Lens coatings

[Barney]

What do they do?

Is there a massive difference between a single coated lens or a multi coated lens?

 

[Gav.]

Differant layers do differant jobs, they block UV or IR, some add water and oil repellancy.
They can help with reflections/ghosting/flares.

 

[Barney]

Differant layers do differant jobs, they block UV or IR, some add water and oil repellancy.
They can help with reflections/ghosting/flares.

Thanks Gav,

On an un-coated lens do you think that coloured filters will have more or less the same effect?

 

[Musicman]

On an un-coated lens do you think that coloured filters will have more or less the same effect?

Yes, they will

With Canon FD lenses, which I am most familiar with across comparable versions, single coated lenses broadly tend to have less contrast than multi-coated ones, but a yellow filter will still work fine on either.

 

[StephenM]

Reduce reflections. Light loss on each air/glass surface about 5%. Thst's why zoom lenses waited for coatings. Multi coats reduce loss to about 1%. Single between the two.

Coatings are fractions of a wavelength, so wavelength specific.

In haste at services heading for NEC.

 

[woof woof]

Lens coatings can also increase light transmission. This was discovered by Lord Rayleigh when he tested some tarnished glass. I found that interesting little ditty out by accident when reading something one day.

Just on lens coating effects. I used to have quite a few film era lenses of various ages and it was interesting to see how earlier ones performed compared to later ones. I had more Minolta Rokkor lenses than anything else, from the MK1's to the last MD's and it was interesting seeing how things steadily moved on within one manufacturer over the years. Some people go for single coated rather than multi for the look.

 

[StephenM]

Coatings are metallic oxides.

For more details see this book

Applied Photographic Optics

Selected by the American Library Association's 'Choice' magazine as

www.routledge.com

My copy is at home. I am not...

 

[StephenM]

Yes, they will

With Canon FD lenses, which I am most familiar with across comparable versions, single coated lenses broadly tend to have less contrast than multi-coated ones, but a yellow filter will still work fine on either.

Just in passing, Paul Strand had some (all?) of his uncoated lenses coated. He then found he had to reduce his development times due to the higher contrast.

Flare isn't just hot spots, it's a loss of contrast. The camera can also introduce it. There was a very interesting article with figures in the BJP Almanac a few years ago - say 1960 give or take.