Gamma measures how fast an option's directional exposure (delta) changes
as the underlying moves. Market makers who sell you options must hedge that changing
exposure with S&P 500 futures and shares — and because their books are enormous,
how they hedge shapes how SPX itself trades. Reading the dealers' aggregate
gamma position — gamma exposure, or GEX — tells you which of two very
different market environments you are trading in.
Positive vs negative gamma regimes
Positive gamma — dealers hedge against price: they sell as
the market rises and buy as it dips. The result is slower, grindier, mean-reverting
tape with muted volatility. Fading extremes tends to work; chasing tends not to.
Negative gamma — dealers hedge with price: they must sell
weakness and buy strength. Moves extend further and faster in both directions,
breakouts stick more often, and stop placement matters far more.
The boundary between the two is the zero-gamma flip: the level where
the dealers' net gamma crosses zero. Above it, expect the damped regime; below it, the
accelerated one. Knowing which side of the flip SPX is on is arguably the single most
useful piece of options context an intraday trader can have.
Walls, magnets and pinning
Call wall — the strike carrying the most positive gamma. Heavy
hedging supply appears as price rises into it, so rallies frequently stall or
"pin" there, especially on expiry days.
Put wall — the deepest negative-gamma strike. It often acts as
support on the first touch, but a decisive break below it flips hedging pressure to
selling and can turn an orderly dip into a flush.
Gamma magnets — between large concentrations, price finds paths of
least resistance; thin-gamma pockets are traversed quickly, while big strikes attract
price toward them as hedges unwind.
Max pain — the expiry price that minimizes the total payout to
option holders. It is not a law of nature, but late on expiry days hedging decay
(charm) often drifts price toward it.
Adding charm: the four intraday regimes
Gamma alone tells you how price moves — grindy or violent. Charm
(delta decay: how an option's delta drifts purely as time passes) tells you which
direction that hedging leans as the session ages. Reading the two together gives a
far better daily map than either alone:
Positive gamma + supportive charm — the classic grind-up day. Dealers
damp volatility and their decay-driven hedges lean toward buying dips, so shallow pullbacks
get bought and price drifts higher into the close.
Positive gamma + suppressive charm — still slow and range-bound, but the
lean is the other way: pops get sold, and the tape stays capped or bleeds gently lower.
Negative gamma + supportive charm — volatile with an upward bias.
Dealers chase strength on the way up while decay hedging adds bid under dips; moves are
quick and pullbacks shallow.
Negative gamma + suppressive charm — the dangerous combination. Dealers
sell weakness and charm piles on more selling, producing the fast, one-way downtrend days
where dip-buying is punished.
Practical use: let gamma set your tactics (fade vs. chase) and charm set your
directional bias for the day.
Trading intraday gamma zones
Beyond the headline walls, the per-strike gamma profile splits the ladder into two kinds of
territory, and they behave very differently:
Gamma peaks (barrier zones) — concentrations of gamma where hedging
absorbs order flow. Price struggles to pass through them, so they act as support or
resistance and are the places to watch for bounces and rejections.
Paths of least resistance (magnet zones) — thin-gamma pockets between
peaks where there is little hedging to slow price down. Price traverses them quickly, and a
strong one can act as a magnet that price travels toward once it leaves a peak.
The highest-quality setups come from confluence: a gamma peak that lines up
with a technical level you already care about. Two common shapes — a bounce off a peak that
sits on key support, with the next magnet zone above as the target; or a failed peak that
releases price into a magnet zone below, which becomes the objective for a short. Gamma zones
can also stand on their own, but they are most reliable when price structure agrees.
How SPX Lens computes it
The live heat map rebuilds the dealer gamma profile every few
minutes from the 0DTE chain's open interest and greeks (calls positive, puts negative —
the standard dealers-long-calls / short-puts assumption), then marks the call wall, put
wall, zero-gamma flip and max pain directly on the strike ladder and tracks how they
migrate through the session on the intraday gamma map. One honest caveat: open interest
is published once daily, so intraday changes reflect gamma re-pricing as spot and
volatility move — not a proprietary flow model.