How to Use Projected Aids Like Slides and Filmstrips in Teaching

When a teacher relies solely on verbal explanations and the chalkboard, only so much learning can happen. Students process information differently, and a large share of them are predominantly visual learners. Research published in scientific literature consistently shows that combining visual presentation with verbal instruction creates stronger memory pathways than either method used alone. Projected aids – slides, filmstrips, overhead projectors, and instructional television – are among the most powerful tools in this visual-teaching toolkit. Understanding how to use them well is not just a technical skill; it is a core competency for any educator in higher education.

Why use projected aids? 🔗

Traditional teaching methods have clear limitations. Verbal explanations fade quickly from memory, and board writing reaches only those close enough to read it clearly. Projected aids change this dynamic entirely. Studies on the impact of visual aids in the learning process show that retention gains from visual instruction range from a modest 10-15% all the way up to 80%, depending on how effectively the aids are used. That is a significant difference – and it justifies the deliberate effort required to prepare and deploy projected materials well.

Beyond retention, projected aids offer several practical advantages for the classroom. Visual information is processed in a different part of the brain than verbal information, which means presenting content both visually and verbally creates multiple memory pathways simultaneously. This is particularly valuable for students with diverse learning styles, including those who struggle with purely text-based instruction. Projected visuals also allow a teacher to maintain eye contact with students – something that is simply not possible when writing on a board – which helps sustain classroom engagement and communication.

Educators have used projection technology to integrate visual content into classrooms since the late 1800s, and the core purpose has not changed: displaying enlarged, clear images to an entire class simultaneously. What has changed is the variety of tools available, each with distinct advantages depending on the instructional context.

Slides and filmstrips: making learning interactive 🔗

Slides and filmstrips were among the earliest projected aids to gain widespread use in formal education, and for good reason – they bring still images directly into the learning space in a controlled, sequenced way.

Slides 🔗

A slide is a small piece of transparent material on which a single pictorial image, scene, or graphic has been photographed or reproduced. The standard size is 2″ × 2″ (or 5 × 5 cm), and any 35mm camera can produce them. This makes slides unusually flexible – a teacher or even a student can prepare slides from photographs taken during field trips, historical excursions, or scientific observations. Slides can simulate a field trip without actually taking one, illustrate complex concepts with real imagery, and document student activities over time.

When preparing slides for classroom use, sequencing matters. Each slide should represent a single, focused idea. Crowding too much information onto one frame defeats the purpose – the strength of a slide lies in its ability to isolate and highlight. Teachers should also preview slides in the order they will be shown, check focus and brightness, and have a clear narrative plan for what they will say during each frame.

Filmstrips 🔗

A filmstrip is a roll of 35mm transparent film containing a series of related still pictures intended for showing one at a time. Unlike individual slides, filmstrip frames are arranged in a fixed sequence – which makes them well-suited to content that follows a logical progression, such as a step-by-step scientific process or a historical narrative. A standard filmstrip contains between 20 and 50 frames, with narrative information printed at the bottom of each frame or recorded separately on audiotape.

Filmstrip projectors allowed teachers to pause presentations for class discussion by turning a knob, which made them an interactive tool rather than a passive one. This pause-and-discuss structure is still considered best practice in visual instruction today. When using filmstrips, teachers should preview them carefully before class to confirm alignment with learning objectives, use a pointer to direct attention to specific screen details, and – wherever possible – supplement them with handouts or textbooks to reinforce the key ideas.

Instructional television in education 🔗

Television as a teaching tool has a longer history in formal education than many people realize. Closed-circuit TV (CCTV) was used as early as the 1950s by universities to transmit classroom lectures to other campus locations. One of the earliest examples, the Pennsylvania State University CCTV project, was set up to deliver introductory college courses by television to address overcrowded classrooms and faculty shortages. Since then, instructional television has expanded considerably in scope and format.

CCTV in the classroom 🔗

CCTV operates within a closed, internal network – meaning content is broadcast only within a specific building or campus, not to the general public. This gives educational institutions control over what is shown, when, and to whom. Each school can function as a resource centre where classroom teachers prepare video lessons for individual class use through CCTV. It is especially useful for live demonstrations, surgical procedures in medical education, and broadcasting expert lectures across multiple classrooms simultaneously.

Video recordings and pre-recorded content 🔗

Pre-recorded video lessons offer something live instruction cannot: repeatability. A complex procedure or concept can be replayed, paused, and reviewed at the student’s pace. Research established early on that when content was properly designed, viewers could learn as much from instructional television as from a classroom teacher. The key phrase here is “properly designed” – passive viewing alone is not enough. Teachers should pre-screen all video content before showing it, set specific learning objectives in advance, and build in active-response components such as note-taking, structured questions, or post-viewing discussion.

Educational TV programs 🔗

When teachers use educational television programs in class, it shifts the dynamic – the teacher and students become co-viewers who can share and discuss the experience, rather than maintaining the typical one-directional instruction. Teachers can use this shift productively by organizing small-group discussions after viewing, asking students to respond to specific questions, and having groups share their insights with the wider class. The result is deeper engagement with the material than passive viewing would produce.

Overhead projectors (OHP) for visual learning 🔗

The overhead projector remains one of the most widely used projected aids in education, particularly in settings where digital projection is not available or reliable. An OHP uses light to project an enlarged image onto a screen, allowing a small document or picture to be shared with a large audience. The source material is a page-sized transparent plastic sheet – commonly called a transparency, acetate, viewfoil, or foil – placed on the glass surface of the projector.

Structure and operation 🔗

The overhead projector consists of a box with a large aperture on the top surface, a light source below the glass plate, and a projecting mirror and lens assembly above it – hence the name “overhead.” The Fresnel lens on the glass plate concentrates light through the transparency, the objective lens above focuses the image, and a plane mirror reflects it onto the screen behind and above the teacher’s head. A vertical rod beside the box holds the lens assembly, which can be adjusted for focus and image size.

The OHP projects transparencies with brilliant screen images suitable for use in a lighted room – an important practical advantage over filmstrip or slide projectors, which typically need a darkened space. This means students can take notes while the image is displayed, maintaining active engagement rather than simply watching in the dark.

Key advantages of the OHP 🔗

The OHP’s most distinctive advantage is the ability to write or draw directly on the transparency while teaching, with the result projected to the entire class in real time. The enlarging features of the projector allow the educator to write in a comfortable small script in a natural writing position, rather than having to write in oversized text on a board with an arm held out awkwardly. When one transparency is full, it can simply be swapped for a pre-prepared sheet – saving the time that would otherwise be lost erasing and rewriting board content. After class, written material can be washed off the transparency with soap and water and the sheet reused, making it highly cost-effective.

Teachers can also use transparent overlays – additional sheets laid over a base transparency – to build up a concept in layers. This is particularly effective for showing relationships, demonstrating how a system works step by step, or comparing before-and-after scenarios. Marginal notes on the transparency frame can serve as personal cues for the teacher without being visible to students when positioned correctly.

Preparing effective transparencies 🔗

The quality of an OHP presentation depends heavily on how well the transparencies are designed. A transparency that is cluttered, hard to read, or visually confusing will undermine even the best lesson plan. The following principles guide effective transparency preparation.

Text and layout 🔗

Use bold, legible text. Lettering should be large enough for students at the back of the room to read without straining. A minimum text size of 18-24 points is generally recommended for projected content. Use high-contrast combinations – black on white, or dark colours on a light background – to ensure clarity under projection.

Keep it concise. A transparency is not a page of notes. Each one should carry only the key points or a single central idea, with supporting detail communicated verbally. Overcrowding a transparency forces students to read rather than listen, splitting their attention in a counterproductive way. Aim for no more than six lines of text per transparency, with each line carrying no more than six to eight words.

Visual elements and layout 🔗

Incorporate diagrams and graphics. Wherever possible, use diagrams, graphs, charts, or simple illustrations to replace or supplement text. Combining text and visual elements activates multiple cognitive processes, improving overall retention and comprehension – this is precisely why a well-designed transparency outperforms a text-heavy one every time.

Use colour purposefully. Colour on transparencies can direct attention and organize information, but it should be used selectively. Limit each transparency to two or three colours, reserving the brightest or most vivid for the most important information. Randomly applied colour creates visual noise rather than clarity.

Plan for progressive disclosure. Rather than revealing an entire transparency at once, consider covering portions with paper and uncovering them sequentially as you address each point. This keeps student attention focused on the information being discussed, rather than letting eyes drift to content not yet covered in the lesson.

Test before class. Always preview transparencies on the actual projector in the room where they will be used. Focus, alignment, brightness, and readability can all vary depending on the projector model and room conditions. Catching problems before students arrive is far better than troubleshooting mid-lesson.

Projected aids – whether slides, filmstrips, CCTV, instructional television, or the overhead projector – are not simply technological additions to a lesson. Used well, they are fundamental to how complex ideas become comprehensible. Research confirms that visual aids enhance engagement, comprehension, and critical thinking across students with different learning styles, making them among the most inclusive tools available to any educator. The skill lies not just in knowing how these tools work, but in designing content for them deliberately – with the learner’s attention, comprehension, and retention always in view.

What do you think? If you had to choose just one projected aid for your teaching context right now, which would it be and why – and what would you do differently in how you prepare content for it, compared to a traditional lecture? Is there a topic in your subject area where a filmstrip’s fixed sequence or the OHP’s real-time interactivity would genuinely change how students understand the material?

References

1. https://pmc.ncbi.nlm.nih.gov/articles/PMC5256450/
2. https://files.eric.ed.gov/fulltext/EJ1079541.pdf
3. https://www.graduateprogram.org/blog/visual-aids-boosting-retention-and-understanding/
4. https://edtechmagazine.com/k12/article/2013/02/vision-learning-learning-history-classroom-projectors
5. https://www.tetsuccesskey.com/2015/01/projected-av-aids-teaching-learning-process.html
6. http://pascapbi-3a.blogspot.com/2017/01/projected-visual-aids-from-time-to-time.html
7. https://www.tvencyclopedia.org/tv-encyclopedia-5/educational-television
8. https://files.eric.ed.gov/fulltext/EJ1158459.pdf
9. https://communication.iresearchnet.com/educational-communication/instructional-television/
10. https://www.wgu.edu/blog/teaching-strategies-using-educational-television-classroom1712.html
11. https://en.wikipedia.org/wiki/Overhead_projector
12. https://rsisinternational.org/journals/ijriss/articles/effect-of-text-methods-visual-representation-and-learning-combination-on-the-learners-ability-to-retain-information/
13. https://www.researchgate.net/publication/383862512_THE_ROLE_OF_VISUAL_LEARNING_AIDS_ACROSS_DIVERSE_LEARNING_STYLES_IN_HIGH_SCHOOL_EDUCATION