Quick Answers
The main differences between red eye and blue eye are:
- Red eye is caused by blood vessels in the eye becoming visible in photos, while blue eye is a genetic trait causing the iris to appear blue.
- Red eye happens when using a camera flash that reflects off the retina, but blue eyes are always present.
- Red eye can be fixed by removing the flash reflection, but blue eye color is permanent.
- Almost anyone can get red eye in photos, but only people with less melanin in the iris have blue eyes.
What Causes Red Eye in Photos?
Red eye occurs in photos when the light from a camera flash reflects off the blood vessels at the back of the eye. This makes the pupils look red instead of their normal black color.
Here’s a more detailed explanation of what causes red eye:
- Inside the eye is a network of blood vessels that nourish the retina. These blood vessels are normally invisible because they are located behind the iris.
- When a camera flash goes off, the light enters the pupil and reflects off the blood vessels at the back of the eye.
- The reflected light exits the pupil and shows up red in photographs.
- The effect is most pronounced when photographing in a dark setting, as the pupils are dilated to let in more light.
Red eye occurs due to the anatomical structure of the human eye and the way light reflects within it. The blood vessels and retinal tissue at the back of the eye reflect the flash, giving the red color.
Who Gets Red Eye?
Red eye can happen to anyone being photographed with a flash. However, some people are more prone to red eye than others:
- People with light colored eyes: Blue, green and hazel eyes show more obvious red eye since the red reflections contrast more with lighter irises.
- Children: Kids’ eyes fully dilate in low light, allowing more light to reflect.
- People under alcohol or drug influence: Substances that dilate the pupils increase red eye.
No one is immune to red eye, but factors like natural pupil size, iris color and dilation levels affect how apparent it looks. The only sure way to avoid it is taking photos without a flash.
What Causes Blue Eyes?
In contrast to red eye, blue eyes are caused by genetics and melanin levels rather than flash reflections. Here’s an explanation of what makes eyes appear blue:
- Iris color depends on melanin, the pigment that also colors hair and skin. More melanin means a darker iris.
- Eyes with very little melanin have a light blue color. Eyes with more melanin are brown, green or hazel.
- The translucent quality of blue eyes comes from the clear stroma at the front of the iris scattering light.
- People with blue eyes have less melanin concentrated towards the back of the iris, allowing light to reflect back blue.
Unlike red eye which can happen in any eye color, blue eyes are only present in people genetically predisposed to produce less melanin in the iris. The light scattering properties produce the signature blue hue.
Blue Eye Color Origins
Currently, only 8% to 10% of the global population has blue eyes. This trait originated as a genetic mutation that became isolated in European populations:
- A genetic switch known as OCA2 caused low melanin production in the eyes.
- This mutation likely first occurred in the Black Sea region around 10,000 years ago.
- As this founder population reproduced, blue eyes became established in the gene pool.
- Populations remained isolated, allowing the rare mutation to propagate.
Blue eyes are linked to a specific genetic heritage rather than environmental factors or random chance. They have persisted and spread through inheritance from a small founder group originating in the Black Sea area.
Key Differences Between Red Eye and Blue Eye
| Red Eye | Blue Eye |
|---|---|
| Caused by flash reflections | Genetic trait from low melanin |
| Temporary effect | Permanent eye color |
| Happens in low light | Present in all conditions |
| Can occur in any iris color | Only possible with low melanin |
| Can be prevented by removing flash | Cannot be altered |
This table summarizes the main points differentiating these two eye effects. While both involve light interacting with the eye, red eye is a physical reaction while blue eyes are genetic.
Appearance
Visually, red eye and blue eyes are easy to distinguish:
- Red eye – Pupils appear red or pink instead of black. The rest of the eye looks normal.
- Blue eyes – Iris is blue rather than brown, green, or hazel. The eye looks blue in all conditions.
With red eye, only the pupil is affected, while the entire iris is blue in blue eyes. The colors also differ, with red eye showing up pink or vivid red rather than the pale blue of blue eyes.
Permanence
Probably the biggest difference between these two eye effects is their permanence:
- Red eye – Appears temporarily in photos when a flash is used. It does not affect eye color under normal conditions.
- Blue eyes – The blue color is fixed and does not change under any lighting conditions.
You can experience red eye one moment in a photograph then have normal dark pupils the next moment without a flash. Blue eyes remain constant regardless of lighting or camera flash.
Prevalence
These eye conditions also differ in how common they are:
- Red eye – Can happen to anyone with a retina and blood vessels in the eye. Very common.
- Blue eyes – Only present in 8-10% of people worldwide. Much rarer than red eye.
Almost all people will experience red eye if photographed with a flash. Blue eyes, in contrast, only occur in a small fraction of the global population with European ancestry. This makes red eye a nearly universal phenomenon while blue eyes are uncommon.
Fixing Red Eye vs. Blue Eyes
Because red eye and blue eyes have different causes, they require different approaches to “fix” or change the appearance:
Red Eye Solutions
There are several ways to prevent or remove red eye:
- Avoid direct flash – Bouncing flash off ceilings or using diffusers eliminates the light reflection causing red eye.
- Increase ambient light – More ambient light means pupils contract and let in less reflecting flash light.
- Increase flash-to-lens distance – Moving the flash away from the camera lens reduces the reflective intensity.
- Post-processing software – Photo editing tools can digitally remove red eye by sampling and coloring over the pupil.
With good photographing technique and editing, red eye can usually be avoided or eliminated. The effect is temporary and does not require medical treatment.
Blue Eye Options
In contrast, blue eye color cannot be altered easily:
- Tinted contacts – Color contact lenses that cover the iris can temporarily change apparent eye color.
- Eye tattooing – Injecting dye into the thin iris membrane can permanently change eye color.
- Laser surgery – Using lasers to destroy iris melanin can lighten eye color, but has risks.
Contact lenses provide the safest and most reversible way to modify blue eye color. Permanent options like tattooing and laser surgery carry more risks and uncertainties. Blue eyes cannot be reversed easily like removing red eye in photos. The genetic basis of blue eyes makes the color relatively fixed.
Conclusion
Red eye and blue eyes involve very different mechanisms. Red eye occurs from reflected flash light while blue eyes result from low melanin levels in the iris. Blue eye color is a rare, permanent genetic trait most common in those of European descent. Red eye is temporary and can happen to anyone photographed with a flash. While red eye is easily preventable and correctable, blue eye color cannot be altered easily without contact lenses or medical procedures. In summary, red eye is a physical reaction but blue eyes represent an inherited trait.
