Can a plastic-barreled lens be damaged if stored inside a car? Can sunlight damage the lens?

Question

One of the lenses I purchased has this note in the instruction manual: "Do not place lens in direct sunlight or leave it in an extremely hot place such (sic) inside a car. Doing such could damage the internal parts of the lens or cause a fire".

Therefore, there are two parts to my question:

• Can sunlight really damage a lens? I mean, aren't lenses made for using in various situations, such as in sunlight? If I can't shoot in sunlight (obviously not pointing the lens directly to the sun), it makes the lens much less of the good deal it appeared to be.

• Can storing a lens inside a car in sunlight damage a lens? I don't necessarily want to carry all lenses I have in my car with me all the time, so forbidding storage of a lens inside a car for short periods (at most few hours) takes away some of the value the lens has to me.

If it matters, the lens barrel is plastic. And of course, if storing the lens in a car, I have caps on both ends so I won't start a fire!

I find it hard to believe that sunlight would be hot enough to permanently deform the plastic parts of the lens in few hours.

But then again, I do know in some parts of the world sunlight causes car plastic parts to deteriorate, albeit very slowly, so certainly the car shouldn't be where you keep your plastic-barreled lenses all the time completely exposed to the sun.

Answer 1

There are two risks to consider with lenses, and both apply to pretty much every lens made.

---

1. Risks from focused sunlight

Focusing sunlight readily creates a risk of heating materials to dangerous levels, which in turn creates the risk of fire.

Allowing sunlight to pass through an open camera lens is a fire risk, with many Lens & Body combinations being able to burn holes in the camera shutters. - Don't point your lens at the sun...

---

2. Risk of damage from thermal expansion and overheating of parts.

This one really comes down to specifics of the design, and exact materials in question.

While it may be easy to assume that the risk is only with 'cheap plastic parts melting', it actually goes a bit farther than that.

Excessively cheap plastics might noticeably deform in temps as hot as you'll likely find in a car, but most of the risk comes from indirect damage and increase wear. The majority of plastics used for camera lenses aren't going to outright melt or directly deform from such temps, but they may be at risk of increased wear or damage if allowed to be heated too much before use. Plus the risk of premature end of life of a material if allowed to go through thermal cycling.

Thermal expansion is also high on the list of damage sources, and this is not remotely limited to Plastic parts. I have had an all glass and metal lens have its leaf shutter buckle due to heat, and I had used a piece of optical equipment as part of a scientific instrument package that would pull itself out of alignment if we let it get over 40C.

---

Finally there is also another risk: Excessive UV damage to the material if left in sunlight. However this is probably unlikely for the majority of lens models unless left in direct sunlight for ages.

Answer 2

Excessive heat poses a risk to almost any lens by reducing the viscosity of lubricants enough that they flow into areas where they don't belong.

It is common in the used lens market to look for oily aperture blades as a sign that a lens is in trouble.

(If this lube flow is the primary concern then it could very well be the case that you should be less concerned about lenses with plastic barrels than those with metal barrels since the former are less thermally conductive.)

Answer 3

I assume the "cause a fire" is related to sunlight passing through the lens and causing a fire, like lighting a fire with a magnifying glass. Although, who leaves a lens out with no front or rear cover anyway?

If the lens is plastic, it's going to be much more likely to have parts get warped under high heat. The inside of a car on a sunny day can easily get up to 45C (113F). A black interior can get up to 54C (130F).