Grid Flare in Digital Cameras

Have you ever noticed a faint pat­tern of colour­ful cir­cles or dots—most promi­nent­ly red, but also green and blue—when tak­ing a pho­to with a bright light source in the frame? That’s grid flare, although it’s also called flare grid pat­tern and red dot flare. It’s a unique quirk of dig­i­tal cam­era sen­sors that can be dis­tract­ing in cer­tain shots. Although it’s not a flaw in your cam­era or lens­es, under­stand­ing what caus­es it and when it’s most like­ly to occur can help you min­imise it in your pho­tog­ra­phy.

Let’s explore what grid flare is, why it hap­pens, and why it’s more com­mon in some cam­era sys­tems than oth­ers.

What Is Grid Flare?

Grid flare appears as faint, grid-like pat­terns of colour­ful dots around bright light sources in an image. Most occur­rences fea­ture promi­nent red cir­cles arranged in a grid-like struc­ture, which is why some pho­tog­ra­phers refer to it as red dot flare. How­ev­er, if you exam­ine the pat­tern close­ly, you’ll notice the grid also con­tains faint green cir­cles and even fainter blue cir­cles.

This obser­va­tion pro­vides a valu­able clue about its cause. Unlike tra­di­tion­al lens flare and ghosting—caused by reflec­tions and light scat­ter­ing between the ele­ments inside your lens—grid flare is a sen­sor-lev­el phe­nom­e­non. It aris­es from the reflec­tion and dif­frac­tion of light with­in the sen­sor assem­bly, mak­ing it unique to dig­i­tal pho­tog­ra­phy.

Why Does Grid Flare Happen?

Grid flare occurs due to the inter­ac­tion of intense light with the phys­i­cal struc­tures of your camera’s image sen­sor. Here are the main cul­prits:

1. Microlens Diffraction

Each pix­el on a dig­i­tal sen­sor has a tiny lens—called a microlens—placed above it to focus light onto the pho­to­sen­si­tive part of the pix­el. When bright light hits these microlens­es, it can dif­fract (bend) at sharp angles, cre­at­ing pat­terns that align with the pix­el grid. This dif­frac­tion is a sig­nif­i­cant fac­tor in the appear­ance of grid flare.

2. Internal Reflections Within the Sensor Stack

When you look into your cam­era with the lens off, the “image sen­sor” you see isn’t just bare pho­to­sites on silicon—it’s a com­plex stack of lay­ers. Depend­ing on the cam­era, these lay­ers include:

1. Pro­tec­tive glass to shield the sen­sor.
2. The opti­cal low-pass fil­ter (OLPF) man­ages alias­ing and blocks unwant­ed wave­lengths.
3. The colour fil­ter array (CFA) sep­a­rates light into red, green, and blue chan­nels.
4. The microlens array focus­es light onto the pho­to­sen­si­tive pix­els.

Bright, con­cen­trat­ed light can bounce between these lay­ers, cre­at­ing reflec­tions that align with the sen­sor grid and form the grid flare pat­tern.

3. Colour Filter Contribution

The coloured dots in grid flare (red, green, and blue) result from the Bay­er fil­ter array (or the X‑Trans fil­ter array on some Fuji­film cam­eras). This fil­ter deter­mines which wave­lengths of light each pix­el cap­tures. Reflec­tions and dif­frac­tion rein­force these colour sep­a­ra­tions, cre­at­ing the dis­tinct RGB pat­tern seen in grid flare.

Side­note: Cam­eras with Sigma’s Foveon sen­sors only exhib­it red dot flares, as they lack a tra­di­tion­al colour fil­ter array and cap­ture all colours at each pix­el depth.

4. High Pixel Density

Mod­ern sen­sors, espe­cial­ly those in high-res­o­lu­tion cam­eras, pack more pix­els into the same space. This tighter arrange­ment means small­er microlens­es and more poten­tial for dif­frac­tion and inter­nal reflec­tions. Con­se­quent­ly, grid flare is more notice­able in cam­eras with high pix­el den­si­ties.

Why Is Grid Flare More Common in Mirrorless Cameras?

While grid flare can occur in any dig­i­tal cam­era, it’s more com­mon in mir­ror­less cam­eras due to their short­er flange distances—the gap between the lens mount and the sen­sor. This design places the rear lens ele­ment much clos­er to the sen­sor than in DSLRs, caus­ing light to strike the sen­sor at steep­er angles. These sharp­er angles increase the like­li­hood of reflec­tions with­in the sen­sor stack, cre­at­ing the char­ac­ter­is­tic grid-like arti­facts. The short­er dis­tance also ampli­fies inter­nal reflec­tions between the sensor’s lay­ers, mak­ing grid flare more pro­nounced. This issue is espe­cial­ly notice­able with wide-angle lens­es, which are often designed with their rear ele­ments very close to the sen­sor in mir­ror­less sys­tems, fur­ther con­tribut­ing to the effect. By con­trast, the longer flange dis­tances of DSLRs posi­tion the rear lens ele­ment far­ther away, allow­ing light to hit the sen­sor at gen­tler angles and reduc­ing the sever­i­ty of grid flare.

When Is Grid Flare Most Noticeable?

Grid flare tends to appear in spe­cif­ic sce­nar­ios dic­tat­ed by shoot­ing con­di­tions and cam­era set­tings. It is par­tic­u­lar­ly notice­able in high-con­trast scenes fea­tur­ing bright light sources, such as sun­light stream­ing through trees or reflec­tions off shiny sur­faces.

Using small­er aper­tures (e.g., ƒ/8 or small­er) can also make grid flare more pro­nounced. Stop­ping down the lens increas­es the depth of field but caus­es light to strike the sen­sor at steep­er angles, which enhances inter­nal reflec­tions with­in the sen­sor stack and ampli­fies the grid-like arti­facts. If you’re rely­ing on small aper­tures to con­trol scene expo­sure in bright con­di­tions, con­sid­er using a neu­tral den­si­ty (ND) fil­ter instead. ND fil­ters reduce light inten­si­ty while allow­ing you to use a larg­er aper­ture, which can help min­imise the vis­i­bil­i­ty of the grid flare pat­tern.

How to Minimise Grid Flare

Grid flare occurs under spe­cif­ic con­di­tions, so it’s entire­ly pos­si­ble to avoid it with prop­er adjust­ments, such as:

1. Adjust Your Com­po­si­tion
   Refram­ing your shot to change the place­ment or inten­si­ty of bright light sources can elim­i­nate grid flare. Mov­ing the light source out of the frame or alter­ing your shoot­ing angle often resolves the issue.
2. Use a Larg­er Aper­ture with ND Fil­ters
   Small aper­tures (e.g., ƒ/8 or small­er) make grid flare more like­ly, as light hits the sen­sor at steep­er angles, increas­ing inter­nal reflec­tions with­in the sen­sor stack. To main­tain prop­er expo­sure while using a larg­er aper­ture, con­sid­er using a neu­tral den­si­ty (ND) fil­ter. This reduces the over­all light enter­ing the lens, allow­ing you to avoid small aper­tures and elim­i­nate grid flare from your images.

Final Thoughts

Although grid flare can be frus­trat­ing in cer­tain sit­u­a­tions, under­stand­ing why it happens—and why it’s more com­mon in some cam­eras, like mir­ror­less systems—gives you options for work­ing around it. You can keep grid flare under con­trol with a few adjust­ments to your shoot­ing tech­niques. Just remem­ber that there’s noth­ing wrong with your cam­era.