Many modern cars use high brightness LEDs for their rear lights. They tend to be rapidly switched on and off for 'normal intensity' and fully on for 'high intensity' when the brakes are also applied. When driving behind these cars I find the LED lights very distracting - whenever I move my eyes from one spot to another the lights appear to leave a trail of very bright dots caused by their rapid switching. Normal incandescent bulbs do not look like this, nor do the LED car lights when they at full intensity. Domestic items with LED displays also tend to do the same thing (I noticed it on a washing machine today). I also see it to a lesser extent with fluorescent lights.

My daughter also sees the flickering car lights when moving her eyes, but my son does not, and neither do other people I've asked. I understand why LEDs are rapidly switched in this way, and why they appear as a string of dots when I move my eyes - my question is why do some people apparently not see the effect? Is our perception somehow different? I have read reports that the brain 'switches off' visual processing when the eyes are flicked from one point to another - could this 'switching off' vary from one person to another?

Yesterday I tripped over a fence post I had just pulled from the ground. When my face hit the concrete around the bottom of the post, I literally saw stars. Today I have a shiny new black eye and a few questions. What are those stars and what causes them?

Victor Stanwick, Staten Island, US

 ie

• How many megapixels would it have?
• What would its resolution (dpi) be?
• What would its ISO range be?
• What would its colour depth be?
• What is its focal length? How does it's field of view and depth of field compare to a standard 50mm lens?
• The eye doesn't zoom, but does the brain do any of this for us? Its seems like it when concentrating on something or if something attracts our attention.
• At what speed can an object pass the eye before it appears blurred? Ie "shutter speed" equivalent.
• How many "frames per second" can it process?
• I believe the brain compensates for white balance? Does the eye have a natural "default" white balance setting which the brain then compensates for?

As the origins of life and the eye are ocean-based, it makes sense that the properties of the human eye ("why we see what we see") were largely evolved to perform specific tasks suitable for water. The fact that we can only observe a limited range of the electromagnetic spectrum—the part that water doesn't filter out—being a good example.

However, is the fact that we perceive water as being "clear" important? Is our optic system calibrated to see clean water as "clear". Obviously there are many things to factor in here: what the eye receives, how the brain perceives colour, even how we sociologically define colours, but water having "no colour" and not causing alarm or distress, for whatever reason would seem to be a good default for the whole thing.

Does anyone have any thoughts on this?

How do we know that I see red as you see red, or do we even know this at all? also how do we know the vision of other animals eg, if they see in coulour ect.

I have blue eyes and I squint in the light even if it is not a particuarly bright day. I often wear sun glasses when my brown eye friends are fine without. I got to thinking, does the colour of our eyes effect how sensitive they are to light in a similar way to how pale skin is more sensitive to sun light than dark skin?

What I mean is, when looking at a TV, the old ones not flat screens, I get light looking as though it is going out of the TV and upwards and also it is coming out of the bottom of the TV.

This also happens when looking at streetlights, kind of like the childrens drawings of the circular Sun and the rectangular beams of light stretching out.

Also, these 'beams' don't go on for too long, can't gauage the distance because it seems to be realative. The light also is the same colour as ones that are on the TV screen.