How to film a book review or BookTok video with both iPhone cameras
A book review has the same shape as a lot of hands-and-face content — an object held up for the camera, and a face reacting to and narrating it — but the object itself is unusual. A book is roughly portrait-shaped when its cover faces the lens, and turns landscape the moment you open it to a page or a spread, and a line that reads clearly in your hands can turn into an unreadable rectangle once it is written into a phone-sized video. Recording the front and back cameras at once still puts the book and your face into one file from the first sentence, so a review does not need a cover close-up filmed separately and cut in afterwards.
The general setup for simultaneous recording is covered elsewhere; this page is about what changes when the object in frame is a book — choosing a layout that survives the shift from a closed cover to an open spread, keeping a glossy dust jacket from fighting the camera’s exposure, and getting a quoted line both legible and audible.
A closed cover and an open spread are two different shapes
Held up closed, a book’s cover is roughly portrait — taller than it is wide — which happens to sit fairly close to the shape of the vertical canvas dual recording writes to. The moment you open it to show a page or a spread, the object in frame turns landscape — wider than it is tall — and a portrait canvas has nowhere obvious to put the extra width.
Picture-in-picture with the back camera filling the frame handles both shapes without any adjustment, because the whole source frame is scaled to fit the canvas regardless of the shape of whatever is inside it — a closed cover and an open spread just get smaller or bigger within the same rectangle. A left-right split makes the open-spread problem worse, since it crops roughly a quarter off each side of the source frame to fit a vertical canvas, and that outer quarter is exactly where the far edge of an open page sits. Top-and-bottom keeps the full width instead, so it is the safer split for a review that moves between a cover shot and pages.
A glossy dust jacket fights the camera before you do anything
A laminated cover or dust jacket reflects light the way a mirror does at the wrong angle, and a single overhead light or a window can turn part of the cover into a blown-out white patch — that reflection shows up on camera, not just to your eye standing over it. Tilting the book a few degrees relative to the light source usually clears a reflection that tilting the phone cannot, because the glare depends on the angle between the light, the cover and the lens, not on where the camera itself is pointed.
Front and back camera exposure are set independently in a dual recording, each reading only its own frame, so a blown-out patch on the cover in the back camera’s frame does nothing to how your face is exposed in the small window, and the reverse is also true. Tap the back-camera frame once the glare is on screen to lock focus and exposure there; if the reflection is a hotspot rather than a wash across the whole cover, moving the light slightly or tilting the book a few degrees does more than tapping to correct it, since the problem is angle, not exposure value.
Getting a cover title or a quoted line actually legible
The canvas dual recording writes to is 1080 pixels wide, and a picture-in-picture inset or a cropped split half is sampled down from that further still, so a title set in small type or a pull-quote you want a viewer to pause and read needs the lens closer and the layout more generous with the source frame than casually holding the book toward the camera would suggest.
Which back lens is active locks in once recording starts, so decide before you press record. If a spine or a line of small print needs to be legible, the main lens held close generally reads better than the ultra-wide lens held further back — at the same distance, ultra wide’s wider field of view means the book occupies fewer pixels of the frame, and it is that pixel count, not the lens itself, that decides whether the text survives being written into a 1080-pixel-wide file.
Reading a passage aloud needs distance, not volume
Dual camera recording writes one audio track, not one per camera, taken from whatever iOS has selected as the input. Reading a quoted passage aloud is exactly the kind of moment where distance to the phone’s microphone matters more than anything else — get the phone a few inches closer to your mouth while you read the passage, then let it settle back to its normal distance for the parts where you are just holding the book up.
Do not rest the book on the same surface the phone’s stand is on. Setting a hardcover down while you turn to a new passage sends a knock straight through the surface into the microphone at the phone’s bottom edge, which is an easy habit to fall into when one hand is holding the book and the other is turning pages.
A multi-book review is several takes, not one long file
A dual recording runs straight through from record to stop, with no way to pause it mid-file, and a review covering more than one book already has a natural break at the edge of each one — one take per book, plus a separate take for an intro or a wrap-up ranking, is easier to work with than one continuous file spanning all of them.
Shorter takes also help with heat, since two live camera pipelines and a real-time composite draw on the same thermal budget for as long as you are recording. If the phone does get hot enough, DualCam drops a fresh 1080p recording to 720p before it starts, or ends an in-progress one and saves what it has rather than losing the take outright — splitting a review into one take per book makes either outcome far less likely to land in the middle of the one book you most wanted to get right.
Common follow-up questions
Should I use picture-in-picture or split screen for a book review?
Picture-in-picture with the back camera filling the frame is the safer default, because it handles a book’s shape changing from portrait (closed cover) to landscape (an open spread) without cropping either one. If you want a split, use top-and-bottom rather than left-and-right — left-right crops roughly a quarter off each side, which is where the outer edge of an open page sits.
Can I switch to a closer or wider lens partway through, to zoom in on the cover?
No — which back lens is active locks in once recording starts. Layout, the picture-in-picture corner, its size, shape and filter can all change mid-take, but the lens has to be decided before you press record. If legible text matters, start on the main lens held close rather than planning to switch to it later.
Why does part of the cover look washed out even though the room isn’t bright?
A glossy dust jacket reflects light like a mirror at the wrong angle, and that shows up on camera even in an ordinarily lit room. Tilting the book a few degrees relative to the light source usually clears it, since the glare depends on the angle between the light, the cover and the lens, not on exposure.
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