Screen brightness, size and legibility at retail distance
A screen delivers a message only if the message can be read from where the shopper stands. That is a function of screen size, viewing distance, brightness relative to the ambient light, and type size on the creative. Get any of them wrong and the medium delivers presence rather than communication.
These are physical constraints rather than creative preferences, and they are worth understanding before approving artwork.
How does viewing distance drive type size?
Directly. The further away the reader, the larger the type has to be to remain legible, and the relationship is roughly proportional. A screen read from arm's length and one read across an aisle need different creative even at the same screen size.
That is why a single creative deployed across positions with different viewing distances will work at some and fail at others. Specifying the distance is part of specifying the creative.
What does brightness actually need to overcome?
Ambient light. A screen in a dim aisle needs far less output than one facing a shop window in the afternoon, and the specification that matters is brightness relative to the surroundings rather than an absolute figure.
Direct sunlight defeats most indoor screens entirely. Where a position faces a window, either a high-brightness display or a different position is the answer, and a standard screen there is an installation that looks fine at nine in the morning and is blank at three.
What about contrast and colour?
Contrast between text and background carries more of the legibility load than colour does. High-contrast combinations survive glare, reflection and poor viewing angles; low-contrast ones fail first in exactly the conditions a retail environment presents.
Colour choices that work on a designer's monitor in a controlled room routinely fail on a screen with a shopper standing at an angle under fluorescent light.
How does viewing angle matter?
Screens dim and shift colour as the viewing angle widens, and in a narrow aisle much of the audience is at an angle rather than square on. A specification that quotes performance head-on is describing the best case.
Ask about the angle at which the screen is actually viewed in the positions being bought, which is a placement question with a specification consequence.
What size screen is enough?
Large enough for the message to be legible at the viewing distance, which usually means the size follows from the position rather than from a budget. A screen too small for its position is not a cheaper version of the right screen; it is a screen that does not communicate.
What should a creative specification contain?
Minimum type size, safe margins, contrast requirements, file format and duration. The creative specs a network publishes are the operative document and they exist because these constraints are real.
Design to the specification rather than adapting afterwards. Artwork repurposed from a digital campaign and scaled down is the single most common cause of an unreadable in-store ad.
How do you check it works?
Stand where the shopper stands and look. That is the whole test, and it is more reliable than any specification review. If the message cannot be read comfortably in two seconds from that position, it will not be read at all.
Frequently asked questions
How bright does a retail screen need to be?
Bright enough for its ambient conditions, which varies enormously between a windowless aisle and a shopfront position. Specifying a single brightness across a varied estate guarantees that some positions are over-specified and others are unreadable.
Does a bigger screen always perform better?
Only up to the point where legibility is achieved; beyond that the additional size adds presence rather than communication. Budget is usually better spent on the right size in the right position than on a larger screen in a poor one.
What type size should creative use?
The minimum specified for the viewing distance, treated as a floor rather than a target. Most in-store creative would be improved by using fewer words at a larger size.
What about reflections?
Matte or anti-glare finishes help and they do not eliminate reflection from a bright source directly opposite. That is a placement problem before it is a hardware one.
Should creative be tested on an actual screen?
Yes, before flight, on the same type of display in comparable light. A proof approved on a laptop has been approved under conditions the medium does not offer.
How does this differ from outdoor digital advertising?
Outdoor contends with daylight and much greater viewing distances, which drives larger formats and higher brightness. Industry practice for out-of-home is discussed by bodies such as OAAA, and the in-store case is a distinct set of constraints.
What is the simplest legibility rule?
Fewer words, larger type, higher contrast. Nearly every unreadable in-store ad breaks at least two of those three.
### How does the store's own environment change over time?
Lighting is re-lamped, fixtures are repainted, a window display changes the light falling on a screen. Each of those can move a position from comfortably legible to marginal without anything happening to the screen.
That is an argument for checking legibility periodically rather than only at installation. A photograph taken from the shopper's position, once a quarter, is enough to catch the change.
Should creative be designed for the worst position?
Designing for the most demanding viewing conditions in the estate means the execution works everywhere, which in a mixed estate is the safer approach. Designing for the average leaves part of the network showing something that cannot be read.
### How should legibility be verified across an estate?
By photographing a test frame from the shopper's position in a sample of stores and reviewing them together. Differences between stores show up immediately and they are invisible in any specification document.
Sample across the range rather than the convenient stores. The positions most likely to fail are the ones nobody visits, which is also why they fail.
What if some stores fail?
Either fix the position or design to the weakest condition. Accepting that part of the estate cannot read the creative while paying for it is the option nobody chooses deliberately and many choose by omission.
Preparing creative? See the NRS Digital Media creative specs or contact the team.