single vs. multi coat?

[onespeed]

o.k. help me here the biggest difference betwen single and multi coat lenses is?
their liklihood of flare right? and color renditoin so if i used a single coat lens for color i could use a lens hood right?

 

[rover]

With modern coatings the difference may be quite little. Those comments I have seen about the SC 40/1.4 CV lens are very positive about the flare resistance and color rendition. For older lenses your statement should be more true.

A hood will improve the results from a lens in all cases, so yes, use of a hood is important.

 

[onespeed]

i will not even shoot without a hood in fact i have been known to wait weeks to get a hood before i will use a new piece of equipment

 

[Gabriel M.A.]

It's not only flare, but internal reflections too that could cause ghosting. You can see this more often with zoom lenses, or when using cheap filters stuck on your lens that cause reflections/ghosting.

With primes, well, like Rover said, it's more true with older lenses. Although I've noted that one exception to this a few Canon EF primes. But that's another story.

So, long story short: it helps with light transmission; that's their main purpose.

 

[richard_l]

Somewhere I saw a quantitative comparison of the light transmission of uncoated, single coated, and multi coated lenses, but of course I can't find it now. 🙁 Anyhow, single coating was shown to be a significant improvement over no coating at all, but multi coating was only very slightly better than single coating. I.e., there is little if any practical advantage of multi over single coating.

 

[varjag]

IIRC with uncoated glass, you have ~4% reflection from each air-surface boundary. A 4-element uncoated lens can lose as much as 30% of actual light due to reflections and scattering, while more complex designs can ba a full stop or more slower than their "geometric" speed. Indeed, the old photography guides suggest a stop more of exposure for uncoated glass.

Single coating puts this figure down to 1% per surface. Modern multicoating can bring that to small fractions of percent; an additional advantage of MC is that many layers (up to 9 these days) allow for color drift corrections of various sorts of glass (there are dozens of them, with various spectral characteristics) and individual coating layers.