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Mike: Not Needy and Nothing If Not Conservative
I was rather surprised that the result to Wednesday's poll turned out to be a classic bell curve; I thought it might well be an infinitely-rising curve, with the most people choosing the highest number, or, in effect, "all the speed I can get."
So what was my own answer to the question "When you're shopping for a digital camera, what's your minimum standard for high ISO of good quality?" I chose ISO 1600. [I waffled between 400 and 800. —Ctein.] I'm not greedy. Not needy. My requirements are modest. And Lord knows I'm nothing if not conservative. (Big smile.)
The reason has its basis in pure empiricism, as usual. I've simply observed over the years that with every digital camera I've owned or used extensively, from the meanest digicam to the Nikon D700 and D3, no matter how good the high ISOs look, lower ISOs look better.
Don't get me wrong—I'm very grateful for the high-quality high ISO speeds we all now enjoy. I spent the first half-decade of my photographic life shooting a black-and-white film (Kodak Plus-X) that I rated at E.I. 80...and usually shot with a yellow filter! Speed was a constant...issue. And I distinctly remember a brief window in the early years of this millennium when digital image quality had caught up to film at low ISOs but not at high ones, and I'd encounter forum postings from pros saying that before switching to digital, they would have to hold out for high-ISO performance from digital that at least matched that of film.
That period sure didn't last for very long. Canon led the way, but very soon all digital cameras matched film’s best speed. And then exceeded it.
What I do today is simply shoot at the camera’s best ISOs, unless I can’t, in which case I shift to something higher. Doesn’t everybody?
For any given camera, as ISOs increase, image quality deteriorates. It’s not just a question of noise. Sharpness and resolution subtly degrade, as does the richness and purity of colors, dynamic range, and so on. Noise intrudes too, as everyone knows, but I suspect that people who say things like “quality is identical from 100 to 800” are looking only at noise, and nothing else. I’m not saying I can tell the difference between 640 and 500, but there are more differences than just noise over a three-stop ISO range with the cameras I’ve tried.
One exception is that shooting specifically for B&W conversion allows a real increase in usable ISOs. Partly because chroma noise isn’t an issue—and partly, I suspect, because I’m used to grain with B&W and it doesn’t bother me! Well, it doesn’t really bother me in color, either. Not nearly as much as it bothers some. If noise is pretty, I don't mind it.
Still, with image stabilization and reasonably fast lenses, I’ve found I almost never need more than 1600—and seldom that, although it’s luxurious to have that speed in reserve. With the Nikon D3, 1600 was fully usable and 3200 was a reasonable “in a pinch” speed. With the Panasonic GF1 (although I’ve just started using it and reserve the right to change my mind as I work more with raw files), I suspect that 800 is the top “fully usable” speed and 1600 is the “in a pinch” speed. Which is okay for a digicam—it’s a lot better than my now-ancient Sony F-707. ISO 400 was really well beyond that camera's comfort level.
I have no quarrel at all with those who want more and more high ISO speed. I have no doubt they need it. At some point, however, I suspect we’ll reach “market saturation” on high ISO speeds...it’s happened that way with many other marketing/technical parameters in the history of photo techniques, from film size to lens speed. The new D3s indicates that we probably aren’t there yet. I don’t know where the market will decide to stop, but, just personally, I’m good where we are now.
From our Wednesday poll, looks like a fair number of others are reaching that point too.
Mike
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Ctein: I Was Built for Comfort, But I Could Live With Speed
In the thread on the Nikon D3S, quite a few folks expressed serious doubts about the value of such high speeds, arguing, in various forms, that there isn't much merit in trying to produce fine photographs under conditions where we cannot even clearly see what we're photographing. I take firm exception to that position.
Serious, high-quality, fine-grain low-light photography (in contrast to the push-processed, available-darkness kind) has been part of the canon since at least the 1930s. When I was a noob in college in the late '60s and entirely ignorant of that canon, I clearly remember the night I wondered, "Hey, what would happen if, instead of loading with Tri-X or 2475 Recording film and pushing the bejeezus out of it [as I was accustomed to doing in my reportage photography], I set up the tripod, loaded up with Pan-X and pull-processed a bit for range, and just let the exposures take as long as they needed to?"
WOW! Gorgeous! Completely changed my artistic direction. I very quickly mastered night photography, figuring out which slow films had the best reciprocity characteristics and what the compensations needed to be to get accurate results in both B&W and color with exposure times up to 40-50 minutes. I made this one just a few years after I started on this track.
In case you're wondering, no, I did not bracket. It sucked up enough of my life just making those 40-minute masterpieces. I made sure I got it right in one exposure. Carried a paperback and a flashlight in my bag; got a lot of reading done those nights. Metering? Meter off a highlight or a white sheet of paper and it's like boosting your meter sensitivity an order of magnitude. If I could see it, I could meter it. It went like this: meter would tell me I needed 2/3 second at ƒ/2 off of white paper. Okay, that's 5 seconds for a proper grey. Now start stopping down for depth of field. There I am at ƒ/13 for a photo like this one and the nominal exposure time's pushing over 200 seconds. The film I'm using's got a 10X reciprocity correction at 200 seconds. And so, it's reading time!
My first noteworthy bodies of work involved substantial amounts of just that kind of low-light photography (I never cared for Arthur Ollman's available-darkness "grain-o-graphs" when he showed up on the scene). That still includes some of my best photos. Two thirds of the photos in this screen required exposures of 30 seconds or more on slow film. I still routinely make multi-minute, low-light/ISO100-speed photographs (check out the Christmas in California series).
Digital sensors have better reciprocity characteristics, so my exposure times have dropped a lot the past few years; rarely do I need to go beyond a minute these days. Nonetheless, my style remains the same and the results are still artistically satisfying. Would I jump at ISO 100K? Not particularly; I'm okay with tripods and a couple of minutes between frames.
BUT...
There are lots of photos I don't make because the subject matter won't sit still for large numbers of seconds. Do I think having 1,000 times the ISO I now use would open up all sorts of artistic opportunities? Hell, yeah! Is it artistically, conceptually, and philosophically valid? Double-hell, yeah! Photography's never been merely about photographing what you could see; it's always been about photographing what you wanted to see.
"Computer science professor Marc Levoy of Stanford shows off his prototype 'Frankencamera.' It allows programs to be downloaded, much like the iPhone does, and might just change the future of photography." [NPR caption. Photo by Linda A. Cicero]
Scientists at Stanford University are developing a Linux-based open-source camera, hoping to push camera manufacturers into incorporating similar possibilities into commercial products. The article spends a lot of time detailing a not-very-convincing example, but the idea of an infinitely-programmable open-source camera is enticing. Read about "Frankencamera" at NPR. org.
Here's the Project Website.
Mike
(Thanks to Maarten Boerma and Randolph Fritz)
...My coda, anyway. The original post was published on June 21st. A couple of final points:
1. My philosophy has always been that people should have fun with photography any way they want to as long as it's legal and doesn't hurt others. So if anyone wants to make a lifetime study of the science of DoF, I have zero objection.
2. I shouldn't have said, about depth of field (DoF), that "Most of what's out there is 99.75% complete chrome-plated bulldung." That's only the cumulative effect of error-ridden forum-style exchanges between non-experts. Henceforth, I'm going to recommend Paul Van Walree's excellent and well-written page to anyone who asks about the subject.
3. ...Comma, however, I need to reaffirm my commitment never to talk about the subject. What can I say? I backslid.*
4. The flickr slide show that Johnny R created and linked to in the comments was pretty cool (even though the bokeh of that first picture gives me full-blown heebie-jeebies). His comment was antagonistic, which wasn't really necessary, but it did make me feel strange—first time in 12 years I've been criticized for being anti-bokeh....
5. I feel rather sheepish for being very thick about one thing. I had my "duh moment" about this at long last thanks to some of our commenters. The fact is, I'd been reading persistent and (theretofore) inexplicable rants, claims, and misinformation about shallow DoF for something like a year without understanding the reason behind it: it's because people are trying to rationalize their purchase of a full-frame DSLR! Or trying to assert the superiority of the full-frame DSLR they've already bought. Duh! I'm normally pretty good at detecting the psychological underpinnings for any given observed upsurge in hooey, but I wasn't on top of that one. I should have been on to it a lot sooner.
Which leads me to...
6. The smaller size of APS-C and 4/3 sensors is really much more of an advantage than a disadvantage, in my opinion, because it allows us to use shorter lenses for the same angle of view and get more DoF at wider apertures. All else being equal**, I prefer an APS-C or 4/3 sensor to a 35mm or "full frame" one where DoF is concerned.
Which leads me to....
7. We should remind ourselves from time to time that the visual (aesthetic) conventions of photography we're all so used to are essentially an accident of the medium's technical properties. When a fixed-lens camera takes a picture of a flower in the foreground, we expect the background to be out of the DoF and blurry, but there's nothing artistically intentional in that preference—it's only because we've become used to the way in which cameras typically render scenes visually that we think it's appropriate and desirable. We might exploit the innate photographic properties to explore the visual implications of those properties, but that's a case of us adapting to our tools.
What I'm saying is that if the physics of lenses happened to dictate that far focus distances had little DoF and close ones had large DoF, then that's what we'd be used to, and expect, and demand. But there wouldn't be anything innately superior about it aesthetically.
Right now, thanks to Photoshop et al., we are less dependent on the inherent properties of camera vision than ever before (for better or worse). And it's quite possible that we shall soon be entering an era when the visual properties of imaging systems will be enormously more varied and flexible than they are now. When that happens, the properties of "camera vision" will be even less fixed, and in that case peoples' expectations and preferences will evolve further. When that happens, artistic intention will play a greater role than it does now. For the time being, however, DoF is less a parameter that we have to "control" than it is a property we can't do all that much about, and which we must simply accept.
And finally...
8. Don't obsess about it. That's my recommendation, anyway. Pay attention, study your pictures, and you'll get a feel for DoF eventually. At that point, as well as in the meantime, it is what it is. A picture either works or it doesn't.
Mike
*Past tense of backslide, meaning to relapse into temptation, bad habits, or practices previously foresworn.
**The problem, as I've written elsewhere, is that all else is not equal. The APS-C and 4/3 viewfinders are not as good, and the cameramakers have not seen fit to provide us with more than a hodgepodge of lenses designed for the reduced-size formats, complicating lens choice considerably. But the reason I like full-frame cameras is for their viewfinders and because they restore traditional focal-length lenses to their traditional angles of view, and (secondarily) because of their somewhat improved high-ISO characteristics—not for any reason having to do with DoF.
By Ctein
I don't know why this myth about the depth of field being utterly independent of focal length (for constant magnification) keeps on going, because it's easy to prove that it's wrong and sometimes it really matters that it's wrong.
Nonetheless, it is a myth and it is wrong.
Here's the real skinny. At close working distances, depth of field is nearly independent of focal length. In fact here's a handy approximate equation for depth of field that depends solely on circle of confusion (c), aperture (f), and on-film (or sensor) magnification (M):
DoF (on either side of the subject) = c*f*(M+1)/(M*M)
As you decrease the magnification, lens focal length starts to become more important. As you get close to the hyperfocal distance, to maintain comparable total depth of field, the magnification becomes inversely proportional to the focal length of the lens rather than being independent of it!
A good rule of thumb is that for just about any photography you do indoors, depth of field isn't going to be affected by focal length, just on-film magnification. But as you start photographic more distant subjects, the effect of focal length increases and eventually becomes as important as aperture.
At intermediate distances, the total depth of field (in front of and behind the subject combined) decreases as the focal length of the lens increases, for the same on-film magnification (and same aperture and circle of confusion). The distribution also changes. The shorter focal length lens will always have less depth of field in front of the subject than the longer focal length lens, but it will have more depth of field behind the subject than the longer focal length lens. In other words, for the shorter lens the depth of field is not only greater but more asymmetric.
These comparison photos illustrate how changing the focal length of the lens can change depth of field even when the on-film magnification stays the same. The photograph in the upper left was made with a 25mm lens and the one in the upper right with a 300mm lens. The lower photographs are enlargements of the ones directly above them.
I moved the camera to keep the on-film magnification 0.02X, but the distance between the targets didn't change and both photographs were made at ƒ/11. The front target is equally sharp in both photographs, but the far target is much blurrier in the 300mm photograph than in the 25mm photograph.
This graph shows how depth of field changes with on-film magnification for the 25mm and 300mm lenses. At closer distances (greater magnifications) focal length has minimal effect on depth of field; it becomes increasingly important as the distance increases. Notice that the total depth of field is always greater for the shorter lens, but the shorter lens has less depth of field in front of the subject and more depth of field behind it than the longer lens does.
Assuming you don't want to take my word for any of this, you can prove it yourself any one of several ways:
1. Mathematically—if depth of field really depends upon magnification and not lens focal length, you should be able to recast the depth of field equations using magnification as one of the variables so that focal length drops out entirely. Give it a try! Good luck!
2. Numerically—set up a spreadsheet with the depth of field equations that computes depth of field in front of and behind the subject as a function of on-film magnification (for a given f-stop and circle of confusion, of course). Try it out on a bunch of cases.
3. Pragmatically—pull out some of your lenses that still have depth of field markings on them. Compare the depth of field of markings between, oh say, your 50mm lens and a 300mm lens at distances that would correspond to the same on-film magnification (about six times further for the 300mm lens).
4. Logically—consider two extremes. First hyperfocal distance. Go to your textbook and pull out the standard equation for hyperfocal distance. Figure out what on-film magnification it corresponds to. You'll see that the magnification varies inversely with the focal length of the lens. No, that's not an artifact of having the far distance go to infinity. You could pick a far depth of field that was huge but finite, like say, 1 km, and plug that into the full depth of field equations and you'd get the same result as close as matters.
5. Reductio ad absurdum—consider the depth of field in front of the subject for any particular lens and situation you choose. It'll be some finite number. Now imagine swapping that lens for a lens of shorter focal length; to keep the on-film magnification the same (which, according to myth, will keep the depth of field the same) you will have to move proportionately closer to the subject. Keep making the lens shorter and shorter. At some point the total distance from the shorter lens to the subject is going to be less than the near-side depth of field you calculated for the longer lens.
I might have lost my cool a bit in the the "P.S." to the "What's a 'Fast Lens'?" post below. I apologize for that.
My problem is that I've been sensitized. I was the editor of a technical photography magazine for six years. Depth-of-field (DoF) is a subject that is deeply beloved of wannabe photo-tech writers, and few things could create instantaneous dismay deep in my editor's heart like opening a submission and finding yet another beautifully prepared, extensive, arcane article on DoF. DoF is perhaps the ultimate hell of photo-tech—graspable enough so many people think they can understand it (or think they should!), complex enough so that very few really can. Whenever the subject really gets going, great reams of material are spewed forth "explaining" it, always—always—strewn with considerable content that happens not to be true. Assuming any given reader engages with said great mass of verbal matter, he comes out the other side usually no more enlightened, and possibly considerably more confused. Finally, add to those conditions the simple fact that a technical understanding of DoF is not required for the successful practice of photography, and you begin to appreciate the extent of my exasperation with the subject.
(By the way, the other day I finally figured out why "grammar police" types can seem to be so fussy and cross. It's because they keep correcting the World, and the World keeps making the same mistakes anyway. If you tell your child three times to hang up the wet towel in the bathroom and he doesn't, you're not that irritated. When you've told him 700 times and you still come into the bathroom and find the damp towel in a moldy pile on the counter, you might well be incensed. So do you see my point? No matter how many times I remind people that "loose" is the opposite of "tight" and "lose" is the opposite of "win," people are still going to misspell it—because it's different people all the time, and there are an inexhaustible supply of them. It's like having 40,000 children, each one of whom needs to be trained to hang up the towel. The first three people I correct, I'm perfectly calm. By the 700th, I'm about to "loose" my mind. Anyway, you see the problem: educate one photographer about DoF, or ten, or a hundred—at however great a cost of time and effort—and you still have numberless millions to go. It's Sisyphean.)
In any event, I've just added more material to the end of the original post. Ctein chimed in. It's now longer. And hopefully a bit more clear. But it's beginning to flirt with becoming yet another of those great masses of verbal matter on DoF with which the literature of photography, and now the internet, is littered.
End-around
Anyway, I figured I might try to do a quick, painless end-around on the subject, and try to tell you what actually matters about DoF. I'm going to ignore the technical explanation: because That Way Lie Dragons; Abandon Hope All Ye Who Enter there; etc. I'm doing that on purpose, so please don't write to fill me in.
1. By far—by far—the most important factor in how much DoF you'll get is your distance setting. The farther the distance between the lens and whatever it's focused on, the more you'll get in the DoF.
2. Next most important: the focal length of the lens relative to the size of the film/sensor. Again, on principle, let's forget all the tech-talk about what's "really" going on and the scientific explanations and all that. All you need to remember is that the longer the lens, the less apparent DoF there will be in your shots. And, big jumps matter, little ones not so much; there's not that much difference between an 85mm and a 100mm, or between a 24mm and a 20mm. Very roughly speaking, when there's a 2x or 1/2x difference in focal length, you're going to have noticeably different DoF characteristics to learn.
3. Last: aperture setting. When I was teaching, all my kids had to memorize the following phrase: "The higher the number the smaller the hole the greater the depth of field." Can you see differences? Of course. But again, it takes relatively bigger jumps to really matter all that much. The other two factors matter more.
Quick'n'dirty
Photography is a visual medium, so let's take a look at a couple of examples of point 1, above. I'm saying that your distance setting is the biggest determinant of DoF. Take a look at these two shots:
In both of the above examples, I've focused on the tree trunk in the middle of the frame. I was standing about thirty feet away from it. There are some differences in the two pictures, mainly because most lenses are at their crappiest wide open and this lens is a fairly crappy little lens, so the lower picture looks a little worse. And the much closer branch-tips in the upper right are a little crisper in the ƒ/5.6 shot. But when your distance setting is 30 feet with a 28mm lens, the aperture isn't going to have very much effect on apparent DoF. No matter what the maximum aperture of the lens, you're going to have a hard time getting anything out of focus with this focal length lens at this distance setting.
Now look at the same two-aperture difference at a much closer distance setting, wider aperture first this time:
In this case, you can actually see a little difference in the blur, because you actually have some blur. In both of these, the focus was placed on the flower in the middle of the foreground, at the bottom of the frame. (I should have been a little more careful with exposure and framing. Sorry. Then again, if I made everything perfect, I'd never get anything done.) Now, obviously, there's some difference here. There should be: the aperture has been stopped down two stops. The flower is indeed a bit more "isolated" in the top, wide-open shot, and the blurry parts are indeed a bit blurrier. But just look back and forth between the house details at the top of the frame. There's some difference, all right....but it's not that much difference.
So in the top pair, you'd have a hard time opening up the aperture enough to introduce any blur; in the bottom shot, you'd have a hard time stopping down enough to eliminate all the blur. The point is that the top shot is pretty much going to have no blur, and the bottom shot is going to have some blur, with this camera and lens. And that's because of focus distance, mainly.
In any case, where DoF is concerned, don't sweat the small changes too much—whether this or that sensor is slightly larger or slightly smaller, whether this or that lens is ƒ/1.7 or ƒ/2.4, whether you're focused at 10 feet or 12 feet. When learning to manage sharpness and blur, it's the big swings that make more noticeable differences.
Hope this helps. But if it's just more verbiage added on to the great whacking pile of internet blather about DoF for you, well...at least you've got my sympathies!
Featured Comment by FS: "I am surprised that nobody has referred so far to this little gem: The Ins and Outs of Focus by H. M. Merklinger (Warning: PDF download):
"This is about infinity focus versus using DOF scales. The idea ist to focus on infinity, and then stop down so that the actual opening of the aperture is about the same size as the smallest object to b resolved."
Mike replies: I was looking all over for a current source for Harold's book yesterday, and was stymied. I had no idea the entire book was a free PDF download. Thanks!
Harold's methods are a bit quirky, but his two books are a fine brief introduction to the understanding of focus and DoF.
There's been some talk about whether this or that lens is "fast" or not since the DP1 came out sporting an ƒ/4 fixed lens. How "fast" is the Olympus E-P1 lens, really?
The concept of "lens speed" (referring to maximum aperture) has been variable over the years. Without launching into a history lesson, it's all been relative—Tessar-type designs are limited to fairly small apertures, for example, and first reaching ƒ/2.8 with a Tessar-type was an achievement. Generally speaking, though, lens speed was a prestige camera feature in the middle third of the 20th century, more or less, and cameramakers competed to see which could out-do the next. The market rewarded this tendency until ƒ/1.4 became common in normal lenses (the further from "normal" a focal-length is, generally, the harder it becomes to make the lens a fast one). Several cameramakers reached further than that, most notably with Walter Mandler's famous Leitz Noctilux, and several makers, Canon in particular, reached ƒ/1.4 with some fairly wide lenses for 35mm. The other famous fast lens early on was the 85mm ƒ/1.4 Zeiss Planar, which has long and interesting history that continues right down to the present day, in a fine lens released very recently. But the market as a whole didn't much care—ƒ/1.4 at the normal focal length turned out to be the point of sufficiency for most photographers where lens speed was concerned. Options that do better than that have sporadically been available, but have never achieved much in the way of popularity.
Of course, film speed has to be factored into that. During the only two stretches of time that I used Leica rangefinders—the first time for a period of about two years in '91–'93, the second time for something closer to a single year around '96 or thereabouts—I used Summicrons. (Leica, unique among cameramakers, names its lenses according to the lenses' maximum aperture; all the "Summicrons" are ƒ/2 lenses.) I was shooting Tri-X, rating it at E.I. 200. Also—somewhat oddly in retrospect—I never used either of those Summicrons at ƒ/2! The first main lens I used was a fourth-version (now called the "pre-ASPH") 35mm Summicron (which I once rather infamously dubbed "the King of Bokeh"), and the second time I used a custom-coated collapsible 7-element 50mm Summicron from the early 1950s. Neither lens was much good wide open, so I avoided the open aperture (and, for the most part, one stop down as well, if I could).
One might well ask, why use a Summicron if you're not going to use the lens wide open? It's a good question, especially since, on a Leica, you don't need to use the lens to see in the viewfinder. That, of course, was the other driver of lens speed: SLRs caught fire in the market starting in the 1960s, and, when you look through an SLR, you're looking through the lens you have mounted on the camera, generally at its wide-open aperture. The slower the lens, the dimmer the view. And why is that important? For focusing, of course. Photographers who have come of age since 1985 or so are probably aware that everybody used to focus manually, but only if you experienced being dependent on it can you really appreciate how important it was to have a good, snappy groundglass and a crisply fast lens to see through. On SLRs, you might never shoot at ƒ/1.4 with an ƒ/1.4 lens, but that maximum aperture was still very important nonetheless.
The increasing popularity of zoom lenses in the 1980s and '90s changed the equation again. Very broadly speaking, zooms are two stops slower than equivalent primes; if a premium normal prime lens is ƒ/1.4, a premium normal zoom is ƒ/2.8; cheaper, smaller lenses in each case might be one or two stops slower than that. This was really only practicable because of the parallel advent of autofocus. Slow zooms, especially mated to cheap finders, would have been very difficult to focus manually.
Nowadays, of course, another factor has once again changed the meaning of lens speed is the high-ISO capability of digital cameras. I distinctly remember the brief juncture at the beginning of the 2000s when digital image quality became good enough to tempt serious photographers, but the "speed" (we call it ISO, even though it strictly isn't) of sensors didn't yet match that of film. That changed quickly. Image quality still declines with increasing ISOs, but the general consensus is that every sensor/firmware package has a fairly well defined limit of "usable" image quality—and, with larger sensors, the number is usually amazingly high when you compare it to similar limits applied to film. My personal standard is that if a DSLR has good quality at ISO 800 and usable quality at ISO 1600, I'm happy. My current DSLR does considerably better even than that.
Image stabilization yields yet another twist to the story. IS is a "tripod replacement," not a "film-speed replacement," and that does have implications for how it's useful and how it's used. Even so, one or two stops' worth of further flexibility in low light or with long teles is often quite valuable.
The long and the short of it is this: in 1992 I was shooting with an M6 and Tri-X rated at E.I. 200, using an ƒ/2 lens that had poor image quality wide open, meaning that I avoided shooting wide open. The new Olympus E-P1 that we've been discussing for several days here has an ƒ/2.8 normal lens. But it probably also has "good as Tri-X" image quality at ISOs up to 800 or so, and its built-in image stabilization probably yields one or two stops' worth of shutter speed into "tripod territory." Let's say for the sake of argument that the newer lens design is also acceptable in terms of image quality wide open (even though that still remains to be seen). What that means is that, even according to these fairly conservative calculations, that I gain two stops in exposure index ("film speed") (ISO 200 to 800) and up to two stops in shutter speed (thanks to IS) using the two lenses at the same effective widest aperture (ƒ/2.8). And you're not dependent on the lens for the brightness of a TTL (through-the-lens) optical viewfinding image.
Or, put it this way: given the presence of all these conditions, ƒ/2.8 is the new ƒ/2.
You can say "more speed is never bad," but in practice, the market will eventually decide on a point of sufficiency, just like it does with all technical parameters in which various makers compete to satisfy real demand. The "point of sufficiency" is where most people decline to pay for further improvement (or buy it only for status). We might already have reached that point with megapixels and sensor speed, with 24 and usable 6400 respectively in the most advanced devices. (Only time will tell. The manufacturers will overshoot the point of sufficiency, but as they do, fewer people will pay for the increased performance.) However, for a small personal snapshot camera designed to be handy and portable—given that it has a large sensor with good high-ISO performance and IS—an ƒ/2.8 lens seems fast to me.
P.S. Comment: "But I'm not so concerned about exposure, I'm concerned about achieving limited depth of field to isolate subjects."
Not picking on the person who wrote these particular words (or any individual who might have written similar words) personally...but this is total internet hooey. It's something the "thousand monkeys in a room" on the internet have convinced themselves is an issue. It isn't. Or it shouldn't be, to any pictorial photographer shooting pictorial subjects.
In this particular case: a) you don't use a 35mm-e on anything to "isolate subjects"; and b) the difference between ƒ/2 and ƒ/2.8 for "isolating subjects" is very slight, marginal at best; and c) isolating subjects has much more to do with how you use the lens than with a one-stop difference in aperture on that lens. Finally, d) most people who consider themselves "concerned" with "isolating subjects" just as often don't have enough depth of field as too much. I see the evidence all the time, in pictures, all over the place, everywhere. Here's just one (a sample from the E-P1 and 17mm lens). Just one of millions...do you see that this photograph doesn't have enough depth of field for the subject? (The only reason I can pick on this picture is that it's a sample of the new lens wide open, and is not presented as something that's aesthetically intentional. I try not to pick on actual pictorial pictures by actual amateur photographers who might be hurt or offended by having themselves used as an example of what not to do.) O, if I could but count the number of out-of-focus dog's noses I've seen because the earnest but hapless photographer was trying to blur the background....
The problem in photography from 1840 until about 2005 with rare exceptions (fashion photographers and their once-fashionable 300mm ƒ/2.8s come to mind) was to get enough depth of field. The problem was almost never too much. And then came the theoreticians of the shared armchair and their picayune calculations of sensor size and diffraction and all else that's much talked of in numberless fora but wrong....
Best advice: unless you're doing technical work, and have extremely strict conditions and/or requirements to deal with, and you thoroughly understand the issues from a practical as well as a (real) technical standpoint, then ignore everything you come across on this subject. Most of what's out there is 99.75% complete chrome-plated bulldung. (And as you can see, the persistence of the error—and the knowledge that it's never, ever going to go away—makes Mike a mite testy.) —Mike
I've watched the furor over the matter of the "missing" optical viewfinder (OVF) on the Olympus E-P1—not only here but all over the web—with bemused curiosity. Maybe I just understand camera design a bit more thoroughly than the average bear, but, to me, it was a given from the very first that a Micro 4/3 camera wouldn't have an OVF. At least, not a built-in, all-purpose one. Not a surprise.
It's a case of classic opposing design parameters. My standard example of an opposing design parameter is a sailboat hull. You can have a hull that goes fast through the water, or you can have a hull that holds a lot of cargo. But you can't optimize for both at the same time. The more one parameter is optimized, the more the other is compromised. For a given amount of speed you can try to optimize capacity, and for a given amount of capacity you can try to optimize speed, but to say you want both to be optimized at the same time is oxymoronic, like saying you want long hair but you want it really short.
The situation is a little more complicated in the case of an OVF on a camera, because we're looking at more than just two parameters, but we should at least ascribe the problem to its real cause: the trouble is the popularity of zoom lenses.
Once you decide to provide interchangeable lenses, then you must provide a zoom. Photographers functioned well for 7/8ths of the medium's history without zooms to speak of, but now most people want them, and if a company wants to sell cameras then it has to provide a zoom or zooms. And once the decision is made to provide a zoom lens, then any non-TTL (through the lens) OVF is out. It's not just that a good non-TTL zooming optical finder is difficult to implement, and it's not just that any such finder would be large and expensive. The problem is that the physical bulk of lens gets in the way of the finder's view.
Even on a rangefinder Leica, some of the more recent premium primes are large enough to block a significant portion of the view. The picture above is a quick shot taken with a D700 and 28mm of the view through a Leica M7 .58 viewfinder. The gray bars are the framelines (they're brighter to the eye). Despite the "ventilated" lens hood on the 35mm Summilux ASPH lens, the lens blocks the lower right-hand portion of the field of view. (That strange-looking structure in the yard is a "square foot garden
Zooms are bigger than prime lenses, even fast premium Leica primes. Big zoom, small camera? A built-in optical finder in a small or even medium-sized non-TTL camera is going to be blocked by the lens.
So the camera's designers have a couple of choices. They can stick to a single-focal-length fixed lens, in which case an OVF makes good sense. They can stick with a set of moderate primes (i.e., no superwides or super-teles), in which case they can still design a built-in OVF (that's the classic rangefinder solution), although it would be considerably more complicated, and compromises start to enter into it. Or they can dispense with the OVF altogether in favor of an electronic viewfinder (EVF) (this is what the Panasonic G1's designers opted for). Or they can dispense with the built-in OVF and provide a clip-on type suited only for one lens of one focal length (the Oympus E-P1 solution, so far).
But all this garment-rending and teeth-gnashing about the E-P1 not having an OVF is just...misguided. Mistaken. Not gettin' it. Just try imagining it—what is it you want? How would it work? What would the problems be? Try imagining it, and you'll see. You want handling like a Porsche or hauling like a semi? You can't have both at once.
The trouble is that the market as a whole demands its zooms. To murder the old saying about having your cake and eating it too, you can't find the view and zoom it too.
Thank you!
