off-center subject – metering gets thrown off.

Exposure differences between multiple shots.

AE Lock prevents the iPhone camera from recomputing exposure for every shot. Maintain full control in tricky lighting.

Use auto HDR for high contrast scenes

High Dynamic Range (HDR) is a feature on iPhone that blends multiple exposures to capture more detail in high contrast scenes. It’s especially useful for sunny outdoor shots which often have both very bright and very dark areas. HDR brings out shadow and highlight details that would be lost at a single exposure.

Here’s what iPhone’s auto HDR does:

Automatically activates in high contrast lighting.
Shoots a normal exposure, underexposure, and overexposure.

Blends the 3 images together into one optimized photo.

Effects of HDR:

Brings out shadow detail.

Preserves bright highlight detail.
Reduces blown out skies.
Adds overall contrast and detail.

Auto HDR works great in most situations. You can disable it in rare cases where you need full control over exposure and don’t want any automatic adjustments. Overall, keeping Auto HDR on provides the best contrast and detail when lighting gets challenging.

Bracket exposure manually for HDR

While the iPhone’s Auto HDR works very well, you can take HDR exposure into your own hands using a manual bracketing technique. This involves taking multiple photos at different exposures, then blending them together after the fact using editing software.

To manually bracket iPhone photos for HDR:

Use exposure compensation to take one photo at -1 EV (underexposed).
Take another at +1 EV (overexposed).
Take a normally exposed photo at 0 EV.

Blend the 3 photos in post using Photoshop, Lightroom, or dedicated HDR software tools.

Manual bracketing allows you to take full control over the HDR effect. You can also blend more than 3 exposures for even more dynamic range. Just keep in mind you’ll need access to editing software after the shoot to merge the bracketed photos.

Use Portrait mode for depth of field control

Portrait mode on the iPhone (and Selective Focus on older models) simulates the effect of a wide aperture lens to artistically blur backgrounds. Here’s how it works:

Detects faces/subjects and digitally separates them from the background.
Applies a simulated lens blur effect to the background areas.
Maintains a sharp foreground subject.

This uses computational photography to mimic the bokeh effect of an SLR lens with a fast aperture like f/1.8. It’s not adjusting the actual aperture since the iPhone has a fixed aperture. But the simulated blur looks convincing.

Portrait mode tips:

Works best with medium subject distance and clear separation between subject and background.

Try moving closer to the subject and farther from the background.
Non-human subjects like pets often need more separation from background.
You can adjust software blur after the fact – start low to look more natural.

Use Portrait mode to direct attention to subjects by artistically blurring distracting backgrounds. It brings a professional SLR-like look easily to iPhone photography.

Does the iPhone have a neutral density (ND) filter?

No, iPhones do not have a built-in neutral density filter. A neutral density (ND) filter is an external attachment that blocks some amount of light from entering the lens. It allows you to use slower shutter speeds in bright light.

Here are some options for adding an ND filter to your iPhone:

Clip-on ND lenses – Attach directly over iPhone lens. Offer variable ND strength.
Lens adapter rings – Attach an ND filter to a lens mount adapter.
ND filter sheets – Thin sheets place directly over iPhone lens.

Stackable ND filters – Use multiple filters together for stronger ND effect.

Types of ND filters:

ND2 – Reduces light 1 stop (50%)

ND4 – Reduces light 2 stops (25% light)
ND8 – Reduces light 3 stops (12.5% light)
ND16 – Reduces 4 stops (6.25% light)

Use ND filters to achieve long exposures for silky water, light trails, and other creative effects during bright daylight. They give you exposure control options the iPhone lacks on its own.

Conclusion

The iPhone camera provides users with simple, intuitive ways to adjust exposure like tap-to-focus, exposure compensation, and auto HDR. More advanced exposure controls are possible with third party camera apps and attachable lenses/filters. Learn how aperture, shutter speed, ISO, and metering influence exposure to take your iPhone photography to the next level.