Tutorial: Shoot at Middle Apertures

"Aperture" come from "apertura," which means "hole" in Latin, and refers to the variable opening in the lens. The f-numbers, as they're known, are odd and appear mysterious to the uninitiated:

ƒ/1,   ƒ/1.4,   ƒ/2,   ƒ/2.8,   ƒ/4,   ƒ/5.6,   ƒ/8,  ƒ/11,   ƒ/16,   ƒ/22,   ƒ/32,   ƒ/45,   ƒ/64,   ƒ/90

Photographers find it helpful to memorize this sequence.

The sequence is "an approximately geometric sequence of numbers that corresponds to the sequence of the powers of the square root of 2" (Wikipedia), but you don't need to know that. What's easiest to remember is that every other one approximately doubles or halves. Each single one doubles or halves the amount of light that the aperture allows to pass through the lens: that is, ƒ/1.4 lets in twice as much light as ƒ/2, ƒ/11 lets in half as much light as ƒ/8, and so forth.

The aperture is defined (Wikipedia again) thusly:

The f-number of an optical system (such as a camera lens) is the ratio of the system's focal length to the diameter of the entrance pupil ('clear aperture'). It is a dimensionless number that is a quantitative measure of lens speed, and an important concept in photography. It is also known as the focal ratio, f-ratio, or f-stop. It is the reciprocal of the relative aperture. The f-number is commonly indicated using a hooked f [like this: ƒ] with the format 'ƒ/N, where N is the f-number.'

The f-stop is a measure of lens speed, "speed" in this case referring how much light is able to pass through a particular lens. The f-ratios of a lens are stable properties of that lens when you hold it in your hand when it's attached to nothing...and they do not change when you put the lens in front of variously-sized recording substrates such as sensors or film.

Generally, spherical lenses, and most aspheres, perform best—and the resulting pictures look best—when you use middle apertures.

Konica T3 viewfinder diagram: What do those funny "Aperture Scale"
numbers mean and where should I put the "Meter Needle"?

It was one of the very first things I learned in photography. Shooting with my Dad's shutter-priority Konica T3's, I wondered where the aperture needle in the viewfinder should fall and what those odd numbers meant. Dad's friend Arnie Gore, a commercial studio photographer from Milwaukee (you can read the great story of his Nikita Khrushchev picture here), told me the needle just needed to be "somewhere in the middle," and to avoid the top two numbers and the bottom number. Crude, but it's actually still pretty good advice. The reason to have a wide aperture lens is so it's there when you need it (and, in the old days, to make an SLR easier to focus)—not to shoot at that aperture constantly and unthinkingly.

With most lenses, for best

performance, stick to

middle apertures

Two things happen theoretically with lens performance in the case of most lenses. First, aberrations diminish as you stop the lens down. Then, diffraction begins to soften the image as you stop down too much. So with most lenses there is an "optimum aperture"—that's the aperture at which aberrations are not further improved by stopping down more, but at which diffraction is not increased needlessly. Another way of saying this is that it's the widest aperture at which diffraction is the limiting function. A lens that's so good that this pertains at its widest aperture is said to be "diffraction limited."

You don't need diffraction-limited lenses for pictorial photography. In fact, as I said in the post "Bazooka Joe," you don't need good lenses for pictorial photography: artistic expression can potentially be achieved with a lens that has any kind of properties.

As a rough rule of thumb (assuming you want what is misnamed "optical quality"), the optimum aperture on fast lenses (ƒ/1.4 and faster on FF, let's say) will be two or three stops from wide open (ƒ/2.8 or ƒ/4 on that ƒ/1.4 lens) and it will be about two stops down for a slower lens (so, say, ƒ/5.6 on an ƒ/2.8 lens).

Does that mean you should always shoot your ƒ/1.4 lens at ƒ/4? No, because you're also thinking about depth-of-field and how much light you need to pass through your lens given the ambient lighting conditions prevalent at the scene. Also, in practice, the middle apertures of a lens are so close in terms of optical performance that there's not much visual performance difference between, say, ƒ/4 and ƒ/8 on our fast lens. Yes, the optimum aperture might be theoretically best, and yes, you might be able to discern the difference while pixel-peeping—but if viewers can't tell the difference between pictures taken at the optimum aperture and pictures taken at the two apertures next to it, then—if you're considering only sharpness in the plane of focus—it doesn't really matter which of the three apertures you choose.

Basic rule o' thumb, then: for best lens performance, stick to the middle apertures. But among all the apertures, choose the one that will give you the depth-of-field you want or the exposure value you want. Among the middle apertures, the optical performance between the various choices will be so close as to make no easily visible difference.

Depart from the middle apertures when you need to or when you want to; the middle apertures are merely a convenient default.

Mike

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(To see all the comments, click on the "Comments" link below.)
Featured Comments from:

Trevor Johnson: "ƒ/1.2, ƒ/1.7, ƒ/6.3 or ƒ/7.1 are oft encountered in today's world: plus others."

Mike replies: The scale I gave are the whole stops. The ones you list are intermediate values. ƒ/1.2 is one-third stop faster than ƒ/1.4; ƒ/1.7 is a half stop, midway between ƒ/1.4 and ƒ/2; ƒ/6.3 is one-third stop slower than ƒ/5.6; and ƒ/7.1 is one-third stop faster than ƒ/8.

I'm not sure if this is still the case, but in the '90s lens apertures were only accurate to within about a sixth of a stop, so listing apertures in thirds of stops was a bit suspect. But ƒ/1.8 sounds faster than ƒ2, so it's good for marketing. Yet if it is only accurate to within a sixth of a stop then it could be only 1/6th of a stop faster than ƒ/2—a difference most people cannot see—and still be within tolerances. Modern Photography used to list the real f-stops of lenses they tested, and they often weren't quite the same as what the labels claimed.

Greg adds: "Manufacturer's f-stop designations for photographic mirror/reflex are the worst. My 500mm ƒ/8 Nikkor is a half of a stop slower than ƒ/8, and my 600mm ƒ/8 Vivitar Series 1 is actually 2/3 of a stop slower than ƒ/8. Ironically I've found that the f-stop designations for telescope reflex lenses (way smaller market out there for these lenses) are totally accurate and right on."

marcin wuu: "First thing I do with all of my fast primes is take a piece of duct tape and tape the aperture ring down on its widest setting for good. I ain't buyin' those shallow d-o-f monsters to stop them down, damnit."

Mike replies: I initially hoped you were kidding, then I read Jeff's comment in the Comment section. So maybe you aren't.

Luis Aribe: "Just for the record, the Latin is 'apertura,' from which the English 'aperture.'"

Mike replies: Thank you Luis. Fixed now.

Gordon Buck: "Mechanical devices work best in the middle of their design range."

Mike replies: Yes. And to "stress" any such device—and coincidentally to reveal their quality—examine the extremes of those design ranges.

Peggy C.: "Re 'Basic rule o' thumb, then: for best lens performance, stick to the middle apertures.' As someone else pointed out, and the way I heard it, lo these many years ago, was 'ƒ/8 and be there'."

Mike replies: The old photojournalist motto.

s.wolters: "Good statement! But there are exceptions to this smack dab in the middle rule. I am a lucky owner of the Olympus 17mm and 25mm f1.2 lenses. These are designed to be used wide open. Both lenses peak around ƒ/2 to ƒ/2.8, so very close to their widest aperture. But even with these lenses I prefer to start with ƒ/4 to ƒ/5.6 rather than ƒ/1.2. Usually I’m more interested in my subjects than in blur."

Mike replies: True, and that's why it's useful to know your lenses' optimum apertures. Lens designers can optimize their designs for specific f-numbers and specific focus distances. Many lenses are, indeed, being optimized for wider apertures these days. A few, as Scott K. pointed out in the Comments section, are diffraction limited and thus are at their best wide open. It's not necessary to know, but it helps to know.

Comments

[Johan Grahn]

Ah, that Konica Autoreflex T3! My first serious kamera.

[Sal Santamaura]

Even with a D810 and several Sigma Art f/1.4 lenses, I still practice "f/8 and be there." Be there with a tripod and magnify live view to place depth of field where you want it. :-)

[Jeff Clevenger]

Hi Mike,
Excellent reminder about the value of shooting at middle apertures and finding your lens's sweet spot where its technical performance is best. Of course, there are a few cult lenses here and there that people like precisely because of the photos they get when they shoot wide open with them, like my Helios 58mm 44M-6.

I shot wide open with it for about a year until recently and loved the way I settled into the restrictions of using just that aperture, which in fact didn't feel all that restrictive. And I wound up with a bunch of perfectly done pics with in-focus subjects that were nicely rendered, and scintillating out of focus areas that supported those subjects quite politely, even artfully perhaps.

Helped me work quickly too as I didn't give a thought to which aperture setting to use, I just concentrated on finding and framing my subjects. Since for me that usually involves getting down somewhat low to the ground, sometimes in a lot of mud and such when I do streamside shooting of various plants in a natural area, I can't imagine trying to do it with a cumbersome tripod to wrestle with, but to each his or her own.

It helped too that I was using a light, film era prime lens on a modern digital Pentax SLR with image stabilization in the body, using an adapter per usual, though by shooting wide open I was already getting the fastest aperture setting on the lens. Still, the extra margin of stops from image stabilization helped produce a few good shots in low light without bumping up the ISO beyond its home level, which I prefer to hew to.

Now that I am back to my 85mm Tak, it takes me a second to remember I can change the aperture now, and scoot on through to the middle apertures, and when the picture calls for it, be daring and go way stopped down. But choose the right subject and frame it well and it is all good.

(By the way, though I missed the comments cutoff for your earlier post, bravo to you for getting a handsome Nikon FE and 85mm lens. That's my favorite ride in film photography, that family of cameras I mean, the FE, FA, and FM, so light, so nimble, so well engineered, and good luck with yours.)

Thanks,
Jeff Clevenger

[Michael Potter]

Nicely explained, thanks Mike.

[Ted Davis]

As he old Graflex Press Camera-using journos would say " Set it at f8 and leave it there!"

[Martin D]

Yes, yes, yes. Middle apertures are good. They let your lens shine and they force you to get your framing and composition right.

Having said all that, sometimes I wish I could shoot my Fuji 27mm at f/64! There can be little doubt that God created diffraction specifically with the aim of teasing us photographers.

[scott kirkpatrick]

/flameproof suit ON/ The current set of Leica Summicron lenses, first a 50 for the M series, and now 90, 75, 50, and 35mm lenses for the mirrorless L-mount cameras are all diffraction-limited. That is, according to the head of design at Leica, Peter Karbe, you simply set the aperture for the depth of field you desire, from f/2.0 (wide open) on down. I have several of them, and he is right./suit OFF/

[Those would be exceptions to the rule of thumb, then. No need for a flame-retardant suit! --Mike]

[Allan Ostling]

I memorized that sequence when I was nine, looking at my father's Retina IIa. But I learned something else today: that the convention is to write ƒ/2 instead of f/2 (or f2 as I've been doing for decades). Now I need to get the keyboard shortcut for the "hooked" f.

[On the Mac it's Command Option + lower case "f." And you have no idea how glad it makes me to hear somebody say this. The proper form for this is practically a lost cause. --Mike]

Most of us know that there is no merit in defining an "equivalent" f-stop. I hope you will write a future mini-essay on that.

[Allan Ostling]

Mike,

I am a Mac guy, so I tried your suggestion to get the "hooked" f. Command + f doesn't work. But all's well -- the sequence is Option + f.

[Fixed now. I use a wonky keyboard, so I'm never sure what's what. --Mike]

[DavidB]

One reason I use middle apertures is because stopped-down apertures show sensor dust spots (no matter how recently or often it gets cleaned). So middle apertures save me some work.

However, I also do a lot of astrophotography using lenses wide open. I've just recently spent many hours reviewing the plethora of aberations experienced by various lenses when used wide open to shoot stars.

Guide to lens aberations

[Peggy C.]

"Basic rule o' thumb, then: for best lens performance, stick to the middle apertures."

As someone else pointed out, and the way I heard it lo these many years ago, 'f/8 and be there'.

[s.wolters]

Good statement! But there are exceptions to this smack dab in the middle rule. I am a lucky owner of the Olympus 17mm and 25mm f1.2 lenses. These are designed to be used wide open. Both lenses peak around f/2.0 to f/2.8, so very close to their widest aperture. But even with these lenses I prefer to start with f/4 to f/5.6 rather than f1.2. Usually I’m more interested in my subjects than in blur.

[Matt]

This is actually really bad advice for 99% of photographers. Sure, you’ll get a few lp/mm added to the resolution of the picture, but at the cost of not thinking about depth of field. Thinking about what you’re going to focus on is critical. How much of the subject is in focus is also important.

That and, as always, you have to do the dance with what light you’re working with. So in full sun, you’re not going to be using anything under ƒ/8 probably. In practice, I find myself working the ends of the dial more than the middle. ƒ/16 for hyperfocal shooting in sunlight, and ƒ/1.4 or ƒ/2 indoors or at night.

[Mark]

Greg adds: "Manufacturer's f-stop designations for photographic mirror/reflex are the worst."

The difference between f-stop and t-stop? Mirror lenses have a large secondary mirror which will block out light from the centre of the aperture, so presumably there will be significantly less light gathered than from a theoretically perfect lens with the same f-stop.

[Mike Plews]

If I may add on small and unnecessary level of confusion perhaps a passing mention of T stops is in order.
The T stands for "transmission" and it takes into consideration the light absorbed by the lens.
When I was shooting 16mm reversal news film this was an important consideration. We had aftermarket rings attached to our zoom lenses that made it possible to see the aperture without taking you eye away from the viewfinder which was very handy in a dynamic situation. These rings were always marked in T stops not F stops. It wasn't a big difference but it was important as reversal films projected through a TV film chain are not forgiving of poor exposure.
The workhorse lens at that time was the Angenieux 12-120 f 2.2 which was a T2.8 wide open.
On top of all this some cameras had mirror reflex systems and others used a beam splitting prism to for a viewfinder. That prism ate a third of a stop of light and you had to figure that in too.
TTL would have rendered all this moot but that technology just did not exist on TV news rigs in the 1970's.
This is why I have a pile of old Sekonic incident meters in a box in the basement.

[Dwig]

Greg adds: "Manufacturer's f-stop designations for photographic mirror/reflex are the worst."
It's not that the mfgr's f/stop designations are inaccurate. It is, instead, that f/stops are not a perfectly adequate measure of the intensity of the light forming the image. No lens is 100% transparent, light is lost to both absorption and reflection, and not mirror is 100% reflective. T/stops ("transmission stops")are the "corrected" values that reflect the intensity of the light forming the image. Mirror lenses tend to show the greatest difference between their f/stop and T/stop values, though in the cine industry, most lenses are marked in T/stops since matching exposure between different lenses is critical.

[Shaun]

On a 50mm lens, f/2 would give 50/2 = 25mm aperture opening. On a 200mm lens f/2 would have a 100mm aperture opening. It's easy to see why longer lenses don't tend to have apertures faster than f/4.

[Bob Johnston]

When keeping this idea in your head it is easy to forget that a tiny bit of camera shake will more than negate that few lines per mm that you got from stopping down. Of course that is where IBIS or a tripod help.

[KeithB]

"and, in the old days, to make an SLR easier to focus"

It is the case now. Canon (and probably all others) specify the maximum f number they can focus at, and it can vary by focus point) Some lenses, especially long zooms, sometimes trick the camera by reporting the wrong aperture that will allow the camera to focus.

(The new Canon R will allow a lens up to f/11.)

[Stephen S]

Diffraction limits can definitely come into play with slow zoom lenses on cameras with small sensors. The Nikon 1 system starts seeing effects of diffraction at f/8, so the 30-110mm f/3.8-5.6 is one lens you want to use wide-open at 110mm if you're after maximum sharpness. I find the tests from Imaging Resource, formerly on SLRgear, to be really helpful in understanding where the strengths and weaknesses of your lenses lie.

[Bill Langford]

As regards "f/8 and be there", the way it was told to me long ago was the painter Ben Shahn was out to learn a bit of photography from Walker Evans. The advice was frustratingly slim before he was told f/8 and be there, and being there was the most important part. By the way, a bit late for the popular books discussions but
Ben Shahn's "The Shape of Content" (Harvard University Press 1963) is worthwhile for anyone wanting to be an Artist.

[Moose]

"Greg adds: "Manufacturer's f-stop designations for photographic mirror/reflex are the worst."

The difference between f-stop and t-stop?"

I believe Mark is right. As I am sometimes quite geeky, and had several mirror lenses at one time, from 350/5.6 to 1000/11, and including the Sigma 600/8, I measured the actual front lens and the mirror mount in the middle, and did the math.

All came out quite close to the stated F-stop, which is simply a physical ratio. Transmission is another matter, of course.

[Moose]

Might I suggest that all this theory and rules of thumb stuff is just that - stuff?

It's useful to actually take pictures and look carefully at the results, to learn how your lenses produce images, on your sensor/film. Back when I was a rookie, I read all this stuff about how horrible things would get at small apertures (on 35 mm film). And how it got worse at close distances

Then I shot a series of photos of tiny daisies (fleabane) with tripod mounted Olympus 135/4.5 macro lens across the whole range from f4.5 to f45.

Guess what? Diffraction softening wasn't noticeable, on film, with 4000 dpi scans, until f32. Even then it was outweighed, for my purposes, by increased DoF making more of the subject in focus. F45 was, finally, worse.

Many years later, a couple of members of the OM list wrote about the horrors of diffraction softening at f8 or smaller apertures on 4/3 size sensors.

Pragmatist that I am, I shot tests. They were simply wrong, with the sensors of the time, at least. F11 was fine, if not quite ideal, and the extra DoF useful for some subjects.

Now that the sensors have more megapickles, 20 vs. 12 then, f8 is my general limit.

The generalizations also may not apply at extremes. Optimium aperture at the long end of my PLeica 100-400 is F7.1, only about 1/3 stop from wide open. There's a small, but noticeable, improvement in that tiny step down, almost none then to f8, and slowly downhill from there.

[Henning Wulff]

As Mark just said, the mirror in catadioptric lenses reduces light transmission. The f-stop describes only the ratio of the entrance pupil diameter to the focal length, and says nothing about light transmission so doesn’t take the mirror into account.

I had a couple of 500/8 mirror lenses and none reached t/11, let alone t/8. One was in fact very nearly t/16.

[David Dyer-Bennet]

This is all broadly good advice for people who don't already know better. And by "know better" I mean know how to recognize the fairly rare lenses where the general advice is wrong enough to matter in general, and the photographic situations where something else matters more than resolution (like adequate shutter speed to freeze action or blur as desired, or extreme need for shallow or deep depth of field).

Maybe seems a little basic for TOP, but I suspect we loud-mouthed serial commenters that I get to know something about in the comments are more technically expert than the average reader.

[David Dyer-Bennet]

I was told, when I had my 90mm Summicron (bought new about 1974), that it was close enough to diffraction-limited that I could use it at f/2 entirely freely. However, the person who told me this did not have an MTF measuring rig in their living room (I'm not sure I had heard of MTF yet; 1974?). I didn't worry about it, because I tended to use it at f/2 when the picture wouldn't work otherwise, and that was a good enough reason.

[Tim Bradshaw]

I've always read 'f/8 and be there' as not really being about choice of suitable aperture, but rather meaning 'spend less time faffing with your gear and more time being in the right place at the right time'. I prefer that reading, anyway, as it applies to so many of us: 'you're not failing to be a great photographer (guitarist) because you don't have the right camera/lens/.. (guitar/amp/...), you're failing because you aren't getting up and shooting (playing) with the one you do have'.