Multi coated or single coated

[herb]

I see where Cosina Voiglander has offered two of their lenses in either Multi coated or single coated, with the explanation that b/w is better with Single coating.
Is this accurate? Why?

[Ian Grant]

It depends on the lens and the coating. Multi coated lenses are sometimes a touch more contrasty, it's easier to see a difference between a coated and uncoated lens where the internal flare degrades the image slightly giving a smoother look to the tones and softening the micro contrast between them.

To some extent some lenses which are just coated (not MC) may exhibit a slightly smoother tonality than a Multi-coated version of the same lens.

My own experience with some single coated 35mm lenses was there was a significant difference but it varied between manufacturers and there was no visible differences berteen Takumars and SMC Takumars. The term single coated is often used to cover all pre-MC coated lenses, but in practice many lenses already had more than one coating, Zeiss developed the technique of applying more than one coating before WWII.

For LF work I use both coated and Multi coated lenses, I don't find the coated lenses any better or worse.

Ian

[Q.G.]

I see where Cosina Voiglander has offered two of their lenses in either Multi coated or single coated, with the explanation that b/w is better with Single coating.
Is this accurate? Why?

Multicoating (though in theory still a good thing) compared to single coating (which, as Ian explained, rarely are just a single layer coating), is much more a marketing thing than a usefull thing. (The difference between non-coated and even a single layer of coating is, much, much bigger.)
The difference between multi-layer coatings and 'single' layer coatings is extremely small, and you will be hard pressed to discover it in any picture you make.
But it really did, and does, make a difference in the market place. So take advantage of that.

I don't know how B&W would benefit from a single layer coating, compared to a multi-layer coating.
It could be a reversal of the 'factoid' that, given that a single coating could (!) allow more contrast lowering flare, B&W with the opportunities it offers to boost contrast during processing (compared to colour, which offers far less in this respect), you could correct the lower contrast easily.
But how that would make a supposed lesser contrast better for B&W beats me.

I don't know about that smoother tonality, Ian.

[Ian Grant]

Think of how smooth tones becomes when you use a soft focus filter. OK that's the extreme but a small amount of internal reflections/flare is enough to just smooth the edges of how adjacent tones are perceived, without really impacting on sharpness.

Often the term "rounder" tones is used rather than smother.

Ian

[Q.G.]

I don't know, Ian.

A soft focus filter creates "spill", in which light is displaced
Veiling flare (multi)coatings are mant to reduce just throws light over the entire image evenly. It reduces overall contrast. But that does not produce smoother transitions, does it?

[BetterSense]

One theory I've heard is that lesser-coated lenses are faster, because they have more flare, which brings the shadow values out more.

[Ian Grant]

I don't know, Ian.

A soft focus filter creates "spill", in which light is displaced
Veiling flare (multi)coatings are mant to reduce just throws light over the entire image evenly. It reduces overall contrast. But that does not produce smoother transitions, does it?

The flare produces rounder/smother tones because of the fogging effect, it's minimal between a coated and Multi coated lens, except perhaps when shooting into the light.

As the flare cuts the micro contrast that makes for the smoother more rounded transitions.

The effects are as we've said most noticeable between an uncoated and a coated lens, and I've seen it when using a 135mm 1931 Tessar, a nice sharp lens at f22 but you lose clarity fine detail because of the contrast drop. You see the same in the work of photographers like Kertesz with his pre-WWII images.

Then when you use a similar coated lens you retain the fine detail, and I now use a 1950's CZJ 150mm T Tessar, the coatings are heavy and apart from a distinct blue colour balance are as effective as Multi coating.

Can their be a difference between two Cosina/Voigtlander lenses, sigle & Multi coated ? That's the OP's question and the company seem to think so, but just how much we wouldn't know without testing side by side.

Ian

[Q.G.]

Cosina has created a prosperous business based on nostalgia, and offering a single coated lens next to a 'normally' coated one may be a further attempt to turn such feelings into cash. So i'm not sure i'd take their word.
Herb, which one costs more?

The flare, Ian, adds equally to both sides of a transition, whether small or big. So except for lifting both sides of the 'microcontrast' a bit, what else does it do that would create a smoother transition?
I can't think of anything.

[Ian Grant]

Flare like flashing during printing does add equally to both highlights & shadows however it reduces local contrast, but it's not proportional like using development for contrast control so the effect of flare is to lift the shadow side far more than the highlight side in terms of micro contrast.

Ian

[Q.G.]

In an image that consists of different amounts of light at different places?
There are no lower or upper thresholds.
The difference between 2 and 3 is the same as that between 6 and 7.