This is a somewhat inconclusive set of musings about what photographers call lens character, or the way a lens draws.
But before we get into that, I’d like to confess my biases. I’m an engineer by training, and I’ve spent most of my life either doing research, designing things, or managing others who do those things. I have an unromantic approach to camera equipment, and, maybe, and unromantic approach to life, that can be summed up in the following joke:
A pastor, a doctor and an engineer were waiting one morning for a particularly slow group of golfers.
Engineer: “What’s with these guys? We must have been waiting for 15 minutes!”
Doctor: “I don’t know, but I’ve never seen such ineptitude!”
Pastor: “Here comes the greens-keeper. Hi, Dave. What’s with that group ahead of us? They’re rather slow.”
Dave: “Oh, yes, that’s a group of blind fire fighters. They lost their sight saving our clubhouse from a fire last year, so we always let them play for free anytime.”
The group was silent for a moment.
Pastor: “That’s so sad. I’ll say a special prayer for them tonight.”
Doctor: “Good idea. I’m going to contact my ophthalmologist buddy and see if there’s anything he can do for them.”
Engineer: “Why can’t these guys play at night?”
Lens character is often described in the same kind of soaring rhapsody of metaphors that you find in wine newsletters and high-end hi-fi mags.
Breathtaking accuracy, a spacious soundstage, pinpoint localization, deep, powerful bass and thrilling dynamics…
A seamless classic, it offers a symphony of red and black currants, Asian plum sauce, lavender, and underbrush. Sweet Christmas fruitcake characteristics emerge from this magnificent creation. The seamless integration of acidity, tannin, wood and alcohol, the brilliant length and overall compelling complexity and richness make it one of the great classics from this historic estate.
It’s a naïve little domestic, but I think you’ll be amused at its presumption.
Zeiss is cooler, more clinical, more contrasty, lots of micro-contrast, punchier colors. Leica is warmer, more human, lower contrast, more natural colors.
To some extent, imprecise language is necessary in all three cases if the real speaker, wine, or image isn’t available. However, in photography, it’s usually pretty easy to supply an image or two that illustrate what the words are trying to describe. This is done with what I consider remarkable infrequency. I don’t know what the problem is. It’s not like wine, where it’s not practical to include samples with the newsletter (wouldn’t that be nice!), or hi-fi where the mag can’t ship the whole setup to your house so you can experience what they’re talking about. On the ‘net we may not be able to simulate printed output, but we can surely attach screen images at whatever resolution we desire.
There is one difference between wine and the other two cases, and I think it’s the beginning of a better way to think about lens character. There is no one perfect wine, a wine that all the wines in the world are trying to be. Each wine is an expression of what can be done with particular fruit grown in particular places in particular growing seasons. So a description that includes positive and negative metaphors is appropriate, if we can agree on a vocabulary and samples are unavailable. However, anyone who has purchased wine based upon what the seller — or even a disinterested third party – had to say in a newsletter knows that there is many a slip between the description and the lip.
But with hi-fi and lenses, there is an ideal that is out there. With hi-fi, it’s the original sound field, assuming there was one. With lenses, it’s the perfect diffraction-limited optic that brings all wavelengths to a common focus with no distortion, no aberrations, and has no departures from perfection in its rendering of out-of-focus objects. Notice what’s happening here. I’m describing the perfect lens mostly in terms of what it doesn’t do.
And that’s what I think lens character is all about. I think a lens’s character is the totality of its departure from perfection. I further think that the purple prose that gets applied to what some consider to be highly desirable lens character is the description of endearing errors.
That doesn’t make all such talk silly. Perfect lenses are impossibilities. Nearly perfect ones are impractical. You wouldn’t be able to afford one, much less a bag full. Lens designers make tradeoff between types of errors. Some of them bias the tradeoffs in the direction of maximizing one set of criteria. Others pick different things to try to get right. Things not on the list to optimize don’t get optimized.
Photographers want different things out of their lenses. The things that are important to me vary with the subject, the lighting, and my intended use of the images. Lens character that may be a plus in one situation could be a disqualifying drawback in another.
But let’s not get carried away with the descriptive poetry when we talk about lens character. Let’s focus on what the departures from perfection are, and how they fit the intended use of the lens.
Why can’t those guys play at night?