I’d recommend checking a lens thoroughly – even if you’re buying it brand-new.

Over the last few years I have noticed many manufacturers' quality control has slipped and dusty optics are becoming more common straight out of the box.

I've seen brand-new Leica, Nikon, Fuji, Canon and Hasselblad lenses with dust inside – so don't assume because it's expensive it’ll be perfect!

It's true that these marks rarely affect performance but they will affect resale.

Remove both caps and shine a bright light through from the rear – a mobile phone torch works brilliantly. Inside, the lens should be clear and free of misting, marks or dust. Look at the front element and the rear element with the light and make sure there are no scratches or other coating marks.

Talk to the dealer if you have any concerns and, if necessary, arrange an exchange.